Thorax Practice Questions

Q: Which of the following statements about the thoracic duct is incorrect?

It passes through the diaphragm via the esophageal hiatus.. The thoracic duct is a high-yield topic in NEET-PG Anatomy. Here is the breakdown of the question: ### **Explanation of the Correct Answer (Option B)** The statement in Option B is **incorrect**, making it the right answer. The thoracic duct does not pass through the esophageal hiatus (T10). Instead, it enters the thorax through the **aortic hiatus** at the level of the **T12** vertebra. **Concept:** The aortic hiatus transmits three structures, often remembered by the mnemonic **"A-T-V"**: **A**orta, **T**horacic duct, and Azygos **V**ein. Passing through the T12 opening protects the duct from being compressed during diaphragmatic contractions, ensuring continuous lymph flow. ### **Analysis of Other Options** * **Option A:** Correct. The duct begins in the abdomen at the level of L1-L2 as a saccular dilatation called the **cisterna chyli**, which receives lymph from the lower limbs and abdomen. * **Option C:** Correct. After ascending through the posterior and superior mediastinum, the duct arches to the left and terminates at the **"venous angle"** (the junction of the left internal jugular and left subclavian veins) [1]. * **Option D:** Correct. It is indeed the largest lymphatic vessel in the body, measuring approximately 38–45 cm in length. ### **High-Yield Clinical Pearls for NEET-PG** * **Drainage:** The thoracic duct drains lymph from the entire body **except** the right upper quadrant (right head, neck, thorax, and arm), which is drained by the Right Lymphatic Duct. * **Chylothorax:** Injury to the thoracic duct (during esophageal surgery or due to malignancy) leads to the accumulation of milky lymph in the pleural cavity, known as chylothorax. * **Virchow’s Node:** Enlargement of the left supraclavicular lymph node (Trosier’s sign) often indicates metastasis from abdominal malignancies (e.g., gastric cancer) because the thoracic duct carries malignant cells to this site.

Q: The internal thoracic veins are tributaries of which vessel?

Brachiocephalic vein. The internal thoracic veins (also known as internal mammary veins) are the venae comitantes of the internal thoracic artery. They are formed by the confluence of the musculophrenic and superior epigastric veins [1]. **Why the Brachiocephalic vein is correct:** The internal thoracic veins ascend on the posterior surface of the thoracic wall, medial to the internal thoracic artery. On each side, they drain directly into the corresponding **brachiocephalic vein** (innominate vein) at the root of the neck. This is a key anatomical landmark in the superior mediastinum. **Analysis of Incorrect Options:** * **Azygos vein:** This vessel primarily drains the right posterior intercostal veins and the hemi-azygos system. It eventually empties into the Superior Vena Cava (SVC), not the internal thoracic veins. * **Subclavian vein:** While the internal thoracic *artery* arises from the first part of the subclavian artery, the corresponding *vein* does not drain into the subclavian vein; it bypasses it to enter the brachiocephalic vein. * **Internal jugular vein:** This vein drains the brain, face, and neck. It joins the subclavian vein to *form* the brachiocephalic vein but does not receive the internal thoracic tributaries. **High-Yield Clinical Pearls for NEET-PG:** * **Internal Thoracic Artery (ITA):** Arises from the 1st part of the subclavian artery. It is the "gold standard" graft for Coronary Artery Bypass Grafting (CABG) due to its long-term patency. * **Termination:** The ITA terminates in the **6th intercostal space** by dividing into the musculophrenic and superior epigastric arteries [1]. * **Collateral Circulation:** The internal thoracic system provides a vital collateral pathway between the subclavian artery and the external iliac artery (via the superior and inferior epigastric anastomosis) in cases of Coarctation of the Aorta.

Q: The pleura extends beyond the thoracic cage on all the following structures except?

Left xiphisternal angle. The pleura is a serous membrane that generally remains within the confines of the thoracic cage. However, there are specific anatomical sites where the pleural sac extends beyond the bony boundaries, making it vulnerable to injury during surgical procedures or trauma. [1] **Explanation of the Correct Answer:** * **Left xiphisternal angle (Option D):** This is the correct answer because the left pleura deviates laterally at the level of the 4th costal cartilage to accommodate the heart (forming the **cardiac notch**). Consequently, the pleura is absent behind the left half of the lower sternum and the left xiphisternal angle. This area is known as the "bare area of the heart," where the pericardium is in direct contact with the chest wall, allowing for safe pericardiocentesis without risking a pneumothorax. **Analysis of Incorrect Options:** * **Root of the neck (Option A):** The cervical pleura (cupula) extends 2.5 cm above the medial 1/3rd of the clavicle and 3–4 cm above the 1st rib. It is protected by the Sibson’s fascia. [2] * **Costovertebral angles (Option B):** The pleura extends below the level of the 12th rib at the costovertebral angles (specifically the inferomedial part). This is clinically significant during renal surgeries (e.g., nephrectomy), as the pleura can be accidentally breached. * **Right xiphisternal angle (Option C):** Unlike the left side, the right pleura continues vertically down to the xiphisternal joint, meaning it does extend into the right xiphisternal angle. **High-Yield Clinical Pearls for NEET-PG:** * **Sibson’s Fascia:** Also known as the suprapleural membrane; it protects the cervical pleura. * **Bare Area of the Heart:** Located at the 4th and 5th left intercostal spaces. * **Pleural Reflections:** Remember the "2-4-6-8-10-12" rule for surface marking of the lungs and pleura to differentiate their borders.

Q: A 27-year-old mountain climber falls from a steep rock wall and is brought to the emergency department. His physical examination and computed tomography (CT) scan reveal dislocation fracture of the upper thoracic vertebrae. The fractured body of the T4 vertebra articulates with which of the following pairs of the ribs?

Head of the fifth rib. ### Explanation The correct answer is **B. Head of the fifth rib.** **1. Underlying Medical Concept: Costovertebral Articulation** In the thoracic spine, a typical rib (Ribs 2–9) articulates with the vertebral column at two points: the **body** of the vertebrae (costovertebral joint) and the **transverse process** (costotransverse joint). The head of a typical rib articulates with the **superior costal facet** of its own corresponding vertebra and the **inferior costal facet** of the vertebra immediately above it. Therefore, the **T4 vertebra** possesses: * A **superior costal facet** for the head of the **4th rib**. * An **inferior costal facet** for the head of the **5th rib**. Since the question asks which rib articulates with the body of T4, the head of the 5th rib is the correct anatomical match. **2. Analysis of Incorrect Options** * **A. Head of the third rib:** The 3rd rib articulates with the inferior facet of T2 and the superior facet of T3. It does not touch T4. * **C. Neck of the fourth rib:** The neck of a rib is the flattened portion between the head and the tubercle; it does not form a synovial articulation with the vertebral body. * **D. Tubercle of the fourth rib:** The tubercle of the 4th rib articulates with the **transverse process** of the T4 vertebra (costotransverse joint), not the vertebral body. **3. High-Yield NEET-PG Pearls** * **Atypical Ribs:** Ribs 1, 10, 11, and 12 are atypical because they articulate with only one vertebral body (their own). * **T1 Exception:** T1 has a full facet for the 1st rib and a demifacet for the 2nd rib. * **Floating Ribs:** Ribs 11 and 12 have no neck or tubercle and do not articulate with transverse processes. * **Rule of Thumb:** Rib 'n' articulates with the body of 'n' and 'n-1'.

Q: All of the following statements about Sibson's fascia are true, except?

Extension of the tendinous insertion of scalenus anterior. ### Explanation **Sibson’s Fascia** (Suprapleural membrane) is a dense, triangular connective tissue layer that covers the apex of the lung. It acts as a diaphragm at the thoracic inlet, preventing the protrusion of the cervical pleura into the neck during respiration. **Why Option D is the Correct Answer (The False Statement):** Sibson’s fascia is actually an extension of the **scalenus minimus** muscle (not the scalenus anterior). It is considered the flattened, degenerated tendon of this muscle. It originates from the transverse process of the C7 vertebra and spreads out to cover the cervical pleura. **Analysis of Other Options:** * **Option A:** It is attached to the **transverse process of the C7 vertebra** (its apex). * **Option B:** The **subclavian artery** and its branches arch over the superior surface of the fascia, while the cervical pleura lies immediately beneath it. * **Option C:** Its inferior surface is firmly attached to the **cervical pleura** (cupula), providing it with structural support [1]. It also attaches to the inner border of the **first rib**. --- ### High-Yield Clinical Pearls for NEET-PG: * **Function:** It protects the underlying cervical pleura and lung apex and resists intrathoracic pressure changes. * **Morphological Significance:** It represents the spread-out tendon of the **Scalenus Minimus** muscle. * **Relations:** * **Above:** Subclavian vessels and Brachial plexus. * **Below:** Cervical pleura and Apex of the lung. * **Clinical Correlation:** Weakness in this fascia can lead to a "cervical lung hernia," though this is rare. In clinical practice, it must be reflected or incised during surgical approaches to the root of the neck.

Q: Branches of the left coronary artery include all of the following except?

Posterior interventricular branch. The **Left Coronary Artery (LCA)** originates from the left aortic sinus. It typically has a short course before bifurcating into its two primary terminal branches: the **Anterior Interventricular Artery (LAD)** and the **Circumflex Artery (LCX)** [1]. **Why Option D is correct:** The **Posterior Interventricular Branch (PDA)** most commonly (85% of individuals, known as "Right Dominance") arises from the **Right Coronary Artery (RCA)** [1]. In "Left Dominant" individuals (approx. 8-10%), it arises from the Circumflex branch of the LCA. However, in standard anatomical descriptions and for examination purposes, the PDA is considered a branch of the **Right Coronary Artery**. **Why other options are incorrect:** * **Anterior Interventricular Branch (LAD):** This is the major terminal branch of the LCA that travels in the anterior interventricular groove [1]. * **Left Diagonal Artery:** These are branches that typically arise from the LAD to supply the anterolateral wall of the left ventricle [1]. * **Left Atrial Artery:** These are small branches arising from the Circumflex artery (a terminal branch of the LCA) to supply the left atrium. **High-Yield Clinical Pearls for NEET-PG:** 1. **Coronary Dominance:** Defined by which artery gives rise to the **Posterior Interventricular Artery**. (RCA = Right Dominant; LCA = Left Dominant). 2. **Widow Maker:** The Anterior Interventricular Artery (LAD) is the most common site of coronary occlusion. 3. **SA Node Supply:** In 60% of cases, it is supplied by the RCA; in 40%, by the LCA (Circumflex branch). 4. **AV Node Supply:** In 80% of cases, it is supplied by the RCA.

Q: A 36-year-old lady, 3 weeks after a modified radical mastectomy, is unable to extend, adduct, and internally rotate her arm. Which of the following muscles is paralyzed in this patient?

Latissimus dorsi. The patient is presenting with a classic injury to the **Thoracodorsal nerve** (nerve to latissimus dorsi), a known complication of axillary lymph node dissection during a modified radical mastectomy (MRM) [1]. **1. Why Latissimus Dorsi is correct:** The Latissimus dorsi is primarily responsible for **extension, adduction, and internal (medial) rotation** of the humerus (often remembered by the mnemonic "Climbing muscle"). It is supplied by the thoracodorsal nerve (C6-C8), which runs along the posterior wall of the axilla [1]. During an MRM, this nerve is vulnerable to injury while clearing axillary fat and lymph nodes. Damage results in the loss of these specific movements. **2. Why the other options are incorrect:** * **Pectoralis major:** While it adducts and medially rotates the arm, its primary function is flexion (clavicular head), not extension. It is supplied by the medial and lateral pectoral nerves [1]. * **Teres minor:** This muscle is part of the rotator cuff and is responsible for **external rotation** and weak adduction. It is supplied by the axillary nerve. * **Long head of triceps:** Its primary action is elbow extension and stabilization of the shoulder joint during adduction; it does not contribute significantly to internal rotation. **Clinical Pearls for NEET-PG:** * **Nerves at risk during MRM:** 1. **Long Thoracic Nerve:** Supplies Serratus Anterior; injury causes "Winging of Scapula." 2. **Thoracodorsal Nerve:** Supplies Latissimus Dorsi [1]; injury causes inability to "climb or pull up." 3. **Intercostobrachial Nerve:** Most commonly injured; causes numbness/paresthesia in the medial aspect of the upper arm [1]. * The Latissimus dorsi is the most common muscle used for **pedicled flap reconstruction** after mastectomy.

Question 1

Which of the following statements about the thoracic duct is incorrect?

Accepted Answer

It passes through the diaphragm via the esophageal hiatus.

Answer

It begins as a continuation of the cisterna chyli.

Answer

It terminates at the junction of the left subclavian and internal jugular veins.

Answer

It is the largest lymphatic vessel.

Question 2

Which of the following statements about anterior intercostal arteries is INCORRECT?

Accepted Answer

They are the main arteries supplying the intercostal spaces.

Answer

There are two anterior intercostal arteries in each intercostal space.

Answer

They are branches of the internal thoracic artery.

Answer

They are branches of the musculophrenic artery.

Question 3

The internal thoracic veins are tributaries of which vessel?

Accepted Answer

Brachiocephalic vein

Answer

Azygos vein

Answer

Subclavian vein

Answer

Internal jugular vein

Question 4

The pleura extends beyond the thoracic cage on all the following structures except?

Accepted Answer

Left xiphisternal angle

Answer

Root of the neck

Answer

Costovertebral angles

Answer

Right xiphisternal angle

Question 5

A 27-year-old mountain climber falls from a steep rock wall and is brought to the emergency department. His physical examination and computed tomography (CT) scan reveal dislocation fracture of the upper thoracic vertebrae. The fractured body of the T4 vertebra articulates with which of the following pairs of the ribs?

Accepted Answer

Head of the fifth rib

Answer

Head of the third rib

Answer

Neck of the fourth rib

Answer

Tubercle of the fourth rib

Question 6

All of the following statements about Sibson's fascia are true, except?

Accepted Answer

Extension of the tendinous insertion of scalenus anterior

Answer

It is attached to the transverse process of C7

Answer

Subclavian artery arches over it

Answer

Attached to the cervical pleura

Question 7

Branches of the left coronary artery include all of the following except?

Accepted Answer

Posterior interventricular branch

Answer

Anterior interventricular branch

Answer

Left diagonal artery

Answer

Left atrial artery

Question 8

A 32-year-old patient has a tension pneumothorax that can be treated with needle aspiration. To avoid injury to the intercostal neurovascular bundle, in which of the following locations may the needle be inserted?

Accepted Answer

Above the upper border of the rib

Answer

Deep to the upper border of the rib

Answer

Beneath the lower border of the rib

Answer

Between the external and internal intercostals

Question 9

A 36-year-old lady, 3 weeks after a modified radical mastectomy, is unable to extend, adduct, and internally rotate her arm. Which of the following muscles is paralyzed in this patient?

Accepted Answer

Latissimus dorsi

Answer

Pectoralis major

Answer

Teres minor

Answer

Long head of triceps

Question 10

All of the following lie between the 1st rib and the apex of the lung except?

Accepted Answer

Thoracic duct

Answer

Superior intercostal artery

Answer

First posterior intercostal vein

Answer

Sympathetic trunk

Thorax — MCQs

Thorax — MCQs

On this page

Practice by Chapter

Want unlimited practice?