Understandings:
- Nervous and hormonal mechanisms control the secretion of digestive juices.
- Exocrine glands secrete to the surface of the body or the lumen of the gut.
- The volume and content of gastric secretions are controlled by nervous and hormonal mechanisms.
- Acid conditions in the stomach favour some hydrolysis reactions and help to control pathogens in ingested food.
- The structure of cells of the epithelium of the villi is adapted to the absorption of food.
- The rate of transit of materials through the large intestine is positively correlated with their fibre content.
- Materials not absorbed are egested.
Applications and skills:
- Application: The reduction of stomach acid secretion by proton pump inhibitor drugs.
- Application: Dehydration due to cholera toxin.
- Application: Helicobacter pylori infection as a cause of stomach ulcers.
- Skill: Identification of exocrine gland cells that secrete digestive juices and villus epithelium cells that absorb digested foods from electron micrographs.
Guidance:
- Adaptations of villus epithelial cells include microvilli and mitochondria.
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Utilization:
- Syllabus and cross-curricular links:
- Biology
- Topic 1.2 Ultrastructure of cells
- Topic 6.5 Neurons and synapses
- Chemistry
- Topic D4 pH regulation of stomach
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