Even after forceful exhalation, a certain volume of air remains in the lungs, referred to as?

Correct Answer: D

Rationale: Residual volume (RV) is the air remaining after maximal expiration (~1-1.5 L), preventing alveolar collapse and measurable via helium dilution or body plethysmography. Tidal volume (VT, ~500 ml) is normal breath size, not post-forceful exhalation. Expiratory reserve volume (ERV, ~1-1.5 L) is extra air exhaled beyond normal expiration, expelled during forced effort, leaving RV. Vital capacity (VC, ~4-5 L) is the maximum exhailable volume (IRV + VT + ERV), excluding RV. RV's persistence reflects lung elasticity and chest wall limits, ensuring some air stays, distinct from volumes tied to active breathing or maximal efforts, making it the correct term for this residual air critical for maintaining lung structure.

Correct Answer: A

Rationale: Idiopathic pulmonary fibrosis (IPF) scars lung interstitium, reducing elasticity. Functional residual capacity (FRC, ~2.5-3 L) drops (e.g., to 2 L) as stiff lungs limit resting volume true, a restrictive feature. Tidal volume (VT, ~500 ml) decreases, not increases, as breathing shallows to compensate false. Pulmonary vascular resistance rises, not falls, as fibrosis narrows capillaries false. Total lung capacity (TLC, ~6 L) decreases (e.g., to 4 L), not rises, due to restricted expansion false. Lower FRC reflects IPF's mechanics stiff lungs shrink volumes, impair gas exchange, and raise breathing effort, aligning with restrictive pathophysiology and distinguishing it from options contradicting volume and resistance changes.

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.