1. Animal Physiology
Mammalian Nutrition
Mr G R Davidson

2. Composition of Food
Humans are adapted for feeding and digestion so that food molecules can reach the body cells.
The main groups of food we eat are:
Carbohydrates
Fats
Proteins
Vitamins
Minerals
Sunday, September 23, 2018
Mr G Davidson

3. Composition of Food
Carbohydrates contain the elements carbon, hydrogen & oxygen
Fats contain the elements carbon, hydrogen & oxygen
Proteins contain the elements carbon, hydrogen, oxygen & nitrogen
Sunday, September 23, 2018
Mr G Davidson

4. Carbohydrates
Carbohydrates provide us with energy for our normal activities.
They consist of long chains of glucose molecules.
Glucose
Sunday, September 23, 2018
Mr G Davidson

5. Fats
Fats release some energy for our use if required while the rest is stored in adipose tissue beneath the skin.
This is used as insulation.
Each fat is made up of a glycerol molecule joined to 3 fatty acid molecules.
Glycerol
Fatty acid
Sunday, September 23, 2018
Mr G Davidson

6. Proteins
Our body requires protein to build it up and for growth and repairing damaged tissue.
Proteins are built up from long chains of amino acids.
There are only about 20 different amino acids.
Amino acid
Sunday, September 23, 2018
Mr G Davidson

7. Vitamins Vitamins are required for good health.
They do not provide energy.
They act as coenzymes which are required in the various biochemical activities within cells.
Some examples of vitamins, their source and the deficiency disease are given in the table.
Sunday, September 23, 2018
Mr G Davidson

8. Reproductive Disorders
Vitamins
Vitamin
Source
Deficiency Disease A
Milk, fresh veg.
Night Blindness
B1 (Thiamine)
Cereal grains
Beri beri
B3 (Niacin)
Cereal, lean meat
Pellagra
C (Ascorbic acid)
Citrus fruits
Scurvy D
Liver, fish, milk
Rickets E
Wheat germ
Reproductive Disorders K
Green veg.
Blood doesn’t clot
Sunday, September 23, 2018
Mr G Davidson

9. Minerals
Minerals are chemical elements which are required in very small quantities.
They have a whole variety of functions, some of which are shown in the following table.
Sunday, September 23, 2018
Mr G Davidson

10. Haemoglobin in Red Blood Cells Contraction of muscles
Minerals
Mineral
Required For:
Iron
Haemoglobin in Red Blood Cells
Iodine
Thyroxine
Sodium
All cells
Calcium
Healthy teeth & bones
Potassium
Contraction of muscles
Sunday, September 23, 2018
Mr G Davidson

11. Alimentary Canal
The food we eat passes from the mouth to the anus through the “alimentary canal” or gut.
As food passes through this canal it is processed in a number of ways and by a number of organs.
Other organs, such as the salivary glands, liver and gall bladder are attached to the alimentary canal by ducts, and these are called associated organs.
Sunday, September 23, 2018
Mr G Davidson

12. Alimentary Canal Mouth Salivary gland Oesophagus Stomach Liver
Gall bladder
Pancreas
Large intestine
Small intestine
Rectum
Anus
Sunday, September 23, 2018
Mr G Davidson

13. The Mouth
The food is physically broken down into manageable sizes by the teeth.
It is mixed with a fluid called saliva, which contains the enzyme salivary amylase, to digest starch.
Sunday, September 23, 2018
Mr G Davidson

14. The Mouth
Saliva also contains mucus which makes the food easier to swallow.
The food is then moved through the gullet (oesophagus) to the stomach by a process called peristalsis.
Sunday, September 23, 2018
Mr G Davidson

15. Peristalsis Muscles contract here Food moves this way
Muscles relax here
Sunday, September 23, 2018
Mr G Davidson

16. Stomach The stomach is a muscular bag with a valve at either end.
The CARDIAC sphincter at the top allows food in.
The PYLORIC sphincter at the bottom allows food to leave.
Sunday, September 23, 2018
Mr G Davidson

17. Stomach
The stomach wall produces digestive juices from gastric glands which secrete mucus, acid and enzymes.
For digestion to work properly the food must be well mixed with these juices.
The stomach muscles contract and relax to mix up the juices and food.
Sunday, September 23, 2018
Mr G Davidson

18. Gastric Gland Mucus-secreting cell Acid-secreting cell
Mucus and gastric juices secreted into the stomach
Mucus-secreting cell
Acid-secreting cell
Enzyme-secreting cell
Sunday, September 23, 2018
Mr G Davidson

19. Gastric Glands
The mucus-secreting cells release a slimy mucus which sticks to the wall of the stomach and protects it from damage by the strong digestive enzymes.
Sunday, September 23, 2018
Mr G Davidson

20. Gastric Glands
The acid-secreting cells release hydrochloric acid which has 2 functions:
It creates conditions needed to produce active pepsin.
It provides the optimum pH for the enzymes to work.
Sunday, September 23, 2018
Mr G Davidson

21. Gastric Glands
The enzyme-secreting cells release an inactive enzyme called pepsinogen.
Once the pepsinogen comes in contact with the acid, it is converted to an active enzyme called pepsin.
The pepsin can now break down proteins in the stomach to peptides, which will later be broken down further into amino acids.
Sunday, September 23, 2018
Mr G Davidson

22. Stomach
The longitudinal muscles contract to make the stomach shorter and fatter.
The circular muscles contract to squeeze the stomach.
Once the food has been in the stomach for a while, it is released slowly, small drops at a time into the small intestine.
Sunday, September 23, 2018
Mr G Davidson

23. Small Intestine
The food enters the small intestine from the stomach and is moved along by peristalsis.
A number of digestive enzymes break down the large insoluble food molecules to small soluble food molecules before they are absorbed out of the intestine.
Sunday, September 23, 2018
Mr G Davidson

24. Small Intestine
The small intestine’s function is to absorb soluble food molecules and it is well suited to this job in a number of ways.
It is very long (About 6m). The inner surface is folded into thousands of finger-like villi.
The lining of each villus is very thin. (Only one cell thick)
Each villus has a network of vessels for absorbing the food, both blood capillaries and lymphatic vessels. (Lacteals)
Sunday, September 23, 2018
Mr G Davidson

25. A Villus Thin wall Blood capillary Lacteal Sunday, September 23, 2018
Mr G Davidson

26. Absorption
The glucose and the amino acids are absorbed into the blood capillaries.
These tiny blood capillaries all join up to form the hepatic portal vein and transport the absorbed food to the liver.
Sunday, September 23, 2018
Mr G Davidson

27. Absorption
The liver stores most of the glucose as glycogen until it is required, but some glucose remains in the blood.
The amino acids are used in the body for growth and repair, but if there are any excess amino acids, these are broken down by the liver into urea.
Sunday, September 23, 2018
Mr G Davidson

28. Absorption
This is later removed by the kidneys and released in the urine.
Vitamins and minerals are transported to cells where they have special functions which help to keep the body healthy.
Any excess vitamins and minerals are either stored or excreted.
Sunday, September 23, 2018
Mr G Davidson

29. Absorption
Fats and fatty acids are absorbed by the lacteals which contain a fluid called lymph.
This lymph is transported in the lymph vessels which will eventually drain into the blood system.
The products of fat digestion can be used for energy, as insulation or simply stored until required.
Sunday, September 23, 2018
Mr G Davidson

30. Large Intestine
When the food eventually reaches the large intestine (Colon), it is mainly water and indigestible waste materials.
The function of the large intestine is to absorb water back into the bloodstream leaving a semi-solid called faeces.
The faeces is passed into the rectum (bowel) where it is stored until it is eventually eliminated through the anus.
Sunday, September 23, 2018
Mr G Davidson