COMSAE PHASE 1 FORM 113 NEWEST EXAM PREPARATION
WITH COMPLETE QUESTIONS AND CORRECT ANSWERS WITH
RATIONALES | ALREADY GRADED A+||BRAND NEW VERSION!!
SECTION I — FOUNDATIONAL BIOMEDICAL SCIENCES (Questions 1–50)
Anatomy & Embryology
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. The radial nerve is particularly vulnerable in midshaft
humeral fractures.
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.
1
,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 SVC at a
lower level, and the phrenic nerve runs more inferiorly. The thoracic duct is
located more posteriorly in the mediastinum.
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.
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
2
,flexor tendons. Compression causes pain, paresthesia’s, and weakness in the
thumb, index, and middle fingers. The ulnar nerve passes through Guyon's canal.
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.
7. The ligament that prevents posterior displacement of the tibia on the femur is
the:
A. Anterior cruciate ligament (ACL)
B. Posterior cruciate ligament (PCL)
C. Medial collateral ligament
D. Lateral collateral ligament
Answer: B. Posterior cruciate ligament (PCL)
Rationale: The PCL prevents posterior translation of the tibia relative to the femur.
The ACL prevents anterior translation.
8. A 55-year-old woman with a pituitary macroadenoma presents with bitemporal
hemianopia. Which structure is compressed?
A. Optic chiasm
B. Optic nerve
C. Optic tract
D. Lateral geniculate nucleus
Answer: A. Optic chiasm
Rationale: The optic chiasm lies superior to the pituitary sella. A pituitary
3
, macroadenoma expanding upward compresses the decussating nasal retinal
fibers, producing bitemporal hemianopia.
9. The epiglottis is derived from which pharyngeal arch?
A. First arch
B. Second arch
C. Third arch
D. Fourth arch
Answer: C. Third arch
Rationale: The epiglottis arises from the hypopharyngeal eminence (third arch).
The first arch gives rise to muscles of mastication; the second arch gives muscles
of facial expression.
10. Which pharyngeal arch contributes to the muscles of facial expression?
A. First arch
B. Second arch
C. Third arch
D. Fourth arch
Answer: B. Second arch
Rationale: The second arch gives the facial nerve (CN VII) and muscles of facial
expression. The first arch gives muscles of mastication.
Physiology
11. A researcher inhibits the Na⁺/K⁺-ATPase of a cardiac myocyte. Which change is
most likely?
A. Decreased intracellular Na⁺
B. Increased intracellular K⁺
C. Increased intracellular Na⁺
D. Hyperpolarization
Answer: C. Increased intracellular Na⁺
Rationale: The Na⁺/K⁺-ATPase normally exports three Na⁺ ions while importing
4
WITH COMPLETE QUESTIONS AND CORRECT ANSWERS WITH
RATIONALES | ALREADY GRADED A+||BRAND NEW VERSION!!
SECTION I — FOUNDATIONAL BIOMEDICAL SCIENCES (Questions 1–50)
Anatomy & Embryology
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. The radial nerve is particularly vulnerable in midshaft
humeral fractures.
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.
1
,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 SVC at a
lower level, and the phrenic nerve runs more inferiorly. The thoracic duct is
located more posteriorly in the mediastinum.
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.
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
2
,flexor tendons. Compression causes pain, paresthesia’s, and weakness in the
thumb, index, and middle fingers. The ulnar nerve passes through Guyon's canal.
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.
7. The ligament that prevents posterior displacement of the tibia on the femur is
the:
A. Anterior cruciate ligament (ACL)
B. Posterior cruciate ligament (PCL)
C. Medial collateral ligament
D. Lateral collateral ligament
Answer: B. Posterior cruciate ligament (PCL)
Rationale: The PCL prevents posterior translation of the tibia relative to the femur.
The ACL prevents anterior translation.
8. A 55-year-old woman with a pituitary macroadenoma presents with bitemporal
hemianopia. Which structure is compressed?
A. Optic chiasm
B. Optic nerve
C. Optic tract
D. Lateral geniculate nucleus
Answer: A. Optic chiasm
Rationale: The optic chiasm lies superior to the pituitary sella. A pituitary
3
, macroadenoma expanding upward compresses the decussating nasal retinal
fibers, producing bitemporal hemianopia.
9. The epiglottis is derived from which pharyngeal arch?
A. First arch
B. Second arch
C. Third arch
D. Fourth arch
Answer: C. Third arch
Rationale: The epiglottis arises from the hypopharyngeal eminence (third arch).
The first arch gives rise to muscles of mastication; the second arch gives muscles
of facial expression.
10. Which pharyngeal arch contributes to the muscles of facial expression?
A. First arch
B. Second arch
C. Third arch
D. Fourth arch
Answer: B. Second arch
Rationale: The second arch gives the facial nerve (CN VII) and muscles of facial
expression. The first arch gives muscles of mastication.
Physiology
11. A researcher inhibits the Na⁺/K⁺-ATPase of a cardiac myocyte. Which change is
most likely?
A. Decreased intracellular Na⁺
B. Increased intracellular K⁺
C. Increased intracellular Na⁺
D. Hyperpolarization
Answer: C. Increased intracellular Na⁺
Rationale: The Na⁺/K⁺-ATPase normally exports three Na⁺ ions while importing
4
