form 4 biology chap6 pt6

LEARNING OUTCOME 1 Identify the part of the digestive system

where the formation of faeces takes place.

LEARNING OUTCOME 2 Describe the formation of faeces.

• Undigested materials fibre (cellulose) + excretory product (bile pigments, dead cells) + bacteria + water enter colon (peristalsis)

• 90% of water + minerals are absorbed into the bloodstream faecal material becomes more solid = faeces.

LEARNING OUTCOME 3 Explain the role of microorganisms in the

colon & the effect of antibiotics on them.

•Synthesis of vitamin B12 & vitamin K

•Conversion of cellulose to simple sugar

•B12 : formation of rbc•K : synthesis of blood clotting factors

Overuse of antibiotics?

Reduce the good microbial population eg. E.Coli

LEARNING OUTCOME 4 Explain defaecation & the importance of high fibre diets.

•Defaecation : the elimination of faeces from the body through the anus.

•Faeces is stored temporarily in rectum full sphincter muscles relax rectal wall contracts the faeces ejected via the anus.

THE IMPORTANCE OF HIGH FIBRE DIETS.

The action of peristalsis is stimulated by fibres

A high fibre diet is very important for : Give bulk to the intestinal contents Helps to absorb water Prevent constipation

LEARNING OUTCOME 5 What is the problem related to

defaecation?

•Constipation Haemorrhoids (piles) Colon cancer

CONSTIPATION

The difficulty or infrequent evacuation of the bowels (elimination of faeces).

Faeces becomes dry & hard difficult to eliminate.

To prevent eat foods high in fibres, drinking more fluid

HAEMORROIDS (PILES) Swollen veins in the

rectum or anus.

Constipation EXCESSIVE pressure exerted on the veins.

Itchiness, pain & rectal bleeding when the veins rupture.

COLON CANCER Develops gradually.

A cell divides actively form a polyp malignant (month years later).

Symptoms : change in frequency of bowel movement, blood in faeces, abnominal pain, discomfort, weight loss.

Closely link to diet @ is hereditary.

Consume high-fibre & low fat diet.