Thorax Practice Questions

Q: Which structure does not pass through the aortic opening?

Vagus nerve. The diaphragm has three major openings, and remembering the structures passing through them is high-yield for NEET-PG. The **Aortic Opening** is located at the level of the **T12** vertebra. It is an osseo-aponeurotic opening (not a muscular one), meaning it does not constrict during inspiration. ### Why the Vagus Nerve is the Correct Answer The **Vagus nerve (CN X)** does not pass through the aortic opening. Instead, the left and right vagus nerves form the esophageal plexus and enter the abdomen as the anterior and posterior vagal trunks by passing through the **Esophageal Opening** at the level of **T10**. ### Analysis of Incorrect Options * **Aorta:** As the name suggests, the Aorta is the primary structure passing through this opening to become the abdominal aorta. * **Azygos vein:** This vein ascends through the aortic opening on the right side of the aorta. * **Thoracic duct:** This major lymphatic vessel ascends through the aortic opening, typically situated between the aorta and the azygos vein. ### High-Yield NEET-PG Pearls To remember the structures passing through the Aortic Opening (T12), use the mnemonic **"AAT"**: 1. **A**orta 2. **A**zygos vein 3. **T**horacic duct **Summary of Major Diaphragmatic Openings:** * **Vena Caval (T8):** Inferior Vena Cava, Right Phrenic nerve. * **Esophageal (T10):** Esophagus, Vagus nerves, Esophageal branches of left gastric vessels. * **Aortic (T12):** Aorta, Azygos vein, Thoracic duct. *Clinical Note:* Because the aortic opening is behind the diaphragm (posterior to the median arcuate ligament), blood flow in the aorta is not compromised during diaphragmatic contraction.

Q: The interior of the right atrium is partially divided into two parts by which structure?

Crista terminalis. The interior of the right atrium is embryologically and anatomically divided into two distinct parts by the **crista terminalis**, a vertical muscular ridge. [1] ### 1. Why Crista Terminalis is Correct The crista terminalis serves as the internal boundary separating: * **Sinus Venarum:** The smooth-walled posterior part derived from the embryonic sinus venosus. It receives the SVC, IVC, and coronary sinus. [1] * **Atrium Proper:** The rough-walled anterior part derived from the primitive atrium, characterized by musculi pectinati. Externally, this ridge corresponds to a shallow groove called the **sulcus terminalis**. ### 2. Why Other Options are Incorrect * **Musculi Pectinati:** These are the parallel muscular ridges found only in the anterior part (atrium proper) and the auricle. They do not divide the atrium into two parts. * **Fossa Ovalis:** This is an oval depression on the interatrial septum, representing the site of the fetal foramen ovale. It separates the right atrium from the left atrium, not the interior of the right atrium itself. * **Sinus Venarum Cavarum:** This is the name of the smooth posterior *part* itself, not the dividing structure. ### 3. High-Yield NEET-PG Pearls * **SA Node Location:** The Sinoatrial (SA) node is located in the upper part of the sulcus terminalis, just below the opening of the SVC. * **Valve of IVC (Eustachian Valve):** Directs oxygenated blood from the IVC toward the foramen ovale in fetal life. * **Triangle of Koch:** Located in the right atrium; its boundaries are the **Tendon of Todaro**, the septal leaflet of the tricuspid valve, and the orifice of the coronary sinus. It contains the **AV node**.

Q: Which of the following is the uppermost structure in the hilum of the right lung?

Bronchus. In the anatomy of the lung hilum, the arrangement of structures differs between the right and left sides, which is a high-yield topic for NEET-PG. **Why Bronchus is Correct:** On the **right side**, the principal bronchus divides into two before entering the hilum: the **Eparterial bronchus** and the **Hyparterial bronchus**. The Eparterial bronchus (so named because it lies *above* the pulmonary artery) is the **uppermost structure** in the right hilum. [1] **Analysis of Incorrect Options:** * **Superior pulmonary vein:** This is the most **anterior** structure in both the right and left hila, but not the highest on the right. * **Bronchial artery:** These are small nutritional vessels usually located on the posterior aspect of the bronchi; they do not occupy the superior-most position. [1] * **Inferior pulmonary vein:** This is consistently the most **inferior** structure in the hilum of both lungs. **High-Yield NEET-PG Pearls:** 1. **Mnemonic for Superior-to-Inferior arrangement:** * **Right Hilum:** **B-A-V** (Eparterial **B**ronchus → Pulmonary **A**rtery → Pulmonary **V**ein). * **Left Hilum:** **A-B-V** (Pulmonary **A**rtery → **B**ronchus → Pulmonary **V**ein). Note that the Pulmonary Artery is the highest structure on the left. 2. **Anterior-to-Posterior arrangement:** This is identical for both lungs: **V-A-B** (Pulmonary **V**ein → Pulmonary **A**rtery → **B**ronchus). 3. **Pulmonary Ligament:** A fold of pleura extending downwards from the hilum that allows for the expansion of pulmonary veins during increased venous return.

Q: During an emergency thoracotomy, an incision is made greater than 1 cm lateral to the sternal margin. This incision will preserve which of the following structures?

Internal mammary artery. **Explanation:** The **Internal Mammary Artery (IMA)**, also known as the Internal Thoracic Artery, is a branch of the first part of the subclavian artery. It descends vertically behind the costal cartilages, approximately **1 cm lateral to the sternal margin** on each side. During an emergency thoracotomy or the placement of a chest tube, incisions must be made carefully to avoid vascular injury. By making an incision **greater than 1 cm lateral** to the sternum, the surgeon ensures they stay lateral to the course of the IMA, thereby preserving it. **Analysis of Options:** * **Internal Mammary Artery (Correct):** Its anatomical location (1 cm lateral to the sternum) makes it the primary structure at risk during parasternal incisions. * **Intercostal Artery & Vein (Incorrect):** These vessels run along the **inferior margin** of each rib within the costal groove. They are avoided by making incisions or inserting needles at the **superior border** of the rib, regardless of the distance from the sternum. * **Superficial Epigastric Artery (Incorrect):** This is a branch of the femoral artery found in the inguinal region/lower abdomen; it is not relevant to the thoracic anatomy involved in a thoracotomy. **High-Yield Pearls for NEET-PG:** * **Safe Zone:** For needle thoracocentesis (tension pneumothorax), the needle is inserted in the 2nd intercostal space in the mid-clavicular line or 4th/5th in the mid-axillary line. * **IMA Usage:** The IMA is the "gold standard" conduit for Coronary Artery Bypass Grafting (CABG) due to its superior long-term patency. * **Anatomy:** The IMA terminates in the 6th intercostal space by dividing into the **musculophrenic** and **superior epigastric** arteries.

Q: Occlusion of the left anterior descending artery will lead to infarction of which area?

Anterior wall of the left ventricle. The **Left Anterior Descending (LAD) artery**, often called the "widow-maker," is a branch of the Left Main Coronary Artery. It travels in the anterior interventricular groove and is the most common site of coronary occlusion. **Why the correct answer is right:** The LAD provides the primary blood supply to the **anterior wall of the left ventricle** and the **apex** of the heart. Additionally, it supplies the **anterior 2/3rd of the interventricular septum** via its septal branches. Therefore, occlusion leads to an anteroseptal myocardial infarction (MI). **Analysis of Incorrect Options:** * **A. Posterior part of the interventricular septum:** This area (the posterior 1/3rd) is supplied by the **Posterior Interventricular Artery**, which usually arises from the Right Coronary Artery (RCA) in right-dominant hearts. * **C. Lateral part of the heart:** This region is primarily supplied by the **Left Circumflex Artery (LCX)**. * **D. Inferior surface of the right ventricle:** The inferior (diaphragmatic) surface of the heart is supplied by the **Right Coronary Artery (RCA)**. **NEET-PG High-Yield Pearls:** 1. **Artery of Sudden Death:** The LAD is the most frequently occluded artery in MI (approx. 40–50% of cases). 2. **ECG Correlation:** LAD occlusion typically shows ST-elevation in leads **V1 to V4** [1]. 3. **Conductive System:** The LAD supplies the **Right Bundle Branch** and the **Anterior Fascicle** of the Left Bundle Branch; occlusion can lead to bundle branch blocks. 4. **Coronary Dominance:** Determined by which artery gives rise to the Posterior Interventricular Artery (85% RCA = Right Dominant).

Q: The supraventricular crest is located between which of the following structures?

Pulmonary orifice and atrioventricular orifice. The **supraventricular crest** (crista supraventricularis) is a thick muscular ridge located in the **right ventricle**. It serves as the anatomical boundary that separates the rough, inflow part of the ventricle from the smooth, outflow part (infundibulum/conus arteriosus). 1. **Why Option A is correct:** The right ventricle receives blood from the right atrium through the **tricuspid (atrioventricular) orifice** and ejects it through the **pulmonary orifice**. The supraventricular crest is positioned precisely between these two openings, arching over the anterior cusp of the tricuspid valve [1]. This separation helps streamline the flow of blood from the inflow tract to the outflow tract. 2. **Why other options are incorrect:** * **Option B:** The **fossa ovalis** is a feature of the interatrial septum in the **right atrium**, not the ventricle. * **Option C:** The junction between the superior vena cava and the right atrium is marked externally by the **sulcus terminalis** and internally by the **crista terminalis**. * **Option D:** The right and left coronary arteries arise from the **aortic sinuses** in the ascending aorta [1], unrelated to the internal muscular ridges of the right ventricle. **High-Yield Clinical Pearls for NEET-PG:** * **Inflow vs. Outflow:** The inflow part of the right ventricle is characterized by **trabeculae carneae**, while the outflow part (infundibulum) is smooth-walled. * **Moderator Band:** Also known as the **septomarginal trabecula**, it carries the right branch of the AV bundle and is another key landmark in the right ventricle. * **Embryology:** The smooth outflow tracts of both ventricles are derived from the **bulbus cordis**.

Question 1

A patient who has suffered severe chest trauma in an automobile accident is found to have fluid in the right pleural space. A thoracentesis reveals the presence of chylous fluid in the pleural space, suggesting a rupture of the thoracic duct. In which regions of the thorax is the thoracic duct typically found?

Accepted Answer

Posterior and superior mediastinum

Answer

Anterior and middle mediastinum

Answer

Anterior and superior mediastinum

Answer

Middle and superior mediastinum

Question 2

Which structure does not pass through the aortic opening?

Accepted Answer

Vagus nerve

Answer

Aorta

Answer

Azygos vein

Answer

Thoracic duct

Question 3

The interior of the right atrium is partially divided into two parts by which structure?

Accepted Answer

Crista terminalis

Answer

Musculi pectinati

Answer

Fossa ovalis

Answer

Sinus venarum cavarum

Question 4

Which of the following is the uppermost structure in the hilum of the right lung?

Accepted Answer

Bronchus

Answer

Superior pulmonary vein

Answer

Bronchial artery

Answer

Inferior pulmonary vein

Question 5

During an emergency thoracotomy, an incision is made greater than 1 cm lateral to the sternal margin. This incision will preserve which of the following structures?

Accepted Answer

Internal mammary artery

Answer

Intercostal artery

Answer

Superficial epigastric artery

Answer

Intercostal vein

Question 6

Sympathetic innervation of the heart is by which spinal nerve segments?

Accepted Answer

T1-T5

Answer

T1-T3

Answer

T3-T7

Answer

L1-L5

Question 7

Occlusion of the left anterior descending artery will lead to infarction of which area?

Accepted Answer

Anterior wall of the left ventricle

Answer

Posterior part of the interventricular septum

Answer

Lateral part of the heart

Answer

Inferior surface of the right ventricle

Question 8

At the level of the arch of the aorta, what is the anatomical relationship between the left vagus nerve and the left phrenic nerve?

Accepted Answer

Left phrenic nerve is anterior and the left vagus nerve is posterior.

Answer

Left phrenic nerve is posterior and the left vagus nerve is anterior.

Answer

Both nerves are in the same plane anteroposteriorly.

Answer

The relationship between the nerves is variable.

Question 9

In postductal coarctation of the aorta, collaterals may be formed by all of the following, except?

Accepted Answer

Vertebral artery

Answer

Suprascapular artery

Answer

Subscapular artery

Answer

Posterior intercostal arteries

Question 10

The supraventricular crest is located between which of the following structures?

Accepted Answer

Pulmonary orifice and atrioventricular orifice

Answer

Atrioventricular orifice and fossa ovalis

Answer

Superior vena cava and right atrium

Answer

Right and left coronary artery

Thorax — MCQs

Thorax — MCQs

On this page

Practice by Chapter

Want unlimited practice?