Free Human Digestive System MCQs with Answers

31. Bile differs from the other digestive juices in that it

• A. contains a strong acid
• B. contains pepsin
• C. digests starch
• D. contains no digestive enzyme

Explanation: Bile helps fat digestion purely physically, by emulsifying large drops into tiny ones that lipase can attack. Every other major juice contributes an enzyme, making bile the odd one out.

32. The final products of protein digestion are

• A. fatty acids and glycerol
• B. glucose
• C. amino acids
• D. maltose

Explanation: Proteases and peptidases cut polypeptides down to single amino acids, which are absorbed and rebuilt into the body's own proteins. Fatty acids come from fats and glucose from carbohydrates.

33. Complete digestion of fats yields

• A. glucose and water
• B. fatty acids and glycerol
• C. starch
• D. amino acids

Explanation: Lipase splits the three ester bonds of a triglyceride, releasing glycerol and three fatty acids. These are absorbed into the lacteals rather than the blood capillaries.

34. The microscopic finger like projections of the epithelial cells of each villus are called

• A. microvilli
• B. villi
• C. cilia
• D. flagella

Explanation: Microvilli multiply the absorptive surface a further twenty times beyond the villi themselves. Cilia and flagella are motile structures, so the name similarity hides a different function.

35. Blood carrying the products of digestion from the intestine is delivered first to the

• A. heart
• B. kidneys
• C. lungs
• D. liver, by the hepatic portal vein

Explanation: The liver screens, stores and adjusts nutrients before they enter the general circulation, regulating glucose and detoxifying harmful substances. Sending blood straight to the heart would bypass this control.

36. Diarrhoea occurs when

• A. the large intestine absorbs too much water
• B. digestion proceeds too rapidly in the stomach
• C. the intestinal contents move too quickly for adequate water absorption
• D. the villi absorb too much glucose

Explanation: When contents rush through, the large intestine cannot reclaim enough water and the faeces stay liquid, risking dehydration. Too much absorption has the opposite effect, causing constipation.

37. Constipation results from

• A. very rapid peristalsis
• B. slow movement of contents through the large intestine with excess water absorption
• C. excess secretion of bile
• D. overactivity of the salivary glands

Explanation: The longer contents linger, the more water is reabsorbed and the harder and drier the faeces become. Fibre adds bulk that speeds transit, which is why roughage prevents it.

38. Marasmus, the wasting disease of starving children, is caused by a diet deficient in

• A. calories and protein overall
• B. vitamin C only
• C. iron only
• D. iodine only

Explanation: Marasmus reflects total starvation, with loss of muscle and fat, while kwashiorkor is protein deficiency with adequate calories, causing oedema. The two malnutrition syndromes are distinguished by exactly this point.

39. The taking of food into the body is called

• A. digestion
• B. assimilation
• C. absorption
• D. ingestion

Explanation: Ingestion is simply intake; digestion breaks food down, absorption moves the products into blood, and assimilation uses them in cells. Each step of nutrition has its own term.

40. The mucus secreted by the cells of the stomach wall serves mainly to

• A. digest cellulose
• B. kill every bacterium swallowed
• C. protect the stomach wall from acid and pepsin
• D. absorb glucose

Explanation: A layer of mucus shields the epithelium from hydrochloric acid and pepsin, which would otherwise digest the stomach itself. When this protection fails, ulcers can form.