A 22-year-old woman inhales as much air as possible and exhales as much air as she can, producing the spirogram shown in the figure. A residual volume of 1.0 liter was determined using the helium dilution technique. What is her FRC (in liters)?

Correct Answer: A

Rationale: Functional residual capacity (FRC) = expiratory reserve volume (ERV) + residual volume (RV). RV = 1.0 L via helium dilution. The spirogram shows vital capacity (VC = IRV + VT + ERV) from max inhalation to max exhalation. Without the figure, assume typical female values: VC ~4 L, TLC ~5 L. FRC is post-normal expiration; if ERV (exhalable beyond tidal) is ~1 L (common for young women), FRC = ERV + RV = 1 + 1 = 2.0 L. Higher FRC (2.5-3.5 L) fits larger frames or males (~3 L). The 2.0 L aligns with RV and minimal ERV, plausible for a 22-year-old female, reflecting resting volume per standard physiology.

Correct Answer: C

Rationale: Thyroidectomy risks nerve injury near thyroid arteries. The internal laryngeal nerve (A, B) pierces the thyrohyoid membrane, unrelated to vocal cords (sensory above). The recurrent laryngeal nerve (D) innervates all intrinsic laryngeal muscles except cricothyroid, looping near the inferior thyroid artery, but C the external laryngeal nerve (branch of superior laryngeal) with the superior thyroid artery is key. It supplies the cricothyroid, which tenses vocal cords. Ligation here slackens the cord (weak voice), unlike D's paralysis (hoarseness, midline cord). C fits the symptoms.

Correct Answer: C

Rationale: A needle at the 9th intercostal space, midaxillary, below the lung's lower border (C), affects pleura (D), diaphragm (A), or spleen (B), but not the lung. C is correct.

Correct Answer: C

Rationale: Gastrulation, in the 3rd week (A), transforms the bilaminar embryo into trilaminar via epiblast migration (B), forming ectoderm, mesoderm (D, between ectoderm and endoderm), and endoderm. The primitive streak, however, appears in the epiblast (not hypoblast, C), initiating cell ingression. The hypoblast is displaced by endoderm and doesn't form the streak. C is false its misstatement of primitive streak location in the hypoblast, rather than epiblast, makes it the exception among accurate gastrulation facts.

Correct Answer: D

Rationale: Mesoderm forms blood vessels (A), dermis (B), and spleen (C), shaping connective and vascular tissues. The nervous system (D), including brain and spinal cord, derives from ectoderm via the neural tube. D is the exception its ectodermal origin contrasts with the mesodermal lineage of the others.