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Small Intestine

Small Intestine. Prof. K. Sivapalan. Small Intestinal Motility. Segmental movement [mixing 7/min in ileum] Peristalsis [propagation average 1 cm/min]. Stimulated by stretch of the wall (dietary fibers). Obstruction causes over distention and violent peristalsis which causes colicky pain.

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Small Intestine

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  1. Small Intestine Prof. K. Sivapalan.

  2. Small Intestinal Motility • Segmental movement [mixing 7/min in ileum] • Peristalsis [propagation average 1 cm/min]. • Stimulated by stretch of the wall (dietary fibers). • Obstruction causes over distention and violent peristalsis which causes colicky pain. • Facilitated by, • Parasympathetic stimuli • Gastro-enteric reflex. • Inhibited by, • Sympathetic stimuli. • Irritation to mucosa can cause peristaltic rush and diarrhoea. • Injury to peritoneum causes reflex inhibition and paralysis of the intestine- Paralitic ileus. • Migrating Motor Complex Small Intestine

  3. Intestinal Secretions • Brunner’s glands in duodenum secrets thick mucus in response to acid to protect from acid. • Crypts of Liebercühn • water and electrolytes similar to ECF, 2000 ml/day [?Much more] • Enzyme enterokinase. • Cell division and migration to top of villi- life span of the epithelial cell is 5 days • Control of crypts of Liebercühn - • autonomics- no effect • VIP- vasodilatation, may stimulate. Small Intestine

  4. Intestinal Villi • Surface area: • Intestine [cylinder]- 0.33 M2 • Valvulae c.- 1.00 M2 • Villi- 10.0 M2 • Microvilli- 200 M2 • Surface enzymes: • Disaccharidases • Peptidases • Nucleic acidases • Cells at the top face constant aberration and hypoxia Small Intestine

  5. Fat Absorption • Fat is emulsified by bile salts and lipase digests it. • Micelles formed in the presence of bile salts. • Fatty substences diffuse into the mucosal cell. • Chylomicrons formed and released by exocytosis into ECF. • Chylomicrons are taken by the lymph vessels. Small Intestine

  6. Absorption of CHO and Protein. • Na+ pushed into ECF by active transport • Na+ enters cell from lumen. • The channel is a co-transporter of glucose, maltose and amino acids, peptides. • This is secondary active transport - Importance of salt and glucose in re-hydration. • Rate of absorption and dietary fibers Small Intestine

  7. Circulation in Villus • Every villus has a central lacteal which transports chylomicrons. • Blood with oxygen goes towards the tip and nutrients away from the tip. • Arrangement of vessels sets up counter current flow preventing transport of oxygen to tip and nutrients out. • The muscle in the villus contracts from time to time and empties it into the circulation. Small Intestine

  8. ILLEO-CAECAL Valve Small Intestine

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