Sense of course of a working life first attested 1803. v. 1590s, to charge at a tournament, from career (n.). The meaning move rapidly, run at full speed (1640s) is from the image of a horse passing a career on the jousting field, etc. Related: Careered; careering.
Contractions of the stomach muscle, called peristaltic waves, grind, crush and mix the food producing a liquefied substance called chyme.. The pyloric sphincter separates the stomach from the duodenum. This valve keeps food and gastric juices in the stomach until liquefied enough to proceed into the duodenum.
The chest cavity and abdomen are separated by a sheet of muscle, the diaphragm. The esophagus is the tube through which food and drink pass from the mouth to the stomach, and it travels through an opening in the diaphragm, the hiatus. Hence the name hiatal hernia.