Write a note on peristalsis and sphincter function in stomach.
- Peristalsis involves the contraction of the muscle behind the food and relaxation of the muscle infront of the food giving rise to a thrust that pushes the food forward through the digestive canal.
- A wave of contraction followed by relaxation in muscles helps in forward movement of food in oesophagus.
- The wall of the oesophagus is made up of two kinds of smooth muscles.
- The inner layer consists of circular muscles and the outer layer of longitudinal
- Contraction of the circular muscles results in narrowing of the oesophagus just behind the bolus. So the food is squeezed downwards.
- Contraction of the longitudinal muscles infront of the bolus widen the tube, this result in shortening of that particular part of the oesophagus.
- Contraction and relaxation of these muscles bring in a wave - like motion that propels the food bolus into the stomach by the action called as peristalsis.
- Peristalsis is involuntary and under the control of autonomous nervous system.
B) Sphincters functions in stomach :
- Pyloric sphincter is present at the opening of stomach into the duodenum (small intestine). .
- The pyloric sphincter squeezes only small quantities of food i.e., chyme into duodenum at a time.