NBME 28 Questions with Answers &
Explanations | Latest Update
1
Exam Section 1: Item 1 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
A 25-year-old man is brought to the emergency department because of severe abdominal pain,
nausea, and vomiting for 1 hour. The pain originates in the left flank and radiates to his groin. His pulse
is 100/min, respirations are 18/min, and blood pressure is
150/100 mm Hg. Physical examination shows tenderness of the left flank and the left lower quadrant
of the abdomen. Bowel sounds are mildly hypoactive. Test of the stool for occult blood is negative.
Which of the following best explains these findings?
Colon neoplasm
Diverticulitis
Epididymitis
Renal infarction
Torsion of the testis
Ureteral calculus - ✔✔F.
Ureteral calculus typically presents with colicky, unilateral flank pain radiating to the groin, and with
gross or microscopic hematuria. Pain may be significant enough to trigger nausea, as in this case.
The common types of urinary tract calculi are calcium oxalate or
phosphate, ammonium magnesium phosphate, uric acid, and cystine. On urinalysis, red blood
cells without casts are common. Fever, dysuria, and pyuria would not be expected unless there
was a concomitant infection. Treatment for ureteral calculus is
symptomatic with pain control and nausea relief. Most ureteral calculi pass spontaneously after a period
of observation for patients with well-controlled pain and no signs of sepsis or infection. Stone removal
by shock wave lithotripsy or endoscopic removal is an
option for patients requiring emergency therapy. It is also an option for patients with persistent
obstruction, uncontrolled symptoms, or failure of stone progression. In general, stones smaller than
5 mm will pass without operative assistance. Obstructing stones may
require temporary placement of a ureteral stent to prevent hydronephrosis and renal
parenchymal injury.
,Incorrect Answers: A, B, C, D, and E.
Colon neoplasm (Choice A) would be unlikely in an otherwise healthy young patient with no family
history of polyposis syndromes and acute, severe, flank pain. It would typically present with
insidious weight loss, anemia, constipation, or blood per rectum. In
addition, test for stool for occult blood is negative, making this diagnosis unlikely.
Diverticulitis (Choice B) can present with left lower quadrant abdominal pain and tenderness but
would be less abrupt in presentation and typically present with fever, diarrhea, and hyperactive bowel
sounds. It would be unlikely to cause flank pain.
Epididymitis (Choice C) is a common cause of painful scrot
2
Exam Section 1: Item 2 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
Which of the following types of sensory information is compromised by lesions of the structure at
site X in the photograph shown?
Conscious proprioception
Pain sensation
Two-point discrimination
Unconscious proprioception
Vibration sense - ✔✔D.
The anterior lobe of the cerebellum (labeled X, pictured in cross-section as an arborized brain area
posterior to the brainstem and anterior to the primary fissure of the cerebellum) mediates
unconscious proprioception. The anterior lobe of the cerebellum receives
information from the spinocerebellar tract about proprioception, or body position, that is gathered
from muscle stretch and tension receptors on the ipsilateral side of the body. This proprioceptive
information is transmitted outside of conscious awareness. The deep
cerebellar nuclei use this proprioceptive information to control motor learning, movement course
changes, and balance. Damage to the anterior lobe of the cerebellum, which commonly occurs in
chronic alcoholism, may lead to broad-based gait ataxia.
Incorrect Answers: A, B, C, and E.
,Conscious proprioception (Choice A), two-point discrimination (Choice C), and vibration sense (Choice
E) are mediated by the dorsal column-medial lemniscus pathway, which relays this sensory information
up the spinal cord to the thalamus and terminates in the
primary sensory cortex in the parietal lobe. The cortex is a high-order brain area involved in
several conscious brain functions, which reflects this pathway's mediation of the conscious (rather
than unconscious) awareness of proprioception.
Pain sensation (Choice B) is mediated by the spinothalamic pathway. The spinothalamic pathway
transmits information about pain, temperature, and crude touch up the spinal cord to the
thalamus, terminating in the primary sensory cortex.
Educational Objective: The anterior lobe of the cerebellum mediates unconscious proprioception,
whereas conscious proprioception is controlled by the dorsal column-medial lemniscus pathway.
Lesions of the anterior lobe of the cerebellum can result in broad-
based gait ataxia.
%3D
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3
Exam Section 1: Item 3 of 50
National Board of Medical Examiners®
Comprehensive Basic Science Self-Assessment
Moving the forearm against resistance from palm-down to palm-up (supination) position requires
the use of which of the following muscles?
Biceps brachii
Brachialis
OC) Triceps
Flexor carpi radialis
Pronator teres - ✔✔A.
The biceps brachii muscle has two main actions, flexion of the elbow joint and supination of the
forearm. The biceps brachii contains two proximal heads, with the short head attaching to the coracoid
process of the scapula and the long head entering the shoulder
, joint and attaching to the supraglenoid tubercle. The distal biceps tendon inserts on the bicipital
tuberosity of the proximal radius. Because of its orientation crossing the elbow joint, contraction of
this muscle causes elbow flexion. Its eccentric insertion on the
proximal radius allows for it to wind around the radius during pronation and unwind when
contracted from around the proximal radius during supination.
Incorrect Answers: B, C, D and E.
The brachialis muscle (Choice B) originates on the anterior surface of the humerus and crosses the
elbow inserting on the tuberosity of the ulna. It does not wrap around the ulna and the ulna does not
rotate. Because of this, it does not contribute to supination or
pronation.
The triceps muscle (Choice C) serves to extend the elbow joint. Proximally, it originates from the
infraglenoid tubercle of the scapula (long head), just proximal to the radial groove (lateral head), and
just distal to the radial groove (medial head). Distally, it inserts on
the olecranon process of the ulna. Contraction of this muscle extends the elbow and does not
contribute to rotation.
Flexor carpi radialis (Choice D) originates on the medial epicondyle of the humerus and inserts on
the second and third metacarpal bones. This allows for flexion of the wrist.
Pronator teres (Choice E) is a muscle of the proximal forearm that extends from the medial
supracondylar ridge of the humerus and inserts on the lateral aspect of the radius. Contraction along
this axis will promote pronation, not supination.
Educational Objective: The biceps brachii
4
Exam Section 1: Item 4 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
A 35-year-old man is admitted to the hospital because of a 5-day history of fever and dyspnea.
He underwent a bone marrow transplantation 6 months ago; the procedure was complicated by
severe graft-versus-host disease. His temperature is 38°C
(100.4°F), and respirations are 30/min. Scattered crackles are heard on auscultation of the chest. A
chest x-ray shows patchy infiltrates. A transbronchial biopsy specimen shows findings consistent with
cytomegalovirus infection. Intravenous administration of
ganciclovir is begun. This drug interferes with the function of which of the following enzymes?
A) DNA polymerase
Explanations | Latest Update
1
Exam Section 1: Item 1 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
A 25-year-old man is brought to the emergency department because of severe abdominal pain,
nausea, and vomiting for 1 hour. The pain originates in the left flank and radiates to his groin. His pulse
is 100/min, respirations are 18/min, and blood pressure is
150/100 mm Hg. Physical examination shows tenderness of the left flank and the left lower quadrant
of the abdomen. Bowel sounds are mildly hypoactive. Test of the stool for occult blood is negative.
Which of the following best explains these findings?
Colon neoplasm
Diverticulitis
Epididymitis
Renal infarction
Torsion of the testis
Ureteral calculus - ✔✔F.
Ureteral calculus typically presents with colicky, unilateral flank pain radiating to the groin, and with
gross or microscopic hematuria. Pain may be significant enough to trigger nausea, as in this case.
The common types of urinary tract calculi are calcium oxalate or
phosphate, ammonium magnesium phosphate, uric acid, and cystine. On urinalysis, red blood
cells without casts are common. Fever, dysuria, and pyuria would not be expected unless there
was a concomitant infection. Treatment for ureteral calculus is
symptomatic with pain control and nausea relief. Most ureteral calculi pass spontaneously after a period
of observation for patients with well-controlled pain and no signs of sepsis or infection. Stone removal
by shock wave lithotripsy or endoscopic removal is an
option for patients requiring emergency therapy. It is also an option for patients with persistent
obstruction, uncontrolled symptoms, or failure of stone progression. In general, stones smaller than
5 mm will pass without operative assistance. Obstructing stones may
require temporary placement of a ureteral stent to prevent hydronephrosis and renal
parenchymal injury.
,Incorrect Answers: A, B, C, D, and E.
Colon neoplasm (Choice A) would be unlikely in an otherwise healthy young patient with no family
history of polyposis syndromes and acute, severe, flank pain. It would typically present with
insidious weight loss, anemia, constipation, or blood per rectum. In
addition, test for stool for occult blood is negative, making this diagnosis unlikely.
Diverticulitis (Choice B) can present with left lower quadrant abdominal pain and tenderness but
would be less abrupt in presentation and typically present with fever, diarrhea, and hyperactive bowel
sounds. It would be unlikely to cause flank pain.
Epididymitis (Choice C) is a common cause of painful scrot
2
Exam Section 1: Item 2 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
Which of the following types of sensory information is compromised by lesions of the structure at
site X in the photograph shown?
Conscious proprioception
Pain sensation
Two-point discrimination
Unconscious proprioception
Vibration sense - ✔✔D.
The anterior lobe of the cerebellum (labeled X, pictured in cross-section as an arborized brain area
posterior to the brainstem and anterior to the primary fissure of the cerebellum) mediates
unconscious proprioception. The anterior lobe of the cerebellum receives
information from the spinocerebellar tract about proprioception, or body position, that is gathered
from muscle stretch and tension receptors on the ipsilateral side of the body. This proprioceptive
information is transmitted outside of conscious awareness. The deep
cerebellar nuclei use this proprioceptive information to control motor learning, movement course
changes, and balance. Damage to the anterior lobe of the cerebellum, which commonly occurs in
chronic alcoholism, may lead to broad-based gait ataxia.
Incorrect Answers: A, B, C, and E.
,Conscious proprioception (Choice A), two-point discrimination (Choice C), and vibration sense (Choice
E) are mediated by the dorsal column-medial lemniscus pathway, which relays this sensory information
up the spinal cord to the thalamus and terminates in the
primary sensory cortex in the parietal lobe. The cortex is a high-order brain area involved in
several conscious brain functions, which reflects this pathway's mediation of the conscious (rather
than unconscious) awareness of proprioception.
Pain sensation (Choice B) is mediated by the spinothalamic pathway. The spinothalamic pathway
transmits information about pain, temperature, and crude touch up the spinal cord to the
thalamus, terminating in the primary sensory cortex.
Educational Objective: The anterior lobe of the cerebellum mediates unconscious proprioception,
whereas conscious proprioception is controlled by the dorsal column-medial lemniscus pathway.
Lesions of the anterior lobe of the cerebellum can result in broad-
based gait ataxia.
%3D
Previous
Next
3
Exam Section 1: Item 3 of 50
National Board of Medical Examiners®
Comprehensive Basic Science Self-Assessment
Moving the forearm against resistance from palm-down to palm-up (supination) position requires
the use of which of the following muscles?
Biceps brachii
Brachialis
OC) Triceps
Flexor carpi radialis
Pronator teres - ✔✔A.
The biceps brachii muscle has two main actions, flexion of the elbow joint and supination of the
forearm. The biceps brachii contains two proximal heads, with the short head attaching to the coracoid
process of the scapula and the long head entering the shoulder
, joint and attaching to the supraglenoid tubercle. The distal biceps tendon inserts on the bicipital
tuberosity of the proximal radius. Because of its orientation crossing the elbow joint, contraction of
this muscle causes elbow flexion. Its eccentric insertion on the
proximal radius allows for it to wind around the radius during pronation and unwind when
contracted from around the proximal radius during supination.
Incorrect Answers: B, C, D and E.
The brachialis muscle (Choice B) originates on the anterior surface of the humerus and crosses the
elbow inserting on the tuberosity of the ulna. It does not wrap around the ulna and the ulna does not
rotate. Because of this, it does not contribute to supination or
pronation.
The triceps muscle (Choice C) serves to extend the elbow joint. Proximally, it originates from the
infraglenoid tubercle of the scapula (long head), just proximal to the radial groove (lateral head), and
just distal to the radial groove (medial head). Distally, it inserts on
the olecranon process of the ulna. Contraction of this muscle extends the elbow and does not
contribute to rotation.
Flexor carpi radialis (Choice D) originates on the medial epicondyle of the humerus and inserts on
the second and third metacarpal bones. This allows for flexion of the wrist.
Pronator teres (Choice E) is a muscle of the proximal forearm that extends from the medial
supracondylar ridge of the humerus and inserts on the lateral aspect of the radius. Contraction along
this axis will promote pronation, not supination.
Educational Objective: The biceps brachii
4
Exam Section 1: Item 4 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
A 35-year-old man is admitted to the hospital because of a 5-day history of fever and dyspnea.
He underwent a bone marrow transplantation 6 months ago; the procedure was complicated by
severe graft-versus-host disease. His temperature is 38°C
(100.4°F), and respirations are 30/min. Scattered crackles are heard on auscultation of the chest. A
chest x-ray shows patchy infiltrates. A transbronchial biopsy specimen shows findings consistent with
cytomegalovirus infection. Intravenous administration of
ganciclovir is begun. This drug interferes with the function of which of the following enzymes?
A) DNA polymerase
