Semilunar cartilage inside the Laryngo tracheal chamber is

Correct Answer: A

Rationale: The correct answer is A: Arytenoid. Semilunar cartilages are located inside the laryngotracheal chamber and help maintain the patency of the airway during respiration. The arytenoid cartilages are paired, pyramid-shaped structures that sit on top of the cricoid cartilage. They play a crucial role in vocal cord movement and manipulation. Explanation of other choices: B: Cricoid cartilage is a complete ring-shaped cartilage located below the thyroid cartilage in the larynx, providing structural support to the airway. C: Sternohyal is a strap-like muscle attached to the sternum and hyoid bone, not a cartilage found in the laryngotracheal chamber. D: Petrohyal is part of the hyoid apparatus in some animals but is not found in the human larynx.

Correct Answer: D

Rationale: The correct answer is D because all three pathways (classical, lectin, and alternative) converge at the point of C3 activation, leading to the formation of C3b that binds to the cell wall of an infected cell or pathogen. In the classical pathway, C3 is activated by C4b2a complex; in the lectin pathway, it is activated by mannose-binding lectin-associated serine proteases; and in the alternative pathway, it is activated by spontaneous hydrolysis of C3. Therefore, the end result of all three pathways is the activation of C3 and subsequent binding of C3b to the cell wall. Choices A, B, and C are incorrect because each pathway alone does not lead to the activation of C3b and binding to the cell wall; it is the combined action of all three pathways that achieves this end result.

Correct Answer: D

Rationale: Dalton's law states that in a mixture of gases such as air, the total pressure exerted by the mixture of gases is equal to the sum of the partial pressures of each individual gas in the mixture. This means that each gas in a mixture behaves independently of the others. Therefore, choice D is correct as it directly reflects Dalton's law. Choices A, B, and C are incorrect because they do not accurately describe Dalton's law and its principle of partial pressures in gas mixtures.

Correct Answer: B

Rationale: Low pH (acidic conditions) causes hemoglobin to release oxygen more readily, enhancing oxygen delivery to tissues during internal respiration. External respiration (A) involves gas exchange in the lungs, not affected by pH. Carbon dioxide transport (C) is influenced by pH, but not directly related to oxygen binding. Hemoglobin synthesis (D) is the production of hemoglobin molecules, not influenced by pH during oxygen binding. Therefore, the correct answer is B as low pH primarily affects oxygen release during internal respiration.

Correct Answer: D

Rationale: The correct answer is D: sudden infant death syndrome (SIDS). SIDS is the leading cause of death for children under 1 year old due to unexplained reasons, typically occurring during sleep. A: Motor vehicle accidents are more common in older children. B: Falls are also more common in toddlers who are more mobile. C: Cardiac congenital malformations are a significant cause of death but are not the leading cause in this age group.