KRAHM’s
Human and Social Biology
Revision Text
Adapted from the following texts:
Human and Social Biology for CSEC
by Peter Givens, Pamela Hunte, Yvonne Quan Kep, Mark Morris
Human and Social Biology for CSEC Examinations
by Phil Gadd
Human and Social Biology (Revision Guide)
by Phil Gadd
April 2017
KHM
TABLE OF CONTENTS
Topic
Page number
Living Organisms
Topic
Page number
Excretion and Homeostasis
3
40
Characteristics of Living Things
3
The Kidney
40
Cell Theory
3
The Skin
42
Photosynthesis
6
Homeostasis
43
Movement of Substances
across Membranes
6
Feeding Relationships among
Organisms
Coordination and Control
45
The Brain
46
7
Reflex Actions
47
The Carbon and Nitrogen Cycle
9
The Eye
48
Nutrition
11
The Endocrine System
50
7 main nutrients
11
The Reproductive System
53
Constipation
14
Male and Female Reproduction
53
Diarrhoea
15
Menstrual Cycle
56
Balanced Diet
16
Methods of Birth Control
58
Malnutrition
16
Body Mass Index
18
Mitosis and Meiosis
61
The Human Teeth
19
Inheritance
63
The Digestive System
21
Enzymes
21
Process of Digestion
22
Absorption
24
The Respiratory System
26
Rescue Breathing
27
Cellular Respiration
27
61
Disease and its Impact on
Humans
25
Gaseous Exchange
The Circulatory System
Heredity and Variation
66
Common Disease
67
Vectors
69
Methods to Control the Growth
of Microorganisms
71
Immunity
72
Drugs
73
Impact of Health Practices on
the Environment
30
74
Components of Blood
32
Pollution
74
Arteries, Veins and Capillaries
33
Water Purification
76
Heart Disease
34
Sewage Disposal
77
Lymphatic System
35
Solid Waste Management
78
The Skeletal System
36
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LIVING ORGANISMS
Objectives
 Describe the characteristics of living organisms
 Compare the structures of unspecialized plant and animal cells and select microbes
 State the functions of cell structures
 Identify selected cells which make up the human body
 Distinguish between osmosis and diffusion
 Explain the importance of osmosis, diffusion and active transport in living systems
 Explain the process of photosynthesis
 Explain the ways in which other organisms depend on plants directly or indirectly for food
 Explain the principles of a food chain
 Construct a food chain from a selected habitat
 Identify the trophic level of organisms in the food chain
Characteristics of Living Things
Excretion – the release of metabolic waste, toxic substances and any substances in excess of
requirements
Movement – the change in position or direction of the body or part of the body
Growth – a permanent increase in size, dry mass and the number of cells
Irritability – the ability to detect and respond to stimuli (changes in the environment)
Reproduction – the ability to produce new individuals of the same species
Nutrition – obtaining food in order to produce energy and provide materials for building up body
cells
Respiration – the release of energy from food substances to do work in the body
Made up of cells
Cell Theory
A cell is the structural unit of most organisms. All organisms are made up of cells.
Functions of Cell Organelles in Plant and Animal Cells
Nucleus – contains chromosomes which control the cell’s activity
Cytoplasm – a jelly-like material where most of a cell’s chemical reactions occur
Vacuole – a fluid filled space that gives the cell support
Mitochondrion – site of aerobic respiration (energy production)
Endoplasmic reticulum – transports substances around the cell; called rough endoplasmic reticulum
if there are ribosomes attached to it
Ribosome – makes proteins from amino acids
Cell membrane – semi-permeable outer cell lining; protects cell from surrounding environment;
controls which substances enter and leave the cell; keeps cell contents in correct proportions
Cell wall – a cellulose structure in the plant cell; supports cell when it is fluid filled; gives cell its
regular shape
Chloroplast – site of photosynthesis in the plant cell; contains the pigment chlorophyll which
absorbs light energy
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Typical plant cell
Typical animal cell
Microbes
Bacteria
Bacteria have a simple cell structure. They are surrounded by cell walls, which are not made of
cellulose, used to keep the cell’s shape and preventing it from bursting. Some bacterial species are
surrounded by a slime capsule that protects against other organisms and reduces the chances of
drying up. They have a nucleoid region with a loop of DNA within the cytoplasm – they have no
nucleus. Some bacterial cells have flagella for moving through water or other fluids. Some reproduce
by making spores (small reproductive structures) which germinate and divide in suitable conditions.
Fungi
Most fungi are multi-cellular. Each cell has a nucleus and a cell wall made of chitin. They reproduce
by making spores that are carried by the wind. Most feed on dead or decaying matter. They require
water for growth, oxygen for aerobic respiration and a suitable warm temperature.
Structure of a human virus
Structure of a mould fungus
Viruses
Viruses are only visible under a microscope. They are not cells, but particles made up of genetic
material (DNA or RNA) surrounded by a protein coat. All viruses are parasites that enter the cells of
other organisms (host) in order to multiply. They do not respire, cannot make their own protein or
genetic material. They take over host cells to produce new viruses. They can reproduce very quickly
and do not respond to antibiotics.
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Cell Specialisation/Differentiation
There are two types of cells in multi-cellular organisms:
Unspecialised cells - those which divide and have no specific function, e.g. stem cells
Differentiated cells - those which develop to perform one specific function. These cells form
tissues, e.g. muscle cell for muscle contraction; nerve cell to transmit nerve impulses
Differentiated cells are important because they allow the organism to be as efficient as possible at
carrying out its functions.
Type of Cell
Muscle cell
Neurone
(nerve cell)
Epithelial cell
Ovum (egg
cell)
Sperm
Red blood cell
Structure
Cytoplasm is full of contractile
proteins
Long thin process between two
parts of the body
Function
Contracts to bring about movement
Comprises of an uninterrupted
layer of cells with small spaces
between them; some free (apical)
surface is covered in cilia – short,
thin structures that move back and
forth.
Largest cell in the human body;
cytoplasm has stored energy;
nucleus has chromosomes
Long thin cell with very little
cytoplasm; cell has many
mitochondria; nucleus has
chromosomes; long flagellum
No nucleus; cytoplasm filled with
haemoglobin
Transmits electrical impulses over a long
distance from one part of the body to
another
Covers most external and internal body
surfaces, e.g. hollow organs, glands and
outer layer of skin; Cilia move mucus in
one direction, e.g. along air passages
Female gamete; contains stored energy to
keep the zygote alive after fertilisation;
nucleus contains genes from the mother
Male gamete; mitochondria release energy
for swimming to meet the ovum; flagellum
moves back and forth to propel the cell;
nucleus delivers genes from male to ovum
at fertilisation
Haemoglobin transports oxygen; no
nucleus facilitates more haemoglobin and
allows the cell to change shape to move
through capillaries
Tissue – a collection of similar cells working together to carry out the same function
There are 4 main types of tissues
1. Epithelial – covers and protects surfaces
2. Connective – connects between body organs and ‘packs’ between them
3. Nervous – conducts nerve impulses around the body for coordination
4. Muscle – contracts to bring about movement
Organ – a collection of different tissues working together to carry out one function, e.g. the heart is
made up of muscle tissue, nervous tissue, connective tissue and epithelial tissue
Organ system – a collection of different organs and tissues working together to carry out one major
function
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Movement of Substances across Membranes
Substances can enter or leave a cell either passively (diffusion, osmosis) or actively (active transport).
Diffusion
Diffusion is the movement of molecules or ions from a region of high concentration to a region of
low concentration until they are evenly distributed. It depends on the difference in the
concentrations of particles in two places. The difference in the concentrations is called the
concentration gradient.
Examples of diffusion in organisms
Place
Small intestine
Lungs
Lungs
Particles which move
Digested food products
Carbon dioxide
Oxygen
Capillaries
Oxygen and dissolved
nutrients
Carbon dioxide and waste
Neurotransmitters
Carbon dioxide
Capillaries
Synapse (gap)
Leaf
From
Small intestine lumen
Alveoli
Blood around the
lungs
Blood
To
Blood in villus capillary
Blood around the lungs
Alveoli
Body cells
Neurone
Air space between
mesophyll cells
Blood
Neurone
Chloroplast
Body cells
Osmosis
Osmosis is the overall movement of water from a dilute solution to a more concentrated solution
through a semi-permeable membrane. It is a special type of diffusion, where water moves from a
higher concentration of water to a lower concentration of water until the two concentrations
become equal.
Examples of osmosis in organisms
1. Absorption of water by plant roots
2. Re-absorption of tissue fluid into the venule ends of the blood capillaries
3. Absorption of water by the alimentary canal — stomach, small intestine and the colon
4. Cell membranes are selectively permeable — allow the passage of water and certain solutes
Turgid cells refer to those which are full of water so that the contents push against the cell wall.
Flaccid cells refer to those that have lost water and become limp.
Plasmolysis refers to the movement of the cell surface membrane away from the cell wall when the
cell loses water.
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Active Transport
Active transport is the energy demanding transfer of a substance across a cell membrane. It carries
substances against its concentration gradient, i.e. from a region of lower concentration to a higher
concentration. ATP generated by respiration supplies the energy for active transport.
Examples of Active Transport
1. Re-absorption of glucose, amino acids and salts by the proximal convoluted tubule in the
kidney
2. The absorption of mineral nutrients by plant roots
3. Sodium/potassium pump in cell membranes (especially nerve cells and red blood cells)
Photosynthesis
Photosynthesis is the chemical process by which green plants make their own food in the presence
of light energy.
This is done by converting light energy from the sun into chemical energy in glucose. The glucose
that is made is stored as starch and converted into other molecules.
Raw materials
Water – absorbed by root hairs by osmosis in the soil
Carbon dioxide – from the air through the stomata of plant leaves
Products
Glucose (sugar) – stores of chemical energy
Oxygen – by-product
Photosynthesis takes place in the chloroplasts found in the palisade and spongy mesophyll cells in
leaves of plants. Chloroplasts contain the green pigment chlorophyll which intercepts and traps light
energy and enzymes that catalyse reactions to make glucose.
Uses of glucose
Much of the glucose is converted to starch and stored. Glucose is broken down during respiration to
release energy for growth and cell activities. It can be converted to carbohydrates, lipids and
proteins and used for growth. It is also converted to starch and stored, e.g. potatoes, yam, rice,
dasheen.
Uses of oxygen
Some oxygen is used for respiration. Excess oxygen diffuses out of the leaf through the stomata.
Feeding Relationships among Organisms
Plants provide food for many living organisms, either directly if they are herbivores that eat them,
indirectly if they are carnivores that eat live herbivores, or decomposers that feed on dead animals
and plants. The sun is the ultimate source of energy for most life on earth.
Producers – organisms that make their own food by photosynthesis
Consumers – organisms that feed on producers
Herbivore – organisms that feed on plants only
Carnivore – organisms that feed on animals only
Omnivore – organisms that feed on both plants and animals
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Food chain – a simple diagram that shows the feeding relationship between organisms; it shows how
energy passes from one organism to another
Food web – shows the interconnections of many food chains
Trophic level – the position an organism occupies in a food chain
Decomposers – bacteria and fungi that feed on dead and decaying matter
Energy Flow and Loss
Plants capture only a small percentage of the sun’s light energy that reaches them.
Energy is lost as food passes up the trophic level, which limits the number of animals at each
consumer trophic level. Reasons for the energy lost up the trophic levels include:
 Undigested and unabsorbed food passes out in faeces
 Much energy used for respiration
 Energy lost as heat to the environment
Terrestrial food web
Aquatic food web
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THE CARBON AND NITROGEN CYCLE
Objectives
 Describe the recycling of carbon and nitrogen in nature
Carbon Cycle
The carbon cycle shows how carbon atoms are continuously taken up, converted into compounds
and then recycled. The element carbon (C) is found in all organic molecules.
 CO2 is taken from the atmosphere and from water, e.g. lakes and oceans, by photosynthesis in
plants, algae and some photosynthetic bacteria
 CO2 is released to the atmosphere and to water by respiration, which occurs in all organisms
 CO2 is released to the atmosphere by the combustion of wood and fossil fuels
 Fossil fuels are formed from the dead and fossilised remains of organisms, e.g. coal, oil, gas,
peat
 Carbon compounds, such as carbohydrates, fats and proteins, pass along food chains from
plants to herbivores and then to carnivores
 Decomposers feed on dead and decaying plant and animal matter and release CO 2 by their
respiration
 Some carbon compounds are not decomposed; instead they accumulate in carbon sinks.
Eventually these carbon compounds that have not decomposed form fossil fuels
Nitrogen Cycle
The nitrogen cycle is the circulation of nitrogen in the atmosphere and nitrogen-containing
substances in soil and living organisms. The element nitrogen (N) is found in many organic
molecules.
Importance
 Convert nitrogen from its un-reactive form (nitrogen gas) to its reactive forms (nitrates,
nitrites and nitrogen oxides)
 Makes nitrogen available for biological molecules, e.g. proteins, DNA, RNA
 Allows nitrogen to be reused by living organisms
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Main processes of the nitrogen cycle
1. Nitrogen fixation
Nitrogen fixation is the process in which bacteria convert nitrogen gas from the air into ammonium
ions and nitrates.
Nitrogen can be fixed by:
 Bacteria that live in soil and convert nitrogen gas to nitrates in the soil to be absorbed by
plants
 Bacteria that live in plant roots nodules, e.g. legumes, convert nitrogen gas to nitrates in
plants
 Lightning that causes nitrogen and oxygen to react together to form nitrogen oxides that form
nitrates in the soil
2. De-nitrification
De-nitrification is the process in which nitrates in the soil are converted to nitrogen gas by
denitrifying bacteria. Denitrifying bacteria live in water-logged soils and survive in conditions with
very low oxygen. De-nitrification reduces soil fertility because it removes nitrates in the soil.
3. Decay
Plants and animal decompose to ammonium compounds in the soil by fungi and bacteria. Animal
wastes, e.g. faeces and urine, are decomposed by bacteria in the soil.
4. Nitrification
Nitrification is the process in which ammonium compounds are converted to nitrates by nitrifying
bacteria in 2 steps:
i. Ammonium compounds are converted to nitrites in the soil by nitrosomonas bacteria.
ii. Nitrites are converted to nitrates in the soil by Nitrobacter.
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NUTRITION
Objectives
 Describe the major nutrients and their sources
 State the function and the main sources of vitamin A, B 1, C, D and the minerals calcium and
iron
 State the functions of water in the body
 State the role of dietary fibre in the body
 State the cause, symptoms and treatment of deficiency diseases
 Describe the causes and effects of constipation and diarrhoea
 Explain what is meant by a balanced diet
 Explain the effects of malnutrition on the human body
 Determine Body Mass Index (BMI)
Nutrient – a food substance that provides energy and is necessary for the growth and repair of living
organisms.
7 main nutrients:
Proteins
Carbohydrates
Vitamins
Water
Lipids
Minerals
Roughage
Proteins
Proteins are large molecule made from amino acids. They contain carbon, nitrogen, hydrogen,
oxygen. Some also contain sulphur, phosphorus.
Importance: Cell repair and cell growth
Form main parts of protoplasm (cytoplasm and nucleus) and makes up cell structures
Form the structural part of enzymes
Form an important part of insulin and haemoglobin
Sources: meat, fish, eggs, milk, legumes, nuts
Carbohydrates
Carbohydrates are groups of molecules made by plants that supply much of our energy. They contain
carbon, oxygen and hydrogen. There are three types of carbohydrates:
1. Monosaccharides – the simplest carbohydrates. Food sources include biscuits, cakes and
honey.
2. Disaccharides – made up of two monosaccharides. Food sources include cane and beet sugar,
fruit and milk
3. Polysaccharides – complex carbohydrates made of long chains of many simple sugar units.
Food sources include bread, pasta, potato, cassava and yams
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Reducing sugars are the simplest carbohydrates that produce a brick-red precipitate in blue
Benedict’s Solution. They include:
 All monosaccharides, e.g. glucose, fructose, galactose
 All disaccharides except sucrose, e.g. maltose and lactose
Non-reducing sugars are complex carbohydrates, which remain blue in Benedict’s Solution. They
include:
 The disaccharide sucrose
 Polysaccharides, e.g. starch, glycogen, cellulose
Lipids (Fats and Oils)
Lipids are made up of fatty acids and glycerol.
Importance: Secondary source of energy (long term store of energy)
Good storage compounds
Provide insulation and protection
Reserves found under skin and around organs
Solvent for fat-soluble vitamins (vitamins A,D,E,K)
Make hormones
Brain development in infants
Important part of cell membrane
Sources: butter, margarine, lard, peanuts, milk, cheese, castor oil seeds, pork
Minerals
Minerals are inorganic substances needed in small amounts by organisms.
Mineral
Iron
Iodine
Calcium
Phosphorus
Sodium and
potassium
Rich Sources
Liver; eggs; dark, green,
leafy vegetables; kidney;
red meats
Seafood; iodised table salt;
cheese
Dairy products; dried
beans and peas; tinned
tuna/salmon; green
vegetables
Fresh vegetables; dairy
products; liver; meat;
eggs; fish; nuts
Fresh vegetables; milk;
liver
Function
Forms haemoglobin in red
blood cells
Deficiency Results
in:
Anaemia
Production of thyroxine
which controls metabolic
rate
Formation of bones and
teeth; assists in blood
clotting; muscle contraction
Goitre and
reduced growth
ATP production; formation
of bones and teeth,
formation of DNA and RNA
Nerve impulse conduction
Rickets
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Rickets
Rarely deficient
KHM
Vitamins
Vitamins are organic substances needed in small amounts in the body
The 2 types of vitamins:
1. Water soluble vitamins – vitamin B, C
 Easily assimilated in the body and mixes with blood
 Need to be eaten regularly because excess is excreted
2. Fat soluble vitamins – vitamin A, D, E, k
 Absorbed from fats and oils in the diet and can be stored in the body
Vitamin
A (retinol)
Rich Sources
Fish liver oil, milk, butter,
margarine, dark green
and yellow/orange
vegetables, fruit, egg
yolk
B1 (thiamine)
Yeast; egg yolk; liver;
whole grain rice and
wheat, kidney
C (ascorbic acid) Citrus fruits, tomatoes,
cherries, green
vegetables
D (calciferol)
Milk, fish liver oils, eggs,
sweet potatoes,
vegetable oils; made in
the body in the presence
of sunlight
Function
Good vision, esp. in dim
light; Maintains healthy
hair, skin and gums;
promotes bone and
teeth formation; aids in
fat storage; increase
resistance against
infections
Help convert carbohydrates into glucose to
produce energy
Maintains healthy skin,
teeth and gums; aids
growth and repair of
damaged tissue;
strengthens immune
system; assists in
absorption of iron
Assists in calcium and
phosphorus absorption
Deficiency Results in:
Night blindness
Beri-beri (swollen legs and
digestive problems)
Scurvy (weakened blood
capillaries, bleeding gums)
Rickets (affects bone
growth)
Water
Water makes up ⅔ of the human body
Functions:
Solvent for chemical reactions to take place
Forms part of all body fluids
Transports nutrients and waste products through cells and around the body
Improves digestion and excretion
Provides cell support
Allows absorption of water-soluble vitamins
Maintains proper body temperature
Sources: green, leafy vegetables, milk, fruits, liquids
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Dietary Fibre (Roughage)
Dietary fibre cannot be digested and remains as bulk in the gut
Functions:
Allows peristalsis to occur - a series of controlled muscular movements that push food
down the gut
Allows for easy elimination of faeces - soft and digested foods do not stimulate
peristalsis
Prevent constipation and haemorrhoids - retains water causing softer, bulkier faeces
Sources: bran products, vegetables, fruits, nuts, beans
Constipation
Constipation is the inability or difficulty to defecate. It occurs when bowel movements become
difficult or less frequent. Going longer than 3 days without a bowel movement causes faeces to
become harder and more difficult to pass.
Causes:
Inadequate fluid intake
Inadequate fibre in the diet
Change in regular diet or routine
Stress, anxiety or depression
Inadequate activity or exercise
Ignoring the urge to pass stools
Side effects of some medications
Symptoms: Infrequently and/or difficulty having bowel movements
Swollen abdomen
Hard, lumpy, abnormally hard/small stool
Abdominal pain
Vomiting
Treatment: Drinking 2 – 4 extra glasses of water
Drinking warm liquids
Eating fruits and vegetables
Eating prunes and/or bran foods
Taking a mild laxative or stool softener (only when necessary)
Prevention: Eating high fibre foods
Drinking plenty of fluids
Exercising regularly
Reducing ignoring the urge to pass stool
Reducing the intake of starch foods
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Diarrhoea
Diarrhoea is the passing of loose or watery faeces more than 3 times a day. The body can become
dehydrated quickly as a result of the loss of water in the faeces.
Causes: Occurs when fluid cannot be absorbed from bowel contents or when extra fluid is secreted
into the bowel. Can be caused by:
 Consuming contaminated food or water
 Consuming too much alcohol and/or coffee
 Allergic reactions to food
 Intestinal damage
 Laxative abuse
 Medication side effects
Symptoms:
Abdominal bloating or cramps
Sense of urgency to pass stool
Fever
Headache
Thin, loose or watery stool
Nausea and/ or vomiting
Loss of appetite
Treatment: Often goes away without treatment because the immune system automatically fights
the infection. These steps can help:
 Drink plenty fluids to avoid dehydration
 Let it run its course
 Take over the counter anti-diarrhoeal medicines
 Avoid fatty, spicy or heavy foods
Food poisoning is a very common cause of diarrhoea. It can be prevented by:
1. Washing hands thoroughly after using the toilet and before eating or preparing foods
2. Cleaning toilet, including handle and seat, with disinfectant, especially after each bout of
diarrhoea
3. Keeping flies, roaches, rodents and other animals away from food
4. Cleaning working surfaces and kitchen equipment thoroughly before and after use
5. Avoiding storing raw and cooked foods together
6. Ensuring that food is kept properly refrigerated
7. Cooking food thoroughly
8. Avoiding the consumption of food past its expiration date
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Balanced Diet
Diet – the quantity and quality of the different types of food that a person eats
Balanced diet – a diet that provides energy and nutrients in the right quantities to remain in good
health
Food group – a group of different foods that provide the same nutrients in roughly the same
proportions
Food Group
Staples
Nutrient Supplied
Carbohydrates, minerals, vitamins, fibre
Legumes
Vegetables
Proteins, carbohydrates, fibre
Vitamins, minerals, fibre, water
Food from animals
Fruits
Proteins, fats and oils
Fats and oils
Fibre, vitamins, minerals, water,
carbohydrates
Lipids, vitamin A (in enriched margarines)
Sources
Rice, bread, yam, potato,
cereals
Peas, peanuts, soya, beans
Egg plant, bell pepper, callaloo, carrot, pumpkin
Meat, poultry, fish, egg, milk,
cheese
Orange, ripe bananas, mango,
guava
Margarine, butter, peanuts,
oil
Factors Affecting Energy Needs of Different People: size, sex, age, occupation, and climate.
Malnutrition
Malnutrition is the result of lack of a balance in the diet, caused by either a shortage of nutrients or
eating too much of them.
Examples: Starvation Anorexia nervosa Kwashiorkor
Obesity
Bulimia nervosa
Marasmus
Starvation
Starvation is a shortage or complete lack of food that extends over a period of time. It leads to a
deficiency of energy and nutrients. It is the most extreme form of malnutrition and can lead to
permanent organ damage and death.
Causes: Imbalance between energy intake and expenditure
Effects: Loss of muscle mass
Diarrhoea
Skin rash
Oedema
Heart failure
Irritability
Lethargy
Treatment: Rest and warmth; glucose followed by food in small quantities that increase over time.
Obesity
Obesity is a medical condition where a person is 30% or more above their recommended weight
(being overweight due to having too much body fat).
N.B. – obesity ≠ overweight
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Cause: Taking in more calories than the body needs (the body stores unused calories as fat).
This can be caused by:
Excessive alcohol consumption
Environment
Inactive lifestyle
Genes and family history
Health conditions
Emotional factors
Medicines
Treatment: Having a lifestyle change, e.g. active lifestyle; eat healthy well-balanced meals, etc.
Taking medication
Surgery, e.g. Gastric binding/bypass, liposuction
Risks: Coronary heart disease; hypertension; stroke; type-2 diabetes, prostate cancer, cervical
cancer, arthritis
Anorexia Nervosa
Anorexia is a psychological eating disorder that makes persons lose more weight than is considered
healthy for their age and height by not eating enough.
Causes: The exact causes are unknown; however, factors thought to play a role include genes,
hormones and social factors.
Symptoms: Blotchy, yellow skin
Extremely thin
Extreme sensitivity to cold
Treatment: Aimed at restoring normal body weight and eating habits. Treatment includes increasing
social activity; reducing the amount of physical activity; using schedules for eating.
Bulimia Nervosa
Bulimia is an illness where persons binge on food then purge themselves to prevent weight gain.
Purging may include: vomiting, excessive exercise, laxative or diuretic abuse.
Causes: Combinations of factors thought to play a role, e.g. genes, trauma, cultural factors,
psychological factors, social factors
Symptoms: Compulsive exercise
Suddenly eating large amounts of food then disappearing right away
Regularly going to the bathroom after meals
N.B. – Persons with bulimia are usually at a normal weight
Complications:
Oesophageal damage
Dehydration
Constipation
Dental cavities
Treatment: Support groups for patients with mild conditions and no health problems; therapy for
those that don’t respond to support groups.
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Marasmus
Marasmus is a protein-energy malnutrition (PEM). It is a severe form of malnutrition consisting of
chronic wasting away of fat, muscle and other body tissues and is prevalent in areas with chronic
hunger, contaminated water supply and inadequate food supply.
Causes: Inadequate amounts of protein and carbohydrates in the diet
Symptoms: Persistent diarrhoea
Fatigue
Lethargy
Full or partial paralysis
Dizziness
Weight loss
Loss of bladder and/or bowel control
Complications: Untreated marasmus may cause:
Growth problems in children
Joint deformity and destruction
Loss of strength
Organ failure or dysfunction
Unconsciousness or coma
Loss of vision
Treatment involves a special feeding and rehydration plan and close medical observation. These
include intravenous fluids, oral rehydration solutions and naso-gastric feeding tubes.
Kwashiorkor
Kwashiorkor is a protein-energy malnutrition (PEM) often found in children and commonly seen in
developing regions of the world with famine, limited food supply and low levels of education.
Causes: Inadequate amounts of protein in the diet despite a reasonable intake of calories
Symptoms: Decreased muscle mass
Failure to gain weight or grow
Irritability
Lethargy
Diarrhoea
Fatigue
Increased susceptibility to infections
Protruding belly
Complications: Untreated kwashiorkor may cause coma, permanent mental and physical disability
and shock.
Treatment: Correct blood and body fluid levels and treat any infections. Then reintroduce food
slowly starting with small amounts with carbohydrates then high protein foods and vitamin and
mineral supplements. N.B. – many malnourished children may develop lactose intolerance.
Body Mass Index (BMI)
BMI is used to determine the relative weight and nutritional status of individuals, whether obese,
healthy or underweight.BMI is calculated using the following formula:
BMI = Body mass (in kilograms)
-------------------------------------Height (in metres) 2
or
Body mass in pounds x 703
-------------------------------------Height (in inches) 2
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THE HUMAN TEETH
Objectives
 Relate the types of teeth present in an infant and an adult human to their roles
 Describe the importance of teeth in the process of digestion
 Describe the structure and function of a typical tooth
 Outline guidelines for the care of teeth
 State the causes of tooth decay
 Describe the process of tooth decay
Human Teeth
The teeth are accessory organs of the digestive system in the mouth that aid in mechanical digestion.
Functions: For mastication (chewing) - They cut, tear and grind food in the mouth
Enables food to be mixed with saliva
Allows food to be swallowed easier
Humans usually develop 2 sets of teeth over a lifetime.
1. Milk Dentition: also known as baby, deciduous, primary or temporary teeth, these are the
first set of teeth that erupt about 6 months after birth. They consist of 8 incisors, 4 canines, 8
premolars (20).
2. Permanent Dentition: replaces milk dentition around age 6, the last of which to emerge are
wisdom teeth (32).
Types of Teeth
Type
Incisor
Canine
(cuspids)
Premolar
(bicuspids)
Molar
Incisor
Number in
Adult
8
4
8
12
Form and Function
Located at the front of the mouth, relatively flat or ‘chiselshaped’ and used for cutting into food.
Have a single pointed surface used for tearing and shredding
food.
Usually have 1 or 2 roots, have larges surfaces with 2 main
cusps for grinding food.
Located at the back of the mouth, are blunt and have 2 to 3
roots. Have 4 cusps for crushing and grinding food.
Premolar
Canine
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Premolar
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Parts of the Tooth
Part
Crown
Enamel
Dentine
Root
Pulp cavity
Cement
Gum
Jaw bone
Function
Visible part of the tooth; surface for biting and crushing food
Hardest part of the tooth mostly made of calcium phosphate; prevents wear
Forms the bulk of the tooth; protects the pulp
Embedded in the jaw; holds tooth in place
Softer, inner structure of the tooth that contains nerve endings that provide
sensitivity and blood vessels that carry oxygen and nutrients in for cell use and
remove waste products.
Connective tissue layer that binds root tightly against jaw bone and gum
Supports tooth and protects jaw bone and root
Supports and provides a socket for the tooth
Care of Teeth
The following guidelines can be used to help take
care of teeth:
1. Brush regularly and properly at least twice
daily, preferably after every meal to remove
plaque
2. Brush with fluoride-containing tooth paste to
strengthen the enamel
3. Floss daily to remove debris between teeth
4. Change toothbrush every 2-3 months
5. Use mouth rinse (containing fluoride) after
brushing to remove some remaining food
particles
6. Eat nutritious and balanced meals that
contain calcium, phosphorus, vitamin C,
Section through a molar tooth
vitamin D.
7. Avoid sugary and starchy foods which can
remain on tooth surfaces and acidic foods and beverages that can damage the enamel.
8. Visit your dentist (twice yearly) for professional cleanings and oral exams.
Tooth Decay
Tooth decay results in the formation of dental cavities caused by a combination of food, bacteria,
not brushing teeth regularly and the improper brushing of teeth.
Plaque is a clear, sticky substance that covers teeth and gums that is produced by saliva, mucus, food
and bacteria. It can be controlled by proper brushing and flossing. If not removed, it hardens into
tartar.
The Process of Tooth Decay
Tooth decay is caused by bacteria living on food left on teeth. The foods are fermented by the
bacteria to produce acids. The acids destroy the enamel and the dentine, exposing the pulp cavity
and allow bacteria into the living tissue. The cavity made holds more food allowing the same process
to continue, resulting in tooth decay.
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KHM
THE DIGESTIVE SYSTEM
Objectives
 Explain the properties, role and importance of enzymes involved in digestion
 Investigate the effects of temperature and pH on the activity of amylase and catalase in the
digestive process
 Identify the various structures of the digestive system
 Relate the structures of the digestive system to their functions
 Describe the process of digestion and absorption of food in the alimentary canal
 Distinguish between egestion and excretion
 Terms Associated with Digestive System
 Describe what happens to the products of digestion after their absorption
 Describe the structure of a villus in relation to absorption
Terms Associated with Digestion
Digestion - The breakdown of food from large complex molecules into smaller simpler ones so it can
be absorbed through the blood stream
Mechanical digestion – The breakdown of large pieces of food into smaller pieces by chewing or the
churning action of the stomach
Chemical digestion – The breakdown of large, insoluble molecules into smaller, soluble molecules by
enzymes
Mastication – The chewing of food so it can be broken down into smaller pieces
Absorption – The movement of soluble molecules (digested foods, salts, vitamins, water) into living
cells
Assimilation – The use of food molecules in the body, e.g. using amino acids to make proteins,
store glucose as glycogen, store fatty acids and glycerol as fat
Ingestion – The intake of food into the body
Egestion – The removal of undigested food is eliminated from the body
Excretion – The process whereby metabolic waste is eliminated from the body
Enzymes
Enzymes are biological catalysts that are made by cells to speed up chemical reactions in the body
(catalysts speed up chemical reactions). They catalyse reactions that would otherwise take too long
to enable us to survive by reducing the energy needed for the molecules to react together. They
remain unchanged at the end of the reaction.
Properties of Enzymes
1. Proteins
2. Catalysts - they are not changed by the reaction and can be used multiple times
3. Specific - they act on a particular substrate
4. pH and temperature sensitive - they work best at certain pH and temperatures
5. Change substrate to products
6. Denatured (inactivated) at high temperatures and destroyed by boiling
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Role and Importance of Enzymes in Digestion
Enzymes break down large food molecules into smaller ones so that they can diffuse through the
intestinal wall into the blood. Large food molecules cannot pass through the intestinal wall.
Large food molecules – starch, protein, fats
Small food molecules – glucose, amino acids, fatty acids, glycerol
Amylase: Converts starch to maltose.
Optimum pH – 7 or very slightly higher; optimum temperature - 30⁰C
Catalase: Converts hydrogen peroxide to water and oxygen. Optimum pH – 7
Functions of Digestive System Structures
Structure
Mouth
Function (in digestion only)
Food is ingested
Structure
Pancreas
Salivary
glands
Oesophagus
Secretes saliva containing
salivary amylase and mucus
Carries food from mouth to
stomach
Churns food and secretes
gastric juices
Produces bile
Stores bile
Carries bile to duodenum
Controls amount of food
leaving stomach
Pancreatic
duct
Duodenum
Stomach
Liver
Gall bladder
Bile duct
Pyloric
sphincter
Ileum
Caecum
Colon
Rectum
Anus
Function (in digestion only)
Secretes pancreatic juice
with digestive enzymes
Carries pancreatic juice to
duodenum
Secretes intestinal juice with
digestive enzymes
Absorbs digested food
through epithelial wall
Absorbs some water
Absorbs water and salts
Stores faeces
Egests faeces
Process of Digestion
Mouth:
Food ingested and mechanical digestion takes place (mastication) so that the food can be swallowed.
Chemical digestion - Food is mixed with saliva and is lubricated for swallowing. Saliva contains
salivary amylase which converts starch to maltose.
The tongue pushes food to the back of the mouth to be swallowed. After swallowing, food move
down oesophagus to the stomach
Stomach:
Mechanical digestion - Food is mixed by contraction of muscular walls
Chemical digestion - Gastric juices released. It is composed of:
i. Hydrochloric acid (HCl) which kills bacteria, provide acidic conditions for pepsin to work and
stop salivary amylase activity
ii. Pepsin - activated by HCl and breaks down large proteins to shorter polypeptides
iii. Rennin (found in young children) - causes milk to clot so it can be acted upon by pepsin
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Food is then converted into chime and exit through the pyloric sphincter into the small intestine.
Small Intestines:
Duodenum – the 1st part of small intestine where food is digested. It receives:
i. Bile from gall bladder via the bile duct to emulsify fats. Bile contains sodium bicarbonate that
neutralises stomach acid
ii. Pancreatic juice from pancreas via the pancreatic duct that contains:
 Sodium bicarbonate that neutralises stomach acid
 Trypsin which break down peptides
 Lipase which breaks down fats to fatty acids and glycerol
 Pancreatic amylase which breaks down starch to maltose
Ileum – the largest part of small intestine where intestinal juice is secreted. In the ileum:
 Maltase breaks down maltose to glucose
 Peptidases break down peptides to amino acids
 Absorption takes place
Colon (large intestine):
Absorption of water and salts from faeces occur in the colon. Faeces are stored here for a short
period of time.
N.B. – Faeces are made up of undigested food, dead cells and bacteria.
Rectum and Anus:
Faeces are stored in the rectum and passed out by egestion through the anus.
End products of digestion
The end products of digestion are glucose, amino acids, fatty acids and glycerol.
Fate of End Products of Digestion
Glucose and amino acids diffuse into villi blood capillaries. These capillaries lead to the hepatic portal
vein that leads to the liver. Fatty acids and glycerol enter villi cells.
Glucose: Some is distributed to body cells to be used for respiration. Excess glucose is converted to
glycogen in liver and muscles, where it is stored.
Fatty acids and Glycerol: These are reformed to fats within the lacteals of villi. They then pass into
the blood stream via lymph vessels of the lymphatic system. Some are stored around vital
organs for insulation and protection.
Amino Acids: They can be assimilated (used for making new cell material, repairing damaged tissue
and forming enzymes and hormones). Excess amino acids cannot be stored; they are
deaminated in the liver (converted into carbohydrates by the removal of the nitrogen group).
The nitrogen group is converted to urea and is excreted in urine.
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Absorption
The ileum is well adapted for absorption to take place. The ileum has many villi which increase the
surface area for absorption.
Structure of a Villus
Structure
Micro-villi
Lacteal
Feature
Tiny finger-like projections
Extensive and found at the
centre of villi
Blood capillaries
Lead to hepatic portal vein
Epithelial cells
Single cell layer with many
mitochondria
Mucus cells
Found in the epithelium
Function
Provides larger surface area for absorption
Absorb fatty acids and glycerol that are
reformed into lipids and transports them
into the lymphatic system
Absorb glucose and amino acids and
transports them to the liver
Allows diffusion of digested food.
Mitochondria supply energy for active
transport of molecules
For food passage
Human digestive system
Section through a villus
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KHM
THE RESPIRATORY SYSTEM
Objectives
 Explain the importance of breathing in humans
 Relate the structures of the respiratory tract to their functions
 Describe the breathing mechanism
 Outline the factors affecting rate of breathing
 Explain the concept of vital capacity
 Distinguish between gaseous exchange and breathing
 Identify characteristics common to gaseous exchange surfaces
 Differentiate between aerobic and anaerobic respiration
 Explain the role of ADP and ATP in the transfer of energy
 Explain the technique of mouth-to-mouth resuscitation
 Explain the effects of cigarette smoking
Structure and Function of Parts of the Respiratory System
Structure
Nasal cavity
Epiglottis
Larynx (voice box)
Trachea (windpipe)
Cartilage
Bronchus
Bronchioles
Pleural membrane
Pleural fluid (lubricant)
Rib cage
Intercostal muscles
Diaphragm
Function
Filter, warm and moisten air
Prevent food entering the trachea
Contain vocal cords that produce sound
Allow passage of air to bronchus
Prevent collapse of trachea
Allow passage of air to lungs
Allow passage of air to alveoli
Surround lungs and enclose pleural fluid
Allow lung movement during breathing
Protect lung and heart; provide muscle attachment
Contract and relax to change the volume of thorax
Separate thorax from abdominal cavity; contract and relax to change
the volume of thorax
Breathing
Breathing is the movement of air into and out of the
lungs. It allows the lungs to take up oxygen from the
air and remove carbon dioxide from the body so
that their body concentrations can remain fairly
constant.
Breathing Mechanism
This shows how the movement of intercostals and
diaphragm changes the volume and pressure of the
thoracic cavity, facilitating the movement of air in
and out of the lungs.
Human respiratory system
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External intercostal muscles
Internal intercostal muscles
Diaphragm
Rib cage
Volume
Pressure
Movement of air
Inspiration
Contract
Relax
Contracts (flattens)
Moves up and out
Increases
Decreases
Air flows in
Expiration
Relax
Contract
Relaxes (arches)
Moves down and in
Decreases
Increases
Air flows out
Control of the Rate of Breathing
The medulla oblongata controls the breathing rate automatically by monitoring blood CO 2 levels.
As CO2 levels increase, the carotid arteries chemo-receptors send impulses to the medulla
respiratory centre. The medulla signals breathing movements to become deeper then faster
(increase breathing rate) to supply more oxygen and remove CO 2. Breathing rate decreases as CO2
levels are reduced.
Lung Capacity
Tidal air - the volume of air breathed in
and out during quiet breathing (½ L).
Found by breathing out the amount
you would normally expire during
quiet breathing.
Expiratory reserve - the amount of air
that can be blown out after
expiration of tidal air (1 ½ L). Found
by blowing out all the air you can
after breathing out during quiet
breathing.
Inspiratory reserve - the additional air
that can be drawn in after
expiration of tidal air (1 ½ L).
Vital capacity - the volume of the most air that can be blown out after fully breathing in. Found by
breathing in as far as you can and then blowing out as much air as you can.
Residual volume - the amount of air that cannot be removed from lungs by expiration (1 L)
Gaseous Exchange
Gas exchange is the diffusion of O 2 and CO2 out of the blood in the alveoli of lungs. It allows for the
supply of O2 and removal of CO2. The physical process that facilitates gas exchange is diffusion.
The gas exchange surface (respiratory surface) is the alveoli in the lungs which are surrounded by
many blood capillaries.
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Gas Exchange in the Alveolus of Lungs
The blood in capillaries contains less O 2
than the alveoli so O2 diffuses from
alveoli into the blood in the capillaries.
The blood in capillaries contains more
CO2 than the alveoli so CO2 diffuses out
of the blood in capillaries into the
alveoli.
Characteristics of Gas Exchange Surfaces
1. They are permeable - to allow
gases to pass through
2. They are thin (1 cell thick) - to
provide a short pathway for diffusion to take place
3. They have large surface areas - the larger the surface area , the faster the rate of diffusion
4. They are moist - to allow O2 and CO2 to dissolve to diffuse through alveoli walls
5. They have a rich blood supply - to bring CO2 to the surface and remove O2
Component
Oxygen
Carbon dioxide
Nitrogen
Water vapour
Temperature
Inspired Air
21%
0.03%
78%
Variable (depends on humidity); usually dry
Variable (usually cooler – room temp.)
Expired Air
16%
4%
78%
Moist
Warm (body temp.)
Inspired and Expired Air
Rescue Breathing (Mouth-to-Mouth Resuscitation)
Rescue breathing should only be administered when a person stops breathing. It is administered to
restart breathing by blowing in expired air. Expired air contains about 4 – 6% CO2 that stimulates the
medulla to initiate breathing. The 16% O 2 in expired air is enough to enter the blood in lungs and aid
recovery. Chest movements stimulate the intercostals.
1. Place the injured person on their back.
2. Use one hand to gently press the head back and two fingers under the chin to push the lower
jaw upward.
3. Pinch the nostrils, make a good seal around their mouth with your lips, take a deep breath
and breathe out deeply. Repeat twice.
4. Check that the injured person’s chest is rising and falling.
5. Give 10 breaths per minute and check for circulation every minute
6. When the person is breathing normally, put them in the recovery position.
Cellular or Tissue Respiration
Cellular respiration is the process by which the energy in food is made available for a cell to do work.
Glucose and fat are the most common chemicals from which energy can be released.
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Aerobic Respiration
Aerobic respiration utilises oxygen obtained when we breathe and occurs in the mitochondria of
cells. Glucose is combined with oxygen and is broken down into carbon dioxide and water. Energy is
released at each step of the breakdown of glucose. The energy is used to convert adenosine
di-phosphate (ADP) to adenosine tri-phosphate (ATP). Each ATP molecule acts as a packet of energy.
C6H12O6 + 6O2
6CO2 + 6H2O + energy (2880 kJ)
Anaerobic Respiration
Anaerobic respiration occurs in the cytoplasm of cells without oxygen. Glucose is not completely
broken down.
Anaerobic respiration in yeasts:
C6H12O6
2C2H5OH + 2CO2 + energy (210 kJ)
Anaerobic respiration in humans:
C6H12O6
2C3H6O3 + energy (150 kJ)
Human cells usually respire aerobically, except during strenuous activity. After a while of sustained
activity, the oxygen supply becomes inadequate, even with the increase breathing and heart rate,
causing the muscle cells to respire anaerobically. A smaller amount of energy is produced during
anaerobic respiration.
Fatigue occurs when the lactic acid (waste product) accumulates in the muscles and causes them to
ache.
Oxygen debt is the oxygen required to convert the lactic acid back to glucose so that it can be
broken down completely in aerobic respiration.
Role of ADP and ATP in Energy Transfer
The energy stored in ATP is released when it is converted to ADP. ATP is energy rich and is easily
broken down to ADP. The ADP produced is changed back to ATP by the addition of a phosphate
group and energy.
ATP
ADP + P + Energy
ADP + P
ATP
Effects of Cigarette Smoking
Cigarette smoking contributes to deaths from lung cancer and heart attacks and can affect persons
directly from smoking or from inhaling second hand smoke. Cigarette smoke has over 4000
substances in it. The important ones are nicotine, tar and carbon monoxide.
Main Effects of Tars
Tars contain hydrocarbons, phenols and fatty acids which causes cancer of lungs and mouth. Tar in
smoke is a carcinogen, i.e. chemicals that produce cancer.
Main Effects of Carbon Monoxide
Carbon monoxide combines with haemoglobin and reduces the oxygen-carrying capacity of red
blood cells. Haemoglobin is not available to combine with O 2 thus reducing the efficiency of cellular
respiration.
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Main Effects of Nicotine
 Affects neurotransmitter substances
 Cause blood platelets to adhere by increased fatty acids in blood (thrombosis and
atherosclerosis)
 Hardens artery walls causing arteriosclerosis
 Increase antidiuretic hormone (ADH) secretions
 Release adrenaline
Lung Damage
Chronic Bronchitis
This is condition in which the bronchi and bronchioles become inflamed and obstructed with
phlegm. This causes continuous heavy coughing up of phlegm. This mucus interferes with lung
defences leading to bacterial infections. Phlegm accumulation and narrowing of bronchioles makes
breathing difficult.
Factors Affecting the Rate of Breathing
Factor
Reason
Rest / sleep
Carbon dioxide is removed and inactivity means little is produced
Fresh air
Only 0.03% carbon is present
Drugs
Stimulants increase metabolic rate while depressants decreases it
Exercise
Carbon dioxide and lactic acid accumulate in the blood
Weight
More work has to be done with a larger body
Anxiety
Adrenaline released increases the metabolic rate
Environmental factors
Poor ventilation accumulates carbon dioxide in inspired air
Air pollution by cars increases carbon dioxide in inspired air
Combustion
All burning increases inspired carbon dioxide
Altitude
Low pressure affects breathing and muscles work harder to
compensate; lack of oxygen above 3000m causes carbon dioxide to
increase in the blood
Smoking
Carbon monoxide is converted to carbon dioxide and inspired;
causes shortness of breath; particles constrict bronchioles
Illness
E.g. asthma constrict bronchioles
29
increasing breathing rate decreasing breathing rate
Emphysema
This condition occurs when alveoli walls are destroyed causing larger air spaces to be formed. Larger
air spaces lead to smaller surface areas for the uptake of oxygen. Lungs lose their elasticity as fibrous
tissue is laid down.
KHM
THE CIRCULATORY SYSTEM
Objectives
 Explain the need for a transport system in the human body
 Identify the materials which need to be transported around the human body
 Relate the structures of the heart to their functions
 Describe the structure and function of the heart
 Describe the structure and function of the circulatory system in humans
 Explain the concept of blood pressure
 Relate the components of the blood to its function
 Explain the process and the importance of blood clotting
 Relate the structures of the arteries, veins and capillaries to their functions
 Explain the cause and effects of heart attacks
 Describe the structure and function of the lymphatic system
 Describe how tissue fluid and lymph are formed
Circulatory System (Cardiovascular System)
This is a transport system comprising of the heart, blood vessels, blood cells, platelets and plasma.
Why Have a Circulatory System?
In single-celled organisms, the distance between the surface to the centre is very small so simple
diffusion is efficient to supply nutrients to cell parts and remove waste products.
Multi-cellular organisms have more bulk than single-celled organisms. The distance between surface
and centre is much greater and diffusion is not efficient enough to deliver nutrients to all cells of the
body. Also, they do not have enough body surfaces to obtain enough oxygen to all cells. Therefore a
circulatory system is needed to carry substances to and from all cells in the body.
Materials Transported Around the Human Body:
Glucose
Amino acids
Oxygen
Carbon dioxide
Hormones
Antibodies
External structures of the human heart
Heat
Internal structures of the human heart
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The Parts of the Heart
Structure
Vena cava
Right atrium
Right ventricle
Pulmonary artery
Pulmonary vein
Left atrium
Left ventricle
Aorta
Function
Carries deoxygenated blood from the body into the right atrium
Receives deoxygenated blood from the body and pumps it into the right
ventricle
Pumps deoxygenated blood into the pulmonary artery
Carries deoxygenated blood from the heart to the lungs
Carries oxygenated blood from the lungs to the left atrium
Receives oxygenated blood from the pulmonary veins and pumps it into the
left ventricle
Pumps oxygenated blood into aorta
Carries oxygenated blood from the left ventricle to rest of the body
The Heart as a Double Pump
The heart pumps blood to all parts of the body. It acts as a double pump, i.e. each RBC will pass
through the heart twice.
 Right side drives deoxygenated blood to the lungs
 Left side drives oxygenate blood to all other parts of the body
In a single circulation, the blood pressure would drop too low by time it reaches the lungs. Therefore
the heart utilises a double circulation to maintain the blood pressure both to the lungs and the body.
It also ensures that oxygenated and deoxygenated blood are kept separate.
There are 2 circulations of blood:
1. Pulmonary circulation: the passage of blood from the heart to the lungs and back to the heart
2. Systemic circulation: the passage of blood from the heart, around the body and back to the heart
Blood Pressure
This is the force exerted on the walls of the arteries that is needed to pump blood to all parts of the
body. There must be a difference in pressure between arteries and veins for blood flow to occur.
 Arteries – high blood pressure
 Capillaries – lower blood pressure
 Veins – lowest blood pressure
The blood has 2 different pressure readings:
1. Systole: when the heart muscles are contracting
2. Diastole: when the heart muscles are relaxing between beats
Blood pressure readings: Systole/Diastole
Healthy young adult: 120mmHg/ 80mmHg
Systolic pressure: 100 – 139 mmHg
Diastolic pressure: 60 – 89 mmHg
A heart beat is the combined contractions of the atria and ventricles. The heart beats at about 72
beats per minute.
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Blood Flow Through the Heart
One complete heart beat is called a cardiac cycle and involves the following stages:
a. Diastole – atria and ventricles relax and blood enters the heart from the vena cava and
pulmonary veins.
b. Atrial systole – both atria contract at the same time, decreasing their volume, thus
increasing their blood pressure, pushing blood into the ventricles.
c. Ventricular systole – both ventricles contract after the atria have contracted (atria are
now relaxed), decreasing their volume, thus increasing their blood pressure, pushing blood
into the pulmonary artery and aorta.
Components of the Blood
Blood is a fluid containing dissolved substances and cells. It is made up of:
Red blood cells (erythrocytes)
Platelets
Serum
White blood cells (leucocytes)
Plasma
Comparison of RBC’s, WBC’s and Platelets
Shape
Red Blood Cells
Biconcave discs
White Blood Cells
Some irregular (phagocyte);
some discs (lymphocyte)
Platelets
Irregular fragments
Size (across)
8 µm
20 – 60 µm
approx.2 µm
Number /
mm3
Where
formed
Nucleus &
mitochondria
Function
4 – 5 million
8 – 10 000
250 000
Red bone
marrow
No
Boone marrow, spleen
Bone marrow
Yes
No
Transport O2
from lungs to
tissue and some
CO2 from tissues
to lungs
Defence against infections by
phagocytosis (phagocyte) and
production of antibodies
(lymphocyte)
Release factors to activate
the blood clotting process
Plasma and Serum
Plasma - The liquid part of the blood which has soluble fibrinogen dissolved in it
Functions
1. Transport CO2, mainly as bicarbonate, from tissues to lungs
2. Transports waste from tissue to excretory organs
3. Transports nutrients from intestine to liver and then to tissue
4. Transports hormones from ductless glands to effector organs
5. Transports heat to all parts of the body
6. Supplies tissue fluid to tissues
Serum - The remainder of the blood after RBC’s, WBC’s and clotting factors have been removed. It is
used in diagnostic tests, e.g. testing for iron deficiency.
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Factors Affecting the Ability to Transport Oxygen
 Anaemia – mostly caused by a lack of iron in the diet.
 Carbon monoxide – this gas binds permanently to haemoglobin, thus reducing the volume of
oxygen that can be carried by RBC’s and causes drowsiness and death.
 High altitudes – there is less oxygen in the air at high altitudes. Persons living or travelling
there acclimatise by forming many more RBC’s.
Blood Clotting
A blood clot consists of a mesh of fibres that trap blood cells and platelets at the surface of the
wound.
Importance:
 Prevents infection by preventing the entry of pathogens through damaged skin
 Prevents excessive blood loss from damaged blood vessels
Mechanism of Blood Clotting
1. Platelets and damaged blood vessels release thrombokinase (enzyme)
2. Thrombokinase acts on prothrombin (blood protein) and converts it into thrombin in the
presence of calcium ions
3. Thrombin acts on soluble fibrinogen (plasma protein) and converts it into insoluble fibrin
4. Fibrin forms a mesh to trap blood cells and platelets to form the clot
– Prothrombin is made in the liver in the presence of vitamin K.
Arteries, Veins and Capillaries
Artery
Thick, elastic, muscular walls
Vein
Thinner wall with less elastic tissue
No valves
Valves (semilunar valves) to prevent
backflow
Blood under low pressure
Blood flows smoothly
Normally carries deoxygenated blood
Blood under high pressure
Blood flow in spurts
Normally carries oxygenated
blood
Carries blood from the heart
Lies deep in the body
Low volume of blood
Small internal diameter
(lumen)
Carries blood to the heart
Lies near body surface
High volume of blood
Large internal diameter (lumen)
Capillary
Very thin wall, i.e. one cell
thick
No valves
Blood under low pressure
Blood flows smoothly
O2 and CO2 exchanged
here
Connects an artery to a
vein
Forms a network
Low volume of blood
Small internal diameter
Capillaries are permeable for
the exchange of substances
between blood and tissue fluid.
As the cells are thin there is a
very short distance for diffusion
of O2 and CO2.
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Pacemaker
The pacemaker is a region of nervous tissue in the right atrium, called the sino-atrial node, that
controls the rate and rhythm of the heart beat. It is stimulated by nervous impulses and hormones
(e.g. adrenaline). Muscles in the sino-atrial node contract and emit electrical impulses along tracks
to the atria and then to the ventricles causing them to contract.
An artificial pacemaker is a small device placed in the thorax that uses electrical impulses to prompt
the heart to beat at a normal rate.
Functions
Help control an abnormal heart rhythm (fast/slow)
Coordinate electrical signalling between the atria and ventricles
Adjust heart rate to changes in activity
Monitor and record the heart’s electrical activity and heart rhythm
Heart Disease
These are all the diseases of the heart and circulatory system. They include coronary heart disease,
heart failure, heart valve disease and strokes.
Coronary thrombosis: the blockage of or reduced blood flow in the coronary artery, commonly
caused by atherosclerosis and arteriosclerosis.
Coronary artery: the blood vessel that supplies blood to the heart muscle
Atherosclerosis: occurs when the internal diameter of the arteries become reduced due to
cholesterol (fatty material) deposits on the walls
Arteriosclerosis: occurs when the walls or the arteries harden and become less elastic
Coronary Heart Disease
This includes coronary thrombosis and angina (pain across the chest, left arm and shoulder caused
by insufficient blood to the heart muscle) causing the cardiac muscle tissue to die, resulting in a
heart attack.
Hypertension
This is consistently high blood pressure. Hypertension increases the risks of cardiovascular problems,
e.g. angina, stroke, heart attack. It is more likely in persons who smoke, are overweight, drink
excessive alcohol, exercise little or eat a high fat and/or salt diet.
Heart Attack (myocardial infarction)
The heart requires a constant supply of oxygenated blood to nourish it. Coronary thrombosis
reduces the oxygen supply to the heart leading it to become oxygen starved, causing the heart
muscle cells to die and stop contracting. This is a heart attack. Healing of the heart muscle begins
soon after a heart attack and forms a scar over the damaged area. The new scar tissue does not
contract thus reducing the heart's pumping ability.
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Lymphatic System
The lymphatic system is a second transport system in the human body which consist of a network of
organs, lymph nodes, lymph ducts, and lymph vessels that make and move lymph from tissues to the
bloodstream.
It is a major part of the body's immune system that includes the tonsils, spleen, and thymus.
Functions
 Transport tissue fluid back into the blood
 Transports fats, particularly from villi to blood
 Remove excess fluid, protein and foreign material from tissue spaces
 Body defence – microbes are destroyed in lymph glands by WBC’s
Lymph Nodes - Soft, small, round- or bean-shaped structures
 They usually cannot be seen or easily felt
 Located in clusters in various parts of the body, such as the neck, armpit, groin, and inside the
centre of the chest and abdomen
 Make immune cells that help the body fight infection
 Filter lymph fluid and remove foreign material such as bacteria and cancer cells
 When bacteria are recognized in the lymph fluid, the lymph nodes make more WBC’s, which
causes the nodes to swell
 The swollen nodes are sometimes felt in the neck, under the arms, and groin.
Lymph is drained tissue fluid. It is a colourless fluid that transports lipids and contain many WBC’s.
It flows in one direction due to valves in large lymph vessels.
Tissue fluid is leaked plasma from capillaries that surrounds the cells transporting substances
between tissue and blood.
Lymph vessels pass through lymph nodes and carry lymph to the subclavian vein (base of the neck).
The subclavian vein returns lymph back to the blood.
Formation of tissue fluid and lymph
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THE SKELETAL SYSTEM
Objectives
 Identify the major bones of the skeleton
 Relate the structure of the skeleton to its functions
 Relate the structure of a typical bone to its functions
 Distinguish between bone and cartilage
 Explain the importance of cartilage
 Distinguish between tendons and ligaments
 Identify a hinge joint, fixed joint and ball and socket joint
 Describe movement in the hinge joint, fixed joint and ball and socket joint
 Explain how skeletal muscles function in the movement of a limb
 Identify the biceps and triceps of the upper arm
 Explain the importance of locomotion to man
 Evaluate the factors which adversely affect the skeletal system
Functions of the Skeleton
1. Support – provides the framework for the rest of the body to allow movement and maintain
shape and suspends the soft parts
2. Protection – provides protection from physical damage to our soft tissues, e.g. skull protects
brain; ribcage protects heart and lungs
3. Movement – provides a solid structure for muscle attachment; some bones act as levers to
allow movement
4. Production of blood cells – RBC’s and WBC’s are made in the red bone marrow of long bones
5. Storage – bone tissue stores calcium, which is used for muscle contraction, sending nerve
impulses and blood clotting. Yellow bone marrow stores fat.
6. Breathing – intercostals muscles move the rib cage up and down to help increase and
decrease the volume of the thorax for breathing in and out
The Structure and Function of Skeletal Tissue
Tissue
Bone
Cartilage
Tendon
Ligament
Skeletal Muscle
Structure
Hard matrix of calcium
phosphate with tough
collagen fibres
Tough, but flexible matrix
Properties
Hard and rigid
Tough matrix containing
white collagen fibres
Tough but flexible matrix
containing yellow elastic
fibres
Made up of many muscle
fibres containing contractile
proteins
Tough and does not
stretch
Tough and elastic
Cushioning layer at the
end of bones; smooth
glossy appearance
Can contract
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Function
Protection; support;
muscle attachment for
movement
Prevents bone rubbing on
bone (reduces friction);
spreads load (acts as a
shock absorber)
Connects muscle to bone
Join bone to bone to
allow movement at a joint
Allows movement;
maintains posture
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Bones
Made up of 2 types of tissues:
1. Compact bone
 Solid, hard outside part
 Makes up most of the
human skeleton
 Holes and channels run
through it carrying blood
vessels and nerves from the
periosteum (outer
membrane covering)
2. Spongy (cancellous) bone
 Spongy layer inside
compact bone
 Made up of a mesh-like
network of trabeculae (tiny
pieces of bone)
 Site of RBC and WBC
production
Diagram of a long bone
Structure of a Long Bone
Long bones are not solid, but contain a marrow-filled cavity that gives a strong yet light structure.
 The rounded head is made up of spongy bone which is light but strong
Joints
Joints occur where 2 bones meet. Without joints movement would be impossible. They are classified
by their range of movements. There are 3 groups of joints:
1. Fixed, immovable or fibrous joints – no movement occur
2. Slightly movable joints – allows a small degree of movement
3. Synovial or freely movable joints – allows friction-free movement
 Hinge joint – movement in one plane
 Pivot joint – rotation
 Ball and socket joint – movement in any plane
 Gliding joint – have flat articulating surfaces that slide over one another easily
Function of Skeletal Muscle
Skeletal muscle tissue is attached to the skeleton and brings about movement. It is made up of a
large number of cylindrical muscle cells separated by connective tissue. Its contraction is under
conscious control. They are found in pairs that work against each other to move bones (antagonistic
pairs).
There are at least 2 types of skeletal muscle fibres:
1. Slow twitch fibres
 These mainly use fatty acids as their source of energy and, since they have a store of
lipid, fatigue slowly. They develop more in distance running athletes.
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2. Fast twitch fibres
 Theses mainly use glucose as their source
of energy and, because they lack an energy
store, fatigue quickly. They develop more in
sprinting athletes.
Point of Origin – the point of attachment of a muscle to
the bone that does not move when the muscle
contracts
Point of Insertion – the point of attachment of a muscle
to the bone that moves when the muscle
contracts
Upper arm muscle attachments
Biceps and Triceps
Properties
Location
Point of origin
Point of insertion
Biceps
Triceps
Lies above the humeLies at the back of the humerus
rus
2 points on the scapula 3 points (2 on the upper part of the
humerus; 1 on the scapula)
Radius
Ulna
Movement of the Arm
Muscles contract antagonistically, i.e., one
contracts while the opposing one relaxes to
bring about movement across a joint. Biceps
and triceps work antagonistically to bend and
straighten the arm at the elbow.
Flexing the arm: The biceps contracts and
shortens and pulls on the radius while
the scapula holds firm. Triceps is relaxed.
Extending the arm: Triceps contracts and
shortens and the ulna is drawn nearer to
the scapula. Biceps is relaxed.
Locomotion
Locomotion is the movement from place to
place. Humans are bipedal, which allows us to
stand upright. Locomotion is important because
it helps us to:
i. move away from danger
ii. find food
iii. escape predators
iv. exercise
v. find a mate.
Human skeleton
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Factors Affecting the Muscular and Skeletal Systems
i. Diet
 Protein is needed for collagen fibres.
 Calcium and phosphates are needed to harden the bone matrix.
 Vitamin D stimulates the uptake of calcium from the gut.
 Deficiencies in calcium and vitamin D can lead to osteoporosis.
 People who consume more energy than required store fat that add weight to the body
and increase strain on muscles.
ii. Posture
 Posture is the position of the body. Good posture allows the muscles to use as little
energy as to maintain the position of the body. Poor posture puts a strain on muscles
causing them to lose their tone. More energy is needed by the muscles to keep the
body upright, leading to fatigue and backache.
N.B. - Muscle tone is the partial contraction of muscle that helps to maintain posture
iii. Obesity
 Excess body fat puts much strain on the skeleton, especially the joints. People who are
overweight and obese increase their risk of developing arthritis.
iv. Bending and Lifting
 Poor posture during lifting can damage the back.
v. Exercise
 Regular exercise causes more capillaries to develop inside the muscles, the muscles to
become larger, muscle tone to improve, joints to become more flexible.
 Extreme forms of exercise may lead to the risk of muscle and bone damage.
 Lack of exercise makes muscles weak, flabby and slack and joints lose their flexible
movement and strength.
vi. Arthritis
 Painful condition in the joints; cartilage may become worn and ligaments distorted.
vii. Foot wear
 High heeled shoes cause bad posture by putting extra strain on leg muscles.
 Corns are caused when toes rub against the inside of the shoe.
 Bunions are caused by wearing narrow, pointed or high-heeled shoes that lead to the
joints at the base of the big toe being swollen and the bones becoming deformed.
 Hammer-toe is when the big toe is pushed inwards and crushes the adjacent toe,
causing it to bend and point downwards.
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EXCRETION AND HOMEOSTASIS
Objectives
 Explain the importance of excretion in human beings
 Explain the roles of the organs involved in excretion
 Relate the structures of the kidney to their function
 Relate the structures of the skin to their functions
 Explain the concept of homeostasis
 Explain the concept of feedback mechanisms
 Describe the regulation of blood sugar
 Explain the regulation of water
 Distinguish between heat and temperature
 Describe the regulation of temperature
Excretion
Excretion is the removal of waste products of metabolism from the body and substances in excess of
requirements. Metabolic waste refer to products made by chemical reactions in the body, e.g.
carbon dioxide, urea, hydrogen peroxide. The human excretory products are carbon dioxide, urea,
bile pigments, water and mineral salts.
Importance: Excretions are toxic. If allowed to accumulate to high concentrations they would
damage the body tissues.
Main Excretory Organs and Their Products
Skin – sweat (urea and salts) is secreted and evaporates from the surface of the skin
Kidney – excrete nitrogenous waste (urea and salts) and responsible for regulating body fluid
concentration
Lung – carbon dioxide and water vapour are removed during exhalation
Liver – processes toxic materials and makes them harmless
The Kidneys
 Paired bean shaped, dark red organs attached
to the back of the abdomen
 Composed of tiny tubules called nephrons
that filter blood and produce urine
 Function – get rid of toxins and excess water
and controls blood composition
The Nephron
Part
Bowman’s capsule
Convoluted tubules
Loop of Henle
Collecting ducts
Function
Ultrafiltration – blood pressure forces fluid part of the into the tubule
Selective re-absorption of glucose, salts and water into the blood
Absorption of water by osmosis from collecting ducts to concentrate urine
Concentration of urine; pass urine to ureter
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Ultrafiltration
Ultrafiltration is a process that
separates very small particles of
different sizes, e.g. molecules or
ions.
The afferent arteriole has a larger
diameter than the efferent
arteriole causing blood in the
glomerulus to be under high
pressure. The pressure forces
substances that are small enough
through the capillary walls, into the
Bowman’s capsule. Large blood
protein molecules and RBC’s do not usually pass through. The fluid formed in the Bowman’s capsule
is called the glomerular filtrate or ultrafiltrate and is mainly made up of water, glucose, salts
(sodium, chloride, potassium), amino acids and urea.
Selective Re-absorption
The glomerular filtrate contains useful substances which the body needs. Therefore, the body
reabsorbs them into the blood capillaries from various parts of the nephrons.
 Proximal Convoluted Tubule – all glucose is reabsorbed by active transport into the
capillaries
 Loop of Henle – some water is reabsorbed into the capillaries by osmosis
 Distal Convoluted Tubule – salts and some water reabsorbed into capillaries; maintain correct
salt concentration in the blood
 Collecting Duct – re-absorption of some water into capillaries (under control of ADH)
N.B. – Urine is a mixture of urea, water and salts.
Kidney Failure
Causes of kidney failure
include: blood loss,
blood poisoning, severe
dehydration,
severe
burns, hypertension and
diabetes.
Diagram of a nephron
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The Skin
The skin is the largest organ in the human body. It helps us to resist infections, excrete, avoid
dehydration, regulate temperature and covers the body. It is composed of many tissues and is made
up of 3 layers:
1. Epidermis – thinner outer tissue of the skin composed of 2 layers
a. Malpighian (germinal) layer
 Single layer of cells that die to form cornified layer (cell life is 21 days)
 Divide to produce replacement cells for those rubbed off on the skin surface
 Contain melanin (pigment) that gives colour to skin and protects underlying tissues
against U.V light
 Convolutions of this layer form fingerprints
b. Cornified layer

Upper layer of the epidermis made up of dead cells containing keratin

Waterproof layer that protects the underlying tissue against mechanical injury and
prevents the entry of pathogens

Replaced by new cells from the malpighian layer
2. Dermis – inner layer of the skin, which is composed of many tissues, such as nervous, muscle
and connective tissues
3. Subcutaneous fat – tissue immediately below the dermis, which forms an insulating layer and
provides food storage
Section through the skin
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Homeostasis
Homeostasis is the ability of an organism to maintain a constant internal environment in spite of
changes from the surroundings. The control mechanisms are automatic and self-regulatory and
ensure that cells survive and function efficiently.
There are 2 types of mechanisms
1. Negative feedback mechanism
 A system in which a change from the normal state is detected and triggers corrective
actions to restore the normal state
 More common in the body, where the body detects changes initiates a mechanism to
bring it back to normal
E.g. – control of body temp., water balance, blood sugar, pH
2. Positive feedback mechanism
 Less common in the body, where a stimulus initiates more of the same reaction
 E.g. – oxytocin production in childbirth that stretches the birth canal which stimulates
more oxytocin to be produced.
Regulation of Carbon Dioxide
Respiring muscles produce CO2 in the blood. When CO2 blood concentrations increase,
chemoreceptors in the carotid arteries detect the increase. The chemoreceptors pass impulses to
the respiratory centre of the medulla.
The medulla sends nerve impulses to the intercostals and diaphragm causing them to contract
deeper and faster. This increases the rate and depth of breathing to supply more O 2 and remove the
CO2. Breathing rate decreases as CO2 blood concentration decreases.
Regulation of Blood Sugar
The regulation of glucose involves the pancreas and liver, and the hormones insulin and glucagon.
Insulin lowers the blood sugar concentration while glucagon raises it. Low concentration of blood
glucose causes loss of consciousness. High concentration of blood glucose results in its excretion in
urine. Adrenaline releases more glucose in the blood during vigorous activity
Normal blood glucose concentration: 80 – 150 mg/100cm3
Insulin
Insulin is secreted from the beta cells of the islets of Langerhans in the pancreas. Receptors in the
islets of Langerhans detect an increase in blood sugar. The increase causes the β -cells to secrete
insulin. Insulin causes the liver to convert the excess glucose to glycogen, which increases the uptake
of glucose in body cells. Insulin also converts some sugar to fat and increase sugar oxidation.
Glucagon
Glucagon is secreted from the alpha cells of the islets of Langerhans in the pancreas. Receptors in
the islets of Langerhans detect a decrease in blood sugar. The decrease causes the α-cells to secrete
glucagon. Glucagon acts on the liver cells to cause the breakdown of glycogen to glucose.
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Regulation of Water
Osmoregulation is the control of the body’s water content by osmosis. It involves the maintenance
of the concentration of the body fluids by controlling the water and salt content of the blood.
Kidneys are largely responsible for the water balance in the body. One kidney function is to control
the correct amount of water and salts in body fluids. Water can also be secreted by skin and lungs.
Osmoreceptors in the hypothalamus detect the amount of water in the blood which flows past them
If there is not enough water, the osmoreceptors cause the pituitary gland to secrete anti-diuretic
hormone (ADH). ADH causes the capillaries around the collecting ducts in the kidney nephrons to
reabsorb more water from urine, producing less, more concentrated urine. If there is too much
water, ADH is not secreted, producing a large amount of dilute urine.
Heat vs. Temperature
Heat is a form of energy measured in Joules (J).
Temperature is a degree of hotness or coldness measured in degrees Celsius (⁰C) or Kelvin (K).
Regulation of Temperature
Humans maintain a constant body temperature and are fairly independent of environmental
temperature. This is done by balancing heat production and heat loss. The skin helps maintain a
constant body temperature. The hypothalamus acts as a thermostat. It contains thermoreceptors
which sense the temperature of blood running through it. The thermoreceptors send messages
along the nerves to the parts of the body that regulate temperature.
When cold the body produces and save heat:
 Muscle work – some muscles contract and relax very quickly (shivering) to produce heat
 Increased metabolism – the speed of chemical reactions increase releasing more heat
 Hair raised – the erector muscles in the skin contract pulling the hair up on end trapping more
air for insulation ( but only produces goose pimples in humans)
 Vasoconstriction – the blood vessels near the surface of the skin become constricted allowing
less blood to the body surface which decreases amount of heat loss to the air
When hot the body loses more heat:
 Hair flattens – the erector muscles in the skin relax, so that the hair lies flat to decrease the
insulating air layer
 Vasodilation – the blood vessels near the surface of the skin become dilated allowing more
blood to the body surface enabling heat to be lost from the blood to the air
 Increased sweating – secreted sweat lies on the surface of the hot skin and the water in it
evaporates taking heat from the skin with it, cooling the body
 Decreased metabolism – less activity so less heat is produced
Diabetes
Diabetes insipidus is a condition where the body produces large volumes of dilute urine due to the
lessened secretions of ADH from pituitary gland. This prevents the kidneys from reabsorbing water
into the bloodstream.
Diabetes mellitus is a condition where the body fails to regulate the concentration of glucose in the
blood.
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COORDINATION AND CONTROL
Objectives
 Describe the main divisions of the nervous system
 Describe the functions of the parts of the brain
 Distinguish between a neurone and a nerve
 Explain the functions of motor and sensory neurones and spinal synapses
 Describe the mechanisms of a reflex action
 Explain the process by which voluntary actions occur
 Distinguish between a voluntary and involuntary action
 Explain the response of the sense organs to stimuli
 Relate the internal structures of the eye to their functions
 Explain how images are formed in the eye
 Explain accommodation in the eye
 Describe the causes of and corrective measures for eye defects
 Distinguish between endocrine (hormonal) and nervous control systems
 Identify the sites of hormone production
 Explain the roles of selected hormones in the human body
The Nervous System
The nervous system is a network of cells enabling rapid response to changes in the environment. Its
functioning involves the stimulus, receptors, nerve cells and effectors (muscle or gland). It can be
divided into:
1. Central nervous system (CNS) - brain and spinal cord
2. Peripheral nervous system (PNS) - Cranial nerves, spinal nerves and autonomic nerves.
The PNS connects the CNS with sense and effector organs.
Autonomic nervous system
The autonomic nervous system controls the internal (involuntary) activities of the gut and glands. It
is composed of:
1) Parasympathetic nervous system - rest and digest
2) Sympathetic nervous system - fight and flight
Definition of Terms
Stimulus - a change in the external or internal environment of an organism which brings about a
response
Response - a change in the activity of a part or the whole of the organism, which results from the
stimulus
Receptor - the organ or cell that detects a specific stimulus and initiates a nerve impulse
Conductor - specialised conductor cells (neurones) that transmit nerve impulses
Effector - the organ or cell (muscle or gland) that responds to a stimulus or the arrival of a nerve
impulse
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The Brain
The brain acts as a central exchange for
information passed to it from all the
sensory
receptors. It coordinates various actions of the
body and stores information (memory). It is
located within the cranium which has an
opening for the spinal cord to pass. In the brain,
grey matter is found on the outside and white
matter on the inside. The brain has 4
inter-connecting chambers called ventricles
that contain cerebrospinal fluid (CSF) and is surrounded by tough membranes called meninges.
Parts of the Brain
1. Cerebrum: Its outer cortex consists of neurone cell bodies and convolutions (folds) while
inner cortex is formed from axons or neurones. The sensory area controls smell, sight,
hearing, and skin sensations, while the motor area controls muscles of arms, legs, eyes and
hands.
2. Cerebellum: The cerebellum is concerned with the muscular coordination of the body
including balance, posture and locomotion. It receives sensory impulse from muscles and eyes
and sends motor impulses to skeletal muscles.
3. Medulla oblongata: This is a reflex centre that controls involuntary muscular actions, e.g.
blood pressure, heart beat, coughing, breathing, swallowing, yawning and sneezing.
4. Hypothalamus: This is a reflex centre that regulates some aspects of homeostasis. It
coordinates the autonomic nervous system and controls the pituitary gland. It regulates
hunger, sleep, thirst, body temperature, water balance and blood pressure.
5. Pituitary gland – this is an endocrine gland, i.e. secretes many hormones.
Terms Associated with Nerves and Neurones
Nerve - made up of bundles of neurones and appear as white threads
Neurone – an individual nerve cell that transmit impulses along its length
Motor neurone - conduct an impulse outward from the CNS to the effector organ
Sensory neurone - conduct incoming impulses from the sense organs to the CNS
Relay neurone - connect sensory to motor neurones
Nerve impulse - a wave of electrochemical changes that travels in one direction along a neurone
Synapse - a gap between terminal parts of neurones
and dendrites
Neurotransmitter - chemical transmitters that
travel through the synapse
Mechanism for Synapse
1. Nerve impulse causes the release of
neurotransmitters from vesicles
2. Neurotransmitters pass across the gap to the
other neurone and attach to the receptor
3. Impulse flows in other neurone
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Spinal Cord
The spinal cord passes from the base of the brain down the vertebral column and acts as a relay
system for impulses and a centre for coordinating actions. It connects brain with peripheral nerves.
In the spinal cord, white matter is found on the outside and grey matter on inside. The cord gives off
paired nerves that come from dorsal (back) and ventral (front) roots. It contains a central canal that
holds cerebrospinal fluid which provides nutrients and transports substances.
Reflex Actions
A reflex action is a quick automatic response to a stimulus, not involving the cerebrum of the brain. It
does not require conscious control and protects the body quickly from danger.
E.g. – spinal reflexes and cranial reflexes
Reflex arc – the pathway between the receptor and effector
Spinal Reflex Action
This involves transmission of impulses along spinal nerves. Impulses pass from skin sense organs, to
spinal cord and straight back to effector muscles. It involves sensory, relay and motor neurones in its
reflex arc. E.g. - knee-jerk reflex, reaction to painful stimuli
Knee-jerk Reflex: Spinal reflex without relay neurone
Mechanism:
1. Stimulus is given – pressure on tendons just below the patella
2. Stretch receptors detect the pressure on the tendons
3. Sensory neurone transmits the impulse to the motor neurone in the spinal cord
4. Impulse from motor neurone causes the leg muscles to contract, pulling the foot forward
Reaction to Painful Stimuli: example pricking finger on pin
Mechanism
1. The pin stimulates pain receptors in the skin.
2. Pain receptors send impulses to the CNS along the sensory neurone.
3. Impulses reach the end of the sensory neurone where they cross a synapse to a relay neurone
and then another synapse to a motor neurone.
4. The motor neurone transmits impulses to the effector—a muscle in the arm.
5. The muscle responds to impulses from the motor neurone by contracting and shortening
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Cranial Reflex Action
These are reflexes in the head region, e.g. blinking and constriction or dilation of the pupil in light.
Pupil Reflex: Allows the iris to contract and dilate to change the size of the pupil.
The pupil controls the amount of light which enters the eye and protects the retina from
‘over-exposure’.
Mechanism:
1. High levels of light strike photoreceptors (rods and cones) in retina
2. Nerve impulse transmits along sensory neurone of optic nerve
3. Impulse coordinated by relay neurones in midbrain
4. Relay neurone transmit impulse through motor nerves to muscle in iris to make pupil smaller
Voluntary Actions
Voluntary actions are those actions controlled by conscious decisions. They are more complex and
may have variable outcomes.
Process
1. Your own thoughts or stimulus starts a nerve impulse in the brain
2. The brain decides whether or not to respond to the stimulus
3. The impulse passes down the white matter of spinal cord
4. Motor neurones in spinal cord transmit the impulse to the effector muscle that will act to
bring about the desired action
Section through the human eye
Formation of Images in the Eye
Objects in our environment reflect light. Light rays from the object travel in a straight line to the
eyeball and pass through the pupil. The
cornea refracts the light towards the
retina. The light stimulates photoreceptors
of the retina, which send impulses along
the optic nerve to the brain. The image is
formed upside down and back-to-front on
the retina. The brain interprets the image
of size, shape, colour and distance away
from object.
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Function of the Structures of the Eye
Part of the Eye
External eye muscles
Sclera
Choroid
Conjunctiva
Feature/ Description
Muscular tissue
Thick, white fibrous layer
Dark pigmented layer behind
the retina; contains blood
vessels
Thin, transparent layer of
cells
Cornea
Transparent part of sclera
Aqueous humour
Vitreous humour
Transparent liquid
Jelly-like material
Lens
Transparent
Retina
Contains rods and cones
(photoreceptors)
Suspensory ligaments
Strong fibrous tissues
Ciliary muscle
Thin muscle around the lens
Optic nerve
Large sensory nerve
Blind spot
Fovea (yellow spot)
Pupil
Iris
Point in retina with no photoreceptors
Depression in the retina consisting only of cones
A hole in the iris
Circular pigmented structure
Function
Moves eyeball in socket
Protects eyeball against damage
Prevents internal reflection; supplies
retina with nutrients and oxygen and
removes waste
Protects the cornea
Greatest refraction (bending) of light rays
onto the retina
Maintains shape of the eye
Maintains shape of the eye
Makes fine adjustments to focus light onto
the retina
Light sensitive layer
Holds the lens in place and involved in
focusing light
Contracts to make the lens thicker for near
vision
Transmits nerve impulses from retina to
brain
Point where optic nerve leaves the eye
Provides detailed vision; detects colour
Allows light into the lens
Controls amount of light entering the eye
Accommodation
Accommodation is the adjustment of the lens for focusing on near and distant objects. The activity of
eye involves: 1) Alteration in pupil size to adjust light strength
2) Alteration in lens shape according to the distance of the object from the eye
Focusing on distant objects:
The ciliary muscles relax, pulling the suspensory ligaments tight, thinning the lens. The thin lens
refracts the light less, focusing the image sharply on the retina.
Focusing on near objects:
The ciliary muscles contract, slackening the suspensory ligaments, making the lens more rounded. A
curved lens refracts more light.
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Defects in Vision
A vision defect is any condition that prevents proper focusing of light on the retina.
Cataract: Occurs when the lens becomes opaque and light cannot pass through, so the person is
unable to see. It can be corrected through surgery.
Astigmatism: Occurs when the surface of the lens or cornea is irregularly curved. Lines of different
orientations come to focus at different points in the eye. It can be corrected by cylindrical lenses that
balance out these irregularities.
Glaucoma: Occurs when too much fluid gathers in front of the lens, causing a build up of pressure
within the eye. The increased pressure can damage the optic nerve. Vision is poor and the sufferer
may experience sightless areas in the field of vision. Early stages can be treated with eye drops and
oral medication. Later stages may require surgery to treat it.
The Endocrine System
The messages sent out by the endocrine system are hormones. A hormone is a chemical messenger
that travels in the blood all around the body to stimulate its target organ. A target organ is any organ
that responds to a specific hormone. Hormones are produced in endocrine glands.
Endocrine (Hormonal) vs. Nervous Control System
Hormones are chemical substances which are secreted from endocrine (ductless) glands into the
blood and regulate body processes.
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Hormonal Coordination
Message
Complex organic chemical
Transport
Speed
In blood
Slow (except adrenaline)
Long-lasting , may affect many
body parts
Stimuli from sense organs affect
ductless glands
By pituitary gland
Metabolic in nature, e.g. growth
dwarfism
Effect
Production
Main Coordination
Disease
Nervous Coordination
Impulse: charge difference produced
by ions
Membrane of neurones
Fast
Immediate control directed to one part
Stimuli from sense organs affect
neurone membranes
By brain
Paralysis or mental illness
Roles of Selected Hormones in the Body
Hormone
Secreted by
Adrenaline
Adrenal gland
Thyroxine
Insulin
Glucagon
Anti-diuretic
hormone (ADH)
Growth hormone
(GH)
Thyroid gland
Pancreas (β -cells
of islets of
Langerhans)
Pancreas (a-cells
of islets of
Langerhans)
Pituitary gland
Pituitary gland
Function
Prepares the body for fight
or flight; convert glycogen
to glucose during high
activity
Other Points
Controls growth and
metabolic rate
Contains iodine (too
much iodine leads to
goiter); deficiency
causes dwarfism and
mental retardation
Causes liver and muscles to
convert glucose to
glycogen for storage
Lack of insulin can cause
type II diabetes
Causes liver to release
glucose into the blood
Causes kidneys to reabsorb
water from urine
Stimulates growth
51
Lack of GH causes
dwarfism; too much
causes gigantism
KHM
Roles of Reproductive Hormones in the Body
Hormone
Secreted by
Follicle stimulating
hormone (FSH)
Pituitary gland
Luteinising
hormone (LH)
Pituitary gland
Testosterone
Testes
Oestrogen
Ovary follicles
Progesterone
Corpus luteum
(after ovulation);
placenta (during
pregnancy)
Prolactin
Pituitary gland
Oxytocin
Luteotrophic
hormone (LTH)
Function
Stimulates the growth of
follicles and production of
oestrogen
Controls ovulation; forms
corpus luteum
Controls development of
male sex organs and
secondary sexual
characteristics
Controls development of
female secondary sexual
characteristics; thicken
uterine wall; control
menstruation
Prepares uterine wall for
implantation; maintains
uterine lining; stops
ovulation; stimulates
prolactin secretion
Helps initiate and maintain
breast milk production in
pregnant and nursing
women
Pituitary gland
Causes uterine
contractions during labour
Pituitary gland
Stimulates testes to make
testosterone; stimulates
corpus luteum to secrete
progesterone
52
Other Points
Its production is
associated with positive
feedback mechanism
KHM
REPRODUCTIVE SYSTEM
Objectives
 Distinguish between sexual and asexual reproduction
 Describe the structure and function of the reproductive system in human beings
 Describe the menstrual cycle
 Explain ovulation, fertilisation, implantation and development of embryo
 Describe the birth process
 Outline the importance of pre-natal and post-natal care
 Explain how birth control methods prevent pregnancy
 Explain the advantages and disadvantages of birth control methods
 Discuss the issues related to abortion
 Explain the importance of family planning
 Reproduction is the ability of the organism to produce new individuals of the same species.
Asexual vs. Sexual Reproduction
Asexual Reproduction
Involves only one parent (no mate needed)
Part of the parent forms the offspring
Offspring genetically identical to parents
(clones)
Common among some single-celled organisms
Many offspring produced quickly
No variation in offspring
Sexual Reproduction
Involves both parents (requires both sexes)
Fusion of male and female gametes
(fertilisation)
Offspring has a fusion of the characteristics
of both parents
Occurs mostly in higher multi-cellular
organisms
Small number of offspring produced
Genetic variation in offspring
Structure and Function of the Male Reproductive System
The function of the male
reproductive system:
1. Produce sperm
2. Deliver sperm to the
female reproductive
system
Human male reproductive system
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Structure
Testis
Epididymis
Scrotum
Vas deferens
(sperm duct)
Cowper’s gland
(bulbo-urethral
gland)
Prostate gland
Seminal vesicles
Urethra
Urethra muscle
Erectile tissue
Penis
Foreskin
Function
Contain seminiferous tubules that produce sperm; secretes testosterone.
Seminiferous tubules also contain nurse cells that nourish and protect the
developing sperm.
Stores sperm
Suspends testes outside the body cavity at lower temperature
Transports sperm to the urethra
Secretes part of seminal fluid containing lubricant
Secretes part of seminal fluid containing alkalis to buffer residual urine in
urethra and acidity of vagina
Secretes part of seminal fluid containing amino acids and sugar as the
energy source for the sperm
Transport sperm and urine
Contracts to ejaculate sperm
Fills with blood to erect penis
Inserted into vagina during intercourse
Covers the end of the penis
Structure and Function of the Female Reproductive System
The function of the female reproductive system:
1. Produce ova
2. Allow fertilisation to occur
3. Provide the right environment for the zygote to foetus
Human male reproductive system
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Structure
Ovary
Oviduct funnel
Oviduct (fallopian tube)
Uterus
Cervix
Vagina
Vulva
Function
Produce ova; secrete oestrogen
Collects ova released from the ovaries
Contains ciliated epithelium which move ova from the ovary to uterus;
site of fertilisation
Where the foetus develops during pregnancy; supplies the foetus with
nutrients
A ring of muscles at the end of the uterus; allows blood and cells to pass
out during menstruation; allows sperm to enter during intercourse
Receives penis during intercourse; passage for baby at birth
Surrounds vaginal opening
Disorders of the Reproductive System
Cancer is the uncontrolled division of cells which produces a lump or growth called a tumour.
i. Ovarian cancer
 This is cancer of the ovaries with risk factors such as:
 A family history of ovarian cancer
 Never having a baby
 Starting menstruating before age 12 and menopause after 50
 Being unable to get pregnant
ii. Cervical cancer
 This cancer is caused by human papilloma virus (HPV) and occurs when abnormal cells
on the cervix grow out of control. High risk persons include:
 Promiscuous females
 Females that started having sex at an early age
 Females infected with an STI
 Risk can be reduced by having regular pap smears.
iii. Prostate cancer
 This is caused by an enlarged tumour in the prostate. Risks factors include a fatty diet
and lack of exercise. Risk can be reduced by having regular prostate examinations and
prostate specific antigen tests. Signs and symptoms may include:
 Blood in urine
 Painful or burning sensation during urination/ ejaculation
 Weak or interrupted urinary stream
 Frequent need to urinate
iv. Testicular cancer
 A common type of cancer that can be detected as new lumps on the testes. If detected,
there is an excellent chance of full recovery.
 Males between ages 15 – 40 are encouraged to regularly examine their testes to detect
any abnormalities.
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The Menstrual Cycle
The menstrual cycle is a series of changes that takes place in the female body to prepare for the
possibility of pregnancy coordinated by hormones. The cycle itself is typically averaged at 28 days.
The menstrual cycle is counted from the 1st day of one period to the 1st day of the next period. It
includes the following processes:
 Menstruation: the elimination of the thickened uterine lining (endometrium ) through the
vagina
 Ovulation: the release of an ovum from a mature ovary follicle in the ovary
 Fertilisation: the fusion of the male and female gamete to form the zygote (in the fallopian
tube)
 Implantation: the embedding of the embryo into the uterine lining (occur approx. 7 days
after fertilisation)
Day 1:
Progesterone and oestrogen levels
drop after previous cycle which
signals the uterine lining to be shed.
Bleeding lasts about 4 – 7 days.
Day 7:
Bleeding has stopped. FSH stimulates
follicles to develop on ovaries. Each
follicle contains one ovum.
Day 7 – 14:
One follicle reaches maturity causing
oestrogen
levels to increase.
Oestrogen causes the uterine lining
to thicken and stops the release of
any more FSH.
Day 14:
LH causes mature follicle to burst and
release ovum from ovary follicle
(ovulation). The ruptured follicle
develops into the corpus luteum
which
secretes
progesterone.
Progesterone maintains the thickness
of the uterine lining.
Day 25 – 28:
No fertilisation occurring: Corpus luteum and ovum degenerates causing a drop in progesterone
leading to the shedding of the uterine lining and ovum (menstruation).
Fertilisation occurring: Corpus luteum continues to secrete progesterone to maintaining the uterine
lining for pregnancy and to prevent the release of another ovum.
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Development of the Embryo
Fertilisation occurs when one sperm with 23 chromosomes combine with an ovum with 23
chromosomes to produced a fertilised ovum (zygote) that has 46 chromosomes in all.
After fertilisation, the zygote moves down the oviduct it divides by mitosis to form a ball of cells
(embryo). The embryo gets nutrients from the yolk sac. When the embryo reaches the uterus it
implants itself into the lining. The embryo cells divide and grow and the placenta grows along with
the embryo.
By 11 weeks after fertilisation, the cells organise into different organs changing the embryo to a
foetus. At this stage the foetus grows until it is ready for birth.
Placenta: Finger-like projections that form between the embryo and the uterine wall which allows
the exchange of nutrients and waste products between mother and baby without the mixing
of blood.
Umbilical cord: Joins the placenta to embryo. It contains an artery that takes blood and waste from
the foetus into the placenta and a vein that returns blood and nutrients to the foetus.
Amnion: Strong membrane surrounding the embryo which secretes amniotic fluid that helps support
the foetus and acts as a shock absorber to protect the developing foetus from mechanical
damage.
The Birth Process
Birth follows 40 weeks (9 months) after fertilisation. There are 3 stages of birth:
Stage 1: Foetus stimulates maternal pituitary gland to secrete oxytocin. This starts uterine
contractions that cause the amnion to burst allowing the fluid to pass out. Contractions cause
further release of oxytocin which causes more contractions (positive feedback mechanism).
Stage 2: Increased uterine contractions push the baby through the cervix and then the vagina.
Stage 3: Baby is expelled head first. Uterine wall continues contracting to expel the afterbirth
(placenta and umbilical cord).
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Prenatal (ante-natal) Care
This includes the care and advice needed during pregnancy for the mother along with checks on the
foetal growth. Aspects include:
 Healthy diet
 Mild exercise and rest
 Health precautions, e.g. avoiding infections, tobacco, alcohol and other drugs
 Regular doctor visits to provide blood tests, blood pressure measurements, urine analysis,
weight gain and uterus size
Post-natal Care
This provides advice to the mother on her diet, behaviour and care for the baby. Aspects include:
 Checks on the baby’s growth and development
 Checks to ensure no uterine bleeding and damage or infection of cervix and vagina
 Education on the value of breast milk and weaning the baby onto semi-solid and solid foods
 Vaccination program to baby to help build up active immunity

Diphtheria, whooping cough, tetanus, meningitis, hepatitis B, measles, mumps, rubella, pneumonia,
tuberculosis, chicken pox
Breast Feeding
Prolactin stimulates milk production in mammary glands. Suckling stimulates the release of milk. The
first milk is a yellow-coloured fluid called colostrum that is rich in nutrients for growth and
antibodies for protection against infections. Benefits of breast feeding include:
i. Ensures maternal care from birth
ii. Give baby passive immunity (breast milk contains antibodies from mother)
iii. Gives baby all essential nutrients except iron
Birth Control (Family Planning)
Birth control includes all methods used to regulate or prevent the birth of children. It is used in
family planning, fertility control or Planned Parenthood. Family planning is controlling the number
and timing of births in a family. Benefits of family planning include:
 A small family allows more time for care and education to be given to each child
 A small family is less expensive to upkeep (both parents and children can benefit from extra
money available
 Allows preparation for children because they would be expected
 Reduce the number of births to help control the population growth
 Parents may decide to have a career before starting a family
Methods of Birth Control
1. Natural Methods – using no artificial means
a. Abstinence: avoiding sexual intercourse
 It is 100% effective in preventing pregnancy and STI’s but requires self-discipline
and control.
b. Withdrawal Method: withdrawing the penis from vagina before ejaculation
 It is an unreliable method because ejaculation can occur prematurely.
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c. Rhythm Method: restricting sexual intercourse to the ‘safe period’.
th
th
 There I no intercourse between the 11 – 17 day of the menstrual cycle (fertile
period).
 It does not prevent STI’s and is unreliable because the menstrual cycle may vary
making it easy to miscalculate the fertile period.
2. Chemical Methods
 This is the use of spermicidal jellies, creams and foams that destroy sperm in the female
tract during intercourse. They are not very effective on their own but are more effective if
used with a barrier method.
3. Physical or Barrier Methods
a. Condom: A sheath covering the penis that prevents sperm entering the vagina.
 If used correctly, can be a reliable method of birth control and prevent STI’s.
b. Intrauterine Device (IUD): A coiled shape device positioned in the uterus.
 It prevents the fertilised ovum becoming implanted in the uterine wall.
 It is over 90% effective in preventing pregnancy.
c. Diaphragm (Cervical Cap):A rubber dome that fits over the cervix at the upper end of the
vagina
 It prevents the passage of sperm into the uterus, which prevents fertilisation.
 It is about 85% effective in preventing pregnancy.
4. Hormonal Methods
a. Oral Contraceptive Pills: Pills containing hormones related to oestrogen and progesterone
that inhibits FSH and stops the development of ova.
 They prevent ovulation and fertilisation.
 They are 90 – 100% effective in preventing pregnancy.
b. Progesterone –only Pill: Contains progesterone but no oestrogen.
 It works partly by making the woman’s mucus in the cervix thicker preventing
sperm passing through and also by preventing a fertilised ovum implanting.
c. Emergency Contraceptive (‘Morning After’) Pill: A pill containing hormones.
 They should be taken within 72 hours after intercourse to prevent implantation.
5. Surgical Methods: Involve cutting and sealing of tubes through which gametes pass.
a. Tubal Ligation: Cutting and sealing end of the oviduct to prevent ovulation.
 It makes fertilisation impossible.
 It is an irreversible process.
b. Vasectomy: Cutting and sealing the vas deferens to prevent sperm passing from testis to
the rest of the semen.
 It is a reversible process.
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Abortion
Spontaneous Abortion (miscarriage): The loss of a foetus before the 20th week of pregnancy. It
frequently occurs and is a natural way of preventing the birth of some abnormal babies.
Induced Abortion: This can be done either medically using hormones or surgically to remove the
foetus/embryo and placenta from the uterus.
Medical abortion involves the taking of hormones to terminate the pregnancy but only during the
early stages. They are effective up to 9 weeks into pregnancy.
Surgical abortion involves the termination of the pregnancy by either suction in the early stages
(first 6 – 12 weeks) or by scraping in advanced stages of pregnancy (12 – 15 weeks).
Advantages of induced abortions:
 Protects the mother’s health if the pregnancy puts her at risk
 Prevents the birth of a deformed baby
 Terminate unwanted/unplanned pregnancies
Disadvantages of induced abortions
 Death of foetus and/or mother
 May lead to psychological problems in mother
 May cause infertility
 Can be dangerous, especially if procedures are performed by untrained operators
Foetus in uterus
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HEREDITY AND VARIATION
Objectives
 Describe the process of mitosis
 Explain the importance of mitosis
 Describe the process of meiosis
 Explain the importance of meiosis
 Explain why genetic variation is important to living organisms
 Distinguish between genetic variation and environmental variation
 Explain the inheritance of a single pair of characteristics (monohybrid inheritance)
 Describe the inheritance of sex in human beings
 Explain the concept of genetic engineering
 Discuss the advantages and disadvantages of genetic engineering
DNA, Genes and Chromosomes
Chromosomes are long thin structures,
made from DNA, that carry genes. Before
a cell divides it copies it chromosomes so
that each is temporarily made up of two
chromatids. Genes are parts of a
chromosome that control individual
characteristics.
In a diploid cell, chromosomes are found
in homologous pairs. In a haploid cell only one of each pair of homologous chromosomes is present.
Homologous chromosomes are a pair of chromosomes with similar structural features that code for
the same gene. One from the pair comes from the mother while the other comes from the father.
The genetic information needed to control the human body is carried in 23 different chromosomes.
Human body cells are haploid, meaning they contain tow copies of each chromosome (46
chromosomes in total). Human sex cells (gametes) are haploid, meaning that they contain one copy
of each chromosome (23 chromosomes in total).
Mitosis
Mitosis is a type of cell division which makes 2 new cells with exactly the same number and kinds of
chromosomes as the parent cell (diploid cells). It occurs in all body cells except in gamete formation.
Mitosis maintains the species chromosome number, thus ensuring that all body cells have the full
chromosome number.
1. Chromosomes become shorter and fatter (easily seen). Each chromosome makes an exact
copy of itself, forming 2 chromatids joined together by a centromere.
2. The nuclear membrane breaks down and chromosomes line up along the middle of the cell.
3. Chromatids separate and move to opposite sides of the cell becoming new chromosomes.
4. A nuclear membrane forms around each group of chromosomes to make 2 identical nuclei.
5. The cytoplasm divides and the cell membrane develops down the middle of the cell to divide
it into 2 new identical cells (clones).
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Meiosis
Meiosis is a type of cell division which results in the formation of cells containing half the number of
chromosomes as the parent cell (haploid cells). It occurs during gamete formation.
A human cell has 46 chromosomes: 23 from the mother and 23 from the father. Each chromosome
from the mother pairs with a corresponding chromosome from the father. These are called
homologous pairs.
1. Each chromosome makes an exact copy of itself, forming two chromatids joined together by a
centromere.
2. Homologous chromosomes come together and pieces of genetic information are exchanged
between chromatids (crossing over). The chromosomes line up along the middle of the cell.
3. Homologous pairs separate and move to opposite sides of the cell.
4. The cell splits to form 2 cells with the haploid number.
5. The chromosomes line up along the middle of the cell where the chromatids separate from
each other.
6. The nuclear membrane form around each group of chromosomes forming 4 new different
cells.
Meiosis ensures that each daughter cell has the haploid number of chromosomes so that the diploid
number can be restored after fertilisation. It also ensures a different combination of genes in each
daughter cell for variation among offspring.
Variation
Variation refers to the differences between individuals of the same species, which arises as a result
of genetic makeup and environmental conditions.
Genetic variation is a result of genetic inheritance from parents. It is caused be:
 Random assortment of chromosomes during the first division of meiosis
 Random fertilisation
 ‘Crossing over’ during meiosis
 Mutations
It ensures the survival of a species by allowing individuals of a species to adapt to and withstand
changes of the environment. Examples: hair colour, height, eye colour, blood group, sex,
lobed/lobe less ears.
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Environmental variation arises from the effects of the surroundings. Physical characteristics can be
affected by climate, diet, culture and lifestyle. Examples: language, religion, body mass, skin colour.
There are 2 types of variation:
1. Continuous Variation
This refers to the range of forms of certain characteristics in a given population. It is genetically
determined and more likely to be influenced by environmental conditions. Examples include height,
body mass, length of forefinger, hand span.
2. Discontinuous Variation
This refers to clearly defined differences within a population. It is genetically determined and is not
influenced by environmental conditions. Examples include blood group, sex.
Mutations
A mutation occurs when there is a change in the amount or arrangement of DNA in a cell which
alters a characteristic. There are 2 types of mutations:
1. Gene mutation – a change in the arrangement of a single gene. Conditions caused by such
mutations include albinism, Huntington’s disease, sickle cell anaemia.
2. Chromosomal mutation – a change in the number of chromosomes in a cell or a change to
the structure of the chromosome. Conditions caused by such mutations include Down’s
syndrome, Turner syndrome, Klinefelter syndrome, triple X syndrome.
Inheritance
Gene – a segment of DNA on a chromosome
Allele – different forms of the same gene that occupy the same position on homologous
chromosomes.
Genotype – the genetic makeup of an organism with respect to specific alleles.
Phenotype – the characteristics shown due to the effect of the genotype.
Homozygous – alleles at a specific position on homologous chromosomes that are the same, e.g. AA
or aa
Heterozygous – alleles at a specific position on homologous chromosomes that are different, e.g. Aa
Dominant – the allele that shows its effect in the phenotype, even in the presence of a different
allele, and controls the normal condition, e.g. A.
Recessive – the allele that has no effect in the phenotype in the presence of another different allele.
It is expressed only when 2 are present, e.g. a.
Genetic diagrams show the phenotype and genotype of parents and the possible genotypes and
phenotypes of the offspring.
Monohybrid inheritance is the passing down of a single characteristic from parent to offspring and
involves a single pair of genes.
Carrier - a person that appears normal but has the recessive allele along with the dominant allele
(heterozygous).
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Monohybrid Recessive Inheritance
This arises from the inheritance of 2 recessive alleles. The dominant allele controls the normal
condition. Example:
Albinism
An albino lacks the skin pigment melanin and the pigment in the iris.
Dominant allele for normal skin pigment: A
Recessive allele for albino condition: a
Example: Two parents are carriers for albinism. What are the chances of having an affected child?
Their albino child grows up and has children with a normal person. What are the possible genotypes
of their children?
Sex Determination & Sex-Linked Characteristics
Sex determination
Of the 23 pairs of chromosomes in the human cell, 1 pair determines sex. There are 2 types of sex
chromosomes: X and Y.
Female genotype: XX
Male genotype: XY
There is a 50% possibility that a child could be male or female
Sex-linked Characteristics
These characteristics are determined by other genes on the sex chromosomes and are carried on the
X chromosome. They mostly affect males. Haemophilia (bleeder’s disease) and colour blindness are
sex-linked recessive conditions.
Example:
1. A carrier female for haemophilia married a normal male. What is the possibility of their having
a haemophiliac child?
2. A carrier female married a colour blind male. What is the possibility of their having a colour
blind son? What is the possibility of their having a colour blind child?
Sickle Cell Anaemia
In this disorder, RBC’s take a sickle shape instead of the normal biconcave shape.
Normal RBC allele: N
Sickle shaped allele: S
Sickle cell trait: NS (30 – 40% RBC’s are sickle shaped)
Example: If 2 persons with the sickle cell trait were to marry,
a. What are the possible genotypes and phenotypes of their offspring?
b. What is the possibility of their having a child who suffers from sickle cell anaemia?
c. What is the possibility of their having a normal child?
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Genetic Engineering
Genetic engineering is the changing of one or more characteristics of an organism by inserting genes
from another organism into its DNA.
The foreign DNA can come from another individual of the same species, a different species or
synthesised DNA.
Advantages
Improved food quality
Resistance of crops to pests, diseases, environmental conditions and herbicides
Food to match population growth
Treat medical disorders
Growth hormone production to treat dwarfism
Insulin production for diabetics
Vaccines
Cancer and genetic disorders diagnosis and treatment
Disadvantages
Lack of understanding of the impact on human health and the environment
Worked Example of Monohybrid Recessive Inheritance
Using H to represent the normal condition for height and h to represent the recessive allele for
short, what would be the possible genotypes of offspring produced when two heterozygous tall
persons mate?
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KHM
DISEASE AND ITS IMPACT ON HUMANS
Objectives
 Define the terms good health and disease
 Classify diseases
 Differentiate between the terms signs and symptoms
 State the main causes, primary symptoms and possible treatment of asthma
 Explain how asthma affects the respiratory tract
 Discuss the causes, signs/symptoms, treatment modality and prevention of chronic/lifestyle
related diseases
 Discuss the causative agent, signs, symptoms, prevention and control of infectious diseases
 Discuss the cause, symptoms, mode of action, prevention and control of HIV/AIDS
 Describe the effects of sexually transmitted infections (STI’s) on the pregnant mother and
foetus
 Discuss the impact of disease on the human population
 Discuss the effects of malaria and dengue (strain I – IV) on the human body
 Explain the effect of vectors on human health
 Describe the life cycle of the mosquito and housefly
 Explain the importance and methods of controlling vectors which affect human health
 Health and Diseases
 Explain how and why personal hygiene is maintained
 Explain the methods used to control the growth of microorganisms
 Distinguish between disinfectants and antiseptics
 Explain the use of common antibiotics and antifungal agents
 Explain the types of immunity
 Distinguish between immunity and immunization; vaccine and vaccination
 Discuss the use and misuse of drugs
 Explain the social effects of drug misuse on individuals, family and community
Definition of Terms
Health - a state of complete physical, mental and social well-being and free from disease or infirmity
[World Health Organization (WHO)]
Disease is any change from normal health in which the health of the organism is impaired.
A disease can be classified as:
1. Communicable (infectious) – caused by a pathogen and can be passed from one person to
another
2. Non-communicable (non-transmissible) – cannot be passed from one person to another or
acquired from a disease vector
Diseases are detected by signs and symptoms. Symptoms are subjective, i.e. what a person feels.
Signs are objective, i.e. what an observer can detect.
Pathogen - disease causing organisms, e.g. – viruses, bacteria, fungi, protozoa
Vector - an organism that carries a pathogen and transmits it from on host to another.
Host - an organism which a pathogen lives on or inside
Venereal disease – a disease only passed from one person to another during sexual intercourse
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Common Diseases
Disease
Causative
Spread
Influenza
Virus
Droplet
Asthma
Allergens (dust
mites, pollen,
fur etc.)
Triggers
(stress,
exercise)
Airborne
particles
Tuberculosis
Bacterium
Mycobacteium
tuberculosis
Spores in
droplet
Pneumonia
Bacterium
Pneumococcus
Spores in
droplet
Ringworm
Fungus
Tinea
Spores on
floors, towels,
skin
Cholera
Bacterium
Contaminated
Vibrio cholerae water
(especially by
faeces)
Typhoid
Bacterium
Salmonella
Signs and
Symptoms
Shivering,
raised body
temperature,
headache,
fever, sore
throat
Wheezing,
coughing,
shortness of
breath,
inflammation
of bronchiole
tubes
Coughing,
spitting blood,
fever,
becoming pale
and thin
Coughing, red
sputum, fever,
chest pain
Red patches on
body, itching
Vomiting,
severe
diarrhoea,
gastroenteritis,
stomach pains,
dehydration
Contaminated Severe
water and food diarrhoea,
fever, rash,
gastroenteritis
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Control
Treatment
Flu vaccine,
good
ventilation
Rest, hot
drinks,
warmth,
pain killers
Avoid
allergens and
triggers
Use of
corticosteroid
inhaler and
antihistamines
Avoid
overcrowding
Avoid
spitting, BCG
vaccine
Avoid
overcrowding
Antibiotics
Thoroughly
dry skin,
avoid sources
of infection
Proper
disposal of
faeces,
chlorination
of drinking
water
Proper
treatment of
water and
food,
vaccination
Fungicide
ointments
(antifungal
drugs)
Antibiotics
Antibiotics
Antibiotics
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Types of Diseases and Examples
1. Infectious – influenza, typhoid, STIs, dengue, rabies, measles
2. Deficiency – night blindness, beri-beri, scurvy, rickets, anaemia
3. Degenerative – heart disease, Alzheimer’s disease, osteoarthritis, cancer
4. Inherited – albinism, sickle cell anaemia, haemophilia, colour blindness, Huntington’s disease
5. Mental – anxiety, neurosis, stress, depression
6. Self-inflicted – cancer, bronchitis, heart attack, addiction from cigarette smoking, excessive
alcohol consumption and overeating
Sexually Transmitted Infections (STIs)
A sexually transmitted infection can be transmitted by sexual contact, normally sexual intercourse.
STIs can be caused by: viruses (genital herpes, genital warts, HIV/AIDS), bacteria (chlamydia, syphilis,
gonorrhoea) and arthropods (pubic lice).
Common Sexually Transmitted Infections
Disease
Pathogen
Gonorrhoea
Bacterium gonococcus
Syphilis
Bacterium spirilla
Genital herpes
Herpes
simplex type
2 virus
Symptom/Sign
Pus from penis, burning
sensation when urinating,
sterility (blocked oviduct and
inflammation of prostate
and testes)
Hard red ulcers, rash, brain
damage, insanity, death
Blisters around genitals,
rash, itching, pain, severe
headache, muscle ache
Treatment
Penicillin injection
Penicillin injection
No cure, treatment reduces
symptoms.
Prevention: avoid contact
with blisters/ulcers of
infected persons
AIDS
Human immunodeficiency virus (HIV) destroys T-lymphocytes which weakens the immune response
to invading pathogens.
Acquired immune deficiency syndrome (AIDS) causes patients to die from other opportunistic
infections, e.g. pneumonia, tuberculosis.
Causative agent
Human immune-deficiency virus (HIV)
Spread/
infection
Signs/
symptoms
Control
Sexual intercourse, blood transfusions, intravenous injections, mother to foetus
(congenital),breast feeding
Weakened immune system, cough, fever, skin rashes, swollen lymph glands,
lack of WBCs
Avoid sexual relationships with infected persons, avoid unprotected sexual
intercourse, no sharing of intravenous needles, avoid contact with blood from
other persons, screening for virus
No cure, anti-retroviral drugs (expensive, many side effects), education on
sexual behaviour
Treatment
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Effects of STI’s on the Mother and Foetus
Bacteria causing gonorrhoea and syphilis can cross placenta of mother leading to a damaged foetus,
stillbirth and babies born with abnormalities, e.g. eye defects.
Viruses causing HIV and hepatitis can cross placenta of mother to foetus. HIV can also be transmitted
through breast milk.
Mothers with herpes virus have worse symptoms during pregnancy and babies may be infected at
birth leading to nervous complaint, blindness and death.
Mosquito as a Vector
Mosquitoes directly transfer pathogens to humans by biting or piercing the skin and are vectors for
insect borne diseases. Only the female adult mosquito can bite and infect. They are attracted to the
body by the smell of sweat. Mosquitoes require stagnant water for the development of their egg,
larvae and pupa stages.
Life Cycle of a Mosquito
Eggs are laid on the surface film of water. Larvae emerge and hang down from the under-surface of
water. Larvae moult about 4 times and form a comma-shaped pupa and adult structures begin to
form (non-feeding stage). Pupa case splits along the back of the head and thorax and adult climbs
out on water surface, allowing the outer covering to harden. Adults can live 11 – 15 days.
Mosquito vector
Causative agent
Signs/symptoms
Treatment
Malaria
Anopheles
Protozoan
Plasmodium
High fever,
weakness
Drugs e.g.
quinine
Dengue
Aedes aegyptii
(feeds after
dawn and before
dusk)
Virus
DEN 1 to 4
Fever, severe
headaches,
muscle and joint
pain, rash
No specific
treatment, rest
and plenty fluids
Metamorphosis of the mosquito
Houseflies as a Vector
Houseflies transmit pathogens that enter the body in food and cause food poisoning. The major
source of infection includes feeding, defecating and walking from organic waste and faeces to food
eaten. Little pools of digestive juices rich in harmful bacteria is left on food after feeding. The fly may
defecate while flying over food. Bacteria from hairs on the fly’s body may drop off while it walks on
food.
Female can lay 120 – 150 eggs in one batch with 5 batches in one lifetime.
Control: Kill adults, remove breeding grounds, e.g. rubbish heaps.
Disease prevention: Keep food covered, properly store cooking utensils
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Life Cycle of a Housefly
Houseflies undergo complete metamorphosis with distinct
egg, larva, pupa and adult stages. Eggs are laid singly but are
piled in small groups. Larvae emerge within 8 – 20 hours, and
immediately feed on and develop in the material in which the
eggs were laid. Larvae go through 3 moults and complete their
development in 4 to 13 days at optimal temperatures. Pupae
complete their development in 2 – 6 days. Adults can live
15 – 25 days. Without food, adults survive only about 2 – 3
days.
Metamorphosis of a housefly
Rats as a Vector
Rats are opportunistic survivors that often live with and near humans. As pests, they cause
substantial food loss, property damage and transmit diseases that pose a threat to public health.
Diseases Transmitted by Rats
Causative Agent
Part played by Rats
Serve as hosts to vectors (fleas,
Typhus Bacterium: Rickettsia
ticks, lice, mites)
Plague Bacterium: Bacillus
Host to rat fleas (vector)
Feeding, urinating and defecating
Food poisoning and typhoid Bacteria
on food stores
Leptospirosis (Weil’s disease) Bacterium: Leptospira
Urinating on food and in water
Other parasites such as tapeworms and liver flukes can be spread by rats.
Controlling Vectors
Controlling vectors helps prevents the spread of communicable fatal diseases, e.g. leptospirosis,
dengue fever, gastroenteritis. Vectors can be controlled by removing breeding grounds and
destroying the vectors.
Hygiene
Hygiene refers to the various measures a person takes to avoid infection, maintain cleanliness and
ensure good health. It is important for eliminating body odours, social acceptance, the prevention of
infections and the prevention of dental carries.
Ways to maintain hygiene
 Bathing (with soap)
 Washing hair (with shampoo)
 Use warm water while showering
 Dry skin thoroughly
 Wash hands before preparing and eating
meals and after using the toilet





Keep finger nails short and clean
Frequently change and wash clothing
Wear water proof foot wear
Wear light coloured and light weight clothing (cottons and silks)
Proper disposal of wastes
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Methods to Control the Growth of Microorganisms
Pasteurisation
Ultra-high
temperature (UHT)
Boiling
Autoclaving
Canning or bottling
Refrigeration
Dehydration
Osmotic
preservation
Vacuum packaging
Use of smoke
Pickling
Deep freezing
Heat treatment to preserve liquids by destroying most bacteria present.
The liquid is alternately heated and cooled to destroy bacteria that turn it
sour.
Food is heated to over 135⁰C and rapidly cooled before packaging to kill
virtually all microbes and their spores on a wide range of foods.
Water boils at 100⁰C at which few organisms can survive.
Pressurised steam is used to destroy microbes. It is used for the
decontamination of laboratory waste and the sterilisation of laboratory
equipment.
Food contents are processed and sealed in an airtight container providing
long shelf life. The packaging prevents microbes from entering and
proliferating inside.
Food is cooled causing microbe growth to be slowed.
Water is removed from food to prevent growth of microbes.
Sugar or salt is added to the food making it impossible for most microbes
reproduce, e.g. jams, jellies.
Removal of oxygen to prevent aerobic respiration by microbes.
Heat removes water which slows microbe growth.
The addition of ethanoic acid lowers pH reducing growth of microbes.
Food is cooled to below -18⁰C thus preventing the growth of microbes but
not killing them.
Definition of Terms
Disinfection - the use of chemicals to destroy pathogens
Disinfectants - applied to surfaces, equipment or other inanimate objects to eliminate pathogens.
They are stronger and more toxic than antiseptics.
Antiseptics - applied to living skin or tissue to prevent infection by eliminating pathogens.
Antibiotics - a chemical produced by living organisms which destroy bacteria.
Antigen - a large molecule that causes lymphocytes to make and release antibodies.
Antibody - protein molecules that destroy pathogens.
Antitoxin -- antibodies made to destroy toxins.
Sterilisation – the complete destruction of all microorganisms present on a substance
Use of Antibiotics and Antifungal Agents
Antibiotics
Antibiotics are used to reduce and treat infections. Penicillin is the most common antibiotic and can
treat bacterial infections like tonsillitis, gingivitis, mild anthrax, syphilis, gonorrhoea, pneumonia.
Popular penicillin varieties include amoxicillin and ampicillin that are used to treat bacterial strains
that are immune to some penicillins.
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Antifungal agents
These agents are used to treat fungal infections.
E.g. – Antifungal cream can be used to treat ringworm and are liberally applied to the infected area
and its surroundings.
Test for Bacterial Presence
1. Prepare a sterile nutrient agar plate.
 An agar plate is a Petri dish that contains a
growth medium used to culture
microorganisms.
2. Sterilise the nichrome wire loop by passing it
through a flame.
 Nichrome is an alloy of nickel, chromium
and iron.
3. Pass the cooled sterile nichrome wire loop on
the surface (or in the contaminated water) to
be tested.
4. Inoculate the plate by streaking the loop across
the surface of the agar.
 Inoculate – to introduce cells or microbes
into a culture medium.
5. Set up a control plate by dipping a sterile
nichrome wire loop in sterile distilled water
and rubbing it across a sterile nutrient agar
plate.
6. Incubate the 2 plates at 25⁰C for at least 48
hours.
 Incubate – to keep at an optimum temperature for development to take place.
7. Observe plates for bacterial colonies.
 The control plate should be clear while the plate infected with bacteria should show visible
clusters of bacteria.
Definition of Terms
Immunity - the body’s resistance to suffering from a disease.
Vaccine - a biological preparation containing parts of microbes or whole microbes that have been
killed or weakened to stimulate the body’s own immune system to protect against subsequent
infection or disease.
Immunisation - the process where a person is made immune or resistant to an infectious disease,
typically by the administration of a vaccine.
Vaccination - the administration of a vaccine to stimulate an individual's immune system to develop
immunity to a disease.
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Types of Immunity
1. Natural innate active immunity - inborn immunity
2. Natural innate passive immunity - passed from mother to foetus and baby
3. Natural acquired active immunity - antibodies produced by a natural infection, e.g. TB
4. Artificial acquired active immunity - antibodies produced by a vaccine, e.g. polio vaccine
5. Artificial passive acquired immunity - serum injection contains antibody, e.g. antiserum to
snake bites and tetanus
Definition of Terms
Drug - a substance taken into the body that influences chemical reactions in the body.
Prescription drugs - drugs that should be taken under medical advice for the prevention or cure of
diseases.
Drug abuse - the taking of drugs in excess, or for reasons other than their medical use.
Drug dependence - the addiction caused when a person repeatedly take a drug that they rely on for
support.
Psychological dependence - when an individual feels that they must have the drug in order to live.
Physical dependence - when the body’s metabolism is changed due to taking the drug so that when
the drug is removed strong withdrawal symptoms are produced.
Classification of Drugs
1. Narcotic drugs (opiates) - opium, morphine, heroin, methadone (drugs obtained from unripe
seed pods of opium poppy)
2. Sedatives - tranquillisers, sleeping pills (slows down body functions)
3. Stimulants - cocaine, amphetamines, caffeine
4. Hallucinogens - marijuana (cannabis), LSD, ecstasy
5. Performance enhancing drugs - anabolic steroids, hormones, diuretics
6. Alcohol - beer, wines, spirits (affect body tissues and change behaviour)
Social Effects of Drug Misuse
Signs of drug misuse
 Fast mood changes
 Alienation
 Dilated pupils
 Restless condition
 Shortage of money
Effects of drug misuse
 Criminal activity - to support expensive habit
 Increased crime in community - competition for drug sales
 Suicide - drugs leads to frustrations, depression and sense of hopelessness
 Violence
 Prostitution
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THE IMPACT OF HEALTH PRACTICES ON THE ENVIRONMENT
Objectives
 Identify pollutants in the environment
 Discuss the causes of water and air pollution
 Describe the effects of pollutants on human beings and the environment
 Explain methods of controlling pollution
 Describe the water cycle
 Describe simple ways of purifying water in the home
 Describe the processes involved in large scale water purification
 Test water for bacteria
 Discuss the impact of human activities on water supplies
 Explain why contaminated water is detrimental to human beings
 Distinguish between proper and improper sewage disposal practices
 Explain the impact of improper sewage disposal practices
 Compare the treatment of sewage by biological filter and activated sludge methods
 Relate the parts of the pit latrine to their functions
 Explain why the site of pit latrines is important
 Assess the use of pit latrines in the Caribbean
 Evaluate the efficiency of the methods of domestic refuse disposal
 Describe the operations at a landfill
 Discuss the importance of landfills in the Caribbean
 Evaluate the impact of solid waste on the environment
 Analyse measures used to control solid waste volumes
 Distinguish between the terms biodegradable and non-biodegradable
Pollution is the changing and harming of the environment by the action of humans.
A pollutant refers to any substance or form of energy that causes harm when released into the
environment.
Pollution can be categorized according to its source.
Source of Pollutant
1. Domestic
Detergents
Sewage
2. Industrial
CO2
SO2
Heavy metals, e.g. mercury
and lead
3. Agricultural
Pesticides
Fertilisers and farmyard
manure
Methane
Effects on Humans and the Environment
Contains phosphates (a plant nutrient), causes eutrophication
Improper disposal causes eutrophication and water contamination
A greenhouse gas contributing to global warming
Damages plants, forms acid rain, irritates respiratory systems
Accumulates in food chains; harms the immune and reproductive systems
of marine mammals
Kills non-target species, so reducing biodiversity
Run-off into water, causes eutrophication
Emitted by anaerobic bacteria in flooded rice fields and by cattle; also by
landfill sites
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Air Pollution
Air pollution is the contamination of air by any pollutant that modifies the natural characteristics of
the atmosphere.
The types of air pollution, their origin(s) and their consequences
Type of Pollution
Causes
Damage
Global warming
Carbon monoxide,
methane, nitrogen dioxide
Acid rain
Sulphur dioxide, nitrogen
dioxide
Depletion of ozone
layer
Chlorofluorocarbons,
hydrocarbons
Carbon monoxide
Car exhausts, gas
appliances, cigarettes
Drills, loudspeakers, cars,
lorries, aeroplanes
Increase in global temperature causes:
 Polar Ice caps to melt.sea levels rise and low
lying areas are flooded
 Rainfall is reduced in tropics leading to
droughts and famine
 Stronger winds which lead to more storms and
hurricanes
 Low pH in rivers leads to death of fish
 Low pH of soil leads to less photosynthesis by
plants
 Breathing problems in humans
 Damage to limestone and concrete buildings
More ultra-violet (UV) light reaches the Earth’s
surface, increasing mutations which can give rise
to cancers caused
Reduction in the transport of oxygen by the blood
Noise
Hearing problems, headaches, stress
Water Pollution
Water pollution is the alteration of water by pollutants so that it is no longer suitable for the human
needs.
The types of water pollution, their origin(s) and their consequences
Type of Pollution
Causes
Damage
Eutrophication
Nitrates and phosphates in Increases in plant growth on the surfaces of
sewage, farmyard slurry,
ponds, rivers and lakes leading to an algal bloom.
detergents/washing
Oxygen depletion leads to death of aerobic
powders and fertilisers
organisms.
Suspended solids
Domestic and industrial
Makes the water very murky so no light can get to
waste
the plants. Photosynthesis is therefore prevented.
Toxic chemicals
Lead, mercury, zinc, iron,
Miscarriages, birth defects, severe learning
pesticides, oil
difficulties in children. Oil can harm much animal
and plant life.
Radioactivity
Nuclear power stations,
Genetic defects, death
waste from hospitals
Heat
Heated water from
Aerobic organisms in rivers and streams die
industry
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The Water Cycle
Domestic Water Purification
1. Boiling
Boiling water for a few minutes generally destroys all the harmful organisms and makes the
water safe.
2. Addition of chlorine/bleach
Chlorine or bleach will purify water (acts as a disinfectant) but will give the water ‘taste’.
Sterilising tablets that release chlorine can also be used.
3. Use of filter beds
Sand filters may not completely purify the water and the sand needs frequent changing.
4. Desalination plants
Desalination plants remove salt from seawater and are often used where fresh water supplies
are short.
5. Distillation
Distillation involves boiling the water and condensing the steam on a cool surface.
Stages in Large Scale Water Purification
The parts of the water treatment works and the processes that occur include:
 Water source: lake, reservoir or spring
 Screening to remove large floating matter
 Pump to move the water
 Settlement to remove particles of inorganic matter
 Iron and aluminium salts may be added to cause smaller particles to flocculate (clump
together) and settle more quickly
 Filtration to remove fine particles, organic matter and microorganisms
 Digestion by bacteria, fungi and protozoa to get rid of organic matter and most bacteria
 Chlorination to kill any remaining bacteria and other microorganisms
 Transport and storage in the dark to prevent the growth of algae
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Proper vs. Improper Sewage Disposal
Sewage refers to human waste (faeces and urine) from toilets, dirty water from sinks, showers and
baths, drain water and waste from industry, hospitals and abattoirs.
Improper sewage disposal can spread disease pathogens and contaminate drinking water. It occurs
when sewage is disposed into open water, or on land the land and when cracked sewage pipes are
used.
Proper sewage disposal occurs when sewage is removed from houses in pipes together with water
to flush it along.
Sewage Treatment
The process involved in sewage treatment includes:
1. Piping sewage from houses and factories to treatment plant
2. Screening which removes large objects that are incinerated or sent to landfill
3. Grit settling tank where grit and sand settle out, are collected and sent to landfill
4. First sedimentation tank where large particles settle and become sludge
5. Sludge is removed and treated to form methane or agricultural fertiliser
Sludge can be treated by using:
i. Biological filter or percolating filter where sewage is sprayed onto stones covered with
microorganisms, e.g. bacteria and protozoa, which feed on the organic matter and convert
it into simple inorganic matter.
ii. Activated sludge where compressed air is pumped through aeration tanks containing
microorganisms which break down the organic material.
6. Any remaining water (effluent) is then sufficiently unpolluted to be passed into a river or the
sea
Pit Latrines
A pit latrine is a hole at
least 3m deep into
which faeces and urine
drop. Pit Latrines should
be
located
several
meters from the house
and some distance
away from streams,
wells or any source of
drinking water in order
to avoid contamination.
N.B. - Disinfectant
should not be added
since it kills the bacteria
that decomposes the
faeces.
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Solid Waste Management
Landfill Sites
A sanitary landfill site should be dug out of the ground and lined to prevent toxic liquid wastes
leaching away into the soil and entering waterways or ground water. The topsoil is removed first,
then pits are dug and the waste tipped in. The topsoil is replaced so that the land will not be wasted.
Pits made by mining are often filled in this way (land reclamation).
Landfill sites uses machinery to compact the volume, sort out, to recycle and select for different uses
the various wastes. Compacting refuse makes it difficult for vectors, e.g. rats, to penetrate and
reduces the volume to make it easier to handle and take up less space at landfill sites. Soil bacteria
and fungi decompose the organic components of the rubbish into carbon dioxide and methane. As a
result, gases are given off and the volume of rubbish decreases.
Reasons for poor solid waste management in the Caribbean include:
 Lack of space for developing proper sanitary landfill sites
 Not enough finance to purchase and develop suitable sites for waste management
 Objections by local people to incinerators
 Populations that are too small to provide enough waste to support new technologies, e.g.
incinerating waste for generating power
Domestic Refuse and its Disposal
Domestic refuse (garbage) is all the unwanted solids that build up after use in the home. There are
two main components of domestic refuse:
i. Organic matter, such as waste food and garden waste. This can act as a breeding place for
vectors of various diseases
ii. Solid waste refers to all unwanted solids that accumulate after use in the home, e.g. paper,
plastic, metal tins, glass and textiles. These can act as breeding ground for various vectors and
may cause water pollution.
Proper disposal practices include:
 Place waste in bins with tightly fitted lids
 Inspect and clean bins regularly and when necessary
 Ensure waste collection at least once a week
 Avoid kitchen slops
Measures Used to Control Solid Waste Volumes
Most efficient methods – reuse, reduce, recycle.
Reuse: Use again, for the same or different purpose, e.g. bottles
Reduce: Try to buy only what is needed, avoiding unnecessary materials, e.g. extra packaging on
goods
Recycle: Use to make new products, e.g. wood to make paper
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Advantage
Resources and materials will last longer and cost less for future generations
Generate income from recycling
Fewer landfill sites
Less pollution from decomposing waste
Disadvantage
Time consuming to sort waste
Specialized lorries needed for collection
Other methods to control solid waste volumes:
i. Composting – biodegradable waste produced from households can be made into compost.
ii. Incineration – burning is an effective way of removing waste so that it does not have to go to
a landfill.
Biodegradable vs. Non-biodegradable
Biodegradable waste refers to waste that is broken down by organisms. It allows nutrients to be
recycled to the environment. This waste does not take up much space provided the decay is not
prevented. Example: waste food, paper, some plastics.
Non-biodegradable waste refers to waste that will not decay. Such material should be compacted
for disposal in landfill sites if cannot be recycled. Example: most plastics, metal, rubber, glass.
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