Food digestion

• Food digestion occur in the alimentary canal.• Alimentary canal consist mouth, oesophagus,

stomach, small intestine (duodenum,jejunum,illeum), large intestine (appendix, caecum, colon, rectum) and anus.

• Type of digestion : physical digestion (involve breaking up large pieces of food into smaller pieces with chewing and slicing) and chemical digestion (digestive enzyme break down complex molecules into simple soluble molecules) .

Digestion in oral cavity

• Digestive process start in mouth.• Foods were chewing and break into small

pieces to increase the surface area for digestive enzyme to act.

• Presence of food triggers saliva glands (digestive gland) to secrete saliva.

• Saliva contain salivary amylase to hydrolyse starch to maltose.

• Chewed food rolled into mass called bolus and prepare for swallowing into oesophagus.

• Bolus enter oesophagus and move along with peristalsis movement.

Digestion in stomach

• A muscular sac with highly folded inner walls to increase the surface area of the stomach.

• The epithelial lining of stomach contain gastric gland which secrete gastric juice (mucus, hydrochloric acid and enzymes).

• Food were churned and mix with gastric juice by peristalsis movement in the stomach.

• The foods were in state of semi fluid called chyme.

Hydrochloric acid function

• Prepare optimum pH (acidic medium) for enzyme pepsin and rennin to react.

• Kills bacteria • Stop the action of salivary amylase.

Function of enzymes in gastric juice

• Enzyme pepsin –to hydrolyse protein into peptone and polypeptide.

• Enzyme rennin – to catalyse the coversion of caseinogen (soluble protein in milk) to casein (insoluble milk protein).

Digestion in small intestine

• Consist duodenum, jejunum and ileum.

duodenum

• First part of small intestine and do not have digestive gland.

• It receives:- Bile secretion (produce by liver and released from gall bladder).- Pancreatic juice.

Function of bile

• Break up large globules of fats into small fat droplets (emulsifies fats).

• Prepare alkaline medium.• Neutralise acid from stomach.

Pancreatic juices

• Contain enzymes lipase, amylase and trypsin.• Lipase hydrolyse fats into glycerols and fatty

acids.• Amylase hydrolyse undigested starch into

maltose.• Trypsin hydrolyse peptone and polypeptide

into peptides.

Ileum

• Walls of ileum contain many intestinal glands.• Secrete intestinal juice (enzyme erepsin,

sucrase, maltase, lactase and lipase).