BIOL 221 Study Guide - Final Guide: Stratified Squamous Epithelium, Gastric Mucosa, Medulla Oblongata
11 Feb 2020
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Document Summary
The upper esophageal sphincter (ues) controls movement of material from pharynx into esophagus and prevents regurgitation into the throat. The lower esophageal sphincter (also called the les, or gastroesophageal or cardiac sphincter) is a thickening of smooth muscle of inferior esophagus. It is aided by the diaphragm to close bottom of esophagus and helps prevent reflux of acidic gastric juice into the esophagus. If the condition persists then it can lead to full-blown gastroesophageal reflux disease. An esophageal ulcer may also occur as the acid eats through the mucosa. Digestive processes in the mouth, pharynx and esophagus start with ingestion. Mechanical digestion by teeth and the tongue physically break the pieces of food into smaller particles. Chemical digestion begins in the mouth with the action of salivary amylase; this begins the hydrolysis of starch. The ph in the mouth is around 6. 8; the ph in the stomach is around 2.
