Hot answers tagged human-anatomy
This is called achalasia. According to UpToDate, the mechanism for this diseases are generally unknown. What is known, however, is that the esophagus has a neural system called the myenteric plexus and if these ganglion cells in the esophagus are damaged in any way (e.g. physically, followed by Wallerian degeneration, or the primary process of degeneration ...
The structure is called the lower esophageal sphincter: Basically, its function is to prevent the contents of the stomach, including stomach acid, from "backwashing" into the esophagus. The stomach is protected from acid by a protective layer of mucus, while the esophagus is not, so any number of medical issues which cause problems with this sphincter may ...
I don't think this is a complete answer, but I know that historically hair, like horse tail has been used as a part of armor, because it is flexible and difficult to cut through (see dragoon helmet picture). Protection could be one of the primary purposes of facial hair in human males, who are more likely to experience aggression or be hunters.
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