Nokea
Which of these is responsible for the formation of chyme?
- A. bile
- B. mucus
- C. hydrochloric acid
- D. pepsin
Correct Answer: C
Rationale: The correct answer is C: hydrochloric acid. Hydrochloric acid is responsible for creating an acidic environment in the stomach essential for the activation of pepsin and the breakdown of proteins into peptides. This acidic environment also helps in the denaturation of proteins and kills harmful bacteria present in food. Bile (choice A) aids in digestion of fats in the small intestine. Mucus (choice B) helps protect the stomach lining from the acidic environment. Pepsin (choice D) is an enzyme that breaks down proteins but is activated by hydrochloric acid.
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Which of these statements about the pharynx is true?
- A. It extends from the nasal and oral cavities superiorly to the esophagus anteriorly.
- B. The oropharynx is continuous superiorly with the nasopharynx.
- C. The nasopharynx is involved in digestion.
- D. The laryngopharynx is composed partially of cartilag
Correct Answer: B
Rationale: The correct answer is B because the oropharynx is indeed continuous superiorly with the nasopharynx, forming a passage for both air and food. This continuity allows for the passage of food and air between the oral and nasal cavities.
A is incorrect because the pharynx extends from the nasal and oral cavities superiorly to the esophagus posteriorly, not anteriorly.
C is incorrect because the nasopharynx is not involved in digestion; it primarily functions in respiration and contains the openings of the Eustachian tubes.
D is incorrect because the laryngopharynx is not composed partially of cartilage; it is a muscular passage that connects the oropharynx and the esophagus.
What does the liver secrete to aid in digestion?
- A. insulin
- B. bile
- C. gastrin
- D. pepsin
Correct Answer: B
Rationale: The correct answer is B: bile. The liver secretes bile to aid in digestion by emulsifying fats, helping in their breakdown and absorption. Insulin (choice A) is secreted by the pancreas to regulate blood sugar levels, not aid in digestion. Gastrin (choice C) is a hormone produced by the stomach to stimulate the secretion of gastric acid, not by the liver. Pepsin (choice D) is an enzyme produced in the stomach to break down proteins, not secreted by the liver.
Water transport can occur from the lumen of the intestine to the blood stream, or from the blood stream to the intestinal lumen. Which single statement about this phenomenon, below, is actually correct?
- A. A 'flip-flop' mechanism efficiently transports water directly across the enterocyte membrane
- B. Water flows into the gut from the mucosa, during digestion of starch and protein, in order to reduce luminal osmolality
- C. Water is mostly absorbed by movement between the cells lining the gut (enterocytes) via tight junctions
- D. Dietary intake of water is always greater than water movement in the small intestine
Correct Answer: C
Rationale: The correct answer is C because water is indeed mostly absorbed by movement between the cells lining the gut (enterocytes) via tight junctions. This is known as paracellular transport. Water moves through the spaces between the cells due to osmotic gradients and is then taken up by blood vessels. A: The 'flip-flop' mechanism is not a recognized mechanism for water transport in the intestine. B: Water does not flow into the gut from the mucosa during digestion, rather it moves from the gut lumen into the blood. D: Dietary intake of water can vary and may not always be greater than water movement in the small intestine.
The ileocecal valve prevents chyme from entering the _____.
- A. large intestine
- B. small intestine
- C. stomach
- D. duodenum
Correct Answer: A
Rationale: The correct answer is A: large intestine. The ileocecal valve is located between the ileum (part of the small intestine) and the cecum (part of the large intestine). Its primary function is to prevent the backflow of contents from the large intestine into the small intestine, specifically preventing chyme from entering the large intestine prematurely. This allows for proper digestion and absorption of nutrients in the small intestine before the remaining waste material enters the large intestine for further processing. Choices B, C, and D are incorrect as the ileocecal valve specifically regulates the flow of material between the small and large intestines, not other parts of the digestive system such as the stomach or duodenum.
Which of the following is likely to fail to reduce secretion of hydrochloric acid in the stomach:
- A. A H receptor blocker
- B. A nicotinic cholinergic receptor blocker
- C. A muscarinic cholinergic receptor blocker
- D. An inhibitor of the hydrogen-potassium pump
Correct Answer: D
Rationale: The correct answer is D because an inhibitor of the hydrogen-potassium pump directly targets the mechanism responsible for the secretion of hydrochloric acid in the stomach. By inhibiting this pump, the production of acid is reduced.
A H receptor blocker (choice A) and a muscarinic cholinergic receptor blocker (choice C) work by blocking specific receptors involved in stimulating acid secretion. A nicotinic cholinergic receptor blocker (choice B) blocks a different type of receptor that is not directly involved in regulating acid secretion.
In summary, the inhibitor of the hydrogen-potassium pump (choice D) is the most direct and effective way to reduce the secretion of hydrochloric acid in the stomach compared to the other choices.