Q.(a) Describe in detail, the process of digestion in the small intestine. OR
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Start your 14-day free trial to unlock the full solution →Digestion is completed in the small intestine using bile (fat emulsification), pancreatic enzymes and intestinal (succus entericus) enzymes; the end products are then absorbed through the villi.
(a) Digestion in the small intestine:
Partly digested food (chyme) from the stomach enters the duodenum, the first part of the small intestine, where it is acted upon by two secretions delivered through the hepatopancreatic duct:
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Bile (from the liver, stored in the gall bladder): contains bile salts, which do not chemically digest fat but physically emulsify large fat globules into smaller droplets, greatly increasing the surface area for enzyme action. Bile also neutralises stomach acid, making the medium suitable for pancreatic enzymes.
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Pancreatic juice (from the pancreas): contains several enzymes —
- Trypsin (from inactive trypsinogen) digests proteins/peptones into smaller peptides.
- Pancreatic amylase digests starch into maltose.
- Pancreatic lipase acts on emulsified fat, breaking it into fatty acids and glycerol/monoglycerides.
As the partly digested food moves into the jejunum and ileum, glands in the intestinal wall (crypts of Lieberkühn) secrete succus entericus (intestinal juice), containing further enzymes that complete digestion:
- Dipeptidases break peptides down into individual amino acids.
- Maltase, sucrase and lactase break disaccharides (maltose, sucrose, lactose) into monosaccharides (glucose, fructose, galactose).
- Intestinal lipase completes the breakdown of fats.
- Nucleases act on nucleic acids.
Absorption: …
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