Which two regions of a tooth contain living cells?

Correct Answer: D

Rationale: The correct answer is D. Dentin and cementum are the two regions of a tooth that contain living cells. Dentin is the hard tissue beneath the enamel and cementum that forms the bulk of the tooth structure. It contains living cells called odontoblasts responsible for dentin formation. Cementum is the hard tissue covering the tooth root and is essential for anchoring the tooth in the jawbone. Cementum contains living cells called cementoblasts responsible for cementum formation. Therefore, both dentin and cementum are vital regions of a tooth that house living cells involved in tooth development and maintenance. A: Dentin and enamel - Enamel is the outermost layer of the tooth and does not contain living cells. B: Anatomical crown and cementum - Anatomical crown is not a region of the tooth containing living cells. C: Enamel and cementum - Enamel does not contain living cells, only mineralized structures.

Correct Answer: B

Rationale: The correct answer is B: the feces to contain a much higher percentage of fat than normal. The hepatopancreatic ampullar sphincter controls the release of bile and pancreatic enzymes into the duodenum to aid in fat digestion. If it does not relax, fat digestion would be impaired, leading to undigested fat in feces. A: Chyme is the semi-liquid mixture of food and digestive juices in the stomach, not affected by this sphincter. C: Starch and protein digestion mainly occur in the stomach and small intestine, not directly influenced by this sphincter. D: Chyme enters the large intestine after passing through the small intestine, not controlled by this sphincter directly.

Correct Answer: A

Rationale: The correct answer is A: intercalated duct. The aqueous component of pancreatic juice is produced by intercalated ducts, which are responsible for secreting bicarbonate-rich fluid to neutralize the acidic chyme entering the duodenum. Other choices are incorrect because pancreatic islets (B) secrete hormones like insulin and glucagon, acinar cells (C) secrete digestive enzymes, and the duodenum (D) is the first part of the small intestine where pancreatic juice is delivered but not where it is produced.

Correct Answer: C

Rationale: The correct answer is C: low-density lipoproteins (LDL). LDL carries cholesterol to tissues where it is needed for steroid synthesis and bile salt production. LDL is known as the "bad" cholesterol transporter because high levels can lead to plaque buildup in arteries. Micelles (A) are small lipid droplets in the intestine, chylomicrons (B) transport dietary fats, and HDL (D) is known as the "good" cholesterol transporter that helps remove excess cholesterol from the bloodstream.

Correct Answer: D

Rationale: The correct answer is D because flavor signals from tasty, processed food can indeed override satiety signals even after a large meal. This is due to the hedonic aspect of eating, where the pleasure derived from consuming flavorful foods can lead to overeating despite feeling full. The brain's reward system plays a significant role in this process, causing individuals to continue eating beyond their caloric needs. In contrast, choices A, B, and C do not accurately describe the role of the intestine in the development of obesity. Choice A focuses on hormonal imbalances, which can contribute to obesity but does not solely explain the complex nature of obesity development. Choice B oversimplifies the control of energy intake, disregarding the various factors influencing eating behaviors. Choice C places the blame solely on personal choices without considering the physiological and psychological factors that contribute to overeating.