Nokea
Which of the following organs is supported by a layer of adventitia rather than serosa?
- A. esophagus
- B. stomach
- C. small intestine
- D. large intestine
Correct Answer: A
Rationale: The correct answer is A: esophagus. The esophagus is supported by a layer of adventitia, which is a connective tissue layer, instead of serosa, a serous membrane. The esophagus is located in the thoracic cavity, where it is surrounded by connective tissue rather than a serous membrane like the other choices. The stomach, small intestine, and large intestine are all intraperitoneal organs, meaning they are covered by a serosa layer. The esophagus, being a retroperitoneal organ, lacks a serosa layer and is instead supported by adventitia. This structural difference is important for understanding the anatomy and function of these organs.
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The absorption of fructose by intestinal mucosa is
- A. co- transport mechanism
- B. simple diffusion
- C. facilitated transport
- D. active transport
Correct Answer: C
Rationale: The correct answer is C: facilitated transport. Fructose is absorbed through facilitated diffusion using specific carrier proteins in the intestinal mucosa. This process does not require energy input and allows fructose to move down its concentration gradient. Unlike active transport (requiring energy) and co-transport mechanisms (involving multiple substances), fructose absorption occurs through facilitated transport by specific carrier proteins. Simple diffusion is not the main mechanism for fructose absorption due to its hydrophilic nature. Thus, facilitated transport best describes how fructose is absorbed by the intestinal mucosa.
The pacemaker signal generated by the SA node spreads to the ventricles by passing through the AV node. What would happen to the contraction of the ventricles if there was a complete block at the AV node?
- A. the ventricles would cease beating
- B. the ventricles would beat very fast and uncontrollably
- C. the ventricles would contract rhythmically, but more slowly
- D. the ventricles would contract at the same rate as the atria
Correct Answer: C
Rationale: Rationale: A complete block at the AV node would prevent the transmission of the pacemaker signal from the SA node to the ventricles. As a result, the ventricles would not receive the signal to contract at their normal rate. Instead, they would rely on their inherent ability to generate impulses, resulting in a slower, but still rhythmic contraction. This scenario is known as an escape rhythm, where a lower pacemaker takes over in the absence of the SA node signal.
Summary:
A: the ventricles would cease beating - Incorrect, as the ventricles have their own intrinsic pacemaker.
B: the ventricles would beat very fast and uncontrollably - Incorrect, as a complete AV block would lead to a slower rhythm.
D: the ventricles would contract at the same rate as the atria - Incorrect, as the ventricles and atria have different intrinsic rates.
In the production of the aqueous component of pancreatic juice, ______ ions are actively transported into the intercalated duct and sodium ions are exchanged for ______ ions.
- A. bicarbonate; hydrogen
- B. sodium; potassium
- C. bicarbonate; potassium
- D. hydrogen; potassium
Correct Answer: A
Rationale: The correct answer is A because in the production of pancreatic juice, bicarbonate ions are actively transported into the intercalated duct to ensure the alkalinity of the pancreatic juice. Additionally, sodium ions are exchanged for hydrogen ions to maintain the pH balance. This process helps neutralize the acidic chyme entering the small intestine from the stomach. The other choices are incorrect because potassium ions are not directly involved in this specific process, and the exchange of sodium ions for potassium ions does not contribute to the regulation of pancreatic juice pH.
Cholesterol is a major component of atherosclerotic plaque. Cholesterol carried by ______ is linked to coronary heart disease.
- A. micelle
- B. chylomicron
- C. low-density lipoprotein (LDL)
- D. high-density lipoprotein (HDL)
Correct Answer: C
Rationale: The correct answer is C: low-density lipoprotein (LDL). LDL is often referred to as "bad cholesterol" because it carries cholesterol from the liver to the cells, leading to the buildup of plaque in the arteries, which can result in coronary heart disease. Micelles are small lipid structures, not carriers of cholesterol. Chylomicrons are large lipoprotein particles that transport dietary fats, not primarily cholesterol. HDL is known as "good cholesterol" as it helps remove cholesterol from the bloodstream back to the liver for excretion, reducing the risk of atherosclerosis.
The center of the tooth that is filled with blood vessels and nerves is called the ______ and the cavity within the root of the tooth is called the ______.
- A. clinical crown; root canal
- B. pulp cavity; root canal
- C. pulp cavity; dentin
- D. dentin; root canal
Correct Answer: B
Rationale: The correct answer is B: pulp cavity; root canal. The pulp cavity is the center of the tooth filled with blood vessels and nerves, while the root canal is the cavity within the root of the tooth. This is because the pulp cavity contains the pulp tissue, which includes blood vessels and nerves, providing nourishment and sensation to the tooth. The root canal, on the other hand, is the space within the root where the pulp tissue extends down into. Choices A, C, and D are incorrect because they do not accurately describe the specific structures mentioned in the question.