WEEK ONE
SUBJECT: BASIC SCIENCE
CLASS: GRADE 8
TOPIC: DIGESTIVE SYSTEM
MEANING OF DIGESTIVE SYSTEM AND
DIGESTION: Digestive system consists of organs which break
down the food we eat into smaller particles. Digestive system is otherwise
called alimentary canal. Digestion refers to the breakdown of food into smaller
components that can be absorbed into the bloodstream.
THE HUMAN ALIMENTARY CANAL:
This is a long tube which begins from the mouth and ends at the anus. It has
various organs attached to it. This includes;
i.
Mouth
ii.
Tongue
iii.
The stomach
iv.
Small intestine
v.
Large intestine
PROCESSES OF DIGESTION OF FOOD BY
SPECIFIC ENZYMES: The food substances are eaten, chewed
and mixed with saliva at the mouth. The salivary juice called ptyalin partially
digests the food (starch) before the gullet pushes it down into the stomach.
The stomach wall then secretes the gastric juice which continues the digestion
process. The partially digested food called chyme then moves into the small
intestine where different digestion juices are secreted to digest specific food
substances. The digested part of the food would then diffuse into the blood
stream. The undigested food moves to the large intestine where it is stored and
is ejected from the body through the anus.
FOOD
AND THEIR END PRODUCTS
|
Food |
End
product |
|
Carbohydrate |
Glucose |
|
Protein |
Amino
acid |
|
Fat
and oil |
Fatty
acid and glycerol |
ABSORPTION AND STORAGE OF DIGESTED
FOOD: The end product of digestion is capable of passing
through the wall of the small intestine into the blood stream. This happens
through a structure called villa. The process by which the digested food
diffuses through the villa into the blood stream is called absorption.
ASSIGNMENT
OBJECTIVE QUESTIONS:
1.
The enzyme produced by the salivary gland is called A. amylase B. crepsin C.
pepsin D. ptyalin E. trypsin
2.
The structure that helps in the absorption of food in the small intestine is
called A. artery B. capillary C. rectum D. vein E. villium
3.
The creamy semi-fluid of food in the stomach after some hours is known as A.
bile B. chile
C.
chyle D. chyme E. pancreas
4.
The absorption of food takes place in the A. colon B. large intestine C. mouth D.
small intestine E. stomach
5.
The digestion of carbohydrates starts in the A. duodenum B. intestine C. mouth
D. oesophagus E. stomach
6.
The human digestive system consist of the following except A. Mouth B. Stomach
C. Large intestine D. Small intestine E. Lungs
THEORY QUESTIONS:
1.
Differentiate between digestive system and digestion.
2.
List five parts of the human alimentary canal.
3.
Explain the processes of digestion of food by certain enzymes.
4.
What is absorption of food?
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