Thursday 30 April 2020
How are the small intestines in mammals adapted to their functions?
Small intestines consists
of the duodenum and the ileum; most digestion of food occurs in the duodenum;
bile from the gall bladder of the liver is secreted through the bile ducts; and
it is used to emulsify fats/break fat particles into tiny droplets; to increase
the surface area for enzyme action; the pancreaset
secretes pancreatic juice to the duodenum; the juice contains pancreatic amylase; that helps to breakdown the remaining starch into maltose; trypsin; (that
is secreted in its inactive
form, trypsinogen, and activated by
enterokinase enzyme);
hydrolyses proteins into shorter peptides; pancreatic lipase; converts lipids into fatty acids and glycerol; sodium hydrogen carbonate is also produced; to neutralize the acidic chyme from the stomach; and provide a suitable alkaline medium for pancreatic and other intestinal enzymes;
the ileum is long; and narrow; to increase the surface area for complete
digestion of food; and maximum absorption of digested food; highly-coiled; to
reduce speed of food flow; for maximum digestion; and absorption; presence of
villi; and microvilli; to increase surface area; for maximum absorption; dense
network of capillaries; to transport blood; for efficient transport of absorbed
food; presence of lacteals in the villi; for absorption of fatty acids and
glycerol molecules; presence of enzymes: Lipase; for digestion of lipids into
fatty acids and glycerol; maltase; for digestion of maltose to glucose
molecules; peptidase; for breakdown of peptides into amino acids; sucrase; for
digestion of sucrose into glucose and fructose; lactase; for digestion of
lactose into glucose and galactose; goblet cells; produce mucus; to lubricate
the walls of the ileum; for smooth flow of food; coats the walls of ileum to
prevent digestion by peptidase enzyme;
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