COMSAE PHASE 1 THORACIC ANATOMY
PRACTICE EXAM WITH ACTUAL
QUESTIONS AND VERIFIED ANSWERS,
PLUS EXPLAINED RATIONALES/EXPERT
VERIFIED FOR GUARANTEED 100% PASS
2026/LATEST UPDATE/INSTANT
DOWNLOAD PDF
1.
A 27-year-old man sustains a penetrating injury to the right lateral
thorax at the level of the fifth intercostal space in the midaxillary line.
During surgical exploration, the surgeon is concerned about injury to the
intercostal neurovascular bundle. Which arrangement of the major
intercostal neurovascular structures is found within the costal groove,
from superior to inferior?
A. Nerve, artery, vein
B. Artery, nerve, vein
C. Vein, artery, nerve
D. Vein, nerve, artery
Answer: C. Vein, artery, nerve
Rationale: Within the costal groove along the inferior border of each
rib, the principal intercostal neurovascular bundle is arranged from
superior to inferior as vein, artery, and nerve (VAN). The intercostal
nerve is therefore the most inferior component of the main bundle.
This anatomical relationship is clinically important when placing
chest tubes or performing intercostal injections because instruments
should generally pass immediately superior to the rib to reduce risk of
injury to the main bundle.
1
,2.
A patient undergoes thoracentesis for a large pleural effusion. The
physician plans to insert the needle through the ninth intercostal space
along the posterior axillary line. To minimize injury to the intercostal
neurovascular bundle, where should the needle be introduced?
A. Immediately inferior to the ninth rib
B. Directly through the costal cartilage
C. Immediately superior to the ninth rib
D. Through the midpoint of the tenth rib
Answer: C. Immediately superior to the ninth rib
Rationale: The principal intercostal neurovascular bundle travels in
the costal groove along the inferior surface of the rib. Therefore, a
needle inserted immediately superior to the rib below the desired
intercostal space avoids the main VAN bundle. Although smaller
collateral branches can course near the superior border of the rib, the
principal bundle is protected by staying immediately above the rib.
3.
A 45-year-old woman develops a chylous pleural effusion after
extensive mediastinal surgery. Injury to which structure most directly
explains this complication?
A. Azygos vein
B. Thoracic duct
C. Right lymphatic duct
D. Internal thoracic artery
Answer: B. Thoracic duct
Rationale: The thoracic duct transports lymph, including chyle from
intestinal lymphatic vessels, into the venous circulation. It ascends
2
,through the posterior mediastinum and crosses from the right side to
the left side around the level of T5. It ultimately drains into the left
venous angle, formed by the junction of the left internal jugular and
subclavian veins. Injury during thoracic or esophageal surgery can
produce a chylothorax.
4.
A CT scan demonstrates a mass in the middle mediastinum compressing
a structure that normally lies anterior to the roots of the lungs and
courses along the lateral surfaces of the pericardium. Which structure is
most likely compressed?
A. Phrenic nerve
B. Vagus nerve
C. Sympathetic trunk
D. Thoracic duct
Answer: A. Phrenic nerve
Rationale: The phrenic nerves descend through the thorax anterior to
the roots of the lungs and along the lateral surfaces of the fibrous
pericardium. They provide the primary motor innervation to the
diaphragm. The vagus nerves, in contrast, pass posterior to the roots of
the lungs and contribute to pulmonary and esophageal plexuses.
5.
A 62-year-old man has a left hilar lung mass. Imaging suggests
involvement of a nerve traveling posterior to the root of the lung. Which
nerve is most likely affected?
A. Left phrenic nerve
B. Left recurrent laryngeal nerve
3
, C. Left vagus nerve
D. Left sympathetic trunk
Answer: C. Left vagus nerve
Rationale: The vagus nerve passes posterior to the root of the lung,
whereas the phrenic nerve passes anterior to it. The vagus contributes
parasympathetic fibers to the pulmonary plexus and continues toward
the esophageal plexus. This relationship is a key distinction when
interpreting hilar or mediastinal pathology.
6.
A patient develops hoarseness following surgical removal of a mass near
the aortic arch. Which nerve was most likely injured?
A. Right phrenic nerve
B. Left recurrent laryngeal nerve
C. Right recurrent laryngeal nerve
D. Left greater splanchnic nerve
Answer: B. Left recurrent laryngeal nerve
Rationale: The left recurrent laryngeal nerve branches from the left
vagus nerve and loops inferiorly beneath the arch of the aorta near the
ligamentum arteriosum before ascending toward the larynx. Injury
causes vocal cord paralysis and hoarseness. The right recurrent
laryngeal nerve instead loops around the right subclavian artery.
7.
A congenital abnormality causes a persistent connection between the
pulmonary trunk and aortic arch after birth. Which embryologic
structure normally forms the adult remnant connecting these vessels?
4
PRACTICE EXAM WITH ACTUAL
QUESTIONS AND VERIFIED ANSWERS,
PLUS EXPLAINED RATIONALES/EXPERT
VERIFIED FOR GUARANTEED 100% PASS
2026/LATEST UPDATE/INSTANT
DOWNLOAD PDF
1.
A 27-year-old man sustains a penetrating injury to the right lateral
thorax at the level of the fifth intercostal space in the midaxillary line.
During surgical exploration, the surgeon is concerned about injury to the
intercostal neurovascular bundle. Which arrangement of the major
intercostal neurovascular structures is found within the costal groove,
from superior to inferior?
A. Nerve, artery, vein
B. Artery, nerve, vein
C. Vein, artery, nerve
D. Vein, nerve, artery
Answer: C. Vein, artery, nerve
Rationale: Within the costal groove along the inferior border of each
rib, the principal intercostal neurovascular bundle is arranged from
superior to inferior as vein, artery, and nerve (VAN). The intercostal
nerve is therefore the most inferior component of the main bundle.
This anatomical relationship is clinically important when placing
chest tubes or performing intercostal injections because instruments
should generally pass immediately superior to the rib to reduce risk of
injury to the main bundle.
1
,2.
A patient undergoes thoracentesis for a large pleural effusion. The
physician plans to insert the needle through the ninth intercostal space
along the posterior axillary line. To minimize injury to the intercostal
neurovascular bundle, where should the needle be introduced?
A. Immediately inferior to the ninth rib
B. Directly through the costal cartilage
C. Immediately superior to the ninth rib
D. Through the midpoint of the tenth rib
Answer: C. Immediately superior to the ninth rib
Rationale: The principal intercostal neurovascular bundle travels in
the costal groove along the inferior surface of the rib. Therefore, a
needle inserted immediately superior to the rib below the desired
intercostal space avoids the main VAN bundle. Although smaller
collateral branches can course near the superior border of the rib, the
principal bundle is protected by staying immediately above the rib.
3.
A 45-year-old woman develops a chylous pleural effusion after
extensive mediastinal surgery. Injury to which structure most directly
explains this complication?
A. Azygos vein
B. Thoracic duct
C. Right lymphatic duct
D. Internal thoracic artery
Answer: B. Thoracic duct
Rationale: The thoracic duct transports lymph, including chyle from
intestinal lymphatic vessels, into the venous circulation. It ascends
2
,through the posterior mediastinum and crosses from the right side to
the left side around the level of T5. It ultimately drains into the left
venous angle, formed by the junction of the left internal jugular and
subclavian veins. Injury during thoracic or esophageal surgery can
produce a chylothorax.
4.
A CT scan demonstrates a mass in the middle mediastinum compressing
a structure that normally lies anterior to the roots of the lungs and
courses along the lateral surfaces of the pericardium. Which structure is
most likely compressed?
A. Phrenic nerve
B. Vagus nerve
C. Sympathetic trunk
D. Thoracic duct
Answer: A. Phrenic nerve
Rationale: The phrenic nerves descend through the thorax anterior to
the roots of the lungs and along the lateral surfaces of the fibrous
pericardium. They provide the primary motor innervation to the
diaphragm. The vagus nerves, in contrast, pass posterior to the roots of
the lungs and contribute to pulmonary and esophageal plexuses.
5.
A 62-year-old man has a left hilar lung mass. Imaging suggests
involvement of a nerve traveling posterior to the root of the lung. Which
nerve is most likely affected?
A. Left phrenic nerve
B. Left recurrent laryngeal nerve
3
, C. Left vagus nerve
D. Left sympathetic trunk
Answer: C. Left vagus nerve
Rationale: The vagus nerve passes posterior to the root of the lung,
whereas the phrenic nerve passes anterior to it. The vagus contributes
parasympathetic fibers to the pulmonary plexus and continues toward
the esophageal plexus. This relationship is a key distinction when
interpreting hilar or mediastinal pathology.
6.
A patient develops hoarseness following surgical removal of a mass near
the aortic arch. Which nerve was most likely injured?
A. Right phrenic nerve
B. Left recurrent laryngeal nerve
C. Right recurrent laryngeal nerve
D. Left greater splanchnic nerve
Answer: B. Left recurrent laryngeal nerve
Rationale: The left recurrent laryngeal nerve branches from the left
vagus nerve and loops inferiorly beneath the arch of the aorta near the
ligamentum arteriosum before ascending toward the larynx. Injury
causes vocal cord paralysis and hoarseness. The right recurrent
laryngeal nerve instead loops around the right subclavian artery.
7.
A congenital abnormality causes a persistent connection between the
pulmonary trunk and aortic arch after birth. Which embryologic
structure normally forms the adult remnant connecting these vessels?
4
