Thorax — MCQs

Thorax Indian Medical PG Practice Questions and MCQs

Question 631: Posterior relation of hilum of the lung?

A. Azygous vein
B. SVC
C. Vagus nerve (Correct Answer)
D. Arch of aorta

Explanation: ***Vagus nerve*** - The **vagus nerve** descends posterior to the root of the lung before contributing to the esophageal plexus [1]. - This anatomical position makes it a key posterior relation of the hilum [1]. *Azygous vein* - The **azygous vein** arches over the root of the right lung at the hilum anteriorly, not posteriorly [2]. - It drains into the **superior vena cava (SVC)** [2]. *SVC* - The **superior vena cava (SVC)** lies anterior and superior to the hilum of the right lung, receiving the arch of the azygous vein [2]. - It is a major venous structure positioned anterior to the lung root [2]. *Arch of aorta* - The **arch of the aorta** arches superiorly and then descends posterior to the root of the **left lung**, not the right [1]. - It is an important posterior relation to the hilum of the **left lung**, but not generally considered the primary single posterior relation for the hilum of the lung in general.

Question 632: What is the anatomical origin of the thoracic duct?

A. Union of left subclavian vein and left internal jugular vein.
B. Union of right subclavian vein and right internal jugular vein.
C. Continuation of the upper end of the cisterna chyli. (Correct Answer)
D. Formation from the lumbar lymphatic trunks.

Explanation: ***Continuation of the upper end of the cisterna chyli.*** - The **cisterna chyli** is a dilated sac located at the **origin** of the thoracic duct, typically at the level of T12-L2 vertebrae, which receives lymph from the intestinal and lumbar lymphatic trunks. - The thoracic duct proper begins as the **upward continuation** of this cisterna chyli, ascending through the diaphragm into the posterior mediastinum [1]. *Union of left subclavian vein and left internal jugular vein.* - This describes the typical **termination point** where the thoracic duct drains its lymph into the venous system, not its origin [2]. - The thoracic duct empties into the left venous angle, formed by the junction of these two veins [2]. *Union of right subclavian vein and right internal jugular vein.* - The right lymphatic duct, not the thoracic duct, terminates at the **right venous angle**, formed by the junction of the right subclavian and internal jugular veins. - The **thoracic duct** specifically drains into the left side [2]. *Formation from the lumbar lymphatic trunks.* - The **lumbar lymphatic trunks** drain lymph from the lower limbs and abdominal wall and contribute to the formation of the **cisterna chyli**, which then gives rise to the thoracic duct. - While they are part of the drainage pathway leading to the thoracic duct, they are not its direct anatomical origin.

Question 633: Which of the following is not seen in the anterior mediastinum?

A. Thyroid tumor
B. Neurogenic tumor (Correct Answer)
C. Lymphoma
D. Thymoma

Explanation: ***Neurogenic tumor*** - **Neurogenic tumors** typically arise from nerve tissue and are most commonly found in the **posterior mediastinum**. - The posterior mediastinum is the primary location for these tumors due to the presence of the **sympathetic chain**, intercostal nerves, and vagus nerve. *Thyroid tumour* - **Ectopic thyroid tissue** can be found in the anterior mediastinum, and this tissue can give rise to thyroid tumors [1]. - While less common than in the neck, substernal or **ectopic thyroid goiters** and carcinomas can present in this compartment [1]. *Thymoma* - The **thymus gland** is located in the anterior mediastinum, making thymoma (a tumor of the thymus) a classic anterior mediastinal mass [1]. - Thymomas are often associated with **paraneoplastic syndromes** like myasthenia gravis. *Lymphoma* - **Lymphatic tissue**, including lymph nodes, is plentiful in the anterior mediastinum [1]. - **Hodgkin's and non-Hodgkin's lymphoma** frequently present as masses in the anterior mediastinum, often causing symptoms due to compression of surrounding structures [1].

Question 634: Which of the following statements about Sibson's fascia is correct?

A. Part of scalenus anterior muscle
B. Vessel pass above the fascia
C. Covers apical part of lung (Correct Answer)
D. Attached to the inner border of 2nd rib

Explanation: ***Covers apical part of lung*** - **Sibson's fascia**, also known as the **suprapleural membrane**, is a dense fascial layer that covers and reinforces the **apex of the lung** and pleura. - It protects the lung apex and helps to support structures in the **root of the neck**. *Part of scalenus anterior muscle* - Sibson's fascia is a **separate fascial structure** extending from the first rib to the C7 transverse process, and is not a part of the scalenus anterior muscle. - The **scalenus anterior muscle** is one of the muscles of the neck, and while anatomically related by proximity to the fascia, it is not structurally part of it. *Vessel pass above the fascia* - Key neurovascular structures like the **subclavian artery** and the **brachial plexus** pass *below* Sibson's fascia, as the fascia protects the lung apex. - The fascia acts as a barrier, separating the lung apex from the more superficial structures of the neck. *Attached to the inner border of 2nd rib* - Sibson's fascia is primarily attached to the **inner border of the first rib** and the transverse process of the seventh cervical vertebra. - Its attachment to the first rib is crucial for its supportive role over the lung apex.

Question 635: What type of joint is formed by the costal cartilages of the 8th and 9th ribs?

A. Synovial joint
B. Costochondral joint
C. Costovertebral joint
D. Interchondral joint (Correct Answer)

Explanation: ***Interchondral joint*** - The **8th, 9th, and 10th costal cartilages** articulate with the cartilage immediately above them, forming **interchondral joints**. - These are typically **synovial plane joints** that allow for some gliding movement during respiration. *Costochondral joint* - This joint type is formed between the **rib bone** and its respective **costal cartilage**. - These are **primary cartilaginous joints (synchondroses)** and are generally immobile. *Synovial joint* - While interchondral joints are a type of synovial joint, this option is too general and does not specify the unique anatomical arrangement. - Synovial joints are characterized by a **joint capsule**, **synovial fluid**, and **articular cartilage**, allowing for free movement. *Costovertebral joint* - This joint is formed between the **head of a rib** and the **bodies of two adjacent vertebrae** and their intervertebral disc. - It is a **synovial plane joint** crucial for respiratory mechanics, but not related to the articulation of costal cartilages with each other.

Question 636: Which of the following structures does not pass through the aortic opening?

A. Aorta
B. Thoracic duct
C. Phrenic nerve (Correct Answer)
D. Azygos vein

Explanation: Phrenic nerve - The **phrenic nerve** passes through the **caval opening** (venae caval foramen) in the central tendon of the diaphragm, along with the inferior vena cava, or pierces the diaphragm anteriorly. - It does not pass through the **aortic opening**, which is located more posteriorly and inferiorly [1]. *Azygos vein* - The **azygos vein** typically passes through the **aortic opening** of the diaphragm alongside the aorta and thoracic duct. - This anatomical arrangement allows the vein to ascend into the thorax from the abdomen. *Aorta* - The **aorta** itself, specifically the **descending thoracic aorta**, passes through the **aortic opening** to become the abdominal aorta. - This is the largest of the three major diaphragm openings, located anterior to the 12th thoracic vertebra. *Thoracic duct* - The **thoracic duct**, the main lymphatic vessel of the body, also passes through the **aortic opening** of the diaphragm. - It accompanies the aorta and azygos vein as it ascends from the abdomen into the thorax.

Question 637: Anterior Mediastinal nodes are included in which level of lymph nodes?

A. I
B. V
C. VI (Correct Answer)
D. VII

Explanation: ***VI*** - Level VI lymph nodes are the **prevascular and retrotracheal nodes** located in the **anterior mediastinum** [1]. - According to the **IASLC (International Association for the Study of Lung Cancer)** lymph node mapping system, Level 6 nodes are specifically classified as anterior mediastinal nodes [1]. - These include nodes anterior to the superior vena cava and ascending aorta, and nodes between the trachea and esophagus [1]. *I* - Level I lymph nodes are located in the **low cervical, supraclavicular, and sternal notch** regions. - These are **extra-thoracic nodes** and not part of the mediastinal compartments. - They represent the highest mediastinal, supraclavicular, and sternal notch nodes [1]. *V* - Level V lymph nodes are the **subaortic (aortopulmonary window)** nodes [1]. - These are located in the space between the **aorta and pulmonary artery**, lateral to the ligamentum arteriosum [1]. - While mediastinal, they are specifically in the aortopulmonary window, not classified as anterior mediastinal. *VII* - Level VII lymph nodes are the **subcarinal nodes** located below the carina in the **middle mediastinum** [1]. - These nodes are positioned in the space beneath where the trachea bifurcates into the main bronchi [1]. - They are classified as middle mediastinal nodes, not anterior mediastinal nodes.

Question 638: Food can commonly get obstructed in the esophagus at all of the following locations except

A. Crossing of left bronchus
B. Crossing of arch of aorta
C. Crossing of the hemiazygous vein (Correct Answer)
D. Diaphragmatic aperture

Explanation: Food can commonly get obstructed in the esophagus at all of the following locations except ***Crossing of the hemiazygous vein*** - The **hemiazygos vein crosses the vertebral column** at T7-T9 to drain into the azygos vein; however, this anatomical relationship does not typically create a constriction or point of obstruction for the esophagus. - While it is in proximity, its course does not physically compress or narrow the esophageal lumen in a manner that would commonly cause food impaction. *Crossing of left bronchus* - The **left main bronchus crosses anterior to the esophagus** at the level of the carina (T4-T5), causing a natural indentation and narrowing of the esophageal lumen. - This anatomical narrowing, coupled with the rigid structure of the bronchus, makes it a common site for food impaction, especially for larger boluses. *Crossing of arch of aorta* - The **arch of the aorta crosses anterior and to the left of the esophagus** at the level of T3-T4, creating another significant anatomical constriction. - This bending and compression by a large, typically pulsatile vessel forms a natural bottleneck where swallowed food can easily become lodged. *Diaphragmatic aperture* - The **esophageal hiatus of the diaphragm** (T10) is the most distal natural esophageal narrowing, where the esophagus passes through a muscular opening before joining the stomach. - This narrow opening, surrounded by the crura of the diaphragm, is a very common site for food impaction, particularly when the opening is physiologically or pathologically narrowed (e.g., in cases of hiatal hernia or tight diaphragmatic attachments).

Question 639: Which is the narrowest portion of the esophagus?

A. At the diaphragmatic aperture
B. At the cricopharyngeal sphincter (Correct Answer)
C. At the crossing of the left main bronchus
D. At the level of the aortic arch

Explanation: ***At the cricopharyngeal sphincter*** - This is the **upper esophageal sphincter (UES)**, representing the **narrowest point of the entire esophagus** with a diameter of approximately **14 mm**. - It is formed by the **cricopharyngeus muscle**, which remains tonically contracted at rest to prevent air entry into the esophagus during respiration. - Located approximately **15 cm from the incisor teeth** at the level of the **C6 vertebra**. - **Clinical significance**: This is the most common site for impaction of foreign bodies and is a critical point during endoscopy. *At the crossing of the left main bronchus* - This represents the **middle constriction** where the esophagus is indented by the **left main bronchus** (approximately 22-23 cm from incisors). - This is a point of **extrinsic compression** rather than an intrinsic anatomical narrowing. - Diameter here is approximately **15.5 mm**, making it wider than the upper esophageal sphincter. - Foreign bodies and food boluses may lodge here, but it is not the narrowest point. *At the level of the aortic arch* - The **aortic arch** causes significant indentation and extrinsic compression, adjacent to the bronchial constriction. - This is also part of the **middle constriction** of the esophagus. - Despite this indentation, the lumen diameter is still greater than at the cricopharyngeal sphincter. *At the diaphragmatic aperture* - The esophagus passes through the **esophageal hiatus** at the level of **T10 vertebra** (approximately 40 cm from incisors). - This represents the **lower constriction** with a diameter of approximately **16-19 mm**. - While clinically important for hiatal hernias and lower esophageal sphincter pathology, it is the **widest of the three anatomical constrictions**.

Question 640: All veins open in sinus venarum except -

A. SVC
B. Coronary sinus
C. Anterior cardiac vein (Correct Answer)
D. Small cardiac vein

Explanation: ***Anterior cardiac vein*** - The **anterior cardiac veins** are unique in that they drain **directly into the right atrium** through small openings (foramina) in the anterior atrial wall, **bypassing the sinus venarum entirely**. - Unlike other cardiac veins, they do **not** drain into the **coronary sinus** or the **sinus venarum**. - They typically number 2-3 veins and drain the anterior surface of the right ventricle. *SVC* - The **superior vena cava (SVC)** opens directly into the **superior part of the sinus venarum** of the right atrium. - It carries deoxygenated blood from the upper body, head, neck, and upper limbs to the heart. *Coronary sinus* - The **coronary sinus** is the largest venous drainage channel of the heart and opens into the **posteromedial part of the sinus venarum**. - It collects blood from most cardiac veins, including the great cardiac vein, middle cardiac vein, and small cardiac vein. *Small cardiac vein* - The **small cardiac vein** drains into the **coronary sinus**, which then opens into the **sinus venarum**. - It runs along the right atrioventricular (coronary) groove and drains the right atrium and right ventricle.

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Thoracic Wall and Diaphragm

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Pleura and Lungs

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Mediastinum

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Heart and Pericardium

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Great Vessels and Azygos System

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Thoracic Duct and Lymphatics

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Autonomic Innervation

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Applied Anatomy and Clinical Correlations

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Thoracic Imaging and Cross-sectional Anatomy

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Embryological Development of Thoracic Structures

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