The pigment containing iron is:

Correct Answer: D

Rationale: Hemosiderin (D) iron-storing pigment accumulates in tissues (e.g., liver, spleen) from RBC breakdown, staining blue on Prussian blue. Urobilinogen (A), bilirubin (B), hematoidin (C) heme metabolites lack iron, excreted or reabsorbed. All' overstates. Hemosiderin's iron link is key, guiding nursing for overload monitoring (e.g., hemochromatosis).

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: D

Rationale: A stab wound in the chest wall causing pneumothorax disrupts the negative intrapleural pressure (normally around -4 to -6 mmHg) that keeps the lungs expanded against the chest wall. When air enters the pleural space, this pressure equalizes with atmospheric pressure, eliminating the force holding the lung open. The lung, due to its elastic recoil, collapses inward toward the hilum, reducing its volume significantly. Conversely, the chest wall, with its outward elastic recoil, springs outward, expanding away from the lung. This results in the lung collapsing and the chest wall expanding, a classic feature of pneumothorax. The lung doesn't expand, as it loses the negative pressure tether, and the chest wall doesn't collapse, as its natural tendency is to spring outward when unrestrained. Other scenarios, like both expanding or fixing at FRC, don't reflect the mechanics of pleural pressure loss, making the collapse-expansion dynamic the expected outcome of such an injury.

Correct Answer: D

Rationale: Residual volume (RV) is the air remaining in the lungs after a maximal, forceful exhalation, typically 1-1.5 liters in adults. It prevents alveolar collapse and maintains gas exchange potential, measurable only indirectly (e.g., helium dilution). Tidal volume (VT) is the air moved in a normal breath (~500 ml), not after forceful effort. Expiratory reserve volume (ERV) is the extra air exhaled beyond a normal expiration (~1-1.5 L), expelled during forced exhalation, leaving RV behind. Vital capacity (VC) is the maximum air exhaled after maximal inhalation (ERV + VT + IRV, ~4-5 L), excluding RV. Inspiratory reserve volume (IRV) is additional air inhaled beyond a normal breath (~2-3 L), irrelevant here. RV's persistence reflects lung elasticity and chest wall mechanics, ensuring some air always remains, distinguishing it from volumes tied to active breathing phases or maximal efforts.

Correct Answer: A

Rationale: Physiological dead space (VD) is the volume of ventilated air not participating in gas exchange, comprising anatomic dead space (conducting airways) and alveolar dead space (non-perfused alveoli). Pulmonary embolism (PE) blocks pulmonary arteries, reducing perfusion to ventilated alveoli, markedly increasing alveolar dead space and thus physiological VD (e.g., from 150 ml to 300+ ml), as large lung regions become wasted ventilation.' Atelectasis collapses alveoli, reducing ventilation and dead space, as unventilated areas don't contribute to VD. Pneumothorax collapses lung tissue, decreasing ventilated volume, not increasing dead space. Bronchoconstriction narrows airways, potentially reducing anatomic dead space slightly, and doesn't directly increase alveolar dead space unless severe hypoxia ensues. PE's perfusion defect creates the greatest VD rise, measurable via increased PaCO2-PECO2 difference, distinguishing it as the most impactful condition among these, reflecting a high V/Q mismatch.