You have to describe the functions of the regions you identified in part 1 in the digestive system.
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Mouth ingests food.
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Salivary glands produce saliva. Saliva is a mixture of water, mucus, salivary amylase (which converts starch to maltose; digestion). Saliva (pH7) moistens and softens food.
Oesophagus: Its function is to carry food from mouth to stomach by Peristalsis.
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Stomach: Only Protein Digestion occurs here.
- Stores food temporarily
- Stomach muscles churn and mix food (also by peristalsis) with gastric juice to form chyme. Gastric juice contains hydrochloric acid (HCl) and enzymes like pepsin.
-HCl is very acidic (pH2), thus it kills bacteria and other microorganisms, as well as stops the action of salivary amylase.
-Provides acidic medium for gastric enzymes to work. Pepsin converts protein to peptides.
Small Intestine is the main site of digestion of food and absorption of nutrients.
Villi lining the small intestine absorbs all nutrients that have been processed throughout the body.
Subdivided into duodenum, and ileum
In the small intestine, chyme stimulates
1. Pancreas to secrete pancreatic juice
2. Gall bladder to secrete bile
3.Intestinal glands to secrete intestinal juice
Pancreatic and intestinal juice contains many digestive enzymes. Bile does not contain enzymes. Bile emulsifies fats, increasing the surface area for lipase action.
Duodenum
- Starch---->maltose by salivary amylase.
- Protein-----> polypeptides by proteases
-Fats-----> fatty acids + glycerol by lipase.
Ileum
- Maltose---->glucose by maltase
- Polypeptides---->amino acids by protease
-Fats--->fatty acids + glycerol by lipase
- Lactose--->glucose + galactose by lactase
- Sucrose --->glucose + fructose by sucrase
Large Intestine : No digestion takes place here.
Absorbs water and mineral salts
Rectum - temporarily stores faeces
Anus - egests (= removal of undigested matter) faeces
Gall bladder - Temporarily storesbile(smelly green substance) secreted by liver.
- Secretes bile in the presence of chyme.
- Bile breaks up large fat droplets into very small fat droplets to increase surface area for lipase action (Emulsification)
Pancreas -Connects to small intestine by pancreatic duct
- Produces pancreatic juice
- Secreteshormones likeinsulin (controls blood glucose concentration) and glucagon
(controls carbohydrate metabolism)
Liver: Produces bile, which is stored in the gall bladder. Deamination of excess Amino acids.
The body cells then uses the digested nutrients to make new materials during
assimilation.I hope you get the idea now.
