Which of the following structures is responsible for filtering lymph and supporting the immune system?

Correct Answer: B

Rationale: Lymph nodes are responsible for filtering lymph and supporting the immune system. They contain immune cells that trap and destroy pathogens, making them crucial in immune response. The other choices, kidneys, pancreas, and liver, do not play a direct role in filtering lymph or supporting the immune system. The kidneys filter blood to remove waste and regulate electrolytes, the pancreas is involved in digestion and blood sugar regulation, and the liver is primarily responsible for detoxification and metabolism.

Correct Answer: A

Rationale: The correct answer is A, mediastinum. The mediastinum is the space between the lungs in the chest that contains the heart, major blood vessels, esophagus, trachea, and other structures. This area separates the lungs into right and left cavities. Choice B, pericardial cavity, is incorrect as it refers to the space that surrounds the heart. Choice C, pleural cavity, is not the correct answer as it is the space between the layers of the pleura surrounding each lung. Choice D, thoracic space, is a vague term and not specific to the space between the lungs.

Correct Answer: B

Rationale: The correct answer is the Laryngopharynx. It is a common passageway for both food and air. The Esophagus (Choice A) is solely for transporting food from the throat to the stomach. The Nasopharynx (Choice C) is primarily involved in the passage of air. The Trachea (Choice D) is responsible for conducting air to and from the lungs and does not play a role in the passage of food.

Correct Answer: A

Rationale: The correct answer is A: Ectoderm. The nervous system develops from the ectoderm, which is the outermost of the three germ layers. The ectoderm gives rise to structures such as the skin, hair, nails, and the entire nervous system. Choices B, C, and D are incorrect because the endoderm gives rise to the lining of the gut and associated organs, the gastroderm is not a recognized germ layer, and the mesoderm forms structures like muscles, bones, blood, and the circulatory system, but not the nervous system.

Correct Answer: B

Rationale: The P-wave in an ECG represents the depolarization of the SA node and the atria, not atrial repolarization. Choice C, ventricular depolarization, is incorrect because the P-wave does not correspond to ventricular activity. Choice D, ventricular repolarization, is also incorrect as the P-wave does not depict ventricular repolarization. The correct interpretation is that the P-wave signifies the initiation of the electrical impulse at the SA node and subsequent atrial depolarization, making option B the correct answer.