NBME Gross Anatomy and Embryology 2

Question 1

A patient presents with inability to abduct the arm beyond 15 degrees after a humeral surgical neck fracture. Which nerve is most likely injured?

Accepted Answer

Axillary nerve

Answer

The axillary nerve wraps around the surgical neck of the humerus and innervates the deltoid, which is responsible for arm abduction beyond 15 degrees.

Question 2

During embryonic development, failure of the pleuroperitoneal membrane to close results in which congenital defect?

Accepted Answer

Congenital diaphragmatic hernia

Answer

Failure of the pleuroperitoneal membranes to fuse closes off the pericardioperitoneal canals, and incomplete closure allows abdominal viscera to herniate into the thorax.

Question 3

A patient with Colles fracture develops inability to oppose the thumb. Which structure is most likely compressed at the wrist?

Accepted Answer

Median nerve in carpal tunnel

Answer

Colles fracture can cause swelling that compresses the median nerve in the carpal tunnel, impairing thenar muscles responsible for thumb opposition.

Question 4

Which embryonic structure gives rise to the adrenal cortex?

Accepted Answer

Intermediate mesoderm

Answer

The adrenal cortex derives from intermediate mesoderm (specifically the mesothelium lining the posterior abdominal wall), while the medulla derives from neural crest cells.

Question 5

A stab wound to the posterior triangle of the neck results in weakness of shoulder elevation and head rotation. Which nerve is damaged?

Accepted Answer

Accessory nerve (CN XI)

Answer

The accessory nerve (CN XI) traverses the posterior triangle and innervates the trapezius (shoulder elevation) and sternocleidomastoid (head rotation).

NBME Practice Test

NBME Practice Test

NBME Gross Anatomy and Embryology 2