Lungs are held tightly to the wall of the thorax due to

Correct Answer: C

Rationale: The correct answer is C because the surface tension of the pleural fluid creates a cohesive force that keeps the lungs adhered to the thoracic wall. This, combined with the negative pressure in the pleural cavity, creates a vacuum effect that maintains the lungs' position. A) The diaphragm and intercostal muscle contractions help with breathing but do not directly secure the lungs to the thorax. B) Tight junctions between the lungs and thorax do not play a significant role in holding the lungs in place. D) Atmospheric pressure does not hold the lungs against the thoracic wall; rather, it helps with breathing by aiding in lung expansion and contraction.

Correct Answer: D

Rationale: The correct answer is D because the Hering-Breuer reflex is a protective mechanism that prevents lung damage from overinflation by inhibiting inspiration. When the lungs are at risk of overinflation, stretch receptors in the lung tissue send signals to the brainstem to reduce or stop inspiration, preventing excessive stretching of the alveoli. Choices A, B, and C are incorrect as the Hering-Breuer reflex is not involved in changes in blood pressure, PO2, or PCO2 regulation.

Correct Answer: D

Rationale: The correct answer is D because all the choices are structural features of the trachea. A is correct as the trachea has C-shaped cartilage rings for structural support. B is correct as the trachea contains smooth muscle fibers that help regulate airflow. C is correct as the trachea is lined with cilia that help sweep mucus and foreign particles out of the respiratory tract. Therefore, all of the above choices are structural features of the trachea, making D the correct answer.

Correct Answer: A

Rationale: The correct answer is A: alveoli. Alveoli are tiny air sacs in the lungs where gas exchange occurs. Oxygen from the air we breathe diffuses into the blood, and carbon dioxide from the blood diffuses into the alveoli to be exhaled. The pharynx, larynx, and trachea are parts of the respiratory system but do not participate in gaseous exchange. The pharynx serves as a passage for air and food, the larynx houses the vocal cords, and the trachea carries air to and from the lungs. Only the alveoli have the thin walls and large surface area necessary for efficient exchange of gases.

Correct Answer: C

Rationale: The correct answer is C: Breathing. Pulmonary ventilation refers to the process of breathing, which involves both inhalation and exhalation. Inhalation is the act of taking in air, while exhalation is the act of expelling air. Therefore, the term "pulmonary ventilation" encompasses both inhalation and exhalation, making choice C the correct answer. Choices A and B are incorrect because they only represent one part of the breathing process. Choice D is incorrect because it suggests that all choices are correct, which is not accurate in this context.