This document contain information regarding Digestion,food,Types of Nutrition,Basic steps of Holozoic Nutrition ,Digestive glands,Digestion in mouth,Digestion in stomach,Digestion in small intestine ,Functions of succus entericus, questions on digestion and absorption.
Chapter-16
DIGESTION AND ABSORPTION
POINTS TO REMEMBER
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 regula-
tion 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.
2123
Dental formula of man : × 2 = 32
2123
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 volun-
tary 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 secre-
tion and which passes from the stomach into the small intestine.
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, 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.
Types of Nutrition
Autotrophic Heterotrophic Symbiotic
Photoautotrophic Chemoautotrophic 1. Saprotorphic (e.g., yeast) (e.g., Rhizobium)
(e.g., green plants (e.g., nitrosomonas 2. Holotrophic (e.g., man, lion)
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 com-
ponents.
(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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