2.3 the human digestive system

Human Digestive System

2.3

Prepared by:Wan Zhi LingLim Chia YeeKong Chee HengCheah Ken JiTeo Jing Tong

PARTS OF THE DIGESTIVE SYSTEM

1.The digestive system consists of all the organs which take part in the digestion of food.

2.The alimentary canal consists of the parts through which food passes from the mouth to the anus.

THE MAIN FUNCTIONS OF THE ORGANS IN THE DIGESTIVE SYSTEM

organs function

Mouth Keeps the food for chewing

Teeth Cut the food into small pieces

Salivary glands Produce saliva containing digestive enzyme (amylase)

Tongue Taste the food

Oesophagus Channels the food from the mouth into the stomach

Stomach Produces digestive enzymes (rennin and protease)

Duodenum Digests the food with the help of enzymes from the pancreas

Pancreas Produces digestive enzymes(amylase, protease and lipase)

Liver Produces bile for emulsifying fats

Gall bladder Stores bile from the liver

Small intestine(ileum)

Produces digestive enzymes and completesthe undiges food

Large intestine Absorbs water from the undigested food

Rectum Keeps the faeces

Anus Lets out the faeces

THE PATHWAY OF DIGESTION OF FOOD

mouth oesophagus

stomach

duodenum

Small intestin

e

Large intestine

anus

THE DIGESTION OF FOOD1. Digestion of food is the process of changing the food

eaten from large complex molecules into small simple molecules which can pass through the cell membrane into the cells of the body.

The process of digestion

Physical Digestive

Chemical Digestive

Physical DigestionWe broken the food into small piece.

Chemical DigestionChanging the large complex food molecules into small simple molecules which can be absorbed by the body.

In The Moutha)The food in the mouth is first cut into small pieces by the teeth and mixed with the saliva.

b)The enzyme in the saliva, amylase will change the starch into maltose.

c)Saliva is alkaline.

In The Oesophagusa)Peristalsis of the wall of the oesophagus pushes the food down the oesophagus into stomach.

b)No digestion of food is occurred here

In The Stomach

a)The food is mixed with the gastric juice produced by glands in the wall of the stomach.

b)Gastric juice contains hydrochloric acid and enzymes(rennin and protease)

c)The hydrochloric acid neutralises the alkali in the saliva and prepares an acidic medium for the two enzymes to act on the food. It also kills bacteria in the food.

d)Rennin coagulates milk so that it is more easily digested.

e)Protease digests proteins into peptones.

Peristaltic movement

In The Duodenum

a)The duodenum is the first portion of the small intestine.

b)In the duodenum, the food is mixed with the bile and pancreatic.

c)Bile is a thick alkaline liquid produced by the liver and stored in the gall bladder. It neutralize the acid in the food from the stomach and changes oil into droplets so that it is easier for any enzymes to act on it.

d)Pancreatic juice is very alkaline. It contains three enzymes-amylase, protease and lipase.

e)Amylase changes starch into maltose. Protease changes proteins into peptones. Lipase changes fats into fatty acids and glycerol.

In The Small Intestinea)The second portion of the small intestine is called the ileum

b)Digestion is completed in the ileum -carbohydrates are digested into simple sugars such as glucose and fructose. -Proteins and peptones are digested into amino acids

THE END