PERISTALSIS

PERISTALSIS

• Peristalsis is the rhythmic, wave-like contraction of the GIT that moves food forward.
• It occurs in the esophagus, stomach, small intestine, and large intestine.

Mechanism of Peristalsis:

1. Contraction of Circular Muscles Behind the Bolus

   • Circular muscles contract behind the food bolus, preventing backflow.

2. Relaxation of Circular Muscles in Front of the Bolus

   • This allows food to move forward.

3. Contraction of Longitudinal Muscles

   • These muscles shorten the segment of the intestine, pushing the bolus downward.

4. Sequential Contractions Continue Along the GIT

   • This ensures smooth movement of food toward the stomach and intestines.

     
     

Types of Peristalsis:

1. Primary Peristalsis

   • Initiated by swallowing and continues as a single wave down the esophagus.

2. Secondary Peristalsis

   • Triggered if food remains in the esophagus, helping move it into the stomach.

3. Gastric Peristalsis

   • Occurs in the stomach to mix food with gastric secretions and push chyme into the duodenum.

4. Intestinal Peristalsis

   • Moves chyme through the small intestine for digestion and absorption.

5. Colonic Peristalsis

   • Slower contractions in the large intestine, pushing undigested material toward the rectum.

Control of Peristalsis

• Intrinsic Control: Enteric Nervous System (Myenteric Plexus) coordinates local contractions.

• Extrinsic Control: Vagus nerve stimulates peristalsis, while the sympathetic system inhibits it.