IGCSE>SECTION-2>6.3 ANIMAL NUTRITION
Class presentations
|
|
|
|
NUTRITION
Define nutrition as taking in of nutrients which are organic substances and mineral ions, containing raw materials or energy for growth and tissue repair, absorbing and assimilating them.
It includes following stages:
The food we eat is made up of large compounds and therefore these have to be broken down into simple and soluble form so that our bodies cells can use them. |
THE DIGESTIVE SYSTEM- ALIMENTARY CANAL PARTS
Explanation of human digestive system through a model.
|
Draw the diagram of human digestive system
|
1. MOUTH AND ORAL CAVITY
|
DENTITION : Refer PPT
2. PHARYNX
It is a common passageway for air and food.
It participates in swallowing It has
|
3. OESOPHAGUS
4. STOMACH
|
5. SMALL INTESTINE
6. LARGE INTESTINE
Animation: Organs of digestion |
Higher Tier : Appendix |
PHYSIOLOGY OF DIGESTION (FUNCTIONING OF DIGESTIVE SYSTEM)
DIGESTION
Digestion is a series of physical and chemical changes by which the complex food is converted into simple and absorbable form.
- Physical digestion: Physical digestion involves breaking large pieces of food into smaller pieces. It involves chewing, mastication, peristalsis, churning, emulsification.
- Chemical digestion: Chemical digestion
involves breaking down large, insoluble molecules into small, soluble ones. It involves enzymes for breaking down the food nutrients.
1. Digestion in oral cavity
Mechanical digestion :
- In the mouth the food is chewed by teeth and mixed with saliva.
- The chewing process breaks the food into pieces which can be swallowed and it also increases the surface area for the enzymes to work on later.
- Salivary gland produced a digestive juice called saliva.
- Saliva contains one enzyme, salivary amylase.
- This enzyme acts on starch and begins to break it down into maltose.
- Medium of digestion is alkaline.
PROCESS OF SWALLOWING
Process of swallowing.
Answer: The airways are cut off. The soft palate closes the nasal cavity; the tongue, the epiglottis and muscles in the glottis, seal the top of the windpipe. |
2. Digestion in stomach
Mechanical digestion:
|
Digestion in stomach: http://www.youtube.com/watch?v=URHBBE3RKEs
|
3. Digestion in small intestine
- The first part of intestine i.e. duodenum receives following secretions.
- Pancreatic juice from pancreas
- Bile juice from liver
PANCREAS
|
LIVER
|
SMALL INTESTINE (ILEUM)
- As well as receiving enzymes made in the pancreas, the small intestine makes some enzymes itself.
- Cells covering the villi make enzymes.
- These enzymes complete the digestion of food.
- Examples:
- Carbohydrase
- Maltase breaks down maltose to glucose.
- Sucrase breaks down sucrose to glucose and fructose.
- Lactase breaks down lactose to glucose and galactose.
- Proteases: Proteases digest polypeptides to amino acids.
- Lipase: Lipase completes the breakdown of fats to fatty acids and glycerol.
4. Digestion in large intestine
- The material passing into the large intestine consists of water with undigested matter, largely cellulose and vegetable fibres (roughage), mucus and dead cells from the lining of the alimentary canal.
- The large intestine secretes no enzyme but the bacteria in the colon digests part of the fibres to form fatty acids which the colon can absorb.
ABSORPTION.
- Enzymes in the gut convert large insoluble molecules to small, soluble molecules. These digested food molecules are transported across the lining of the gut into the blood or lymph by a process called absorption.
- Nearly all the absorption of digested food takes place in ileum region of small intestine.............Why?
- The ileum region has villi (Sing. villus) which are the finger like projections of the epithelium linings, increases surface area for absorption.
VILLI AND MICROVILLI
Structural features of the small intestine: Video: |
PROCESSES INVOLVED IN ABSORPTION OF DIGESTED FOOD
- Absorption of the products of digestion and other dietary items is not just a matter of simple diffusion, except perhaps for alcohols and sometimes water.
- Amino acids, sugar and salts are almost taken up by active transport.
- Water soluble vitamins absorb by diffusion.
- The mineral salts absorbed by active transport.
MOST ABSORBED FOOD GOES STRAIGHT TO THE LIVER........HOW and WHY..?
Role of the hepatic portal vein in the transport of absorbed nutrients.
Explain how the liver is involved in regulating the composition of the blood and in protecting the body against toxic substances.
|
ASSIMILATION
Assimilation as movement of digested food molecules into the cells of the body where they are used, becoming part of the body cells.
|
STORAGE OF EXCESS FOOD.
If more food is taken in than the body needs for energy or for building tissues, such as bone or muscle, it is stored in one of the following way.
DEAMINATION
Deamination :
|
ANIMATION: Deamination
|
Summary of digestive system parts and their function
ANIMAL NUTRITION: WORKSHEET