BPK 205 Lecture Notes - Lecture 33: Bile Acid, Phospholipid, Colipase
5 Nov 2017
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Objectives: describe the oral phase of digestion. Salivary secretion: autonomic, mostly parasympathetic: functions: lubricate/moisten food, solubilize material for taste, initial digestion of starches, antibacterial (lysozyme = antibacterial enzyme, immunoglobulins = antibodies) Chemical/mechanical digestion: gastric contractions continue to break food mix it with gastric acid + chemical digestion secretions produce chyme (soupy, partially digested food) Acidic environment + mucus and bicarbonate = destroy pathogens without harming stomach. Gastric secretions: mucous, parietal and chief cells. Gastric mucous cells: contain mucus droplets released to form mucus layer with bicarbonate (ph ~7) protect stomach from gastric juice (ph ~2) Parietal cells: located stomach epithelium; ach stimulate parietal cells secrete hcl (gastric juice) denature protein + activate pepsin + kill pathogens. Protein: low ph denatures ph pepsin breakdown polypeptides into smaller fragments. Fat: minor (~10% digested in stomach); gastric motility lipids + gastric lipase hydrolyse triglycerides into monoglycerides and free fatty acids (ffas: the small intestinal (si) phase of digestion.
