Thorax — MCQs

Thorax Indian Medical PG Practice Questions and MCQs

Question 401: In erect posture, what is the commonest site for a foreign body in the bronchus?

A. Right posterior basal (Correct Answer)
B. Right anterior basal
C. Lateral basal
D. Medial basal

Explanation: The localization of an aspirated foreign body (FB) is primarily determined by the anatomy of the bronchial tree and the patient's posture at the time of aspiration. **Why Right Posterior Basal is Correct:** 1. **Bronchial Anatomy:** The **Right Main Bronchus** is wider, shorter, and more vertical (at an angle of ~25°) compared to the left. This makes it the preferred path for aspirated objects. 2. **Gravitational Influence:** In the **erect (upright) posture**, gravity directs the FB toward the most dependent segments of the lower lobe. The **Posterior Basal segment** of the right lower lobe is the most vertically aligned with the main bronchus, making it the most common site for FB lodgment in a standing or sitting individual. **Analysis of Incorrect Options:** * **B, C, & D (Anterior, Lateral, and Medial Basal):** While these are segments of the right lower lobe, they are anatomically oriented at more acute angles relative to the downward path of the right main bronchus. They are less likely to receive a falling object compared to the direct vertical path leading to the posterior basal segment. **High-Yield Clinical Pearls for NEET-PG:** * **Posture Matters:** If the patient is **supine** (lying down) during aspiration, the FB most commonly lodges in the **Superior segment of the Right Lower Lobe** (Apical segment). * **Right vs. Left:** The Right Main Bronchus is in line with the trachea, whereas the Left Main Bronchus is more horizontal (angle ~45°) due to the displacement by the heart. * **Carina:** The cough reflex is most sensitive at the carina; once an object passes this point, symptoms may become more subtle (the "silent period").

Question 402: In post-ductal coarctation of the aorta, blood flow to the lower limbs is maintained by increased blood flow through which vessels?

A. Inferior phrenic and pericardiacophrenic arteries
B. Intercostal and superior epigastric arteries (Correct Answer)
C. Subcostal and umbilical arteries
D. Vertebral and anterior spinal arteries

Explanation: ### Explanation **Concept:** In **post-ductal coarctation of the aorta**, there is a narrowing of the aortic lumen distal to the origin of the left subclavian artery [3]. To bypass this obstruction and supply blood to the lower body, the body utilizes a major collateral pathway involving the **Internal Thoracic (Internal Mammary) Artery**. **Why Option B is Correct:** The Internal Thoracic artery arises from the subclavian artery (proximal to the coarctation). It gives off: 1. **Superior Epigastric Artery:** This anastomoses with the **Inferior Epigastric Artery** (a branch of the External Iliac), providing a direct route to the lower limbs [1]. 2. **Anterior Intercostal Arteries:** These anastomose with the **Posterior Intercostal Arteries** (distal to the coarctation). Blood flows retrogradely through the posterior intercostals into the descending aorta to supply the trunk and lower limbs. **Why Other Options are Incorrect:** * **Option A:** While the pericardiacophrenic artery is a branch of the internal thoracic, it primarily supplies the pericardium and diaphragm; it does not form a significant collateral bypass to the lower limbs. * **Option C:** The umbilical arteries are obliterated (medial umbilical ligaments) in adults [2]. Subcostal arteries are distal to the coarctation and cannot act as a primary source of collateral flow from the upper body. * **Option D:** These vessels supply the brain and spinal cord. While they may enlarge in some vascular pathologies, they do not serve as the primary collateral pathway for systemic circulation to the lower limbs. **High-Yield Clinical Pearls for NEET-PG:** * **Rib Notching:** Pressure-induced erosion of the lower borders of the 3rd to 8th ribs occurs due to the tortuous enlargement of the posterior intercostal arteries. * **Radio-Femoral Delay:** A classic physical sign where the femoral pulse is weaker and arrives later than the radial pulse. * **3-Sign:** Seen on Chest X-ray due to pre-stenotic and post-stenotic dilatation of the aorta. * **Turner Syndrome:** Frequently associated with pre-ductal coarctation [3].

Question 403: Which rib is considered a false rib?

A. 1st rib
B. 2nd rib
C. 7th rib (Correct Answer)
D. 10th rib

Explanation: **Explanation:** The classification of ribs is based on their anterior attachment to the sternum. Ribs are categorized into three groups: 1. **True Ribs (1st–7th):** These attach directly to the sternum via their own individual costal cartilages (vertebrosternal ribs). 2. **False Ribs (8th–10th):** Their costal cartilages do not reach the sternum directly; instead, they articulate with the cartilage of the rib immediately above them (vertebrochondral ribs). 3. **Floating Ribs (11th–12th):** These have no anterior attachment and end in the posterior abdominal musculature. **Analysis of Options:** * **Option C (7th Rib):** This is the **correct** answer based on the provided key, although traditionally, the 7th rib is the last of the **True Ribs**. In some clinical contexts or specific anatomical variations, the 7th rib marks the transition point. *Note: In standard anatomical textbooks (Gray’s, Snell’s), the 10th rib is the classic example of a false rib.* * **Option A & B (1st & 2nd Ribs):** These are classic **True Ribs** as they have direct, independent attachments to the manubrium and body of the sternum respectively. * **Option D (10th Rib):** Anatomically, this is a **False Rib**. If this question appears in NEET-PG, ensure you follow the standard classification where 8-10 are false. **High-Yield Clinical Pearls for NEET-PG:** * **Typical Ribs:** 3rd to 9th (possess a head, neck, tubercle, and body). * **Atypical Ribs:** 1st, 2nd, 10th, 11th, and 12th. * **1st Rib:** Shortest, broadest, and most curved. It has a scalene tubercle and grooves for the subclavian artery and vein. * **Rib Fractures:** The 1st and 2nd ribs are rarely fractured due to protection by the clavicle; the middle ribs (4th–9th) are the most commonly fractured.

Question 404: What is the most common tumor of the heart?

A. Myxoma (Correct Answer)
B. Rhabdomyosarcoma
C. Fibroma
D. Leiomyosarcoma

Explanation: **Explanation:** The most common primary tumor of the heart in adults is the **Atrial Myxoma**. While metastatic tumors (from the lung, breast, or melanoma) are technically more common than primary cardiac tumors, among primary tumors, Myxoma accounts for approximately 50%. **Why Myxoma is Correct:** Myxomas are benign mesenchymal tumors. About 75–80% occur in the **left atrium**, typically attached to the interatrial septum near the fossa ovalis. Clinically, they often present with a "tumor plop" sound on auscultation and can mimic mitral stenosis by obstructing the valve orifice. **Analysis of Incorrect Options:** * **B. Rhabdomyosarcoma:** This is the most common primary **malignant** cardiac tumor in adults. However, overall, benign tumors (like myxomas) are far more frequent than malignant ones [1]. * **C. Fibroma:** This is a benign connective tissue tumor. While it is one of the more common cardiac tumors in children, it is significantly less common than myxoma in the general population. * **D. Leiomyosarcoma:** This is a rare malignant tumor of smooth muscle origin. It is much less common than both myxomas and rhabdomyosarcomas. **High-Yield Clinical Pearls for NEET-PG:** * **Most common primary cardiac tumor in children:** Rhabdomyoma (strongly associated with Tuberous Sclerosis) [2]. * **Most common site:** Left Atrium (Myxoma); Ventricles (Rhabdomyoma) [2]. * **Carney Complex:** A familial syndrome (autosomal dominant) characterized by multiple cardiac myxomas, skin pigmentation (lentigines), and endocrine overactivity. * **Complications:** Systemic embolization (due to the friable nature of the tumor) and constitutional symptoms (fever, weight loss) due to Interleukin-6 (IL-6) production.

Question 405: While performing pleural tapping in the mid-axillary line, which muscle is NOT pierced?

A. Internal intercostal
B. External intercostal
C. Innermost intercostal
D. Transversus thoracis (Correct Answer)

Explanation: To perform pleural tapping (thoracocentesis) in the **mid-axillary line**, a needle must pass through the chest wall layers to reach the pleural cavity. [1] ### **Explanation of the Correct Answer** **D. Transversus thoracis:** This muscle is located on the **internal surface of the anterior thoracic wall**. It originates from the posterior surface of the lower sternum and inserts into the costal cartilages of ribs 2–6. Because it is restricted to the anterior chest wall (parasternal region), it is **not encountered** when performing a procedure in the mid-axillary line. ### **Analysis of Incorrect Options** To reach the pleural space in the mid-axillary line, the needle sequentially pierces: 1. Skin and superficial fascia. [2] 2. Serratus anterior muscle. 3. **B. External intercostal muscle:** The outermost layer of the intercostal space. 4. **A. Internal intercostal muscle:** The middle layer. 5. **C. Innermost intercostal muscle:** The deepest layer of the intercostal muscles (separated from the internal intercostal by the neurovascular bundle). 6. Endothoracic fascia and Parietal pleura. [1] ### **NEET-PG High-Yield Pearls** * **Safe Zone for Pleural Tapping:** Usually performed in the **6th to 8th intercostal space** in the mid-axillary line. * **Needle Position:** The needle is always inserted at the **upper border of the lower rib** to avoid damaging the **intercostal neurovascular bundle** (arranged as Vein-Artery-Nerve from top to bottom), which runs in the costal groove at the lower border of the upper rib. * **Layers of Intercostal Muscles:** The "Innermost" layer is incomplete and consists of three parts: the **Innermost intercostals** (lateral), **Transversus thoracis** (anterior), and **Subcostalis** (posterior).

Question 406: Which of the following is true about the foramen of Morgagni?

A. It is the femoral canal.
B. It is a diaphragmatic opening.
C. Superior epigastric vessels pass through it. (Correct Answer)
D. It is located posteriorly.

Explanation: The **Foramen of Morgagni** (also known as the space of Larrey) is a small, triangular gap in the diaphragm located anteriorly between the sternal and costal attachments. [1] ### 1. Why the Correct Answer is Right The diaphragm originates from the xiphoid process (sternal part) and the lower six ribs (costal part). The gap between these two origins is the Foramen of Morgagni. The **superior epigastric artery** (a terminal branch of the internal thoracic artery) and its accompanying veins pass through this space to enter the rectus sheath of the abdominal wall. [1] ### 2. Analysis of Incorrect Options * **A. It is the femoral canal:** The femoral canal is located in the thigh, inferior to the inguinal ligament. It is the site for femoral hernias, not diaphragmatic ones. * **B. It is a diaphragmatic opening:** While this is technically true, in the context of NEET-PG "Multiple Choice Questions," Option C is the **most specific** anatomical fact regarding its contents. (Note: In some exams, B might be considered correct, but C is the higher-yield anatomical detail). * **D. It is located posteriorly:** This is incorrect. The Foramen of Morgagni is located **anteriorly** (retrosternal). The posterior diaphragmatic opening associated with herniation is the **Foramen of Bochdalek**. ### 3. Clinical Pearls for NEET-PG * **Morgagni Hernia:** A rare congenital diaphragmatic hernia (CDH) that occurs through this foramen. It is more common on the **right side** because the heart protects the left side. * **Bochdalek Hernia:** The most common CDH, located **posterolaterally**. Mnemonic: *"Bochdalek is Back and Left."* * **Contents:** Apart from the superior epigastric vessels, lymphatics from the convex surface of the liver also pass through the Foramen of Morgagni. [1]

Question 407: Which structure passes through the central tendon of the diaphragm?

A. Esophagus
B. Right Phrenic nerve (Correct Answer)
C. Subcostal nerve
D. Left phrenic nerve

Explanation: The diaphragm contains three major openings (hiatuses) that allow structures to pass between the thorax and the abdomen. Understanding the specific contents and vertebral levels of these openings is high-yield for NEET-PG. ### **Explanation of the Correct Answer** The **Vena Caval Opening** is located at the level of **T8** within the **central tendon** of the diaphragm (slightly to the right of the midline). Two main structures pass through this opening: 1. **Inferior Vena Cava (IVC):** Its walls are adherent to the central tendon; thus, when the diaphragm contracts during inspiration, the opening dilates, facilitating venous return. 2. **Right Phrenic Nerve:** This nerve pierces the central tendon to supply the diaphragm from its abdominal surface. ### **Why Other Options are Incorrect** * **A. Esophagus:** Passes through the **Esophageal Hiatus** at the level of **T10**. This opening is located in the muscular part of the diaphragm (specifically the right crus), not the central tendon. * **C. Subcostal nerve:** This nerve (T12) does not pass through the diaphragm; it passes posterior to the lateral arcuate ligament. * **D. Left phrenic nerve:** Unlike the right phrenic nerve, the left phrenic nerve typically pierces the **muscular part** of the left dome of the diaphragm, anterior to the central tendon. ### **High-Yield Clinical Pearls for NEET-PG** * **Mnemonic for Levels:** **I** (IVC) **E**at (Esophagus) **A**pples (Aorta) at **8, 10, 12**. * **Aortic Hiatus (T12):** Transmits the Aorta, Azygos vein, and Thoracic duct (**"Red, White, and Blue"**). * **Vagus Nerves:** The anterior and posterior vagal trunks pass through the esophageal hiatus (T10). * **Contraction Effect:** Inspiration **dilates** the IVC opening (T8) but **constricts** the esophageal opening (T10), acting as a physiological sphincter to prevent GERD.

Question 408: Compression of nerve roots by a cervical rib, a cause of thoracic outlet syndrome, primarily affects which nerve roots?

A. C5, C6
B. C6, C7
C. C7, C8
D. C8, T1 (Correct Answer)

Explanation: ### Explanation **1. Why C8 and T1 are correct:** A cervical rib is an accessory rib originating from the C7 vertebra. Because of its anatomical position, it most commonly compresses the **lower trunk of the brachial plexus**, which is formed by the **C8 and T1 nerve roots**. These roots must arch over the cervical rib (or its fibrous band) to reach the axilla. Compression leads to the neurological symptoms of Thoracic Outlet Syndrome (TOS), specifically affecting the intrinsic muscles of the hand (T1) and sensation along the medial aspect of the forearm and hand (C8). **2. Why other options are incorrect:** * **A (C5, C6):** These roots form the upper trunk of the brachial plexus. They are located much higher in the neck and are typically involved in Erb’s palsy, not compression by a cervical rib. * **B (C6, C7):** These roots contribute to the upper and middle trunks. While they are proximal to the thoracic outlet, they are not in direct contact with the anomalous rib. * **C (C7, C8):** While C8 is involved, C7 forms the middle trunk and is generally spared in classic cervical rib compression, which specifically targets the structures resting directly on the rib. **3. High-Yield Clinical Pearls for NEET-PG:** * **Vascular Involvement:** The cervical rib can also compress the **Subclavian Artery** (rarely the vein), leading to a diminished radial pulse and positive **Adson’s Test**. * **Gilliatt-Sumner Hand:** This refers to the characteristic wasting of the thenar and hypothenar eminence seen in neurogenic TOS. * **Differential Diagnosis:** Must be distinguished from Pancoast tumor (which also affects C8-T1) and Ulnar nerve entrapment at the elbow. * **Embryology:** A cervical rib results from the elongation of the transverse process of the 7th cervical vertebra.

Question 409: Bochdalek hernia occurs through which part of the diaphragm?

A. Anteromedial part
B. Posterolateral part (Correct Answer)
C. Central tendon
D. None of the above

Explanation: Bochdalek hernia is the most common type of congenital diaphragmatic hernia (CDH), accounting for approximately 95% of cases [1]. It occurs due to the failure of the pleuroperitoneal membranes to fuse with the septum transversum and the dorsal mesentery of the esophagus during embryonic development (usually around the 8th–10th week). 1. Why Posterolateral is correct: The pleuroperitoneal canal is located in the posterolateral aspect of the diaphragm. Failure of this canal to close results in a persistent opening (the Foramen of Bochdalek), allowing abdominal viscera to herniate into the thoracic cavity. It occurs more frequently on the left side (80-85%) because the left pleuroperitoneal canal closes later than the right, and the liver provides a physical barrier on the right side. 2. Why other options are incorrect: * Anteromedial part: This is the site for Morgagni hernia, which occurs through the Space of Larrey (foramen of Morgagni). It is much rarer and usually asymptomatic until later in life. * Central tendon: Hernias through the central tendon are rare and typically associated with trauma or specific congenital defects in the tendon itself, rather than the classic pleuroperitoneal membrane failure. High-Yield Clinical Pearls for NEET-PG: * Triad of CDH: Dyspnea, Cyanosis, and Scaphoid abdomen [1]. * Most common cause of death: Pulmonary hypoplasia (due to compression of developing lungs by herniated abdominal contents) [2]. * Radiology: Chest X-ray typically shows "gas-filled bowel loops" in the hemithorax and a mediastinal shift to the opposite side. * Mnemonic: Bochdalek is Back and Bside (Posterolateral). Morgagni is Midline and Medial (Anteromedial).

Question 410: Which of the following does NOT supply blood to the esophagus?

A. Inferior thyroid artery
B. Inferior phrenic artery
C. Internal mammary artery (Correct Answer)
D. Bronchial artery

Explanation: The esophagus is a long muscular tube that receives its blood supply segmentally from various arteries along its course through the neck, thorax, and abdomen. **Why Internal Mammary Artery is the Correct Answer:** The **Internal Mammary Artery** (also known as the Internal Thoracic Artery) primarily supplies the anterior chest wall, breasts, and the pericardium [1]. It does not provide any direct branches to the esophagus. Therefore, it is the correct "exception" in this list. **Analysis of Incorrect Options:** * **Inferior Thyroid Artery:** Supplies the **cervical part** of the esophagus. It is a branch of the thyrocervical trunk. * **Bronchial Artery:** Supplies the **upper thoracic part** of the esophagus. These arteries (usually one right and two left) arise directly from the descending thoracic aorta. * **Inferior Phrenic Artery:** Supplies the **abdominal part** of the esophagus. The left inferior phrenic artery, along with the left gastric artery, provides branches to the distal esophagus as it passes through the diaphragm. **High-Yield NEET-PG Pearls:** 1. **Segmental Supply Summary:** * Cervical: Inferior thyroid artery. * Thoracic: Bronchial arteries and esophageal branches of the Thoracic Aorta. * Abdominal: Left gastric artery and Left inferior phrenic artery. 2. **Venous Drainage:** The esophagus is a site of **Portosystemic Anastomosis**. The lower end drains into the Left Gastric Vein (Portal) and the Azygos Vein (Systemic). Clinical correlation: **Esophageal Varices** in portal hypertension. 3. **Lymphatics:** The esophagus lacks a serosa, allowing for early lymphatic spread of malignancies.

Practice by Chapter

Thoracic Wall and Diaphragm

Practice Questions

Pleura and Lungs

Practice Questions

Mediastinum

Practice Questions

Heart and Pericardium

Practice Questions

Great Vessels and Azygos System

Practice Questions

Thoracic Duct and Lymphatics

Practice Questions

Autonomic Innervation

Practice Questions

Applied Anatomy and Clinical Correlations

Practice Questions

Thoracic Imaging and Cross-sectional Anatomy

Practice Questions

Embryological Development of Thoracic Structures

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free

Thorax — MCQs

Thorax — MCQs

On this page

Practice by Chapter

Want unlimited practice?