Understanidngs D.2.U1 Nervous and hormonal mechanisms control the secretion of digestive juices. D.2.U2Exocrine glands secrete to the surface of the body or the lumen of the gut. D.2.U3The volume and content of gastric secretions are controlled by nervous and hormonal mechanisms. D.2.U4Acid conditions in the stomach favour some hydrolysis reactions and help to control pathogens in ingested food. D.2.U5The structure of cells of the epithelium of the villi is adapted to the absorption of food. D.2.U6The rate of transit of materials through the large intestine is positively correlated with their fibre content. D.2.U7Materials not absorbed are egested. Applications D.2.A1The reduction of stomach acid secretion by proton pump inhibitor drugs. D.2.A2 Dehydration due to cholera toxin. D.2.A3Helicobacter pylori infection as a cause of stomach ulcers.
Skills Identification of exocrine gland cells that secrete digestive juices and villus epithelium cells that absorb digested foods from electron micrographs. Nature of Science 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.