DIGESTION OF FOOD AND THE ELEMENTARY CANAL IN MAN
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
v. Small intestine
vi. Large intestine or colon
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
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.
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
1. ENVIRONMENTAL FACTORS AFFECTING AGRICULTURAL PRODUCTION
3. 52. SOIL MICRO-ORGANISMS
4. ORGANIC MANURING
5. FARM YARD MANURE
8. CROP ROTATION
9. GRAZING AND OVER GRAZING
10. IRRIGATION AND DRAINAGE
11. IRRIGATION SYSTEMS
12. ORGANIC MANURING
13. FARM YARD MANURE
16. CROP ROTATION
17. GRAZING AND OVER GRAZING
18. IRRIGATION AND DRAINAGE
49. FORAGE CROP AND PASTURE
50. FORAGE GRASSES
53. TYPES OF PASTURE
COMMON GRASSES AND LEGUMES
56. ESTABLISHMENT OF PASTURES
57. 201. FORAGE PRESERVATION
58. HAY SILAGE
59. FORESTRY IMPORTANCE OF FORESTRY 206. FOREST MANAGEMENT FOREST REGULATION DEFORESTATION AFFORESTATION
60. DISEASES AND PESTS OF CROPS
127. ANIMAL NUTRITION
131. NUTRIENT SOURCES AND FUNCTIONS
133. PROTEIN FATS
136. FEEDING MECHANISMS IN HOLOZOIC ORGANISMS
137. TYPES OF DIETS
138. FATTENING OR FINISHING DIETS
139. LAYER DIETS
140. BALANCED DIETS
141. LACTATION DIETS
143. DISEASE, CAUSES, SYMPTOM CORRECTION
144. RANGE MANAGEMENT AND IMPROVEMENT
145. LIVESTOCK DISEASES
154. PROTOZOAN DISEASES
157. RED WATER FEVER(PIROPLASMOSIS)
158. ENDO PARASITES
159. TAPE WORM
160. ROUND WORM OF PIGS
161. LIVER FLUKE
162. ECTO PARASITES
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
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
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
digestion of protein are amino acids, fats and oil, fatty acid and glycerol while that of starch ends in glucose
ABSORPTION OF FOOD
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 CEACUM AND APPENDIX
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
THE FUNCTIONS OF THE LARGE INTESTINE
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.
FUNCTIONS OF THE DIGESTIVE ENZYMES
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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