Write a note on peristalsis and sphincter function in stomach.
1) 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.
2) A wave of contraction followed by relaxation in muscles helps in forward movement of food in oesophagus.
3) The wall of the oesophagus is made up of two kinds of smooth muscles.
4) The inner layer consists of circular muscles and the outer layer of longitudinal
5) Contraction of the circular muscles results in narrowing of the oesophagus just behind the bolus. So the food is squeezed downwards.
6) Contraction of the longitudinal muscles infront of the bolus widen the tube, this result in shortening of that particular part of the oesophagus.
7) 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.
8) Peristalsis is involuntary and under the control of autonomous nervous system.
B) Sphincters functions in stomach :
1) Pyloric sphincter is present at the opening of stomach into the duodenum (small intestine). .
2) The pyloric sphincter squeezes only small quantities of food i.e., chyme into duodenum at a time.