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Class 11 Biology Chapter 16 Digestion and Absorption Notes

Digestion and Absorption

Digestion : The process in alimentary canal by which the complex food is converted mechanically and biochemically into simple substances suitable for absorption and assimilation. Food : A substance which on taken and digested in the body provides mate- rials for growth, repair, energy, reproduction, resistance from disease or regulation of body processes.

Thecodont : The teeth embedded in the sockets of the jaw bone. e.g., in mammals. Diphyodont : The teeth formed twice in life time e.g., in mammals.

Peristalsis : The involuntary movement of the gut by which the food bolus is pushed forward.

Degluttition : The process of swallowing of food bolus. It is partly voluntary and partly involuntary.

Ruminants : The herbivours animals (e.g., cow, buffalo etc.) which have symbiotic bacteria in the rumen of their stomach which synthesize enzymes to hydrolyse cellulose into short chains fally acids.

Diarrhoea : The abnormal frequent discharge of semisolid or fluid faecal matter from the bowel.

Vomitting : The ejection of stomach contents through the mouth, caused by antiperistalsis.

Dysentry : Frequent watery stools often with blood and mucus and with pain, fever and causes dehydration.

Chyme : The semifluid mass into which food is converted by gastric secretion and which passes from the stomach into the small intestine.

Goblet cells : The cells of intestinal mucosal epithelium which secrete mucus.

Glissons capsule : The connective tissue sheath which covers the hepatic lobules of liver.

Hepatic lobules : The structural and functional units of liver containing hepatic cells which are arranged in the form of cords.

Sphincter of Oddi : The sphincter which guard the opening of common hepato-pancreatic duct.

Villi : The small finger-like folding in the innermost layer of the alimentary canal which increase the absorption surface area.

PEM : Protein Energy Malnutrition.

Basic steps of Holozoic Nutrition : 

(1) Ingestion : Intake of food. 

(2) Digestion : Breaking down of complex organic food materials into simpler, smaller soluble molecules.

(3) Absorption and assimilation : Absorption of digested food into blood or lymph and its use in the body cells for synthesis of complex components. 

(4) Egestion : Elimination of undigested food as faeces.

Digestive glands : (A) Salivary glands (found in mouth).

Three types are :
(i) Parotid
(ii) Sublingual
(iii) Submaxillary.

Secrete saliva which contains ptyalin (Salivary amylase)
(B) Pancreas :
 Secretes pancreatic juice. 

(C) Liver : Secretes bile.
(D) Gastric glands : Secretes gastric juice. 
(E) Intestinal glands : Secretes intestinal juice or succus entericus.


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