Human digestive system is a tube running from mouth to anus. Its main function is to breakdown complex molecules present in the food which cannot be absorbed as such into smaller molecules. These molecules are absorbed across the walls of the tube and the absorbed food reaches each and every cell of the body where it is utilised for obtaining energy.
Read the source and answer the sub-parts that follow.
Generated by claude-sonnet-4-6 · 2026-06-11 09:47 · grounding stimulus
Model Answer
(a) The glands present in the buccal cavity are salivary glands. Their secretion (saliva) contains salivary amylase (ptyalin) which acts on starch (carbohydrates) and breaks it down into simpler sugars.
(b) The two organs with a sphincter muscle at their exit are:
- Stomach (pyloric sphincter)
- Anus (anal sphincter)
(c)
(i) If mucus is not secreted by gastric glands, the inner lining of the stomach will not be protected from the hydrochloric acid and digestive enzymes. This can cause ulcers in the stomach wall.
(ii) If villi are absent in the small intestine, the surface area for absorption of digested food will decrease greatly, leading to poor absorption of nutrients into the blood.
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Explanation
- (a) Salivary glands and salivary amylase acting on starch is standard textbook content — both parts (gland name + substrate) are needed for full credit.
- (b) Pyloric sphincter (stomach exit) and anal sphincter (anus) are the two key sphincters; examiners look for both organ names.
- (c)(i) Mucus protects stomach lining — ulcers is the key consequence. (c)(ii) Villi increase surface area — their absence means reduced absorption. Each point carries 1 mark.