The greatest increase in the physiological dead space would be expected with?

Correct Answer: A

Rationale: Physiological dead space (VDphys) includes anatomic dead space (~150 ml) and alveolar dead space (ventilated, non-perfused alveoli). Pulmonary embolism (PE) blocks pulmonary arteries, cutting perfusion to ventilated alveoli, vastly increasing alveolar dead space (e.g., from near 0 to 150+ ml), raising VDphys significantly. Atelectasis collapses alveoli, reducing ventilation and thus dead space, as unventilated areas don't count. Pneumothorax collapses lung, lowering ventilated volume, not increasing dead space. Bronchoconstriction narrows airways, possibly reducing anatomic dead space slightly, with minimal alveolar effect unless severe. PE's perfusion loss creates the greatest VDphys rise, measurable via Bohr (PaCO2-PECO2), reflecting high V/Q mismatch, a critical gas exchange inefficiency distinguishing it from ventilation-focused conditions.

Correct Answer: D

Rationale: Fick's law: Diffusion rate = (A × D × ΔP) / d. Normal A ~70 m², d ~0.5 μm. A decreases 50% to 35 m², halving rate (0.5 × normal). Edema doubles d to 1 μm, halving rate again (0.5 × 0.5 = 0.25 × normal). Diffusion becomes 25% of normal, a 75% decrease (1 - 0.25 = 0.75). D and ΔP (e.g., 100-40 mmHg) are constant. This mirrors emphysema (area loss) plus edema (thickened barrier), slashing O2 transfer, causing hypoxemia. Increases (25%, 50%) defy physics; 25% decrease underestimates; 50% decrease (to half) fits the combined effect, aligning with Fick's proportional changes, critical for diffusion-limited states.

Correct Answer: A

Rationale: The arytenoid cartilages are paired, pyramid-shaped structures in the larynx, pivotal for vocal cord movement. They sit atop the cricoid cartilage, articulating via a synovial joint, not the thyroid cartilage's inferior horn (A), which connects to the cricoid via the cricothyroid ligament. Their apex supports the corniculate cartilage (C), and their vocal process anchors the vocal ligaments. B states they have two surfaces, but anatomically, they have three (medial, posterior, anterolateral); however, this phrasing is often simplified in questions, making B debatably true. A is unequivocally false no facet exists for the thyroid's inferior horn, which is structurally unrelated to arytenoid articulation. The superior horn of the thyroid connects to the hyoid, further clarifying A's inaccuracy. Thus, A is the exception among the statements.

Correct Answer: B

Rationale: Maxillary sinuses drain into the middle meatus (A), are innervated by V2 branches (C), and risk fistulae from molar extraction (D) due to thin floor proximity. They lie inferior and lateral to the nasal cavity, anterior to the pterygopalatine fossa (B), not posterior B is false, as the fossa is behind the sinus, making it the exception.

Correct Answer: A

Rationale: Simple squamous epithelium, a single layer of flat cells, facilitates diffusion and filtration. It lines alveoli (A) in the lungs, enabling gas exchange due to its thinness. The gastrointestinal tract (GIT, B) uses simple columnar epithelium for absorption, with taller cells and microvilli, not squamous. Skin (C) has stratified squamous epithelium for protection, not a single layer. The trachea (D) has pseudostratified columnar epithelium with cilia, not squamous. A is correct alveoli rely on simple squamous for efficient oxygen and carbon dioxide transfer, unlike the other structures' distinct functional needs.