Well, let's see, the 4 sphincters I can think of are:1. at the end of the esophagus and beginning of stomach, to prevent regurgitation of food and stomach acid into the esophagus2. at the end of...
heart
The heart has four chambers - the left ventricle, left atrium, right ventricle and right atrium. The liver also has four parts.
From the food they eat, the liquids they drink, and the air they breathe.
There are actually 5 types long flat short irregular sesmoid