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Animal Nutrition

Human Digestion

Harrick Tu

on 8 December 2010

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Transcript of Animal Nutrition

Animal Nutrition Mouth Oesophagus St mach Small Intestine Large Intest ne Liver Pancreas Rectum an Anus Learning Outcomes (a) describe the functions of main regions of the alimentary canal and the associated organs: stomach, duodenum, pancreas, gall bladder, liver in relation to ingestion, digestion, absorption, assimilation and egestion of food, as appropriate

(b) describe digestion in the alimentary canal, the functions of a typical amylase, protease and lipase, listing the substrate and end-products Key terms Feeding:
the intake of food into the body

The process whereby large food molecules are broken down into soluble and diffusible molecules that can be absorbed into the body cells

The process whereby digested food materials are taken into the body cells

The process whereby some of the absorbed food materials are converted into new protoplasm or used to provide energy Digestion the mechanical breakdown of food into small particles which increases the surface area to volume ratio so that digestive enzymes can act on the food more efficiently

achieved by teeth, tongue, stomach walls Physical Digestion Chemical Digestion enzymatic hydrolysis of large food molecules such as proteins, starch and fats, into small soluble molecules, which can be absorbed

achieved by digestive enzymes in the mouth, stomach, duodenum and ileum Secretion of saliva makes it easier for food to travel to the gut

Contains salivary amylase which digests starch to maltose

Chewing of food breaks it up just like the hammering action

Increases surface area to volume ratio improve enzyme action

Smaller pieces are easier to swallow Peristalsis When the circular muscles contract, the longitudinal muscles relax the diameter of the gut decreases (lumen constricts) food is squeezed forward from original position.

When the circular muscles relax, the longitudinal muscles contract the diameter of the gut increases (lumen expands) food enters the lumen created. Gastric Juice HCl Acid Proteases Stops the action of salivary amylase with its low pH

Kills certain potentially harmful microorganisms present

Provides an acidic medium for the action of gastric enzymes Stomach is the main site of protein digestion

Class of enzymes which digest proteins are called proteases

Action of pepsin = proteins to polypeptides Consists of the duodenum, jejunum and ileum

Main site of nutrient absorption

Digested foods (simple sugars, amino acids and fatty acids and glycerol) are absorbed by the villi of the small intestine, especially of the jejunum and ileum.
Water and mineral salts are absorbed from undigested food material. Most of the water is absorbed by the ileum. production of bile
storage of iron
protein synthesis
deamination of amino acids
detoxification Liver is the site of carbohydrate conversion insulin converts glucose to glycogen when blood glucose level is high

glucagon converts glycogen to glucose when blood glucose level is low Secretes pancreatic juice, which is alkaline

Pancreatic juice contains 3 enzymes
1. pancreatic amylase
digests starch to maltose
2. trypsin
digests protein to polypeptides
3. pancreatic lipase
digests fats to fatty acids + glycerol Pancreas secretes the hormones insulin and glucagon Absorbtion of water and mineral salts from undigested materials
Undigested material include dietary fibre (cellulose) Large
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