A healthy 10-year-old boy Mohammad Emyan breathes quietly under resting conditions. His tidal volume is 400 milliliters and his ventilation frequency is 12/min. Which of the following best describes the ventilation of the upper, middle, and lower lung zones in this boy?

Correct Answer: D

Rationale: In an upright healthy child, gravity gradients affect ventilation. At rest (VT = 400 ml, RR = 12/min), intrapleural pressure is more negative at the apex (~-10 cm H2O) than base (~-2.5 cm H2O), making apices less compliant and bases more so. Diaphragm movement ventilates lower zones most, where compliance and volume change peak. Studies (e.g., West) show lower lobes get ~4 times more ventilation per unit volume than apices. Thus, ventilation is Lower > Middle > Upper. Equal distribution ignores gravity; Upper > Middle > Lower reverses it. VA = (400 - ~120 ml VD) × 12 ≈ 3.36 L/min, mostly basal, making this the best description of regional ventilation in a healthy boy.

Correct Answer: D

Rationale: The pterygopalatine fossa hosts the maxillary artery (A, via pterygomaxillary fissure), maxillary nerve (B, via foramen rotundum), and pterygopalatine ganglion. The ganglion receives preganglionic parasympathetic fibers from the facial nerve (VII) via the greater petrosal nerve (C), and postganglionic sympathetic fibers from the deep petrosal nerve (carotid plexus), not the lesser petrosal (D), which supplies the parotid via IX. D is incorrect sympathetic input is via deep petrosal, making it the exception.

Correct Answer: B

Rationale: Simple cuboidal epithelium, a single layer of cube-shaped cells, is specialized for secretion and absorption. It lines thyroid gland follicles (B), where it secretes thyroid hormones, and other structures like kidney tubules. The intestine (A) has simple columnar epithelium for nutrient absorption, with taller cells and microvilli. The epidermis (C) is stratified squamous, designed for protection, not a single layer. The trachea (D) features pseudostratified columnar epithelium with cilia and goblet cells for mucus clearance. B is correct thyroid follicles match the description, unlike the others, which serve different functions requiring distinct epithelial types.

Correct Answer: D

Rationale: Red marrow (A) contains hematopoietic cells, producing blood cells. Yellow marrow (B) is mostly adipocytes, storing fat. Yellow can convert to red marrow (C) in anemia to boost hematopoiesis. Yellow marrow lacks significant hematopoietic cells (D), unlike red, making D false. Its fat-dominated composition contrasts with red marrow's active blood cell production, and while conversion occurs, yellow marrow itself doesn't house hematopoietic cells unless transformed, making D the exception.

Correct Answer: B

Rationale: Respiratory bronchioles are lined with simple cuboidal epithelium (B), transitioning from conducting airways' pseudostratified columnar (C) to alveoli's simple squamous (A). Simple columnar (D) is in intestines, not lungs. B is correct cuboidal cells with some cilia and club cells suit gas exchange initiation, unlike others.