Topic D.2: Digestion
Essential Idea: Digestion is controlled by nervous and hormonal mechanisms.
At SHS, Topic D.2 is taught in the following class unit(s):
Statements & Objectives:
D.2.U1 Nervous and hormonal mechanisms control the secretion of digestive juices.
D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut.
D.2.U3 The volume and content of gastric secretions are controlled by nervous and hormonal mechanisms.
D.2.U4 Acid conditions in the stomach favour some hydrolysis reactions and help to control pathogens in ingested food.
D.2.U5 The structure of cells of the epithelium of the villi is adapted to the absorption of food.
D.2.U6 The rate of transit of materials through the large intestine is positively correlated with their fibre content.
D.2.U7 Materials not absorbed are egested.
D.2.A1 The reduction of stomach acid secretion by proton pump inhibitor drugs.
D.2.A2 Dehydration due to cholera toxin.
D.2.A3 Helicobacter pylori infection as a cause of stomach ulcers.
D.2.S1 Identification of exocrine gland cells that secrete digestive juices and villus epithelium cells that absorb digested foods from electron micrographs.
D.2.NOS Serendipity and scientific discoveries—the role of gastric acid in digestion was established by William Beaumont while observing the process of digestion in an open wound caused by gunshot.
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