Opercular gills are found in

Correct Answer: D

Rationale: Opercular gills are found in both Lepidosteus and Polypterus, making choice D the correct answer. Lepidosteus, commonly known as the gar, and Polypterus, known as the bichir, are primitive fish species with opercular gills, which are a key feature in their respiratory system. Anabas, on the other hand, also known as the climbing perch, does not have opercular gills. Therefore, choices A, B, and C are incorrect as they do not possess opercular gills like Lepidosteus and Polypterus.

Correct Answer: D

Rationale: Correct Answer: D Rationale: 1. An injury to tissue can lead to inflammation, activating the immune response. 2. Influenza virus is a foreign pathogen that triggers the immune system to produce antibodies. 3. Cancer cells can be recognized as foreign and targeted by the immune system. 4. Choice D is correct because all options (A, B, and C) can provoke an immune response due to tissue damage, pathogens, or abnormal cells.

Correct Answer: D

Rationale: The correct answer is D: intrapleural pressure. Intrapleural pressure refers to the pressure within the pleural cavity, which is the space between the lungs and chest wall. This pressure is lower than atmospheric pressure, allowing the lungs to remain inflated. In space labeled '4', the pressure should be intrapleural pressure since it represents the pleural cavity. A: Alveolar pressure is the pressure within the alveoli of the lungs, not in the pleural cavity. B: Interpleural pressure is not a term commonly used in respiratory physiology. C: Subalveolar pressure is not a recognized term in respiratory physiology.

Correct Answer: B

Rationale: The correct answer is B: 20. The average human body consumes about 250 ml of oxygen per minute, and the lungs extract roughly one-fourth of this amount. Since the total cardiac output is around 5 liters per minute, and each liter of blood carries approximately 20 ml of oxygen, each 100 ml of blood leaving the alveolar capillaries would carry away roughly 20 ml of oxygen. Choice A (10 ml) is too low, as it does not account for the efficient oxygen extraction by the lungs. Choice C (30 ml) is too high, exceeding the typical oxygen-carrying capacity of blood. Choice D (50 ml) is also too high, as it overestimates the amount of oxygen carried by each 100 ml of blood.

Correct Answer: A

Rationale: If the dorsal respiratory group of neurons in the medulla oblongata were destroyed bilaterally, a person would stop breathing. This group is responsible for initiating inspiration by sending signals to the diaphragm and intercostal muscles. Without this neural input, the respiratory centers in the brainstem would not receive the necessary signals to stimulate breathing. Pulmonary ventilation would not increase markedly or the respiratory minute volume increase because the primary issue is the lack of neural drive for breathing, not an overstimulation of the respiratory system. Tidal volumes would not decrease as a direct consequence of destroying the dorsal respiratory group; it would lead to cessation of breathing altogether.