Thorax — MCQs
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Arrange lung hilar structure from anterior to posterior:- 1. Primary bronchus 2. Bronchial artery 3. Pulmonary vein 4. Pulmonary artery
During a thoracotomy procedure, a surgeon needs to access the posterior mediastinum. Which of the following structures forms the anterior boundary of the posterior mediastinum?
NOT a content of superior mediastinum
Dislocation of the vertebra is uncommon in the thoracic region because:
A patient is admitted with a stab wound in the left anterior chest wall in the parasternal line. Which cardiac chamber is most likely to be injured?
Diaphragm paralysis occurs due to damage to which nerve?
The physician identifies a palpable mass in one breast, and the patient is scheduled for a "Lumpectomy." The breast is anatomically organized into multiple lobes, each containing a separate duct system with connecting lobules, which is important for understanding breast structure and surgical approaches. The normal breast usually contains how many lobes?
Base of heart is formed by
The most common passage for foreign body aspiration is:
Serratus anterior is supplied by which nerve?
Thorax Indian Medical PG Practice Questions and MCQs
Question 601: Arrange lung hilar structure from anterior to posterior:- 1. Primary bronchus 2. Bronchial artery 3. Pulmonary vein 4. Pulmonary artery
- A. 4,3,2,1
- B. 3,4,1,2 (Correct Answer)
- C. 1,2,3,4
- D. 2,3,4,1
Explanation: ***3,4,1,2*** - This order represents the typical arrangement of major structures in the **lung hilum** from anterior to posterior: **pulmonary vein (most anterior)**, **pulmonary artery**, **primary bronchus**, and finally the **bronchial artery (most posterior)**. - The **pulmonary vein** is usually the most anterior structure, while the **bronchial artery** often runs along the posterior aspect of the bronchus [1]. *4,3,2,1* - This order incorrectly places the **pulmonary artery** as the most anterior structure, which is generally not the case in the hilum. - The **primary bronchus** is usually more posterior than the main pulmonary artery. *1,2,3,4* - This order is incorrect as it places the **primary bronchus** as the most anterior structure, which is anatomically inaccurate for the lung hilum. - The **pulmonary veins** are typically the most anterior hilar structures. *2,3,4,1* - This order incorrectly positions the **bronchial artery** as the most anterior component, while it is usually the most posterior or associated closely with the posterior aspect of the bronchus. - The **pulmonary vein** should be anterior to the pulmonary artery and bronchus.
Question 602: During a thoracotomy procedure, a surgeon needs to access the posterior mediastinum. Which of the following structures forms the anterior boundary of the posterior mediastinum?
- A. Descending thoracic aorta
- B. Pericardial sac (Correct Answer)
- C. Azygos vein
- D. Thoracic vertebrae
- E. Sternum
Explanation: ***Pericardial sac*** - The **pericardial sac** (and the diaphragm, inferiorly) forms the anterior boundary of the **posterior mediastinum** [1]. - This anatomical relationship is crucial for surgeons during thoracotomy to distinguish between the middle and posterior mediastinal compartments [1]. *Descending thoracic aorta* - The **descending thoracic aorta** is a large vessel located *within* the posterior mediastinum itself, typically running along its left side [2]. - Therefore, it is a content of the posterior mediastinum, not a boundary. *Azygos vein* - The **azygos vein** is also a major structure *within* the posterior mediastinum, running along the right side of the vertebral column. - It is a content, not a boundary, of this compartment. *Thoracic vertebrae* - The **thoracic vertebrae** form the *posterior* boundary of the posterior mediastinum [1]. - This anatomical landmark gives the posterior mediastinum its name and defines its dorsal limit.
Question 603: NOT a content of superior mediastinum
- A. Arch of aorta
- B. Thymus
- C. Pulmonary trunk
- D. Left superior intercostal artery (Correct Answer)
Explanation: ***Left superior intercostal artery*** - The **left superior intercostal artery** arises from the **costocervical trunk** (a branch of the subclavian artery) and is NOT considered a primary content of the superior mediastinum. - It descends to supply the **first and second (sometimes third) intercostal spaces** on the left side. - While it may pass near the superior mediastinum, it is anatomically classified with the **posterior mediastinum** structures. *Arch of aorta* - The **arch of the aorta** is a major structure within the **superior mediastinum** [1]. - It gives off three major branches: brachiocephalic trunk, left common carotid artery, and left subclavian artery [2]. - It extends from approximately the level of the **second costal cartilage** to the **lower border of T4 vertebra**. *Thymus* - The **thymus gland** is located in the **anterior mediastinum**, NOT the superior mediastinum [1]. - It lies posterior to the sternum and anterior to the pericardium and great vessels. - However, it may extend superiorly into the lower part of the neck, and in some classifications, its superior portion overlaps with the superior mediastinum [1]. *Pulmonary trunk* - The **pulmonary trunk** is located in the **middle mediastinum** within the pericardial sac, NOT the superior mediastinum [1]. - It originates from the **right ventricle** at a level below the superior mediastinum (which extends only to the sternal angle/T4-5 level). - It carries deoxygenated blood from the right ventricle to the lungs.
Question 604: Dislocation of the vertebra is uncommon in the thoracic region because:
- A. The rib cage provides additional stability
- B. Spinous process is long and pointed
- C. The articular processes are interlocked (Correct Answer)
- D. Anterior longitudinal ligament is strong
Explanation: ***The articular processes are interlocked*** - The **articular processes** in the thoracic spine are oriented coronally (in the frontal plane) and interlock, which provides significant stability and limits rotational movement, thus preventing dislocation. - This anatomical arrangement makes it inherently difficult for one vertebra to slide past another, serving as the primary mechanism preventing thoracic vertebral dislocation. *The rib cage provides additional stability* - While the **rib cage** does provide significant additional stability to the thoracic spine through costovertebral and costotransverse joints, this is a contributing factor rather than the primary anatomical reason. - The rib articulations create a semi-rigid thoracic cage, but the question asks for the primary vertebral feature preventing dislocation. *Spinous process is long and pointed* - The **long, pointed spinous processes** of the thoracic vertebrae (especially T5-T8) limit extension through mechanical overlap but do not primarily prevent dislocation of the vertebral bodies. - These processes can fracture under significant trauma, and their role in preventing dislocation is secondary compared to the facet joint orientation. *Anterior longitudinal ligament is strong* - The **anterior longitudinal ligament** reinforces the anterior aspect of the vertebral column and helps prevent hyperextension. - While it provides important ligamentous support, the primary structural stability against dislocation comes from the bony articulation and interlocking of the facet joints, not ligamentous structures alone.
Question 605: A patient is admitted with a stab wound in the left anterior chest wall in the parasternal line. Which cardiac chamber is most likely to be injured?
- A. Right ventricle (Correct Answer)
- B. Aorta
- C. Left ventricle
- D. Right atrium
Explanation: Right ventricle - The **right ventricle** lies most anteriorly in the chest, directly behind the sternum and ribs, making it the most vulnerable chamber to direct anterior stab wounds [1]. - Its position makes it more susceptible to injury from penetrating trauma to the **parasternal region** [1]. *Aorta* - The **aorta** is located more posteriorly and to the left in the mediastinum, making it less likely to be injured by an anterior stab wound unless the penetrating object is very long and deep. - Injury to the aorta would typically present with more severe and immediate **hemorrhage** and hemodynamic collapse. *Left ventricle* - The **left ventricle** is located more posteriorly and to the left, and is largely covered by the right ventricle, making it less exposed to direct anterior penetrating trauma. - A stab wound would need to be more lateral or deeper to reach the left ventricle directly. *Right atrium* - The **right atrium** is located to the right and superior to the right ventricle, but also somewhat posterior to the most anterior aspect of the right ventricle. - While it can be injured, the right ventricle typically presents the largest surface area directly behind the parasternal area.
Question 606: Diaphragm paralysis occurs due to damage to which nerve?
- A. Intercostal
- B. Phrenic (Correct Answer)
- C. Vagus
- D. Hypoglossal
Explanation: Phase 1: Phrenic - The **phrenic nerve** is crucial for respiration as it provides the sole motor supply to the **diaphragm** [1], [2]. - Damage to the phrenic nerve leads to **diaphragmatic paralysis**, impairing breathing [1]. *Intercostal* - **Intercostal nerves** innervate the **intercostal muscles**, which assist in rib cage movement during breathing [2]. - While important for respiration, damage to these nerves alone does not typically cause complete **diaphragm paralysis** [1]. *Vagus* - The **vagus nerve** (cranial nerve X) plays a role in parasympathetic innervation of various organs, including the heart, lungs, and digestive tract [1]. - It does not directly innervate the **diaphragm** for motor function, so damage would not cause diaphragm paralysis. *Hypoglossal* - The **hypoglossal nerve** (cranial nerve XII) primarily controls the movements of the **tongue**. - Damage to this nerve affects speech and swallowing but has no direct impact on **diaphragm function** or breathing.
Question 607: The physician identifies a palpable mass in one breast, and the patient is scheduled for a "Lumpectomy." The breast is anatomically organized into multiple lobes, each containing a separate duct system with connecting lobules, which is important for understanding breast structure and surgical approaches. The normal breast usually contains how many lobes?
- A. 15 to 25 (Correct Answer)
- B. 10 to 12
- C. 2 to 3
- D. 5 to 7
Explanation: ***15 to 25*** - The **mammary gland** is composed of approximately **15 to 25 lobes** arranged radially around the nipple [1]. - Each lobe contains **lobules** that produce milk and drain into a **lactiferous duct** that opens onto the nipple [1]. *10 to 12* - This range is too low for the typical number of **lobes** found in a normal breast. - While it represents a significant number, it does not fully encompass the normal anatomical variability. *2 to 3* - This number is significantly too low and does not reflect the complex anatomical structure of the **breast**, which is designed for milk production and secretion. - A breast with only 2-3 lobes would be highly abnormal and functionally impaired. *5 to 7* - This range also underestimates the typical number of **lobes** present in a healthy breast. - A limited number of lobes would restrict the breast's functional capacity and overall glandular tissue.
Question 608: Base of heart is formed by
- A. RA + LA (Correct Answer)
- B. RV
- C. LV
- D. LV + RV
Explanation: ***RA + LA*** - The **base of the heart** is primarily formed by the **left atrium** and a portion of the **right atrium** [1]. - This posterior aspect of the heart receives the great veins (SVC, IVC, pulmonary veins) and is oriented towards the vertebral column [1]. *RV* - The **right ventricle** forms the majority of the **anterior surface** of the heart, underlying the sternum. - It does not primarily contribute to the anatomical base. *LV* - The **left ventricle** forms the **apex** of the heart and much of the **left border**, but not the anatomical base. - It is responsible for pumping oxygenated blood to the systemic circulation. *LV + RV* - While both ventricles contribute significantly to the bulk of the heart, together they form the **apex** and the **anterior/inferior surfaces**, not the anatomical base. - The base is specifically the posterior aspect formed by the atria.
Question 609: The most common passage for foreign body aspiration is:
- A. Left main bronchus
- B. Right main bronchus (Correct Answer)
- C. Bronchioles
- D. Alveoli
Explanation: ***Right main bronchus*** - The **right main bronchus** is wider, shorter, and more vertically aligned with the trachea compared to the left main bronchus. - This anatomical configuration makes it the path of least resistance for aspirated foreign bodies. *Left main bronchus* - The **left main bronchus** branches off the trachea at a more acute angle and is narrower and longer. - These anatomical features make aspiration into the left main bronchus less common. *Bronchioles* - While foreign bodies can eventually reach the **bronchioles**, the initial aspiration typically occurs into the larger main bronchi. - Smaller foreign bodies might pass further down, but the primary entry point is usually a main bronchus. *Alveoli* - Foreign bodies are highly unlikely to directly reach the **alveoli** upon aspiration due to their small size and the extensive branching of the tracheobronchial tree. - Aspiration usually lodges in larger airways before reaching such distal structures.
Question 610: Serratus anterior is supplied by which nerve?
- A. Axillary nerve
- B. Dorsal scapular nerve
- C. Long thoracic nerve (Correct Answer)
- D. Spinal accessory nerve
Explanation: **Long thoracic nerve** - The **serratus anterior muscle** is innervated exclusively by the **long thoracic nerve**. - Damage to this nerve can lead to **"winged scapula,"** as the serratus anterior is responsible for holding the scapula against the thoracic wall. *Axillary nerve* - The **axillary nerve** innervates the **deltoid** and **teres minor muscles**. - It is responsible for shoulder abduction and external rotation. *Dorsal scapular nerve* - The **dorsal scapular nerve** supplies the **rhomboid major**, **rhomboid minor**, and **levator scapulae muscles**. - These muscles primarily act to retract and elevate the scapula. *Spinal accessory nerve* - The **spinal accessory nerve** (cranial nerve XI) innervates the **sternocleidomastoid** and **trapezius muscles**. - It is primarily involved in head and shoulder movements.
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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