These notes for CBSE Class 11 Biology, Chapter 16, focus on Digestion and Absorption. They define digestion as the conversion of complex food into simple substances for absorption and assimilation, and food as a vital substance for bodily functions. Key terms like Thecodont and Diphyodont teeth, Peristalsis, Degluttition, and Ruminants are explained. The notes also cover conditions like Diarrhoea, Vomiting, and Dysentry, along with Chyme and the role of Goblet cells. Structural components like Glisson's capsule and Hepatic lobules are mentioned, as is the Sphincter of Oddi. The basic steps of Holozoic Nutrition—Ingestion, Digestion, Absorption and Assimilation, and Egestion—are outlined. Finally, the major digestive glands including Salivary glands, Pancreas, Liver, Gastric glands, and Intestinal glands, and their secretions are listed. These notes are ideal for students to revise the chapter's core concepts for exams.
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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.
Digestion is the process in the alimentary canal where complex food is converted mechanically and biochemically into simple substances suitable for absorption and assimilation.
The basic steps are Ingestion (intake of food), Digestion (breaking down food), Absorption and assimilation (absorbing digested food and using it), and Egestion (eliminating undigested food).
The notes cover Salivary glands, Pancreas, Liver, Gastric glands, and Intestinal glands.
Villi are small finger-like foldings in the innermost layer of the alimentary canal that increase the absorption surface area.
Chyme is the semi-fluid mass into which food is converted by gastric secretion, passing from the stomach to the small intestine.
Thecodont refers to teeth that are embedded in the sockets of the jaw bone, as seen in mammals.
Diphyodont teeth are teeth that are formed twice in a lifetime, which is characteristic of mammals.
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