Thorax — MCQs

Thorax Indian Medical PG Practice Questions and MCQs

Question 661: The ventral surface of the adult heart, as seen on gross examination or radiography, is comprised primarily of the

A. Left atrium
B. Left ventricle
C. Inferior vena cava
D. Right ventricle (Correct Answer)

Explanation: The ventral surface of the adult heart, as seen on gross examination or radiography, is comprised primarily of the ***Right ventricle*** - The **right ventricle** forms the majority of the **anterior (ventral) surface** of the adult heart, lying directly behind the sternum and costal cartilages. - This anatomical position makes it the most superficial chamber and readily visible on gross dissection or anterior-posterior radiographic views of the chest. *Left atrium* - The **left atrium** is the most **posterior chamber** of the heart, forming the heart's base and receiving pulmonary veins [1]. - It is not visible on the ventral surface and is instead located closer to the esophagus and vertebral column [1]. *Left ventricle* - While a significant chamber, the **left ventricle** primarily forms the **apex** of the heart and the **left border**, with only a small portion contributing to the anterior surface. - Its bulk is more directed **posterolaterally** and to the left. *Inferior vena cava* - The **inferior vena cava** is a large vein that drains into the **right atrium**, not a chamber that forms a significant portion of the heart's ventral surface. - Its presence is more associated with the **diaphragmatic surface** of the heart as it enters the posterior part of the right atrium [2].

Question 662: Which of the following statements about the hemiazygos vein is incorrect?

A. Does not pierce the left crus of diaphragm
B. Does not drain the esophageal vein directly
C. At T9 level drains into azygos vein
D. Formed by right lumbar azygos and right ascending lumbar veins (Correct Answer)

Explanation: Which of the following statements about the hemiazygos vein is incorrect? ***Formed by right lumbar azygos and right ascending lumbar veins*** - This statement is **INCORRECT** and is the correct answer to this question. - The **hemiazygos vein** is formed by the junction of the **LEFT subcostal vein** and **LEFT ascending lumbar vein**, not the right-sided vessels. - The right-sided counterparts (right subcostal and right ascending lumbar veins) contribute to the formation of the **azygos vein**, not the hemiazygos vein. - This is a fundamental anatomical error that makes this the incorrect statement we're looking for. *Does not pierce the left crus of diaphragm* - This statement is correct (thus a distractor). - The hemiazygos vein typically **does pierce the left crus of the diaphragm** at approximately the T12-L1 level to enter the posterior mediastinum. - Therefore, saying it "does not pierce" would be incorrect, but this option itself is a true statement about standard anatomy. *Does not drain the esophageal vein directly* - This statement is generally correct (thus a distractor). - While the hemiazygos vein can receive some **esophageal tributaries**, the drainage pattern is variable and often indirect. - The **accessory hemiazygos** and **azygos vein** are the primary draining vessels for the esophageal venous plexus. - Direct drainage to the hemiazygos is inconsistent, making this statement anatomically acceptable. *At T9 level drains into azygos vein* - This statement is correct (thus a distractor). - The hemiazygos vein typically crosses the midline at the level of **T8-T9 vertebrae** to drain into the azygos vein. - This is consistent anatomical teaching and represents the normal termination point of the hemiazygos system.

Question 663: The aortic hiatus is formed by the right and left crura of the diaphragm. Which of the following structures does NOT pass through the aortic hiatus?

A. Thoracic duct
B. Left vagus nerve
C. Left gastric vein (Correct Answer)
D. Azygos vein

Explanation: ***Left gastric vein*** - The **left gastric vein** is part of the **portal venous system** and drains into the portal vein. - It **does NOT pass through the diaphragm** via the aortic hiatus or any other diaphragmatic opening. - It has **no anatomical relationship** with the aortic hiatus, making it the best answer to this question. *Thoracic duct* - The **thoracic duct** is the largest lymphatic vessel in the body and **passes through the aortic hiatus** along with the aorta. - It ascends through the aortic hiatus at the **T12 vertebral level** to eventually drain into the left subclavian vein. - It lies posterior to the aorta as it traverses the hiatus. *Left vagus nerve* - The **left vagus nerve** does NOT pass through the aortic hiatus, but it **does pass through the esophageal hiatus** at the T10 level. - It contributes to the **anterior vagal trunk** as it enters the abdomen with the esophagus. - While this structure doesn't pass through the aortic hiatus, it does traverse the diaphragm through a different opening, making it a less definitive answer than the left gastric vein. *Azygos vein* - The **azygos vein** typically **passes through the aortic hiatus** alongside the aorta and thoracic duct. - It may occasionally pass through a separate opening in the right crus of the diaphragm. - It collects deoxygenated blood from the posterior walls of the thorax and abdomen before draining into the superior vena cava.

Question 664: Which of the following structures anchors the breast tissue to the overlying skin?

A. Cooper's ligaments (Correct Answer)
B. Cruciate ligaments
C. Falciform ligament
D. Pectoralis major fascia

Explanation: ***Cooper's ligaments (Correct)*** - These are **fibrous bands** that extend from the deep fascia over the pectoralis major muscle through the breast tissue to the dermis of the skin, providing **support and anchorage** [2]. - They help maintain the **shape and structure** of the breast. - Also known as the **suspensory ligaments of Cooper**, they are the key structures that directly anchor breast tissue to the overlying skin [2]. *Cruciate ligaments (Incorrect)* - These ligaments are found in the **knee joint**, specifically the **anterior cruciate ligament (ACL)** and **posterior cruciate ligament (PCL)**, and are not associated with breast anatomy. - They are crucial for knee stability, preventing excessive **forward and backward movement** of the tibia relative to the femur. *Falciform ligament (Incorrect)* - The **falciform ligament** is a peritoneal fold that attaches the liver to the anterior abdominal wall and diaphragm. - It is an **intra-abdominal structure** with no anatomical connection to the breast. *Pectoralis major fascia (Incorrect)* - The **pectoralis major fascia** is a layer of connective tissue that covers the pectoralis major muscle, providing a deep anchor point for the breast [1]. - However, it is the **Cooper's ligaments** that extend from this fascia *through* the breast tissue to the skin, thus directly anchoring the breast to the overlying skin [2].

Question 665: The root of the right lung does not lie behind which one of the following?

A. Superior vena cava
B. Right atrium
C. Phrenic nerve
D. Right vagus (Correct Answer)

Explanation: ***Right vagus*** - The **right vagus nerve** passes **behind (posterior to) the root of the right lung** [1]. - Therefore, the root of the right lung lies **in front of** the right vagus nerve, NOT behind it. - This is the correct answer to the question asking what the root does NOT lie behind. *Phrenic nerve* - The **right phrenic nerve** passes **in front of (anterior to) the root of the right lung**, running between the fibrous pericardium and the mediastinal pleura [1]. - Hence, the root of the right lung **does lie behind** the right phrenic nerve. *Superior vena cava* - The **superior vena cava (SVC)** is situated **anterior to the root of the right lung** [1]. - Consequently, the root of the right lung **does lie behind** the superior vena cava. *Right atrium* - The **right atrium** is located **anterior to the root of the right lung**. - The root of the right lung **does lie behind** the right atrium.

Question 666: Which myocardial region is most likely to experience ischemia following occlusion of the left anterior descending artery?

A. Left atrium
B. Right ventricle
C. Interatrial septum
D. Anterior wall (Correct Answer)

Explanation: **Anterior wall** - The **left anterior descending (LAD) artery** is a major coronary artery that supplies blood to the **anterior two-thirds of the interventricular septum** and the **anterior wall of the left ventricle**. - Occlusion of the LAD artery, often referred to as the "**widowmaker**," leads to significant ischemia and infarction in these regions due to loss of blood supply [1]. *Left atrium* - The **left atrium** is primarily supplied by branches of the **circumflex artery** and occasionally by the right coronary artery. - Involvement of the left atrium is highly unlikely with isolated LAD occlusion. *Right ventricle* - The **right ventricle** is predominantly supplied by the **right coronary artery (RCA)**. - While there can be some collateral flow, isolated LAD occlusion typically spares the right ventricle. *Interatrial septum* - The **interatrial septum** receives blood supply from branches of both the **right and left coronary arteries**, but mainly from the **right coronary artery**. - Ischemia in this region is uncommon with LAD occlusion, which primarily affects the ventricular septum.

Question 667: Which of the following is an anterior mediastinal tumor?

A. Lymphoma
B. Thymoma (Correct Answer)
C. Aortic aneurysm
D. Bronchogenic cyst

Explanation: ***Thymoma*** - **Thymomas** originate from the **thymus gland**, which is located in the **anterior mediastinum** [1]. - They are the **most common primary tumor** of the anterior mediastinum in adults and can be associated with **myasthenia gravis** (30-50% of cases) [1]. - Thymoma is the classic anterior mediastinal tumor and the most frequent solid mass in this compartment [1]. *Lymphoma* - **Lymphoma** (particularly **Hodgkin lymphoma** and **primary mediastinal B-cell lymphoma**) is also a well-recognized **anterior mediastinal tumor** [1]. - It represents the second most common cause of anterior mediastinal masses, especially in younger patients [1]. - The mnemonic "4 T's" of anterior mediastinum includes "Terrible lymphoma" alongside Thymoma, Thyroid, and Teratoma [1]. - While both thymoma and lymphoma can occur in the anterior mediastinum, **thymoma is the most common primary tumor** in this location [1]. *Aortic aneurysm* - An **aortic aneurysm** is an abnormal dilatation of the **aorta**, which is situated in the **middle and posterior mediastinum**. - It is a vascular pathology, not a tumor, and does not arise from the anterior mediastinal compartment. *Bronchogenic cyst* - **Bronchogenic cysts** are congenital foregut malformations typically found in the **middle mediastinum**, often near the carina or main bronchi. - They are fluid-filled developmental anomalies, not solid tumors of the anterior compartment.

Question 668: Which of the following is related to the mediastinal part of the right lung?

A. Arch of aorta
B. SVC (Correct Answer)
C. Pulmonary trunk
D. Left atrium

Explanation: ***SVC*** - The **superior vena cava (SVC)** lies to the right side of the mediastinum and is intimately related to the mediastinal surface of the **right lung** [1]. - The SVC drains into the **right atrium** and forms an important landmark in the superior mediastinum, immediately adjacent to the right lung hilum [1]. - Creates a prominent **vertical groove** on the mediastinal surface of the right lung [1]. *Arch of aorta* - The **arch of aorta** is located in the superior mediastinum but lies to the **left** of the trachea and mediastinal structures, thus relating more to the **left lung**. - It arches over the root of the left lung and creates an impression on the **left mediastinal surface**, not the right. *Pulmonary trunk* - The **pulmonary trunk** arises from the right ventricle and ascends in the mediastinum, but it is primarily situated **anterior and to the left** of the ascending aorta. - It bifurcates into the right and left pulmonary arteries **anterior to the left main bronchus**, creating impressions mainly on the **left lung's mediastinal surface**. *Left atrium* - The **left atrium** forms the base of the heart and is located on the **left and posterior** aspect of the mediastinum. - It creates an impression on the **left lung's mediastinal surface**, particularly the lower part, but has no direct relation to the right lung.

Question 669: Which airway structure enters the lung at the hilum?

A. Primary/Principal bronchus (Correct Answer)
B. Secondary bronchus
C. Bronchiole
D. Tertiary bronchus

Explanation: ***Primary/Principal bronchus*** - The **primary/principal bronchus** (main bronchus) is the largest airway structure that enters each lung at the **hilum** [2]. - It then divides into secondary bronchi within the lung lobes. *Secondary bronchus* - **Secondary bronchi** (lobar bronchi) branch off from the primary bronchi *after* the primary bronchus has already entered the lung. - They supply the individual **lobes** of the lung. *Tertiary bronchus* - **Tertiary bronchi** (segmental bronchi) are further divisions of the secondary bronchi. - They supply the **bronchopulmonary segments**, which are smaller functional units within the lung lobes. *Bronchiole* - **Bronchioles** are smaller airway passages that branch from the tertiary bronchi and lack cartilage [1]. - They are located deeper within the lung tissue, well past the hilum.

Question 670: The internal thoracic artery is a branch of which vessel?

A. Arch of aorta
B. Subclavian artery (Correct Answer)
C. Superior epigastric artery
D. Thyrocervical trunk

Explanation: Subclavian artery - The internal thoracic artery (also known as the internal mammary artery) is a direct branch of the first part of the subclavian artery. - It descends into the chest and supplies the anterior chest wall, breasts, and contributes to the supply of the diaphragm. Arch of aorta - The arch of the aorta gives off major branches such as the brachiocephalic trunk, left common carotid artery, and left subclavian artery. - While the subclavian artery originates from the arch (or the brachiocephalic trunk on the right), the internal thoracic artery is a more distal branch off the subclavian itself, not directly off the arch. Superior epigastric artery - The superior epigastric artery is actually one of the two terminal branches of the internal thoracic artery, indicating it is a distal continuation, not its origin [1]. - It descends into the rectus sheath to anastomose with the inferior epigastric artery [1]. Thyrocervical trunk - The thyrocervical trunk is a short, thick artery that arises from the first part of the subclavian artery. - Its branches (inferior thyroid, superficial cervical, and suprascapular arteries) primarily supply structures in the neck and shoulder, not the internal thoracic artery.

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

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Thorax — MCQs

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