Life processes
The processes which are required for maintaining the complex, well
organised structure of living organisms are called life processes.
1.
2.
3.
4.
Nutrition
Respiration
Transportation
Excretion
Nutrition
The process of utilization of food by living organisms to obtain
energy is called nutrition
Carbon sources: complex – carbohydrates, sugar
Simple – glucose lactose (organic carbon source)
Plants consume CO2 (inorganic carbon source)
Autotrophs : the organisms that can synthesize their own food
Example: green plants, some bacteria
Heterotrophs : the organisms that cannot synthesize their own food
Example: animals, some fungi
Nutrition in plants
Plants are also called as producers.
Mode of nutrition: autotrophic, heterotrophic
Autotrophic nutrition
Plants prepare their own food by using raw materials such as water,
carbon dioxide and minerals in presence of sunlight. This is called
photosynthesis. Photosynthesis takes place in leaves bearing
chlorophyll. Since they prepare their own food they are called
autotrophs.
Auto- self; trophs- nourishment
All green plants are autotrophs.
Plants absorb water and carbondioxide in the presence of sunlight and
release oxygen.
Raw materials for photosynthesis
CO2: It is obtained from the atmosphere through stomata.
H2O: Roots absorb water along with minerals from soil and transport
them to leaves.
Sunlight: Intensity, duration and quality affects the rate of
photosynthesis
Chlorophyll: It is the green pigment present in leaves in structures
called chloroplasts. It is responsible for the absorption of sunlight.
End product of photosynthesis
6CO2 + 12H20
C6H12O6+ 6O2 + 6H2O
Reactions that take place during photosynthesis
1.
2.
3.
4.
Absorption of light energy by chlorophyll.
Conversion of light energy into chemical energy.
Splitting of water molecule into hydrogen and oxygen.
Reduction of CO2 to carbohydrates.
Photosynthesis in dessert plants
Desert plants take up carbon dioxide at night and prepare an
intermediate which is acted upon by the energy absorbed by the
chlorophyll during the day.
Chlorophyll is necessary for photosynthesis
1. Take a potted plant like croton whose leaves are partly green
and partly white
2. Place this plant in dark for three days
3. Take out the plant from the dark place and keep it in sunlight for
3 to 4 days
4. Pluck the leaf and boil it in water for a few minutes
5. Then boil it in alcohol so as to remove the green colour
6. Pour iodine solution on the colourless leaf and observe the
change in colour of the leaf
Observation
The white parts colourless leaf doesn’t change blue black
indicating there is no formation of starch. Whereas in the green
parts of leaf changes indicating the presence of starch. This shows
that chlorophyll is necessary for photosynthesis to make starch.
Light is necessary for photosynthesis
1. Take a potted plant and place it in a dark room for 3 days.
2. Wrap the centre of one of its leaves with aluminium foil to
prevent sunlight from reaching there
3. Place this plant in sunshine for 3 to 4 days.
4. Pluck the leaf covered with aluminium foil and remove its
aluminium foil
5. Immerse this leaf in boiling water
6. Boil the leaf in alcohol to remove chlorophyll
7. Pour iodine on the leaf and observe the change in colour
Observation
The colour of the leaf in the corners change blue black indicating the
presence of starch where as the colour of leaf at the centre doesn’t
change. Hence light is necessary for photosynthesis.
Heterotrophic nutrition (hetero-other)
i.
ii.
iii.
iv.
Saprophytic
Symbiotic
Parasitic
Holozoic –ingestion, digestion, absorption, assimilation,
egestion
Heterotrophic mode of nutrition in unicellular organisms.
Amoeba: It is filled with a jelly like substance called cytoplasm.
Finger like projections in amoeba called pseudopodia help in
locomotion. It also helps amoeba engulf the food. Amoeba extends
the pseudopodia around the food. The extensions fuse and form food
vacuoles. These food vacuoles are structures that store food. The food
is digested in the food vacuole and then travels outside into the
cytoplasm. The remaining undigested food is thrown out of the
cytoplasm.
Paramoecium: cilia, definite shape.
Digestive system
Digestive system consists of a canal called alimentary canal
1) Moutha. Teeth: Teeth helps in chewing the food. We chew food so
that the complex bigger molecules become softer and
broken down into softer substances.
b. Tongue: Tongue helps in moving the food inside our
mouth and swallow the food
c. Saliva: it is secreted by salivary gland. It consists of
salivary amylase. It helps in moistening the food and break
down carbohydrates.
Enzymes; enzymes are biological catalysts that break down complex
food substances into simpler molecules for absorption
2) Oesophagus – the oesophagus moves the food to the stomach. It
performs peristaltic movement. The rhythmic contraction and
relaxation of alimentary canal propelling the food forward from
oesophagus to the stomach is called peristalsis. Presence of
epiglottis here prevents the entry of food into the wind pipe.
3) Stomach- it is an extendable organ and j shaped organ. There are
various secretion in the stomach
a) HCL –It is secreted by the walls of the stomach. It is highly
acidic. It is used to activate an enzyme called pepsin. It also kills
harmful pathogens in our food when it reaches the stomach.
b) Pepsin –It is used to break down proteins
c) Mucus- HCL will damage or corrode the walls of the stomach.
Inorder to prevent this there is a layer in the walls of the
stomach which is called mucus. Mucus prevents HCl from
corroding the walls of the stomach.
d) Spincter muscle: it guides the entry of food from the stomach to
the small intestine.
ACIDITY: when we don’t have food for a long time the acid (HCL)
in the stomach gets accumulated causing acidity in the stomach.
4). Small intestine –it is the longest section of the whole alimentary
canal and is very highly coiled. This coiling is essential so that the
food digested in the stomach stays in the intestine for a longer period
of time and can be absorbed. It is differentiated into three regions –
duodenum, jejunum, ileum. There are certain enzymes or juices
secreted here. These are intestinal juice from the walls of the intestine,
pancreatic juice from pancreas and bile juice from liver.
a) Bile juice: It breaks down large fat globules into smaller
globules and makes the food alkaline for pancreatic
enzymes to act.
b) Pancreatic juice: the pancreatic juice contains enzymes
such as trypsin for digesting proteins and lipase for
digesting emulsified fats.
c) Intestinal juice: It converts proteins into amino acids, fats
into fatty acids and glycerol and carbohydrates into
glucose.
d) Villi: the small intestine has small finger like projections
called villi. They increase the surface area for absorption.
The major portion of food is digested and absorbed in the
small intestine.
Herbivores have longer intestine than human beings
because they eat grass which contains cellulose. So food
should stay in the small intestine for a long time and get
absorbed
5) Large intestine –water absorption takes place in the large
intestine. The undigested food is passed out to the anus in the
large intestine. Here there is a spincter muscle that regulates the
exit of waste materials from the body out as faeces.
Digestive glands.
1. Salivary glands –it secretes the 1st digestive juice. There
are three pairs namely parotids, sub maxillary and sub
lingual
2. Gastric glands –they are branched tubular glands which lie
in the mucus membrane of stomach. They secrete gastric
juices such as HCL, enzymes and mucus
3. Liver –it is the largest gland that lie below the diaphragm.
Liver has right and left lobes. The cells of the liver are
called hepatic cells and produce bile juice which flow out
of liver through hepatic dust and opens into small intestine
4. Pancreas –it is a soft lobulated gland present between the
lobes of duodenum.
Name of secretion Site of
the
action
gland
Mouth
Salivary Saliva
gland
Stomac
h
Enzymes Food acted End
produce upon
product
d
Salivary Starch
Maltose
amylase
Gastric
gland
HCl,
mucus
Pepsin
Liver
Bile juice Small
intestine
fats
Pancrea
s
Pancreati
c juice
Emulsifie
d fats,
proteins
Small
Trypsin,
intestine lipase
Proteins
Peptons,
polypeptide
s
Glycerol,
fatty acids
Dental caries –or tooth decay
 It causes gradual softening of enamel and dentine. I
 t begins when bacteria acting on the sugars produce acids
causing to demineralise the enamel.
 Masses of bacterial cells together with food particles stick to the
teeth to form dental plaque (sticky deposit).
 Saliva cannot reach the tooth surface to neutralise the acid
because the tooth will be covered with plaque.
 Brushing the teeth after eating removes the plaque. If untreated,
microorganisms may invade the pulp causing inflammation and
infection.
Respiration
The process in which oxidation of organic compound occurs in
cells and the energy is released
Respiration is a chemical reaction whereas breathing is a
physical reaction.
Exchange of O2 and CO2 is called breathing. Breathing differs in
different organisms. Various organisms have various organs to
breathe.
ORGANS
Sponges, coelenterates,
flatworms
Earthworm
Insects: spider, scorpion
Cockroach
Fishes, aquatic arthropods
Amphibians
Reptileas, birds, mammals
Mallusca terrestrial forms
ORGANISM
Body surface
Moist skin
Tracheal tubes: book lungs
Spiracles
Gills
Moist skin
Lungs
Lungs
Stages of respiration
There are three stages in respiration
1. External respiration; Gaseous exchange between environment
and lungs.
2. Internal respiration:
a) gaseous exchange between lungs and blood
b) gaseous exchange between blood and tissues
3. Cellular respiration: oxidation of organic compounds in cell in
which energy is released.
C6H12O2 + 6O2
6CO2 + 6H2O + ATP
Types of respiration
Aerobic respiration
Oxygen is used for the breakdown of glucose. In cellular respiration
glucose combines with oxygen to give carbon dioxide, water and
energy. This is called aerobic respiration. The respiration that takes
place in the presence of oxygen is called aerobic respiration
Anaerobic respiration
Some organisms like yeast can respire in the absence of oxygen.
Yeasts are unicellular organisms. Glucose doesn’t get oxygen and
breaks down into ethanol, carbon dioxide and low amount of energy.
The respiration that takes place in the absence of oxygen is called
anaerobic respiration.
“Yeasts are used in manufacturing of wine and beer as they produce
alcohol during anaerobic respiration.”
Respiration in muscles
Muscles can respire anaerobically for a short period of time. This
happens when there is lack of oxygen. Some activities like running,
playing or doing heavy exercises require high energy. But oxygen is
limited to produce large amount of energy. The glucose in the
muscles produces lactic acid, carbon dioxide and less energy in this
case. Cramps occur when muscles respire in the lack of oxygen. If a
large amount of lactic acid is accumulated we get muscle cramps.
This happens due to the incomplete break down of glucose. Hot water
bath, hot compress or massage can relieve cramps. This is because
they improve blood circulation. As a result oxygen in the blood will
be available to muscle and lactic acid will be broken down into CO2
and H2O.
Aerobic respiration
Occurs in the presence of
oxygen
Complete oxidation of food
takes place
Releases more energy
(38 ATP)
Byproducts -CO2 & H2O
Takes place in higher plants
and animals
Example: humans
Anaerobic respiration
Occurs in the absence of oxygen
Partial oxidation of food takes
place
Releases less energy (2 ATP)
Byproducts –ethanol
Takes place in lower plants and
animals
Example: fermentation
Respiration in plants
Parts that participate in respiration’
Roots: Roots have tiny root hairs that are single cells. The air spaces
between the soil help in respiration.
Leaves : Leaves have tiny pores called stomata. These stomatal pores
open and close for gaseous exchange to take place. It is the medium
of exchange of gases in leaves. Glucose reacts with plants to give
carbon dioxide, water and energy.
Massive amounts of gaseous exchange takes place in the leaves
through these pores for photosynthesis. Since large amounts of water
can be lost in the stomata, the plant closes the pores when it doesn’t
need CO2 for photosynthesis.
Guard cells
The stomata are covered by cells known as the guard cells that are
responsible for the closing and opening of the pore. The guard cells
swell when water flows into them causing the stomatal pore to open
and the pores close when the guard cell shrinks.
Human respiratory system
1. Nasal cavity: Nose has two openings called nostrils for the
entry of air inside. The air is filtered by hairs and mucus. From
here the air passes to the throat and then to the lungs.
2. Pharynx: It is a funnel shaped structure and common passage
for the movement of food and air.
3. Larynx: It is the sound box. It is prominent in males
4. Trachea: The extension of larynx is a short tubular
cartilaginous ring called trachea. It is also called the wind pipe.
Rings of cartilage here prevent air from getting inside the food
pipe.
5. Bronchi: The wind pipe externs further and divide into bronchi.
Each bronchi further divides into bronchioles in the lungs
6. Lungs: Lungs are bag like structure present in the thoralic
cavity. Each lung is covered externally by a double membrane
and has a fluid filled cavity in between them.
7. Alveoli: Within the lungs the bronchioles end up in numerous
air sacs called alveoli. The alveoli are balloon like structures and
provide a surface for the exchange of gases. The walls of the
alveoli contain an extensive network of blood capillaries that
have low oxygen and high CO2 concentrations. This allows o2 to
diffuse into the blood and CO2 to diffuse out of the blood easily.
8. Diaphragm: When we breathe in our ribs raise and diaphragm
flattens and the chest cavity becomes larger causing the alveoli
to expand. As a result the air is sucked into the lungs and fills
the expanded alveoli.
The blood brings CO2 from all parts of the body to the alveoli and the
oxygen in the alveolar air is taken up by blood vessels to be
transported to various cells in the body. During the breathing cycle
when air is taken in and let out, the lungs contain a residual volume
of air so that there is sufficient time for O2 to be absorbed and CO2 to
be released.
Difference between respiration in plants and animals
Plants
Animals
 Respiration takes place as a
 All the parts respire
single unit
individually
 Respiration occurs at a
 Respiration occurs at slow
faster rate
rate
 They produce more heat
 They produce little heat
Transportation
Blood and its composition
Blood is the red colour fluid that flows in our blood vessels. It is
composed of plasma, RBC, WBC and platelets. All these cells are
produced in the bone marrow and released into the cell.
Components of blood
Cellular parts (45%)
fluid (55%)
RBC, WBC, Platelets
Plasma
RBC
These are also known as erythrocytes. They are biconcave in shape.
Mature RBCs lack nucleus. RBCs show the presence of haemoglobin.
It transports oxygen to the required parts. Life span -120 days
WBC
These are known as leucocytes. They are of various types and shapes.
Nucleus is present and they are colourless. They are known as the
warriors of the human immune system. They protect us against
various kinds of infections and pathogens and infections
Platelets
They are also called as thrombocytes. They are fragments of the cell
and oval or round in shape. Nucleus is absent. It helps in clotting of
blood. In case of injury, there is a rupture of blood vessels. So RBC,
WBC comes out of the injured part. During that time platelets
accumulate and help in clotting.
Transfusion the transfer of blood from a healthy person to a patient is
called transfusion.
Plasma
Plasma is mainly made up of water and proteins. Cellular parts such
as RBC, WBC and platelets float in the plasma. It transports nutrients
and waste materials
Haemoglobin
It is the red colour and respiratory pigment that imparts red colour to
the blood. It is mainly made up of iron and proteins.
Functions of blood




It protects us from various kinds of pathogens and infections
Blood helps in clotting when we get injured
Blood helps in transportation of respiratory gases, nutrients.
Blood removes waste materials such as urea from the liver to the
kidney where it is excreted in the urine
 It also carries hormones from the endocrine glands to the target
organs
 Blood regulates body temperature
Lymph the fluid tissue
Lymph is a fluid derived from the blood from plasma. It is more clear
and watery than plasma. It seeps through the capillary walls to fill
tissue spaces. This is known as the interstitial fluid or tissue fluid.
Formation of lymph
Water and other water soluble molecules move out into spaces
between cells and tissues. Large proteins and formed elements stay in
blood vessels. This results in the formation of lymph
Composition of lymph
It consists of water, ions and proteins such as antibody proteins,
albumin, coagulation proteins, dissolved gases, nutrient molecules
and lymphocytes. Lymphocytes are a part of WBCs.
Functions of lymph
 They are important in body’s defence mechanism
 They filter out disease causing organisms and waste products
like fragments of dead cells.
 It carries digested and absorbed fats from intestine
 It drains excess fluid from extra cellular space back into the
blood.
Structure of the heart
The heart is present in between the lungs in the thoracic cavity. It is
separated from the abdominal cavity by diaphragm. Our heart is
hollow muscular organ. The size of the heart is as same as the size of
our fist. Normal heart measures 12 cm in height and 9 cm in width. It
is covered by a membrane called pericardium to reduce friction
during heart beat and protect it from injuries
External structure: it has 4 chambers which are divided by septum to
prevent the mixing of pure and impure blood.
The upper chambers are small in size and are called atrium
The lower chambers are big as they supply blood and are called
ventricles
Internal structure: 2 auricles, 2 ventricles, blood vessels, valves and
apertures.
Atrium ; It’s the receiving chamber of the heart. It is thin walled. It is
separated by intra atrial septum
Ventricles: it’s the discharging chamber of the heart. It is thick walled
because it pumps blood to all parts. They are separated by intra
ventricular septum.
Blood vessels:
 Superior venacava; it takes all the deoxygenated blood from the
above region to the heart. From the head, neck etc.,
 Inferior venacava: it takes all deoxygenated blood from the
lower regions of the body such as legs etc.,
 Systemic aorta: it is the largest artery of the human body. The
oxygenated blood from the heart reaches all other organs
through the aorta.
 Pulmonary artery: it takes impure blood from heart to lungs. All
arteries carries pure blood except pulmonary artery
 Coronary artery: it supplies pure blood to the heart. If there is
block age in the coronary artery we get heart attack.
Valves: they prevent the back flow of blood. Two atrioventricular
valves are present between chambers of the heart and the semilunar
valves are present at the base of two large vessels pulmonary trunk
and aorta.
The contraction of the heart is known as systole and the relaxation
of heart is known as diastole.
Circulation in heart
The right atrium contract and the blood is transferred from the right
atrium to the right ventricle. The right ventricles relax when they
receive blood. The right ventricle contracts and the blood is
transported to the lungs for purification to the lungs. The pulmonary
artery carries impure blood from the heart to the lungs.
The pure blood from the lungs comes to the left atrium via pulmonary
veins. The left atrium contracts and the blood is pumped to the left
ventricles. The left ventricles relax and collects the blood. They then
contract and blood is pumped to all the other organs through the aorta
which is the largest artery
Double circulation
A circulatory system in which the blood travels twice through the
heart in one complete cycle of the body
In double circulation, there are 2 steps namely systemic and
pulmonary circulation.
From the body parts the impure blood reaches the right atrium
through venacava.
From the right atrium the blood reaches the right ventricle.
From the right ventricle the blood reaches the pulmonary arteries
carry the impure blood to the lungs.
The lungs purify the blood by exchanging the gases.
From lungs the pure blood reaches the left atrium through pulmonary
vein.
From the left atrium blood reaches the left ventricle.
From the left ventricle blood reaches the body parts through aorta,
which is the largest artery.
This separation of right side and left side of the heart prevents mixing
of oxy and deoxy blood. This allows
 High efficient supply of oxygen to the body
 Maintaining body temperature in birds and mammals which
have high energy needs.
No. Of chambers
2
3
4
Organism
Fishes
Amphibians and reptiles
Birds and mammals
Circulation in fishes and amphibians
Fishes have 2 chambered hearts. Blood is pumped to the gills and
oxygenated there. Oxy blood passes directly to all the other parts.
Blood goes only once through the heart in one cycle. Therefore it is
called single circulation.
Animals like amphibians and reptiles which do not use energy for the
maintenance of temperature Have 3 chambered hearts and tolerate
some mixing of oxy and deoxy blood.
Blood pressure
Blood pressure it is the force or pressure on the walls of the artery.
There is upper limit and lower limit for B.P. the upper limit is the
systolic pressure and the lower limit is the diastolic pressure. When
the ventricles contract the pressure in the walls of the artery is high
and when the ventricles relax the pressure in the walls of the artery is
less. The normal B.P rate is 120/80 mmHg. It is measured using
sphygmomanometer. High B.P is caused by the constriction of
arterioles, which results in increased resistance to blood flow. It can
lead to the rupture of an artery and internal bleeding.
High B.P –hypertension ; Low B.P –hypotension
Blood vessels
Arteries
They have thick elastic walls
Veins
They have thin walls and valves
They take blood from the heart to
various organs
They collect blood from various
organs to the heart
All arteries carry pure blood
except pulmonary artery
All veins carry impure blood
except pulmonary vein
The pressure of blood in the artery is very high. Therefore to prevent
them from bursting they have thick walls.
Capillaries
On reaching an organ or tissue artery divides into smaller and
smaller vessels called capillaries, the smallest vessels that are one
cell thick to bring blood in contact with each and every cell.
Exchange of materials between the blood and the surrounding takes
place across capillaries.
The capillaries then join together to form veins.
Mechanism of clotting
Thromboplastin + prothrombin + calcium = thrombin
Thrombin + fribrinogen = fibrin
Fibrin + blood cells = clot
Thromboplastin –from injured tissue;
Prothrombin –inactive thrombin present in plasma;
Calcium –required for activating prothrombin
fibrogen –soluble protein in blood plasma
Transportation in plants
Structure of roots
Roots consist of small hair like structures which are known as root
hairs. Root hairs are the smallest figures that absorb water. Root
hairs are the elongation of the cell membrane of the outer surface of
roots. There are many cells within the root hair in a region called
cortex
The final cell inside the root hair is known as the xylem. Water is
transported from the roots to the leaves with the help of xylem
through a process called osmosis.
(OSMOSIS: The movement of water molecules from a higher
concentration to a lower concentration through a semi permeable
membrane)
Semi permeable –any covering which would allow the passage of
certain substances.
The water is higher in the soil than in the root hair. Therefore water
from the soil moves into the root hair. Once the root hair gets filled
the water moves from the root hair into the cortex. Water from all
the cells in the cortex move into the xylem.
In the xylem tissue roots, stems and leaves are interconnected to
form a continuous system of water conduction to reach all parts of
the plants. There is steady movement of water into root xylem
creating a column of water that is steadily pushed upwards. This
pressure moves water over the heights from xylem in plants.
Xylem is present in the centre and unidirectional.
Xylem consists of tracheids, xylem parenchyma, xylem fibres and
vessels. All cells are dead except xylem parenchyma
Transportation of food in plants
Food is produced in leaves through photosynthesis. This
photosynthesis produces carbohydrates in soluble form. From the
leaves the food will be transported to roots and stems downwards and
to the upwards to the leaves and other parts through the phloem. This
transport of soluble products of photosynthesis to various parts of the
plant is called translocation.
Translocation takes place in sieve tubes with the help of companion
cells bidirectionally.
Food is stored as energy in the form of starch in the roots –tubers.
Tubers are roots in which energy is stored as starch. Ex: carrot, potato.
Energy from the food is stored in some stems. Ex: ginger, turmeric.
Phloem is present in the edges.
The translocation in phloem is achieved by utilising energy. Materials
like sucrose are transferred into phloem tissue using energy from ATP.
This increases osmotic pressure in the tissues. Therefore water moves
into phloem. This pressure moves the materials in the phloem to other
tissues which have low pressure.
In this way phloem transports food, amino acids and other substances
according to the plant’s need.
This transportation is called active transport as it utilises energy for
transportation.
The conducting cells in phloem are sieve tubes. They also have
companion cells, phloem parenchyma and phloem fibres. All cells are
living cells except phloem fibres.
Transpiration
Loss of water in the form of vapour through the aerial parts of the
plant (stomata present in the leaves) is called transpiration.
Transpirational pull: transpiration creates a suction which pulls up
water from the xylem cells of roots
Importance of transpiration
 Helps in absorption and upward movement of water and
dissolved minerals from roots to leaves
 Helps in temperature regulation
Diurnal variation
Day- stomata is open. Transpirational pull is the major driving force
in water movement in xylem.
Night – root pressure is important factor in water transport.
Excretion
The biological process of removal of harmful metabolic wastes from
the body is called excretion
Cells of different organisms do different kinds of work and thus
generate different kinds of waste.
Metabolism –the sum of all chemical reactions inside a cell.
Excretion in unicellular organisms
Excretion is unicellular organisms are simple. Diffusion and osmosis
are the two basic processes at cellular level. They help cells release or
exchange substances within the surrounding. Every unicellular
organism thus throws out the waste through osmosis and diffusion.
Excretion in plants
They are multicellular with simple organisation. They have ability to
remove waste near the site where the waste is produced.
 Oxygen which is released as a waste during photosynthesis is
directly released out by the stomata
 Other wastes such as resins, gums are accumulated in dead
tissues such as the bark of the tree or the old xylem. Apart from
this plants also store their cellular waste in the vacuole.
 They also accumulate wastes in the leaves that are about to die
and fall down.
 Excess water is removed by transpiration.
 Plants also excrete some waste into the soil.
Human excretory system
Urea is the most toxic metabolic waste produced in a large quantity.
Most of the metabolic reactions in our body include proteins or amino
acids. The common waste produced by these metabolic reactions is
ammonia. We can neither eliminate ammonia immediately nor store it.
The liver absorbs the ammonia (more toxic waste) and converts it into
urea (less toxic waste). The urea is then released into the blood.
Structure of the kidney
Kidney: Kidneys are bean shaped organs. They are located on either
sides of the vertebral column at the back. This is why people suffering
from kidney problems suffer from lower back pain. The central part
of the inner side of the kidney is called hilum. Any substance entering
or leaving the kidney passes through hilum. Blood vessels nerves and
urether are connected to the kidney through the hilum.
Blood vessels in the kidney
There are 2 vessels in the kidney. The renal artery carried pure blood
that contains urea to the kidney. The kidney will filter out urea and
passes out pure blood. The renal vein carries pure blood without urea
out of the kidney
Internal structure
Internally kidney is divided into 3 parts. The outermost region is
called cortex. The middle region is called medulla. Medulla consists
of multiple triangular structures called renal pyramid. The inner most
region is called pelvis which directly connects to the urether. Blood
travels 60 times a day through the kidney.
Nephrons
There are very tiny mysterious filters known as nephrons in the
kidney. There are roughly 1 million nephrons in each kidney. If we
place all the nephrons horizontally they will approximately cover
about 16 kilometres. Nephrons are also known as kidney tubules.
Bowman’s capsule
Parts: Glomerulus, PCT, DCT, Henle’s loop and collective duct.
It is a cup shaped organ consisting of a number of blood capillaries
called glomerulus. The tubule near the Bowman’s capsule is the
proximal convoluted tubule and that far from the Bowman’s capsule
is called distal convoluted tubule. The u- shaped loop is called
Henle’s loop and connects both PCT and DCT. Lastly there is a
collective duct that collects waste products.
Working of nephron
Our kidney filters out urea continuously. They collect urea along with
water and some salts which together forms urine.
The blood with water salts nitrogenous wastes glucose amino acids
etc., enters the nephron through the afferent artery. The filtration of
blood takes place due to the pressure in the glomerulus and passes
through the efferent artery. As a result salts, urea, amino acids, and
large amount of water are filtered out.
The filtrate moves down to the tubular part of the nephron where
major parts of water, glucose and salts are selectively reabsorbed and
thus urine becomes concentrated.
Some substances may be secreted in the final secretion tubule. This
final filtrate is now collected by the collecting duct of the kidney.
From each kidney arises a narrow tube caller ureter whic connects the
kidney and urinary bladder. The 2 tubes are about 80 cm in length and
carry urine downwards and open to the urinary bladder.
Each ureter opens into a muscular urinary bladder which opens to the
outside of the body by a tube called urethra. The urinary bladder can
hold about 0.5l of urine until its release. The urge to discharge urine is
under nervous control
Composition of urine and its regulation
Urine is the translucent, pale yellow and slightly stinky substances
that is excreted out of our body every few hours.
Physical properties
 It is clear and pale yellow in colour due to presence of
urochrome pigment. The intensity of yellow colour changes
with the amount of water we drink.
 Urine is slightly acidic in nature with pH of 6
 Its relative density is 1.03 to 1.04.
 Urine is odourless but can have a pungent smell of ammonia
Any change in the physical properties is a sign of abnormality.
Composition of urine
96 % water
2% ions like Na,
2% urea
K, salts ammonia etc.,
Average urine output –1 –1.5l per day
Consumption of more water: intensity of yellow colour will be less
Consumption of less water: intensity of yellow colour will be more
Artificial kidney (haemodialysis)
If our kidney get affected there will be a problem in filtering out toxic
wastes from our blood. In case of a kidney failure an artificial kidney
can be used. Artificial kidney is a device used to remove nitrogenous
waste products from the blood through dialysis.
Working of artificial kidney
Artificial kidneys contain a number of semi permeable lining
suspended in a tank filled with dialysing fluid with the same osmotic
pressure as that of blood. The blood contains nitrogenous wastes
whereas the dialysing fluid does not.
The patient’s blood is passed through these tubes. During this passage
the waste products from the blood diffuses into the dialysing fluid.
The purified blood is pumped back to the patient’s body. This is in
similar to the function of the kidney but selective re-absorption
doesn’t take place. In a healthy adult the volume of initial filtrate is
about 180l. But the volume excreted is 1 –2 litre a day due to selective
re-absorption.