Animal nutrition
Nutrition: Taking in nutrients to be used for energy, growth and development, it include
 Organic substances: carbohydrates, proteins, fats, vitamins, fibre.
 Inorganic substances: Water, minerals.
Balanced diet: Provides necessary nutrients in correct amounts and proportions to maintain health.
Energy requirements depend on
1. Age:
 Babies need calcium and vitamin D for bones and teeth.
 At puberty child need glucose for energy and proteins for growth.
 Old people eat less as metabolism slow down, need protein for repair.
2. Sex :
 Males need:
 More energy due to more physical work, and larger body.
 More proteins to build more muscles and later puberty.
 Females need
 More iron to replace hemoglobin lost in menstruation.
 Pregnant females need more
 Calcium for bone and teeth formation and Iron for new baby RBCs.
 Proteins for growing fetus.
 Breast feeding female needs energy to move and protein for milk production.
3. Activity: heavy workers as miners need more energy than light workers.
Malnutrition: caused by not eating a balanced diet.
1. Obesity: being very fat due to taking energy more than that used up, they are prone to
 Heart disease, diabetes, and strokes.
 Strain on muscles and joints as knee joint and psychological effect.
Control:
 Balanced meals with more roughage and less fats and carbohydrate.
 Regular exercise to increase energy use.
2. Kwashiorkor: babies are underweight with swollen abdomen due to lack of protein and lot of
carbohydrates due to poverty. If put onto high protein diet they grow normally again.
3. Marasmus: Child is underweight with muscle wasting and wrinkled skin, prone to, infections .due
to shortage of protein and energy in diet in undeveloped countries e.g. due to drought, wars.
4. Constipation: due to lack of fiber (roughage) , cellulose cell wall that is undigested. Found in.
Fruits and vegetables and whole meal bread which contains bran. (outer husk of cereal grains)
Function:
1. Prevent constipation: it retain water and forms a bulk in the large intestine which
stimulates peristalsis. Lack of fiber cause constipation due to less peristalsis.
2. Prevent obesity: sense of stomach fullness and replaces fat and sugar in diet.
5. Starvation: no enough food to feed all people who can die.
6. Scurvy see latter, and coronary heart disease: in transport chapter
1
Human nutrition
Human teeth
Types:
Incisors
Canines
Sharp edges at the front.
Pointed, cone shaped.
For biting off pieces of food At either side of incisors
Cutting and tearing food.
Premolars & molars
Wide surface
Premolars 2 cusps, 2 roots
Molars 4 cusps, more than 2 roots
Grinding food during chewing.
Cusps slide against each other for grinding and crushing food
Molars at the back are called wisdom teeth they grow at later age.
Structure:
Crown: part above the gum and root embedded in gum.
Enamel: cover crown, hardest substance in the body but dissolved by acids.
Dentine: under the enamel, have channels containing living cytoplasm.
Pulp cavity: contain nerves for sensation, blood vessels to give dentine O2 &nutrients.
Cement: cover the root and anchor the teeth to the jaw.
Fibers: from cement to jaw bone, it allows teeth to move slightly when biting or chewing.
Dental decay (caries): causes
1. Poor dental hygiene.
2. Plaque containing bacteria, saliva and sugar form on and in between teeth & next to gums.
3. Bacteria in plaque respire sugar changing it into acid.
4. Acid dissolve enamel and dentine forming cavity & expose nerves causing tooth ache and abscess.
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Human nutrition
Prevention:
1) Changing diet:
 Avoid eating much refined sugar, better with meals.
 Calcium, vitamin D, strengthens enamel and dentine.
2) Regular brushing after meals, and before going bed for 3-4 minutes.
 Removes plaque, if left to harden it form tarter not removed by brushing.
 Toothpaste: has
1. Fluoride: hardens enamel in children so teeth more resistant to decay.
2. Alkaline (pH 8.5) neutralizes acids in the mouth.
3. Anti-bacterial agent which kills bacteria.
3) Use dental floss, and visit dentist regularly.,
4) Adding fluoride to drinking water.
Lower part of the tooth softens before upper part with acid:
 Crown is covered by enamel, but root doesn’t, covered with cement and dentine.
 Enamel is harder than cement and dentine.
Alimentary canal
Muscular tube from mouth to anus.
Sphincters: rings of muscle which contract to keep food in one part for certain time.
Peristalsis: rhythmic wave of contraction and relaxation of muscle in its wall to push food forwards.
Duodenum
Ileum
Colon
All digestive juices contain water and mucus from goblet cells
 Mucus: lubricant, stick food into bolus for and protect wall of alimentary canal from enzymes.
 Water:
 Solvent for dissolving food to taste it and for easier chewing, swallowing and egestion.
 Hydrolysis in chemical digestion.
 For enzyme activity.
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Human nutrition
Ingestion: taking food and drink into the body through mouth.
Digestion:
 Mechanical digestion: breakdown of food into smaller pieces by teeth without chemical
change to food molecules to increase surface area for enzyme action and for easy swallowing.
 Chemical digestion: breakdown of large insoluble molecules into small soluble ones that can be
absorbed by the blood by breakdown of molecular bonds by enzymes.
1. Mouth and teeth are: responsible for:
 Ingestion using teeth lips and tongue.
 Chewing:
 Grind food to increase its surface area so easier for enzymes to work on it.
 Mixes food with saliva to form a bolus and dissolve soluble part of food.
 Saliva made in three pairs of salivary glands, made of water , mucus and salivary amylase
 Begin starch digestion to maltose as food stays in mouth for short time.
 Its action stops in the stomach as pH is acidic so enzyme is denatured.
2. Esophagus: behind the trachea .Food is pushed down the esophagus by peristalsis.
 Behind bolus: circular muscles contract, longitudinal relax, pushing food forward.
 In front bolus: circular muscles relax, longitudinal contract, making lumen wider.
 Circular and longitudinal muscles work antagonistically
During swallowing
 Soft palate closes the nasal cavity.
 Epiglottis (cartilage) closes the trachea.
1.
2.
3.
4.
3. Stomach:
 Under the diaphragm to collect food, it has strong muscular wall
 Pits contain cells that produce pepsin, others produce HCL and Goblet cells secrete mucus.
1) Mechanical digestion in stomach: contraction and relaxation of muscles in stomach wall
Churns food and mixes it with enzymes forming semi liquid chyme.
2) Chemical digestion: gastric juice stomach secretes most water in a digestive juice.
 Pepsin: a protease which break proteins to amino acids.
 HCL
 Give optimum pH for pepsin (pH2).
 Kill bacteria in food by denaturing their enzymes.
After one or two hours, sphincter relax, chyme pass into the duodenum.
Stomach is protected from pepsin and HCL by:
1) Pepsin is secreted as inactive pepsinogen, activated by HCL.
2) Mucus form a coat on stomach lining, protect from enzymes and HCL.
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Human nutrition
4. Small intestine: between stomach and colon, 5 m long.
 Part near stomach is duodenum.
 Part near the colon is ileum.
The duodenum: food is mixed with bile and Pancreatic juice.
A. Bile: greenish yellow fluid, contain no enzymes ,made in liver, stored in gall bladder and
Flows to the duodenum through bile duct, consist of:
 Bile pigments: from break down of old RBCS hemoglobin in liver and excreted with faeces.
 Bile salts :for
 Emulsification of fat into droplets: increase surface area for action of lipase.
 Provide alkaline pH for pancreatic enzyme and neutralizes acidity from stomach.
B. Pancreatic juice: made in pancrease flows to duodenum by pancreatic duct . Consist of:
 Pancreatic amylase break starch to maltose
 Pancreatic protease trypsin which break proteins to amino acids.
 Pancreatic lipase; break emulsified fat into fatty acids and glycerol.
 Sodium hydrogen carbonate : it is alkaline
 Give optimum pH for enzymes in small intestine
 Neutralize gastric HCL.
Gall stones: block bile ducts and stop bile flowing through it into the duodenum, so no bile salts,
less emulsification of fat and less surface area and so digestion of fat takes longer.
End products of digestion:
Cells covering villi make enzymes which stay on cell surface and complete digestion of food.
1. Maltase breaks maltose to glucose.
2. Sucrase breaks sucrose to glucose and fructose.
3. Lactase breaks lactose to glucose and galactose.
4. Protease: finish breakdown of proteins and polypeptides to amino acids.
5. Lipase: break emulsified fat to fatty acids and glycerol.
They are small, soluble and can be absorbed through villi by diffusion.
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Human nutrition
Absorption
Movement of small food molecules and ions through wall of small intestine into blood or lymph.
Adaptation of small intestine for absorption:
 Long: 5 m, gives time for digestion and absorption of food as it slowly passes through.
 Intestinal villi : projections 1 mm long , on inner wall of duodenum and ileum
1. Large number which increase surface area for absorption.
2. Villous epithelium:
 One cell thick: short distance for diffusion to capillaries and lacteals.
 Cells have microvilli which increase surface area for faster absorption.
 Cells have many mitochondria to provide energy for active uptake.
 Goblet cells secrete mucous: protect from enzymes, acids, toxins, physical damage
3. Blood capillaries: transport simple sugars, amino acids, water, minerals, vitamins and some fat
to the liver through hepatic portal vein, then round the body.
4. Lacteals: absorb fats and fat soluble vitamins into the lymphatic system.
5. Muscles at the base empty the lacteals and move villi and help to increase concentration
gradient and absorption.
Effects
1.
2.
3.
of a reduction in absorption of nutrients:
Weight loss
Lack of energy
Malnutrition
 Anaemia → iron , vitamin B12
 Kwashiorkor → protein and
 Marasmus → all nutrients
 Scurvy → vitamin C
 Night blindness →vitamin A
Assimilation
Movement of digested food molecules into body cells and used, becoming part of cells.
Nutrients are taken to the liver by hepatic portal vein
 Some are broken down, some are converted into other substances, and some stored.
 Remainder taken to other parts of the body where they may become part of a cell.
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Human nutrition
Large intestine (colon, rectum):
Wider than duodenum and ileum and has large surface area for
 Absorption of water and salts from food to the blood.
 Store faeces until egested through the anus, have no role in digestion.
Importance of water absorption in the alimentary canal
Prevent diarrhoea and loss of water and ions (dehydration).
 5-10 dm3 / day absorbed from the small intestine.
 0.3-0.5 dm3 /day absorbed from the colon.
Egestion
Passing out food that is not digested or absorbed through anus as faeces.
It is not an excretion because faeces are not a waste product of metabolism.
Faeces are composed of:
 Undigested food as fibre, mucus and bile.
 Bacteria and some dead cells from wall of alimentary canal.
Diarrhoea
Loss of watery faeces if water is not reabsorbed.
Dangers of severe diarrhea:
1. Decrease in plasma volume and dehydration.
2. Loss of minerals and vitamins.
3. Increase in blood concentration and loss of water from cells by osmosis
4. Kidney failure coma and death.
Treatment:
 Give oral rehydration therapy : mixture of salt , sugar and water
 Antibiotics.
Cholera:
1. Cholera bacterium is ingested in contaminated water or food from infected person
2. It breeds in the small intestine.
3. Attach to the wall and release a toxin which stimulates cells to secrete chloride ions.
4. Chloride ions increase concentration of the fluid in the lumen.
5. Water to move by osmosis from vessels in the walls into the gut lumen.
6. Lot of water is lost, causing diarrhea dehydration and loss of salts from blood.
7. If enough fluids is given to replace losses, cholera will recover
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Human nutrition
Vitamins: organic substances needed in tiny amounts to perform specific function
1. Vitamin C ( ascorbic acid ) water soluble
Properties:
 Destroyed by air or if food is canned so should be supplied daily, not stored
 Refrigeration keeps vitamin C content of food.
Source: citrus fruits lemon, oranges & raw fresh vegetables: cabbage, tomatoes, and kiwi.
Function:
 Make collagen protein in skin, gums, and blood vessels.
 Keep good tissue repair.
 Protect cells from ageing.
 Increase immunity and help iron absorption.
Deficiency
Scurvy: disease of sailors (no fresh vegetables)
 Bleeding gums, bruising.
 Pain in joints and muscles and poor healing of wounds and anemia.
Testing for vitamin C: DCPIP test.
DCPIP is a blue liquid and vitamin C causes DCPIP to lose this colour.
1. Measure 2 cm' of DCPIP into a clean test tube.
2. Use a dropper pipette to add lemon juice to the DCPIP.
3. Count how many drops needed for DCPIP to lose its colour.
4. The less number of drops for DCPIP to lose colour, the more vitamin C in this liquid
2. Vitamin D , fat soluble , stored in the body
Source: eggs and fish and liver or made under the skin on exposure to sun.
Function: Help absorption & deposition of calcium in bone & teeth making them strong.
Deficiency
 Rickets: bones become soft and deformed.
 Muscle cramps and stunted growth and fatigue.
Minerals: Inorganic substances needed in small amounts for normal body functions e.g. Ca, K, Na.
1. Iron (Fe)
Source: Red meat, liver, eggs and green leafy vegetables
Function Synthesis of hemoglobin in RBCs this carries oxygen.
Deficiency: Anemia: decrease Hb, and oxygen carrying capacity of blood, causing
 Pale appearance
 Headache, fatigue and shortness of breath on mild effort.
2. Calcium (Ca)
Source: Milk, cheese, and eggs and fish.
Function
 Strengthen bones and teeth enamel.
 Involved in blood clotting and muscle contraction.
Deficiency:
 Brittle bone and teeth more prone to decay.
 Poor blood clotting and uncontrolled muscle contraction
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Human nutrition
9 Human nutrition