What does the term 'peristalsis' refer to?

Correct Answer: C

Rationale: Peristalsis refers to the rhythmic contractions that move food along the digestive tract. This process helps propel food from the esophagus to the stomach and through the intestines for digestion and absorption. It is an involuntary movement controlled by the autonomic nervous system. Choice A is incorrect as it refers to digestion, not movement. Choice B is incorrect as peristalsis is involuntary, not voluntary. Choice D is incorrect as peristalsis does not involve absorption but rather transportation of food.

Correct Answer: A

Rationale: The correct answer is A: Villi. Villi are finger-like projections lining the small intestine that increase surface area for nutrient absorption. This structure is crucial for efficient digestion and absorption of nutrients. The other choices are incorrect because: B: Hepatic portal vein - This structure is not found in the small intestine but connects the intestines to the liver. C: Goblet cells - While present in the small intestine, they are not a defining structure of the small intestine. D: Mesenteries - These are connective tissues that support and hold organs in place, not a structure specific to the small intestine.

Correct Answer: D

Rationale: The correct answer is D: Absorption of calcium. The colon primarily absorbs water, sodium, and chloride, but not calcium. Calcium absorption mainly occurs in the small intestine. The colon's main function is to absorb water and electrolytes, and to store and eliminate waste. Therefore, absorption of calcium does not occur in the colon, making choice D the correct answer. Choices A, B, and C are incorrect as the colon is involved in the absorption of water, sodium, and chloride, respectively.

Correct Answer: A

Rationale: The correct answer is A: Digestive enzymes. The liver produces bile, which contains bile salts that help digest fats in the small intestine. Additionally, the liver produces various digestive enzymes like lipase, amylase, and proteases. These enzymes aid in breaking down carbohydrates, proteins, and fats during the digestion process. Choices B, C, and D are incorrect because secondary bile acids are produced in the intestine, stercobilinogen is a product of bilirubin breakdown in the intestine, and CCK (cholecystokinin) is a hormone produced by the small intestine to stimulate the release of bile and pancreatic enzymes but not directly produced by the liver.

Correct Answer: D

Rationale: The correct answer is D: Duodenum. The duodenum is the first part of the small intestine, not the large intestine. The transverse colon, appendix, and cecum are all parts of the large intestine. The duodenum plays a crucial role in the digestion process, receiving partially digested food from the stomach and further breaking it down with the help of enzymes from the pancreas and bile from the liver. It is important to differentiate between the small and large intestines to understand their distinct functions within the digestive system.