An experiment is conducted in two persons (subjects T and V) with identical VTs (1000 milliliters), dead space volumes (200 milliliters), and ventilation frequencies (20 breaths per minute). Subject T doubles his VT and reduces his ventilation frequency by 50%. Subject V doubles his ventilation frequency and reduces his VT by 50%. What best describes the total ventilation (also called minute ventilation) and Va of subjects T and V?

Correct Answer: B

Rationale: Initial: VT = 1000 ml, VD = 200 ml, RR = 20/min. VE = VT × RR = 1000 × 20 = 20 L/min; VA = (VT - VD) × RR = (1000 - 200) × 20 = 16 L/min. T: VT = 2000 ml, RR = 10/min; VE = 2000 × 10 = 20 L/min (constant), VA = (2000 - 200) × 10 = 18 L/min (increases). V: VT = 500 ml, RR = 40/min; VE = 500 × 40 = 20 L/min (constant), VA = (500 - 200) × 40 = 12 L/min (decreases). T's higher VT boosts VA despite lower RR; V's lower VT cuts VA as dead space dominates. Option B (T: VE constant, VA increases; V: VE constant, VA decreases) fits, showing VT's impact on alveolar efficiency at fixed VE.

Correct Answer: C

Rationale: The quadrangular membrane is a fibroelastic layer in the larynx, intrinsic (B), spanning from the epiglottis to arytenoids. Its upper margin forms aryepiglottic folds (A), and its lower margin thickens into vestibular (false) folds (D). Innervation (C) is sensory via the internal laryngeal nerve (above cords), not the recurrent laryngeal nerve, which supplies muscles below (e.g., vocalis). C is the exception recurrent laryngeal doesn't innervate this membrane.

Correct Answer: B

Rationale: The urinary bladder's epithelium is transitional (B), a stratified type unique to the urinary tract, allowing stretch as the bladder fills. Its surface cells shift from cuboidal to flattened, adapting to volume changes without rupturing. Stratified squamous (A) lines the skin and mouth, resisting abrasion, not stretching. Simple squamous (C), a single thin layer, lines alveoli and capillaries for diffusion, unsuitable for the bladder's mechanical demands. Pseudostratified columnar (D) is in the trachea, with cilia, irrelevant here. Transitional epithelium's ability to transition shapes under tension makes B the correct choice for the bladder's dynamic environment.

Correct Answer: A

Rationale: The vagina is lined with stratified squamous non-keratinized epithelium (A), resisting abrasion and pathogens while staying moist. Simple squamous (B), thin and flat, suits diffusion (e.g., alveoli), not vaginal stress. Transitional (C) lines the bladder, stretching, not relevant here. Simple columnar (D) is in the intestine, not vagina. A is correct its multilayered, non-keratinized nature protects against mechanical and microbial challenges, unlike the others' unsuitable structures.