BIO 203 Lecture Notes - Lecture 1: Ileum, Jejunum, Cecum
10 Aug 2016
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Document Summary
Chemical digestion begins with secretion of salivary amylase. Lysozyme is antibacterial salivary enzyme and salivary immunoglobulins disable bacteria and viruses. Swallowing or deglutition is a reflex that pushes bolus of food into esophagus. As bolus moves down to esophagus, the epiglottis folds down, completing closure of upper airway and preventing food and liquid from entering airways. If low esophageal sphincter does not stay contracted, gastric acid and pepsin can irritate lining of esophagus, leading to irritation of gastroesophageal reflex (heartburn) Stomach has 3 general fxns: storage, digestion, protection. Before food arrives, digestive activity in stomach begins with long vagal reflex of cephalic phase. Once food enters stomach, stimuli in gastric lumen initiates series of short reflexes that constitute gastric phase of digestion. In gastric reflexes, presence of peptides and aa in lumen activate endocrine cells and enteric neurons. When food arrives in stomach, the stomach relaxes and expands to hold increased volume.
