Movements of Stomach & Small Intestine Dr. Wasif Haq

Peristalsis Peristalsis: Involuntary, rhythmic wavelike contractions which move the food through the digestive tract.

Anatomy of Stomach Elastic, muscular bag in left side of abdomen. 3 divisions; (a) Fundus, (b) Body, (c ) Antrum. Orad (Fundus & proximal body) receives ingested food. Caudad (Antrum & distal body) Mixes food & pushes/propels towards small intestine.

Anatomy of Stomach

Storage Function Vagovagal reflex: Allows distention, receptive relaxation of stomach. Initiated by entry of food in stomach. Significance: Muscular tone in stomach decreases allowing stomach to accommodate more quantity of food.

Movements of Stomach Weak, peristaltic waves called “Mixing” waves; mixing of food with gastric secretions by Caudad portion of stomach. Intensity increases from body of stomach towards antrum, pushing the food towards pylorus. Retropulsion: As peristaltic waves reach Pylorus, pylorus muscle contracts, inhibiting gastric emptying into duodenum, food is propelled backwards & upwards in antrum. Retropulsion: Peristaltic constrictive ring + Upward squeezing action.

Emptying of Stomach By strong peristaltic ring like constrictions. As stomach is emptied, these waves begin more upward in stomach, adding more food to Chyme pool. Pylorus pump: Pushing Chyme towards Duodenum through Pylorus. Pyloric sphincter: Increased muscle thickness, slightly constricted all time, allows water & fluid like substances entry, food can only pass in form of Chyme.

Regulation Through signals from Stomach & Duodenum. Duodenum has more powerful control, emptying at feasible rate of digestion & absorption.

Enterogastric Reflex Purpose: Inhibition of stomach emptying through inhibition of Pyloric pump and increased constriction of Pyloric sphincter. If duodenum contains large volume of Chyme, inhibition of stomach emptying through Enteric nervous system, Sympathetic nervous system & inhibition of Parasympathetic nervous system.

1.Increased Chyme in Small Intestine 3.Pyloric pump in stomach inhibited & sphincter powerfully constricted 2. Signal from small intestine to stomach 4. Stomach emptying into small intestine inhibited. Enterogastric Reflex

Hunger Pans Rhythmical contractions in body of stomach when stomach has been empty from hours. Tetanic contraction of stomach for 2-3 minutes, can produce mild pain. Especially important in hypoglycemia.

Universal Problem?Universal Problem?

Small Intestine Movements Digestion & absorption of nutrients. Both movements exerted by both movements. Mixing/ Segmentation Contraction Propulsive Movements

Segmentation COntraction Begin in intestinal wall at spaced interval (hence called ‘segments’), cause mixing of food with small intestinal secretion. Travel 1 Cm in anal direction, also propelling food down the intestinal tract.

Propulsive Movements Forward movement of Chyme. Stronger in proximal intestine than terminal intestine. Travels 3-5 cm before fading/dying off, average movement : 1 Cm/min.

Regulators

Peristaltic Rush Intense irritation of intestinal mucosa causes powerful & rapid peristalsis, sweeping the small intestine contents into large intestine, thereby providing relief of distention & excessive Chyme in small intestine. Occurs in infections induced diarrhea & presence of irritants.

Take Home Message Please respect food & do not waste food. Be thankful to Allah for He Has given you something to eat.