Which of these muscles causes closure of Rima glottidis in case of recurrent laryngeal nerve injury:

Correct Answer: C

Rationale: Recurrent laryngeal nerve injury paralyzes all intrinsic muscles except cricothyroid, but posterior cricoarytenoid (C) abducts cords its loss leaves cords adducted, closing rima. C is correct.

Correct Answer: D

Rationale: Endoderm forms liver (A), pancreas (B), and thyroid (C), via foregut and midgut outgrowths. Dermis (D) derives from mesoderm, forming skin's connective layer, not endoderm. D is the exception its mesodermal origin distinguishes it from endodermal derivatives.

Correct Answer: C

Rationale: Choice C, stating anatomical dead space is significantly large in shallow breathing, is false. Anatomical dead space is the volume of air in conducting airways (about 150 ml in a 75 kg adult) that doesn't participate in gas exchange. Choice A is true; it varies with age due to changes in airway size. ' Fowler's method uses nitrogen washout to estimate it. Choice D is wrong as a description it's Fowler's method, not Bohr's, that plots N₂ concentration (Bohr's uses CO₂ to calculate dead space), but it's still a true statement about measurement options. Choice E is accurate; 150 ml is a standard estimate. In shallow breathing, tidal volume decreases, making dead space a larger fraction of each breath, but the absolute anatomical dead space volume doesn't increase it remains fixed. Thus, ‘significantly large' misrepresents this, making C false.

Correct Answer: C

Rationale: In a pressure-volume loop, work to overcome airway resistance is the area during inspiration where pressure exceeds elastic recoil, typically AECFA (choice C). ABCEA (choice A) includes total inspiratory work (elastic + resistive). ABCFA (choice B) overestimates resistance by including elastic work. ABCDOA (choice D) represents expiratory work, not inspiratory resistance. OAFCDO (choice E) is unrelated. During inspiration from FRC, the curve from A (FRC) to E (peak pressure) reflects effort against resistance and elastic forces; C (end-inspiration) marks full volume. The triangle AECFA isolates resistive work, as pressure above the elastic recoil line (A to C) is due to airflow resistance. This aligns with respiratory mechanics, where resistive work depends on flow and airway caliber, making C the correct area.

Correct Answer: D

Rationale: peripheral chemoreceptors (carotid and aortic bodies) respond to decreased arterial pOâ‚‚, driving ventilation in hypoxia. Choice A is false; the apneustic centre is in the lower pons, not medulla (medulla houses DRG/VRG). Choice B is wrong; central chemoreceptors (medulla) detect CSF pH changes from COâ‚‚, not Oâ‚‚. Choice C is true; aortic body chemoreceptors sense pH drops (acidosis), stimulating breathing. Choice E is false; pOâ‚‚, not COâ‚‚, is the primary arterial driver under normal conditions COâ‚‚ via central chemoreceptors dominates. Peripheral chemoreceptors' sensitivity to low pOâ‚‚ (e.g., <60 mmHg) complements COâ‚‚/pH control, critical in hypoxemia (altitude, disease). This specificity and location make D the accurate statement in ventilatory control.