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Gastric Motility

GASTROINTESTINAL PHYSIOLOGY

Factors Afferting Caslric Emptying

Castrointestinal

hormones

Dtiodenal

chcmoreceptors

Acid

Fats =0=*>

Amino acids/ peptidos

Sec: rei in Cholecystokinin Gastric Inhibitory Peptide (GIP)

Duodenal stimuli eliril Hormonal inhibition of gastric emptying

Decrcased

gaslric

emptying

Scquence of Gastric Motility

2. Wave (A) fading out as pylorus fails to open. A stronget wavo iB) is originating at incisure and is again squeezing gastric contents in both directions

3. Pylorus opens as wave (Bl approaches it. Duodenal bulb is filled, and some contents pass into second portion of dundenum. Wave (C) starting just above incisure

1. Stornach is filling. A mitd peristaltic wave (A) lias started in antrum and is passing toward pylorus. Gastric contents aro chnmed and largely pushed back intn body of stornach

6. I to 4 hours later. stornach is almosl empty. Smali peristaltic: wave empties duodenal bulb with somp reflux into stornach. Kcyerse and antegrade peristalsis present in duodcnuin    <■

4. Pylorus again closed. Wave (C) fails to evacuate contents. Wave <D) starts highcr on body of stornach. Duodenal bulb may contract or may remain filled as peristaltic. wave originating just beyond it empties second poition

5. Peristaltic waves are now originating highcrr on body ot stornach. Gastric contents are evacuated intermittently. Contents of duodenal bulb area pushed passively into second portion as morę gastric contents emerge

Figurę 7.11 Gastric Motiuty-

The motility of the słomach is under neural and hormonal control. As food is swallowed, vagal efferents release vasoactive intestinal f>ep-tide (VIPj to relax the słomach. Mixing and chuming of the food ichyme) results trom contractions beginning in the middle of the stornach and traveling toward the pylorus. Over tirne, smali amounts of chyme are ejected into the duoderium with each contraction wave. The emptying of the stornach varies with the naturę of the contents of the food. For example, the ratę of empting is starch > protein > rat. Also, solid loods empty slower than liquids.The emptying of the stornach is also controlled by hormones rcleased by neie roendocrine cells in the duodenum and jejunum. These cells monitor the intestinal contents and then modulate ther ratc of gastric emptying łupper panel).

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