USMLE Anatomy 3

Question 1

Which cranial nerve exits the skull through the foramen ovale?

Accepted Answer

Mandibular nerve (CN V3)

Answer

The mandibular nerve (V3) exits through the foramen ovale; V1 exits through the superior orbital fissure, V2 through the foramen rotundum, and CN VII through the stylomastoid foramen.

Question 2

A patient presents with weakness of finger abduction and adduction, loss of sensation over the medial 1.5 fingers and hypothenar eminence, and a 'claw hand' deformity affecting primarily the ring and little fingers. Which nerve is most likely injured?

Accepted Answer

Ulnar nerve

Answer

The ulnar nerve innervates the interossei (finger abduction/adduction), hypothenar muscles, and provides sensation to the medial 1.5 fingers; injury causes claw hand due to loss of intrinsic muscle function.

Question 3

The blood-testis barrier, which protects developing germ cells from immune surveillance, is formed by tight junctions between which cells?

Accepted Answer

Sertoli cells

Answer

Sertoli cells form tight junctions with each other to create the blood-testis barrier, separating developing spermatocytes from the systemic immune system.

Question 4

Which of the following structures is located in the posterior mediastinum?

Accepted Answer

Thoracic duct

Answer

The thoracic duct ascends through the posterior mediastinum alongside the descending thoracic aorta, esophagus, and azygos vein before draining into the left subclavian vein.

Question 5

A 68-year-old man presents with progressive hoarseness. Imaging reveals a large aortic arch aneurysm. Which nerve is most likely compressed by this aneurysm?

Accepted Answer

Left recurrent laryngeal nerve

Answer

The left recurrent laryngeal nerve hooks under the aortic arch in the thorax, making it susceptible to compression from aortic arch aneurysms or mediastinal masses causing hoarseness.

USMLE Practice Test

USMLE Practice Test

USMLE Anatomy 3