Absorption is the process by which the end products of digestion pass through the intestinal mucosa blood or lymph. It is carried out by passive, active or facilitated transport mechanisms. Small amount of monosaccharides like glucose, amino acids and some of electrolytes like chloride ions are generally absorbed simple diffusion. The passage of these substances into the blood depends upon the concentration gradients. However, some of the substances like fructose and some amino acids are absorbed with the help of the carrier
ions like Na+. This mechanism is called the facilitated transport.
Transport of water depends upon the osmotic gradient. Active transport occurs against the concentration gradient and hence requires energy. Various nutrients like amino acids, monosaccharides like glucose, electrolytes like Na+ are absorbed into the blood by this mechanism.
# Absorption in buccal cavity :-
No absorption of food takes place in the oral cavity. Only some chemicals/medicines and alcohol are absorbed in buccal cavity.
# Absorption in stomach :-
In the stomach, absorption of water, some salts, alcohol, glucose and few drugs like aspirin takes place.
#Absorption in small intestine -
Iron and calcium ion are absorbed in the duodenum. Maximum absorption take place in jejunum. Vitamin-B12 and bile salts are absorbed in ileum. Millions of microscopic folds or finger like projections are present in the lumen of gut which are called villi, "villus is unit of absorption."
- These villi are supplied with a network of blood capillaries and lymphatic capillaries (lacteals) . The cells that line the surface of villi are called enterocytes and bears numerous microscopic bristle like projections are called microvilli or brush border. These further increase the surface area for the absorption of the nutrients/digested food. On the surface of the mucous epithelium mucous or goblet cells are present and secrete mucus that acts as a lubricant and protects the epithelial surface from damage and digestion.
Absorption of Carbohydrate
- Monosaccharides are absorbed via the capillary blood with in the villus to finally reach into portal vein. Absorption of glucose molecules occurs along with Na+ by active symport (Co-transportation) and fructose is absorbed by facilitated diffusion, because concentration of glucose is higher in lumen where as concentration of fructose is low in cells.
Absorption of amino acid -
- The L-amino acids are naturally occuring and are absorbed by active transport against the concentration gradient while D-amino acid are absorbed passively by diffusion.
- Some amount of dipeptide and tripeptide enter the enterocytes where they are hydrolyzed to amino adds dipeptidases and tripeptidases to get absorbed via portal veins.
Absorption is the process by which the end products of digestion pass through the intestinal mucosa blood or lymph. It is carried out by passive, active or facilitated transport mechanisms. Small amount of monosaccharides like glucose, amino acids and some of electrolytes like chloride ions are generally absorbed simple diffusion. The passage of these substances into the blood depends upon the concentration gradients. However, some of the substances like fructose and some amino acids are absorbed with the help of the carrier
ions like Na+. This mechanism is called the facilitated transport.
Transport of water depends upon the osmotic gradient. Active transport occurs against the concentration gradient and hence requires energy. Various nutrients like amino acids, monosaccharides like glucose, electrolytes like Na+ are absorbed into the blood by this mechanism.
# Absorption in buccal cavity :-
No absorption of food takes place in the oral cavity. Only some chemicals/medicines and alcohol are absorbed in buccal cavity.
# Absorption in stomach :-
In the stomach, absorption of water, some salts, alcohol, glucose and few drugs like aspirin takes place.
#Absorption in small intestine -
Iron and calcium ion are absorbed in the duodenum. Maximum absorption take place in jejunum. Vitamin-B12 and bile salts are absorbed in ileum. Millions of microscopic folds or finger like projections are present in the lumen of gut which are called villi, "villus is unit of absorption."
- These villi are supplied with a network of blood capillaries and lymphatic capillaries (lacteals) . The cells that line the surface of villi are called enterocytes and bears numerous microscopic bristle like projections are called microvilli or brush border. These further increase the surface area for the absorption of the nutrients/digested food. On the surface of the mucous epithelium mucous or goblet cells are present and secrete mucus that acts as a lubricant and protects the epithelial surface from damage and digestion.
Absorption of Carbohydrate
- Monosaccharides are absorbed via the capillary blood with in the villus to finally reach into portal vein. Absorption of glucose molecules occurs along with Na+ by active symport (Co-transportation) and fructose is absorbed by facilitated diffusion, because concentration of glucose is higher in lumen where as concentration of fructose is low in cells.
Absorption of amino acid -
- The L-amino acids are naturally occuring and are absorbed by active transport against the concentration gradient while D-amino acid are absorbed passively by diffusion.
- Some amount of dipeptide and tripeptide enter the enterocytes where they are hydrolyzed to amino adds dipeptidases and tripeptidases to get absorbed via portal veins.