Most of the oxygen transported by the blood is

Correct Answer: B

Rationale: The correct answer is B: bound to hemoglobin. This is because hemoglobin is the protein in red blood cells that carries oxygen from the lungs to tissues throughout the body. Oxygen binds to the iron atoms in hemoglobin, forming oxyhemoglobin. This accounts for the majority of oxygen transport in the blood. A: Dissolved in plasma is incorrect as only a small fraction of oxygen is carried this way. C: In ionic form as a solute in plasma is incorrect as oxygen is not typically found in ionic form in the blood. D: Bound to the same protein as carbon dioxide is incorrect as oxygen binds to hemoglobin, while carbon dioxide primarily binds to different proteins such as carbonic anhydrase.

Correct Answer: A

Rationale: The correct answer is A: alveoli. The alveoli are not part of the bronchial tree; they are the tiny air sacs at the end of the bronchial tree where gas exchange occurs. The bronchial tree consists of the bronchi, terminal bronchioles, and respiratory bronchioles, which are responsible for conducting air into the lungs. Alveoli are located at the end of the respiratory bronchioles and are where oxygen is absorbed into the bloodstream and carbon dioxide is released. Therefore, alveoli are not considered part of the bronchial tree.

Correct Answer: A

Rationale: The correct answer is A: Trachea. Carina is the point where the trachea is divided into the left and right primary bronchi. This anatomical landmark is located at the lower end of the trachea where it bifurcates into the bronchi. The other choices, B: bronchi and C: larynx, are incorrect because the trachea is the structure that is divided at the carina, not the bronchi or larynx. Choice D: none of them is also incorrect because the trachea is indeed divided at the carina. Therefore, the correct answer is A as it accurately describes the anatomical location where the trachea divides.

Correct Answer: D

Rationale: The correct answer is D because during inhalation, the rib muscles and diaphragm contract, expanding the chest cavity which increases its volume. This decrease in pressure inside the lungs allows air to rush in. Therefore, all the actions mentioned in options A, B, and C occur during inhalation. Rib muscle and diaphragm contraction, increased volume in the chest cavity, and decreased air pressure collectively facilitate the process of inhalation. The other choices are incorrect because they do not encompass all the necessary actions that occur during inhalation.

Correct Answer: B

Rationale: The correct answer is B because montelukast is a leukotriene modifier that works by reducing inflammation and promoting bronchodilation in asthma patients. This helps in managing asthma symptoms and improving lung function. A is incorrect because montelukast can cause mild GI side effects such as nausea and diarrhea. C is incorrect because while montelukast helps in controlling asthma symptoms, it does not provide immediate relief during acute episodes. D is incorrect because montelukast is typically used as an add-on therapy and not as a replacement for all other asthma medications.