Each of the following is true regarding the spleen, except:

Correct Answer: C

Rationale: Rationale: C is correct because the spleen is a secondary lymphoid organ, not a primary one. The spleen filters blood, not lymph fluid. A is correct as the spleen is located in the described position. B is correct as the splenic vessels do communicate with the spleen at the hilum. D is correct as lymphocytes and dendritic cells are indeed concentrated in the white pulp. Summary: A, B, and D are correct statements about the spleen. C is incorrect because the spleen is a secondary lymphoid organ, not a primary one.

Correct Answer: A

Rationale: The correct answer is A because at higher temperatures, oxygen dissociation from hemoglobin increases, leading to lower oxygen saturation. This is due to the Bohr effect, where increased temperature shifts the hemoglobin-oxygen dissociation curve to the right. Therefore, the percent of oxygen saturation is greater at 38 degrees Celsius compared to 43 degrees Celsius. Choice B is incorrect because higher temperatures decrease oxygen saturation. Choice C is incorrect as the saturation is not equal at different temperatures due to the Bohr effect. Choice D is incorrect because the saturation at 20 degrees Celsius would be higher than at 38 degrees Celsius.

Correct Answer: C

Rationale: The correct answer is C, vagus and glossopharyngeal nerves. Chemoreceptors in the carotid bodies and aortic bodies detect changes in blood chemistry and send signals to the brainstem. The glossopharyngeal nerve carries signals from the carotid bodies, while the vagus nerve carries signals from the aortic bodies. These signals are crucial for regulating breathing and maintaining homeostasis. The other choices, trigeminal (A) and hypoglossal (B) nerves, are not involved in transmitting signals from chemoreceptors to the brain. Choice D, glossopharyngeal nerve alone, is not correct as both glossopharyngeal and vagus nerves are involved in this process.

Correct Answer: B

Rationale: The correct answer is B: Inability of the heart to pump blood effectively. Heart failure occurs when the heart is unable to pump blood efficiently to meet the body's needs. This can lead to symptoms such as shortness of breath, fatigue, and fluid retention. Explanation: 1. Heart failure is a chronic condition that develops over time due to various factors such as high blood pressure, heart attacks, or heart muscle damage. 2. The inability of the heart to pump blood effectively results in reduced blood flow to the body's organs and tissues. 3. This can lead to a buildup of fluid in the lungs and other parts of the body, causing symptoms like shortness of breath and swelling. 4. A sudden stoppage of the heart (Choice A) would result in cardiac arrest, not heart failure. 5. Accumulation of excess cholesterol in the arteries (Choice C) refers to atherosclerosis, not heart failure. 6. An irregular heartbeat (Choice D) may be a symptom

Correct Answer: B

Rationale: The correct answer is B: expiration. The internal intercostal muscles are used during expiration to decrease the size of the thoracic cavity, increasing the pressure in the lungs, causing air to be pushed out. During inspiration, the external intercostal muscles are used to expand the thoracic cavity. Choice A is incorrect as it refers to inspiration. Choice C is incorrect because internal intercostal muscles are not involved in both inspiration and expiration simultaneously. Choice D is incorrect as there is no specific muscle action associated with a "pause" in breathing.