Transitional epithelium is found in:

Correct Answer: A

Rationale: Transitional epithelium lines the ureter (A), bladder, and urethra, stretching as urine fills these structures. Its stratified cells shift from cuboidal to flat, adapting to tension. The intestine (B) has simple columnar epithelium for absorption, not stretching. The epidermis (C) is stratified squamous, protective, not transitional. Alveoli (D) use simple squamous for gas exchange, not stretch. A is correct transitional epithelium's unique adaptability suits the ureter's urinary role, unlike the others' distinct functions.

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.

Correct Answer: A

Rationale: destroying pre-Bötzinger complexes abolishes automatic respiration, as they generate the inspiratory rhythm in the medulla. Choice B (ventral group) modulates inspiration/expiration; damage impairs but doesn't stop rhythm. Choice C (dorsal group) drives inspiration; loss disrupts but doesn't abolish automaticity. Choice D (pons section) alters patterns (e.g., apneusis) via pneumotaxic/apneustic loss, not cessation. Choice E (rostral transection) preserves medullary function. The pre-Bötzinger complex, a pacemaker cluster, initiates breathing via spontaneous firing, driving phrenic and intercostal activity. Lesion studies confirm its destruction halts rhythm, unlike accessory regions. Thus, A is the critical site for automatic respiration's abolition.