All are derivatives of the neural crest except:

Correct Answer: C

Rationale: Neural crest cells, an ectodermal derivative, give rise to melanocytes (A), Schwann cells (B), and adrenal medulla (D). Melanocytes produce pigment, Schwann cells myelinate peripheral nerves, and the adrenal medulla forms chromaffin cells for adrenaline. Pia mater (C), the innermost meninges, derives from neural tube mesenchyme (possibly mesodermal or ectodermal, but not neural crest). Neural crest contributes to peripheral nervous system and pigment cells, not central meninges. C is the exception its origin outside neural crest lineage distinguishes it from the others.

Correct Answer: D

Rationale: Elastic fibres being more abundant in the bronchi and bronchioles than the upper respiratory tract (choice D) is correct because these structures require elasticity to recoil during expiration, aiding in air movement. Choice A is incorrect as regular (terminal) bronchioles lack glands; glands are found in larger airways like bronchi. Choice B is wrong because the larynx contains cartilage and skeletal muscle, not significant smooth muscle, which is more prominent in the trachea and bronchi. Choice C is false since goblet cells decrease in number in smaller airways like small bronchi and are absent in respiratory bronchioles, which have club cells instead. The abundance of elastic fibres in the lower respiratory tract (bronchi and bronchioles) compared to the upper tract (nasal cavity, pharynx, larynx) supports lung elasticity and function, making D the accurate statement.

Correct Answer: C

Rationale: Choice C is false. Surfactant, produced by Type II pneumocytes (choice E), reduces surface tension (choice B) and stabilizes alveoli (choice A) by equalizing pressure across sizes, preventing collapse. It also lowers alveolar pressure, reducing fluid transudation into capillaries (choice D). However, per Laplace's law (P = 2T/r), surface tension (T) drives pressure (P) inversely with radius (r). Without surfactant, smaller alveoli would have higher pressure and collapse into larger ones (higher T, lower r). Surfactant lowers T more in smaller alveoli, equalizing pressure, not making larger alveoli's T lower than smaller ones' it balances them. Choice C misstates this; larger alveoli naturally have lower pressure due to larger r, but T isn't inherently lower without surfactant's effect. Thus, C contradicts surfactant's role, making it the false statement.

Correct Answer: D

Rationale: Emphysema (choice D) increases lung compliance, unlike others, making it the exception. Compliance is ease of lung expansion (ΔV/ΔP). Lung fibrosis (choice A) stiffens tissue, reducing compliance. Increased pulmonary venous pressure (choice B) causes edema, stiffening lungs. Prolonged unventilation (choice C) leads to atelectasis or surfactant loss, decreasing compliance. Alveolar edema (choice E) adds fluid, reducing elasticity. Emphysema destroys alveolar walls, reducing elastic recoil (floppy lungs), increasing compliance despite impaired function. This contrasts with restrictive conditions (A, B, C, E) that stiffen lungs, lowering compliance. Emphysema's obstructive nature raises FRC but eases expansion per pressure unit, distinguishing D as the state not decreasing compliance.

Correct Answer: B

Rationale: the diaphragm moves 7-10 cm during deep breathing, reflecting its maximal excursion. Choice A is true; it rises (relaxes) for expiration, descends (contracts) for inspiration. Choice C is false; contraction varies regionally, though coordinated. Choice D is wrong; internal intercostals aid expiration, not inspiration (external intercostals assist). In deep breathing, the diaphragm flattens significantly, increasing thoracic volume by 5-10 cm, as seen in fluoroscopy. This drives large tidal volumes (e.g., 3-5 L in vital capacity), unlike quiet breathing (1-1.5 cm). As the primary inspiratory muscle, its descent with effort supports B as the accurate statement, consistent with anatomical capacity in healthy adults.