USMLE Anatomy 1 — Questions and Answers
Question 1: The femoral sheath is divided into three compartments. Which structure occupies the most medial compartment (femoral canal)?
- Femoral artery
- Femoral vein
- Femoral nerve
- Lymphatics and loose connective tissue (Correct answer)
Correct answer: Lymphatics and loose connective tissue
The femoral canal is the most medial compartment of the femoral sheath and contains lymphatics and loose connective tissue, forming the site of potential femoral hernias.
Question 2: A patient presents with weakness of hip flexion and knee extension along with loss of sensation over the anterior thigh and medial leg. Which nerve is most likely damaged?
- Obturator nerve
- Femoral nerve (Correct answer)
- Sciatic nerve
- Lateral femoral cutaneous nerve
Correct answer: Femoral nerve
The femoral nerve innervates the iliopsoas (hip flexion) and quadriceps (knee extension), and its saphenous branch provides sensation to the anterior thigh and medial leg.
Question 3: During a thyroidectomy a surgeon must preserve all intrinsic laryngeal muscles. Which muscle is NOT innervated by the recurrent laryngeal nerve?
- Posterior cricoarytenoid
- Lateral cricoarytenoid
- Cricothyroid (Correct answer)
- Thyroarytenoid
Correct answer: Cricothyroid
The cricothyroid is the only intrinsic laryngeal muscle innervated by the external branch of the superior laryngeal nerve, not the recurrent laryngeal nerve.
Question 4: A patient sustains a stab wound to the posterior triangle of the neck and subsequently develops shoulder droop with difficulty elevating the arm above 90 degrees. Which nerve was most likely injured?
- Phrenic nerve
- Accessory nerve (CN XI) (Correct answer)
- Long thoracic nerve
- Dorsal scapular nerve
Correct answer: Accessory nerve (CN XI)
The accessory nerve (CN XI) traverses the posterior triangle of the neck and innervates the trapezius; its injury causes shoulder droop and impairs full arm elevation.
Question 5: As the ureter descends into the pelvis, it crosses posterior to which structure at the pelvic brim?
- External iliac artery
- Internal iliac artery
- Common iliac artery bifurcation (Correct answer)
- Femoral artery
Correct answer: Common iliac artery bifurcation
The ureter crosses posterior to the bifurcation of the common iliac artery at the pelvic brim, an important landmark during pelvic and urologic surgery.
Question 6: Which of the following best describes the drainage territory of the right lymphatic duct?
- Entire right side of the body
- Right side of the head, neck, thorax, and right upper limb (Correct answer)
- All structures below the diaphragm on the right
- Right lower limb and right side of the abdomen
Correct answer: Right side of the head, neck, thorax, and right upper limb
The right lymphatic duct drains the right side of the head, neck, and thorax plus the right upper limb, emptying into the junction of the right internal jugular and subclavian veins.
Question 7: A patient with a Colles' fracture develops weakness of thumb opposition and loss of sensation over the lateral palm and first 3.5 fingers. Which nerve is most likely affected?
- Ulnar nerve
- Radial nerve
- Median nerve (Correct answer)
- Musculocutaneous nerve
Correct answer: Median nerve
The median nerve innervates the thenar muscles via its recurrent branch and provides sensory innervation to the lateral palm and first 3.5 fingers; it can be compressed in the carpal tunnel following a Colles' fracture.
USMLE Anatomy 1
The femoral sheath is divided into three compartments.
Which structure occupies the most medial compartment (femoral canal)?