digestion of food in the elementary canal


Alimentary canal, also called digestive tract, pathway by which food enters the body and solid wastes are expelled. The alimentary canal includes the mouth, pharynx, oesophagus, stomach, small intestine, large intestine, and anus.

What is the elementary canal?

This is the digestive system in man through which food substances are taken in and by which also nutrients are taken into the blood steam. The elementary canal in man includes the following

i. Mouth
ii. Oesophagus
iii. Stomach
iv. Duodenum
v. Small intestine
vi. Large intestine or colon
vii. Rectum
viii. Anus

Importance of the parts of the elementary canal are as follows

1. Functions of the teeth
i. The teeth are used to cut, grind and chew food into tiny particles
ii. The teeth exposes large area of food for the action of enzymes


Functions of the tongue

i. The tongue helps to roll the food into bolus
ii. The tongue aids the movement of food in the mouth
iii. The tongue allows the mixing of food in the mouth with saliva or ptyalin-enzyme
iv. The tongue aids in swallowing of food into the Oesophagus or gullet


Functions of the salivary gland

i. The salivary gland is part of the digestive system which secretes saliva which in turn contains an enzyme called ptyalin.
ii. The ptyalin as an enzyme that breaks down starch into maltose which is later swallowed into the gullet in form of bolus
iii. It allows for the easy chewing or movement of food in the mouth for swallowing
iv. It also serves as solvent for food

4. Functions of the Oesophagus/Gullet:The Oesophagus connects the mouth to the stomach. The food swallowed is passed down into through the Oesophagus by a movement called peristaltic movement.
internal organs
internal structure of the body


Functions of the stomach:

i. The stomach is a temporary storage for food which takes just a few hours which is then released through the opening of the pyloric sphincter at regular intervals.
ii. In the stomach, the gastric gland secretes gastric juice which contains two enzymes, the RENIN and PEPSIN
iii. The renin acts on milk. It helps to curdle milk.
iv. The pepsin breaks down protein to peptones
v. The gastric gland also secretes hydrochloric acid (HCL) which creates an acid medium for two enzymes to act.
vi. The HCL also helps to kill bacteria in the stomach.
vii. The food is churned by muscular contraction of the stomach wall which enables the mixing of food with digestive juice-enzymes
viii. The churning movement then converts the food in semi-liquid state called chyme


Functions of the DUODENUM

I. The digestion of food takes place in this region of the elementary.
II. The Duodenum contains pancreas which secretes pancreatic juice that contains three enzymes. These enzymes are
1. Amylase: this enzyme converts starch to maltose
2. Lipase: lipase converts fats and oil to fatty acid and glycerol
types of food
world food types
3. Trypsin: trypsin converts proteins and peptones to polypeptides
iii. The pancreatic juice is alkaline and provides that medium for enzymes
iv. The digestion of fats and oil is aided a green alkaline liquid called BILE which is secreted by the liver and stored in the gall bladder.

The bile helps in the emulsification of fats-meaning breaking down fats into tiny droplets

vi. At the end of the digestion in the Duodenum, the food which is now in liquid form called chyme, passes into the ileum or small intestine


The functions of the small intestine

i. The small intestine also known as ileum is found between the Duodenum and large intestine
ii. Two major events takes place in the small intestine
iii. These events are 1. Digestion and 2. Absorption of the digested food

DIGESTION of food also takes place in the small intestine or ileum

v. The intestinal wall secretes intestinal juice which contains the following enzymes, lipase, erepsin, maltase, sucrose and lactase

The lipase converts fats and oil to fatty acid and glycerol


Erepsin converts polypeptides to amino acid


Maltase converts maltose to two units of glucose

ix. Sucrose

converts sucrose to glucose and fructose


Lactase converts lactose to glucose and galactose

In man, the final digestion of food ends in the small intestine.
The end product in the
internal organs of the body

digestion of protein are amino acids, fats and oil, fatty acid and glycerol while that of starch ends in glucose


The end product of digestion of food, which are amino-acids, glucose, fatty acids and glycerol are absorbed in the small intestine by a tiny finger-like structures called villi, Villus for singular.
The folding of the small intestine and the numerous villi presence creates a large surface area for the absorption of digested food nutrients.
The inner surface layer or epithelium of each villus is thin.
This allows the end product by either diffusion or by active transport through it.
The glucose and amino acids are easily absorbed by blood capillaries through the epithelium while the fatty acid and glycerol enter the lacteal where they are carried through the lymph vessels which eventually empty their contents into the blood vessels near the heart.
The blood then carries the fats and other food materials to various parts of the body where they are needed.



The functions of the caecum and appendix are not well defined or known in man but are well known to contain some bacteria which aid minor digestion of cellulose.
Some vitamins such as K and B-complex are partially synthesized in this region



i. The undigested food particles passes into the colon or large intestine.
ii. Here in the large intestine, water is absorbed
iii. This absorption of water, concentrates the waste products and turn them into faeces.
iv. These faeces is finally passed into the rectum and then eventually pushed out of the body through the anus.


Enzymes performs the following function within the body. They are
1. Enzymes helps in breaking down proteins in food into amino acid
2. The help to break down fats and oil into fatty acids and glycerol
3. Enzymes helps to break down carbohydrates into glucose, fructose and galactose
4. The digestive enzymes aids in the absorption of digested food through the addition of water to the food

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Important topics related to the above article

1. Recognizing living things
2. Biology as an enquiry in science
3. Branches of biology
4. Processes of methods of science
5. Usefulness of science
6. Living and non-living things
7. Characteristics of living things
8. Differences between plants and animals
9. Organization of life
10. Complexity of organization in higher organisms
11. Kingdom monera
12. Kingdom Protista
13. Kingdom fungi
14. Kingdom Plantae
15. Kingdom Animalia
16. Cell as a living unit of an organism
17. Form in which living cells exist
18. Structures of plants and animal cells and functions of their components
19. Similarity and differences between plant and animal cell
20. Diffusion
21. Osmosis
22. Plasmolysis
23. Haemolysis
24. Turgidity
25. Faccidity
26. Nutrition
27. Feeding
28. Cellular respiration
29. Excretion
30. Growth

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