COMSAE PHASE 1 FORM 113 PRACTICE
EXAM LATEST 2026 QUESTIONS WITH
VERIFIED ANSWERS AND RATIONALES
SECTION 1: GROSS ANATOMY & EMBRYOLOGY
Question 1
A 23-year-old man sustains a midshaft humeral fracture after
a fall. He is unable to extend his wrist or fingers. Which nerve
is most likely injured?
A. Median nerve
B. Ulnar nerve
C. Radial nerve
D. Axillary nerve
Answer: C. Radial nerve
Rationale: The radial nerve wraps around the spiral groove of
the humerus and innervates the triceps, brachioradialis, and
all wrist/finger extensors. Injury at this location causes
"wrist drop" (inability to extend the wrist and fingers). The
radial nerve is particularly vulnerable in midshaft humeral
fractures .
,Question 2
Which bone articulates with the acetabulum to form the hip
joint?
A. Tibia
B. Fibula
C. Femur
D. Patella
Answer: C. Femur
Rationale: The femoral head articulates with the acetabulum
of the os coxae to form the hip joint, a ball-and-socket
synovial joint. The tibia and fibula form the knee joint, while
the patella articulates with the femur at the patellofemoral
joint .
Question 3
A stab wound to the superior mediastinum most directly risks
injury to which structure?
A. Brachiocephalic vein
B. Azygos vein
C. Phrenic nerve
D. Thoracic duct
,Answer: A. Brachiocephalic vein
Rationale: The left and right brachiocephalic veins unite in
the superior mediastinum to form the superior vena cava. The
azygos vein enters the superior vena cava at a lower level, and
the phrenic nerve runs more inferiorly. The thoracic duct is
located more posteriorly in the mediastinum .
Question 4
During development, failure of the neural tube to close at the
cranial end causes:
A. Spina bifida occulta
B. Anencephaly
C. Meningocele
D. Chiari malformation
Answer: B. Anencephaly
Rationale: Anencephaly results from failure of the cranial
neural tube to close during embryogenesis. Spina bifida and
meningocele are caudal neural tube defects. Chiari
malformation involves herniation of the cerebellar tonsils .
Question 5
Which nerve is compressed in carpal tunnel syndrome?
, A. Ulnar nerve
B. Median nerve
C. Radial nerve
D. Musculocutaneous nerve
Answer: B. Median nerve
Rationale: The median nerve passes through the carpal tunnel
along with the flexor tendons. Compression causes pain,
paresthesias, and weakness in the thumb, index, and middle
fingers. The ulnar nerve passes through Guyon's canal .
Question 6
A patient presents with "foot drop" and a steppage gait.
Which nerve is damaged?
A. Superficial peroneal nerve
B. Deep peroneal nerve
C. Tibial nerve
D. Sural nerve
Answer: B. Deep peroneal nerve
Rationale: The deep peroneal nerve innervates the tibialis
anterior, which is responsible for dorsiflexion. Foot drop with
steppage gait results from weakness in dorsiflexion. The
superficial peroneal nerve innervates foot everters .
EXAM LATEST 2026 QUESTIONS WITH
VERIFIED ANSWERS AND RATIONALES
SECTION 1: GROSS ANATOMY & EMBRYOLOGY
Question 1
A 23-year-old man sustains a midshaft humeral fracture after
a fall. He is unable to extend his wrist or fingers. Which nerve
is most likely injured?
A. Median nerve
B. Ulnar nerve
C. Radial nerve
D. Axillary nerve
Answer: C. Radial nerve
Rationale: The radial nerve wraps around the spiral groove of
the humerus and innervates the triceps, brachioradialis, and
all wrist/finger extensors. Injury at this location causes
"wrist drop" (inability to extend the wrist and fingers). The
radial nerve is particularly vulnerable in midshaft humeral
fractures .
,Question 2
Which bone articulates with the acetabulum to form the hip
joint?
A. Tibia
B. Fibula
C. Femur
D. Patella
Answer: C. Femur
Rationale: The femoral head articulates with the acetabulum
of the os coxae to form the hip joint, a ball-and-socket
synovial joint. The tibia and fibula form the knee joint, while
the patella articulates with the femur at the patellofemoral
joint .
Question 3
A stab wound to the superior mediastinum most directly risks
injury to which structure?
A. Brachiocephalic vein
B. Azygos vein
C. Phrenic nerve
D. Thoracic duct
,Answer: A. Brachiocephalic vein
Rationale: The left and right brachiocephalic veins unite in
the superior mediastinum to form the superior vena cava. The
azygos vein enters the superior vena cava at a lower level, and
the phrenic nerve runs more inferiorly. The thoracic duct is
located more posteriorly in the mediastinum .
Question 4
During development, failure of the neural tube to close at the
cranial end causes:
A. Spina bifida occulta
B. Anencephaly
C. Meningocele
D. Chiari malformation
Answer: B. Anencephaly
Rationale: Anencephaly results from failure of the cranial
neural tube to close during embryogenesis. Spina bifida and
meningocele are caudal neural tube defects. Chiari
malformation involves herniation of the cerebellar tonsils .
Question 5
Which nerve is compressed in carpal tunnel syndrome?
, A. Ulnar nerve
B. Median nerve
C. Radial nerve
D. Musculocutaneous nerve
Answer: B. Median nerve
Rationale: The median nerve passes through the carpal tunnel
along with the flexor tendons. Compression causes pain,
paresthesias, and weakness in the thumb, index, and middle
fingers. The ulnar nerve passes through Guyon's canal .
Question 6
A patient presents with "foot drop" and a steppage gait.
Which nerve is damaged?
A. Superficial peroneal nerve
B. Deep peroneal nerve
C. Tibial nerve
D. Sural nerve
Answer: B. Deep peroneal nerve
Rationale: The deep peroneal nerve innervates the tibialis
anterior, which is responsible for dorsiflexion. Foot drop with
steppage gait results from weakness in dorsiflexion. The
superficial peroneal nerve innervates foot everters .
