Constrictor waves: These are weak peristaltic waves called mixing waves and they begin at the mid to upper portions of the stomach and then move to the antrum every 15-20 seconds.
Constrictor rings: These appear towards the antrum from the body of stomach to propel the food towards the pylorus and a little is expelled into the duodenum for each powerful digging peristaltic action potential-driven constrictor rings. But these peristaltic powerful constrictor waves are opposed by the contraction of the pylorus muscle thereby impeding the movement of the food into the duodenum and moving the food upstream towards the body of the stomach and not the pylorus. The combination of these two actions- upstream movement from the pylorus and the constrictive ring from the antrum causes what is known as retropulsion which thoroughly allows food to be mixed in the stomach leading to formation of chyme.
Chyme that is now produced is a murky paste. The hormone gastrin aids the emptying of the stomach into the duodenum. It not only aids the secretion of acid from the stomach it also helps the motor functions of the body of the stomach. The effect is opposed by the enterogastric nervous reflex from the duodenum. Also hormones of the upper intestine inhibit the emptying of the stomach to include hormones like cholecystokinin, gastric inhibitory peptide (GIP) and secretin. These actions then allow the food to remain in the stomach for as long as it is possible to churn it into chyme.
Gastric glands are divided into two types
Other cells in stomach