Anatomy Flashcards

A patient presents with weakness of shoulder abduction beyond 90° and difficulty with overhead activities. Imaging reveals compression at the spinoglenoid notch. Which specific branch of which nerve is most likely affected?

Answer: Deep branch of the suprascapular nerve

The suprascapular nerve passes through the suprascapular notch to innervate the supraspinatus, then wraps around the spine of the scapula at the spinoglenoid notch to innervate the infraspinatus. Compression at the spinoglenoid notch specifically affects the infraspinatus branch (deep branch), causing isolated infraspinatus weakness. Since the infraspinatus is critical for external rotation and assists in abduction beyond 90°, this results in the described deficit without affecting supraspinatus function.

During a posterior approach to the hip, the surgeon identifies the short external rotators. Which of the following muscles is MOST superior in the anatomical layering of this group, lying directly beneath the gluteus minimus?

Answer: Piriformis

The piriformis is the most superior of the short external rotators of the hip, lying immediately deep to the gluteus minimus and exiting the pelvis through the greater sciatic foramen. The order from superior to inferior is: piriformis, superior gemellus, obturator internus tendon, inferior gemellus, and quadratus femoris. The piriformis serves as the key surgical landmark in posterior hip approaches and its relationship to the sciatic nerve is clinically critical.

A 45-year-old undergoes a parotidectomy. Postoperatively, the patient reports flushing and sweating of the cheek during meals. This is due to aberrant regeneration of parasympathetic fibers innervating which structure?

Answer: Sweat glands of the skin

Frey syndrome (auriculotemporal syndrome) occurs when postganglionic parasympathetic fibers from the auriculotemporal nerve (destined for the parotid gland) aberrantly reinnervate the sweat glands and cutaneous vessels of the overlying facial skin. Since sweat glands receive cholinergic parasympathetic-type innervation (though technically sympathetic postganglionic fibers), the misdirected parasympathetic fibers can activate them during salivary stimulation, producing gustatory sweating and flushing — hallmarks of Frey syndrome.

In a cadaveric dissection, the following structures are identified in the posterior mediastinum: the thoracic duct, azygos vein, and descending aorta. At the level of T8, which structure passes through the diaphragm at the caval hiatus?

Answer: Inferior vena cava and right phrenic nerve

The caval hiatus in the diaphragm is located at T8 and transmits the inferior vena cava along with the right phrenic nerve. The aortic hiatus (T12) transmits the aorta, thoracic duct, and azygos vein. The esophageal hiatus (T10) transmits the esophagus and both vagus nerves. The right phrenic nerve passes through the caval opening rather than through the muscle itself because the IVC is intimately associated with the central tendon where the caval hiatus is located.

A researcher studies the blood supply to the femoral head in adults. Which artery contributes the LEAST to femoral head perfusion after skeletal maturity, making its disruption less clinically significant?

Answer: Artery of the ligamentum teres (obturator artery branch)

In adults, the artery of the ligamentum teres (a branch of the obturator artery) contributes minimally to femoral head perfusion — it is functionally important in children but becomes negligible after skeletal maturity and physeal closure. The dominant blood supply to the adult femoral head comes from the medial circumflex femoral artery via the retinacular arteries (superior and inferior), particularly the superior retinacular vessels. This is why intracapsular femoral neck fractures in adults carry high risk of avascular necrosis — they disrupt the retinacular supply while the ligamentum teres contribution is insufficient to compensate.

A surgical resident is performing a cricothyrotomy in an emergency. After incising the cricothyroid membrane, which structure is at greatest risk of injury if the incision is extended too far laterally?

Answer: Cricothyroid artery

The cricothyroid arteries, branches of the superior thyroid arteries, traverse the superior aspect of the cricothyroid membrane in a transverse anastomotic arch. When a cricothyrotomy incision is extended too laterally, these vessels are at greatest immediate risk of laceration, causing significant hemorrhage that can obscure the airway. The external branch of the superior laryngeal nerve courses along the lateral surface of the inferior constrictor near the cricothyroid muscle but lies more posterior and superior. The recurrent laryngeal nerve runs in the tracheoesophageal groove, posterior to the thyroid gland, well away from the cricothyroid membrane.