Nokea
Which of these processes occurs throughout most of the alimentary canal?
- A. ingestion
- B. propulsion
- C. segmentation
- D. absorption
Correct Answer: B
Rationale: The correct answer is B: propulsion. Propulsion is the process of moving food along the alimentary canal through peristalsis, which is the contraction and relaxation of muscles in the digestive tract. This process occurs throughout most of the alimentary canal, including the esophagus, stomach, small intestine, and large intestine. Ingestion (choice A) occurs at the beginning of the digestive process when food enters the mouth. Segmentation (choice C) is a mixing movement that occurs mainly in the small intestine to aid in digestion. Absorption (choice D) takes place primarily in the small intestine, where nutrients are absorbed into the bloodstream. Therefore, propulsion is the correct answer as it is the continuous movement of food along the digestive tract.
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The small intestine:
- A. Is shorter than the large intestine
- B. Its internal surface area is smaller than the large intestine
- C. It absorbs less water than the large intestine
- D. It contains bacteria as found in the large intestine
Correct Answer: B
Rationale: The correct answer is B because the small intestine has a larger internal surface area compared to the large intestine due to its extensive folding and villi. This increased surface area enhances nutrient absorption efficiency. Choice A is incorrect as the small intestine is longer than the large intestine. Choice C is incorrect as the small intestine absorbs more water than the large intestine. Choice D is incorrect as the small intestine typically does not contain the same amount of bacteria as the large intestine, which is known for its significant bacterial population.
The low pH of the stomach activates enzymes that digest ______ while inactivating enzymes that digest ______.
- A. lipids; proteins
- B. proteins; starch
- C. starch; proteins
- D. nucleic acids; starch
Correct Answer: B
Rationale: The correct answer is B because the low pH of the stomach activates pepsin, an enzyme that digests proteins, while inactivating salivary amylase, an enzyme that digests starch. Pepsin works optimally in an acidic environment, breaking down proteins into peptides. Salivary amylase, on the other hand, works best at a neutral pH and is denatured in the acidic stomach, leading to its inactivation. Choices A, C, and D are incorrect because lipids are primarily digested in the small intestine, and nucleic acids are not directly affected by the stomach's pH.
Which organ produces bile?
- A. Pancreas
- B. Gallbladder
- C. Liver
- D. Stomach
Correct Answer: C
Rationale: The correct answer is C: Liver. The liver produces bile, which plays a crucial role in digestion by breaking down fats. The pancreas (A) produces digestive enzymes, not bile. The gallbladder (B) stores bile produced by the liver but does not produce it. The stomach (D) produces gastric juices, not bile. Therefore, the liver is the only organ that produces bile, making it the correct answer.
Which part of the digestive system is responsible for the mechanical digestion of food?
- A. mouth
- B. stomach
- C. small intestine
- D. large intestine
Correct Answer: B
Rationale: The correct answer is B: stomach. The stomach is responsible for mechanical digestion through the churning and mixing of food with gastric juices, breaking it down into smaller particles. The mouth initiates digestion by chewing and mixing food with saliva, but it primarily focuses on chemical digestion through enzymes. The small intestine is where most of the chemical digestion and nutrient absorption occur, not mechanical digestion. The large intestine's main function is water absorption and the formation of feces, not mechanical digestion. Therefore, the stomach is the correct choice for mechanical digestion in the digestive system.
Which of the following mechanisms most accurately describes how pseudo-membranous colitis caused by Clostridium difficile is produced?
- A. elaboration of an enterotoxin following colonization of the colon
- B. ingestion of a preformed toxin
- C. invasion and destruction of mucosa by the organism
- D. host immune response to the organism
Correct Answer: A
Rationale: The correct answer is A because Clostridium difficile produces toxins, specifically enterotoxins, which cause damage to the intestinal mucosa leading to pseudo-membranous colitis. The organism colonizes the colon and then elaborates the toxins, which disrupt the mucosal barrier.
Choice B is incorrect as there is no preformed toxin ingested; the toxin is produced by the organism after colonization. Choice C is incorrect as Clostridium difficile does not invade and destroy the mucosa directly. Choice D is incorrect as the host immune response is a consequence of the toxin production, not the primary mechanism of disease.