10 USMLE Anatomy and Embryology Questions with Answers and Explanations (Set 1)

These 10 USMLE anatomy and embryology practice questions link anatomy to clinical cases: cranial nerve and muscle injuries, arterial supply and bleeding, nerve injuries in surgery, kidney development, spinal cord levels, pharyngeal arch derivatives, carpal tunnel and inguinal hernias. Each question includes the correct answer and an explanation.

Written by Dr. Ray Makar, MD, author of the Repeated USMLE Questions eBook series.

Prefer video? Watch daily USMLE case questions on MedFocus by Dr. Ray on YouTube.

How to use this page: read the question, pick your answer, then tap Show Answer and Explanation.

Questions

Question 1. A 32-year-old woman visits her physician because she hasn’t been able to protrude and depress her tongue for the last 2 weeks. Which of the following is the most likely affected muscle?

A- Genioglossus muscle
B- Hyoglossus muscle
C- Styloglossus muscle
D- Palatoglossus muscle

The genioglossus muscle is responsible for protruding and depressing the tongue. It is innervated by the hypoglossal nerve (cranial nerve XII). Damage to the hypoglossal nerve or the muscle itself can lead to tongue deviation (if unilateral) or difficulty protruding and depressing the tongue (if bilateral).
Hyoglossus muscle depresses and retracts the tongue. Styloglossus muscle retracts and elevates the tongue. Palatoglossus muscle elevates the posterior tongue and is innervated by the vagus nerve (CN X), not the hypoglossal nerve.
Since the patient cannot protrude and depress the tongue, the most likely affected muscle is the genioglossus.
The correct answer is A

 

Question 2. A 43 year-old woman visits her physician for a follow up after abdominal hysterectomy. During surgery, the obturator nerve was severed. What is the most likely lost due to this injury?

A- Abduction of the hip joint
B- Adduction of the hip joint
C- Flexion of the knee joint
D- Extension of the knee joint
E- Dorsiflexion of the ankle joint

Adduction of the hip joint is induced by the muscles of the medial compartment of the thigh which are innervated by the obturator nerve.
The correct answer is B

 

Question 3. An 80-year-old man is diagnosed with severe atherosclerosis. He has been a heavy smoker for 62 years and also has a long history of hypercholesterolemia. Atherosclerotic occlusion of which of these arteries will cause insufficient perfusion of the urinary bladder?

A- External iliac
B- Inferior epigastric
C- Internal iliac
D- Lateral sacral

The internal iliac artery supplies the bladder through its superior and inferior vesicular branches. This question is basically asking which artery supplies the urinary bladder, masked in a clinical scenario. This is an example of how anatomy is tested in the USMLE Step 1.
The correct answer is C

 

Question 4. A 48-year-old woman is taken for autopsy after she is pronounced dead. Her family found her unresponsive and the ER team performed CPR but she didn’t respond. The autopsy reveals the cause of death as internal hemorrhage from an artery close to the posterior wall of the body of the stomach due to erosion of a gastric ulcer. Which of these arteries is most likely involved in this case?

A- Celiac trunk
B- Left gastric artery
C- Right gastric artery
D- Splenic artery
E- Superior mesenteric artery

Celiac trunk, left gastric and right gastric artery are located close to the anterior wall of the body of the stomach while the superior mesenteric artery is located close to the duodenum. Splenic artery runs close to the posterior wall of the body of the stomach. It arises from the celiac artery and passes around the stomach to supply the spleen.
The correct answer is D

 

Question 5. A 21-year-old Chinese student presents to the clinic for her pre-college physical examination. She tells her physician that she is worried about a solid mass in the roof of her mouth for about 3 years. The patient does not smoke or drink alcohol. She did not lose or gain weight in the last 3 years. On local examination, there is 1.5 inch non-tender mass on her hard palate with definite edges. There are no palpable lymph nodes. What is the most likely diagnosis of this mass?

A- Kaposi’s sarcoma of the palate
B- Lymphoproliferative disease
C- Malignant melanoma of the palate
D- Palatal abscess
E- Torus palatinus

Torus palatinus is a chronic benign bony growth on the hard palate. It is common in young women and Asians. Abscess is an acute condition and should not last that long. Other choices are all malignant and are excluded by history and examination.
The correct answer is E

 

Question 6. A 3-month-old baby is recognized to have a horseshoe kidney. In this case, which of the following structures is known to prevent this abnormally shaped kidney from occupying the correct position?

A- Abdominal aorta
B- Celiac trunk
C- Inferior mesenteric artery
D- Superior mesenteric artery

A horseshoe kidney is a resultant of a condition where the inferior poles of the two kidneys become fused together during development. When the kidneys start to rise from the pelvis, they will encounter the inferior mesenteric artery and thus are unable to rise to their normal locations in the abdomen.
The correct answer is C

 

Question 7. An acrobat fell from a height of about 30 feet on her back during her performance and sustained a serious injury. Her thoracic and abdominal muscles are completely paralyzed. She is still able to breathe as the diaphragm is not paralyzed by this injury. What is the most likely level of her injury?

A- Second cervical
B- Seventh cervical
C- Fifth thoracic
D- First lumbar
E- Third lumbar

The diaphragm, which is innervated by the phrenic nerve, escaped this injury. The phrenic nerve is originated from C3-C5 nerve roots so; the level of injury should be under the level of C5. Injuries of or under the level of T5 would spare some of the thoracic muscles.
The correct answer is B

 

Question 8. A 32-year-old man visits his physician for a follow up after receiving a punch to the right side of his face. He complains of difficulty to chew food on the right side. Examination reveals possible injury to muscles of mastication. Muscles of mastication are derived from which of these structures?

A- Branchial Arch 1
B- Branchial Arch 2
C- Branchial Arch 3
D- Branchial Arch 4
E- Branchial Arch 5

Muscles of mastication are derived from branchial arch 1. Arch 2 gives rise to muscles of facial expression while muscles of the pharynx and larynx are derived from arches 3-6.
The correct answer is A

 

Question 9. A 45-year-old woman working as a secretary visits her physician complaining of tingling and numbness in her hands. Upon conducting a physical examination, the doctor finds that the patient also has decreased sensation in all her fingers, except for the fifth digit. Keeping these in mind, which of the following muscles is usually weakened in patients suffering from this condition?

A- Adductor pollicis
B- Dorsal interossei
C- Lumbricals
D- Opponens pollicis

The patient is suffering from carpal tunnel syndrome. This condition occurs in those who work for long hours with repetitive hand motions, such as typing on a computer. In carpal tunnel, the median nerve gets compressed, which leads to a reduced sensation on the first three as well as one-half digits. There is also a loss of strength in the thumb due to reduced strength of the opponens pollicis and the abductor pollicis brevis.
The correct answer is D

 

Question 10. A 65-year-old man is scheduled for a repair of an abdominal hernia. The patient has an abdominal hernia that can be reduced by pushing the contents of the abdomen back through the external ring. While performing the repair, the surgeon observes that the hernial sac protrudes through the abdominal wall above the inguinal ligament. It is also medial to the inferior epigastric vessels. After observing all these, what can be concluded about the type of a hernia the patient is suffering from?

A- Direct inguinal hernia
B- Indirect inguinal hernia
C- Femoral hernia
D- Hiatal hernia

The patient is suffering from a direct inguinal hernia. This type of hernias is known to protrude directly through the abdominal wall in the Hesselbach triangle. This is surrounded by the inguinal ligament, the inferior epigastric vessels, and the rectus abdominis muscle. The patient’s abdominal contents passed through the wall of the abdomen and went through the external inguinal ring. Many older patients are often diagnosed with direct inguinal hernias. This is because, over a period of time, the pressure and tension exerted on the hernia eventually causes the abdominal wall to give way.
The correct answer is A

 

High-yield points from this set

  • The genioglossus protrudes the tongue (hypoglossal nerve, CN XII).
  • The obturator nerve supplies the hip adductors (medial thigh).
  • The bladder is supplied by vesical branches of the internal iliac artery.
  • A posterior gastric ulcer can erode the splenic artery; a posterior duodenal ulcer, the gastroduodenal artery.
  • Torus palatinus is a benign bony growth in the midline of the hard palate.
  • A horseshoe kidney gets trapped under the inferior mesenteric artery during ascent.
  • The phrenic nerve comes from C3–C5 (“C3, 4, 5 keeps the diaphragm alive”).
  • First pharyngeal arch = muscles of mastication (CN V3); second arch = muscles of facial expression (CN VII).
  • Carpal tunnel syndrome weakens the thenar muscles such as opponens pollicis (median nerve).
  • A direct inguinal hernia passes medial to the inferior epigastric vessels through Hesselbach triangle.

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