Regarding intrapleural pressure, which one is true?

Correct Answer: D

Rationale: Intrapleural pressure (IPP) is the pressure in the pleural space, negative relative to atmospheric (760 mmHg) due to lung (inward) and chest wall (outward) recoil. At FRC, IPP is ~756 mmHg (-4 mmHg); inspiration drops it to ~-6 mmHg, and expiration raises it slightly, but it stays negative in health. It's always less than atmospheric pressure, maintaining lung expansion unless breached (e.g., pneumothorax). It's not just low during inspiration it's consistently subatmospheric. Respiratory muscles adjust IPP but don't equalize it to atmospheric pressure (that's pathological). IPP isn't the alveolar-pleural difference (transpulmonary pressure); it's the pleural cavity's absolute pressure. This constant negativity is vital for lung mechanics, making it the true statement reflecting pleural dynamics.

Correct Answer: A

Rationale: Bronchial asthma features reversible airway obstruction from inflammation and bronchoconstriction. Airway resistance rises due to narrowed bronchi true. During attacks, FEV1/FVC falls below 80% (e.g., 50-60%) as FEV1 drops more true. Bronchodilators (e.g., albuterol) relieve constriction true. Allergies (not listed) often trigger attacks true. However, cough suppressants aren't indicated asthma's productive cough clears mucus; suppressing it risks obstruction and infection false. Treatment prioritizes bronchodilation and inflammation control (e.g., steroids), not cough suppression, which could worsen symptoms. This exception contradicts asthma management, distinguishing it from true statements reflecting pathophysiology and therapy.

Correct Answer: B

Rationale: Solar radiation is the primary energy source for Earth's climate system, delivering ~1361 W/m² at the top of the atmosphere (solar constant), driving weather, ocean currents, and the hydrologic cycle. Geothermal heat (~0.087 W/m²) from Earth's core is minor, mainly affecting tectonics, not climate. Tidal forces from the Moon influence oceans but provide negligible energy for climate. Cosmic background radiation (~2.7 K, microwaves) is far too weak. Solar energy's dominance is evident ~99.97% of climate energy comes from the Sun, absorbed and redistributed via atmosphere and surface processes (e.g., albedo, greenhouse effect), making it the fundamental driver, per climate science (e.g., IPCC), distinguishing it from trivial contributors.

Correct Answer: C

Rationale: A lower tracheostomy involves an incision below the thyroid isthmus, typically between the 2nd and 4th tracheal rings, to create an airway. The superior thyroid artery (A) arises from the external carotid and supplies the upper thyroid, far from this site. The inferior thyroid artery (B), from the thyrocervical trunk, supplies the lower thyroid and lies posterior, near the recurrent laryngeal nerve, but is less exposed. The inferior thyroid veins (C) drain the thyroid plexus into the brachiocephalic veins, running anteriorly across the trachea, making them highly vulnerable during midline incision. The internal jugular vein (D) lies lateral, near the carotid sheath, and is less at risk unless the incision deviates significantly. Anatomical variations (e.g., a thyroid ima artery) exist, but C is the most consistently endangered due to its anterior position and delicate nature.

Correct Answer: A

Rationale: True vocal cords are formed by the vocal ligament (cricovocal membrane) and vocalis muscle, a part of the thyroarytenoid (A), which adjusts tension and adducts cords. Cricothyroid (B) tenses cords externally, thyrohyoid (C) elevates the larynx, and transverse arytenoid (D) adducts arytenoids, but only A directly integrates into the cord structure.