PHSI 208 Lecture 4: GI4
Document Summary
Know the contributions of the stomach to digestion and motility. Know the 3 phases of regulation of gastric acid secretion. Secrete hcl and enzymes to begin protein digestion. Mix and pulverize ingested food to produce chyme. The antril pump (antrum) is responsible for breakdown of food so they can pass through the pyloric sphincter. If the food stuffs are not small enough particles, it is sent back to the antrum. Filling: with the increase of volume in the stomach, pressure stays constant for a while. Nitric oxide mediates receptive relaxation, which is responsible for the constant pressure. Storage: weak mixing occurs in the fundus and the body. (peristaltic contractions). Mixing: strong antral peristaltic contractions in the last third region of the stomach. Strong peristaltic contractions are mediated by enteric nerves and the hormone gastrin. Emptying: depends on the strength of antral contractions. There is a greater rate when being pushed down.