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Gastro-intestinal Physiology General

Gastro-intestinal Physiology General. Prof. K. Sivapalan. Why Eat?. Hunger. Taste and satisfaction. Passing time Energy. Growth. Socialization. Health. Functions of GIT. Tranquility [oral activity] Ingestion. Digestion. Absorption Excretion. Protection- immunity.

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Gastro-intestinal Physiology General

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  1. Gastro-intestinal Physiology General Prof. K. Sivapalan.

  2. Why Eat? • Hunger. • Taste and satisfaction. • Passing time • Energy. • Growth. • Socialization. • Health. GIT Grneral

  3. Functions of GIT • Tranquility [oral activity] • Ingestion. • Digestion. • Absorption • Excretion. • Protection- immunity GIT Grneral

  4. Gastro-Intestinal Tract GIT Grneral

  5. General Organization of GIT Dorsum Mesentery Glands: Goblet cells Mucosal Sub mucosal Glands outside. Mucosa Sub mucosa Sub mucus muscle Sub mucus [Meissner’s] plexus Circular muscle Myenteric [Auerbach’s] plexus Longitudinal muscle. Serosa. GIT Grneral

  6. Smooth muscle in GIT • Smooth muscles in intestine form a syncytium with tight junctions and gap junctions. • Membrane potential shows slow waves. More in pace makers. (Basic electrical rhythm (BER) of gastrointestinal smooth muscle) • When the waves reach threshold level, spike potentials occur. • Muscle tension increases or decreases depending on the number of spikes. • Acetylcholine increases and adrenaline reduces tension. GIT Grneral

  7. Innervation • Sub mucus [Meissner’s] plexus is mainly sensory - stimulated by, irritation, distention or chemicals. • Autonomic afferents from tissues [vagal (80 %) and sympathetic] and Meissner’s plexus go centrally. • Myenteric [Auerbach’s] plexus is motor. • Parasympathetic [Vagus] end on cells of Myenteric plexus. • Sympathetic fibers end on Myenteric plexus, muscles and glands. Sensory neurons GIT Grneral

  8. Gut Reflexes • Coltroll within the gut- secretions, peristalsis, mixing, local inhibitions etc. • Coordinated in para vertibral sympathetic ganglia- enterogastric reflex, colonoilial reflex • Coordinated in brain stem- stomach to stomach: motor and secretary, pain inhibiting entire GIT function, defecation GIT Grneral

  9. Peristalsis. • Coordinated by myenteric plexus • Contraction of circular muscles proximal to the stimulus and relaxation distally. • Longitudinal muscles contract and pull over the contents. • The relaxed circular muscles contract. • The sequence is propagated in oral to caudal direction. GIT Grneral

  10. Migrating Motor Complex • Cycles of motor activity, initiated by motilin, migrate from the stomach to the distal ileum during fasting at 90 minute intervals at 5 cm/min • Clear the stomach and small intestine of luminal contents in preparation for the next meal • Quiescent period (phase I), irregular electrical and mechanical activity (phase II), burst of regular activity (phase III) GIT Grneral

  11. Voluntary and Involuntary Aspects • Searching, cooking, serving, placing in the mouth, mastication- voluntary. • Swallowing- begins as voluntary and ends as involuntary. • Gastric functions- involuntary but affected by moods. • Small intestinal functions- fully involuntary. • Storage of feces- involuntary. • Defecation- starts as involuntary and ends as voluntary. GIT Grneral

  12. Regulation of the functions • Voluntary actions are generally conditioned reflex. • Intrinsic plexus coordinates local reflexes. • Sympathetics inhibit [stimulate sphincters]. • Nerve endings on muscles and glands • Parasympathetic- stimulate [inhibit sphincters]. • Nerve endings on Myenteric plexus [preganglionic] • Pace makers in GIT. GIT Grneral

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