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Animal Physiology. Mammalian Nutrition. Mr G R Davidson. 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. Composition of Food.

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Animal Physiology


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animal physiology

Animal Physiology

Mammalian Nutrition

Mr G R Davidson

composition of food
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

Mr G Davidson

composition of food3
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

Mr G Davidson

carbohydrates

Glucose

Carbohydrates
  • Carbohydrates provide us with energy for our normal activities.
  • They consist of long chains of glucose molecules.

Mr G Davidson

slide5

Fatty acid

Fatty acid

Glycerol

Fatty acid

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.

Mr G Davidson

proteins

Amino acid

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.

Mr G Davidson

vitamins
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.

Mr G Davidson

vitamins8
Vitamins

Mr G Davidson

minerals
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.

Mr G Davidson

minerals10
Minerals

Mr G Davidson

alimentary canal
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.

Mr G Davidson

alimentary canal12

Mouth

Salivary gland

Oesophagus

Stomach

Liver

Pancreas

Gall bladder

Large intestine

Small intestine

Rectum

Anus

Alimentary Canal

Mr G Davidson

the mouth
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 salivaryamylase, to digest starch.

Mr G Davidson

the mouth14
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.

Mr G Davidson

peristalsis

Muscles contract here

Food moves this way

Muscles relax here

Peristalsis

Mr G Davidson

stomach
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.

Mr G Davidson

stomach17
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.

Mr G Davidson

gastric gland

Mucus and gastric juices secreted into the stomach

Mucus-secreting cell

Acid-secreting cell

Enzyme-secreting cell

Gastric Gland

Mr G Davidson

gastric glands
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.

Mr G Davidson

gastric glands20
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.

Mr G Davidson

gastric glands21
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.

Mr G Davidson

stomach22
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.

Mr G Davidson

small intestine
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.

Mr G Davidson

small intestine24
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)

Mr G Davidson

a villus

Thin wall

Blood capillary

Lacteal

A Villus

Mr G Davidson

absorption
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.

Mr G Davidson

absorption27
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.

Mr G Davidson

absorption28
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.

Mr G Davidson

absorption29
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.

Mr G Davidson

large intestine
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.

Mr G Davidson