Thorax — MCQs
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Which of the following is considered a typical intercostal nerve?
Right Recurrent laryngeal nerve loops around?
At what anatomical level does the apex of the lung lie?
The inferior border of the lung in the midaxillary line during normal expiration is at the level of?
Which of the following is not included in the chest wall?
What is the level of the pulmonary valve?
What is the source of preganglionic sympathetic supply to the heart?
Which anatomical structure is located posterior to the transverse pericardial sinus?
What is the anatomical origin of the thoracic duct?
Posterior relation of hilum of the lung?
Thorax Indian Medical PG Practice Questions and MCQs
Question 621: Which of the following is considered a typical intercostal nerve?
- A. First intercostal nerve
- B. Second intercostal nerve
- C. Third intercostal nerve (Correct Answer)
- D. Fourth intercostal nerve
Explanation: ***Third intercostal nerve*** - The **3rd to 6th intercostal nerves** are considered typical because they are confined to their respective **intercostal spaces** and do not extend beyond them. - They supply the **intercostal muscles**, parietal pleura, and skin over the intercostal space [1]. *First intercostal nerve* - This nerve is **atypical** because it has a contribution to the **brachial plexus** which supplies the upper limb. - Its ventral ramus is smaller compared to others and directly contributes to the lower trunk of the brachial plexus. *Second intercostal nerve* - The second intercostal nerve is **atypical** because its lateral cutaneous branch, known as the **intercostobrachial nerve**, supplies the skin of the axilla and medial arm [2]. - This additional distribution outside its intercostal space makes it distinct from typical nerves. *Fourth intercostal nerve* - The **4th intercostal nerve** is also considered a **typical** intercostal nerve (along with the 3rd, 5th, and 6th). - It remains confined to its intercostal space and follows the standard distribution pattern. - While it provides sensory innervation to the skin over the mammary region at the level of the nipple, this does not make it atypical—it simply reflects its dermatomal distribution within its intercostal space.
Question 622: Right Recurrent laryngeal nerve loops around?
- A. Right axillary artery
- B. Right external carotid artery
- C. Right superior thyroid artery
- D. Right subclavian artery (Correct Answer)
Explanation: ***Right subclavian artery*** - The **right recurrent laryngeal nerve** branches from the **right vagus nerve** and loops around the **right subclavian artery** in the neck/upper thorax before ascending to the larynx [2]. - This anatomical arrangement is crucial for understanding its vulnerability during thyroid and neck surgeries. *Right axillary artery* - The **axillary artery** is located in the **axilla (armpit)** and is too far distally to be involved in the looping course of the recurrent laryngeal nerve. - No major nerves directly loop around the axillary artery in a recurrent fashion to supply the larynx [3]. *Right external carotid artery* - The **external carotid artery** supplies structures in the face and neck, and while in proximity, the recurrent laryngeal nerve does not loop around it. - The recurrent laryngeal nerve's path is defined by its association with major arteries emerging from the aorta or great vessels like the subclavian artery [2]. *Right superior thyroid artery* - The **superior thyroid artery** is a branch of the **external carotid artery** and supplies the upper pole of the thyroid gland and larynx. - The recurrent laryngeal nerve is typically deep to the thyroid gland and runs in close proximity to the inferior thyroid artery, not looping around the superior thyroid artery [1].
Question 623: At what anatomical level does the apex of the lung lie?
- A. Above the clavicle (Correct Answer)
- B. Below the clavicle
- C. At the level of the clavicle
- D. At the level of the first rib
Explanation: ***Above the clavicle*** - The **apex of the lung** extends superiorly, projecting into the root of the neck. - It lies approximately **2-3 cm above the medial third of the clavicle**, reaching the level of the neck of the first rib. - This is an important anatomical relationship, as the apex is vulnerable to injury from trauma or procedures in this region. *Below the clavicle* - The main body of the lung lies below the clavicle, but the **apex** specifically refers to the uppermost part that projects superiorly. - The clavicle forms an anterior boundary; the lung apex itself extends beyond this landmark. *At the level of the clavicle* - While part of the lung tissue is at this level, the **true apex** of the lung extends superior to the clavicle. - The clavicle is more of a landmark for the superior border of the thoracic cavity, not the apex itself. *At the level of the first rib* - The apex reaches the **neck of the first rib** posteriorly, but anteriorly it projects **above the clavicle**. - This option confuses the posterior and anterior relationships of the lung apex.
Question 624: The inferior border of the lung in the midaxillary line during normal expiration is at the level of?
- A. 6th rib
- B. 8th rib (Correct Answer)
- C. 10th rib
- D. 12th rib
Explanation: ***8th rib*** - During **normal expiration**, the inferior border of the lung in the **midaxillary line** is typically found at the level of the **8th rib**. - This anatomical landmark is important for clinical procedures such as **thoracentesis** to avoid damaging abdominal organs. *6th rib* - The **6th rib** corresponds to the inferior border of the lung at the **midclavicular line** during normal expiration, not the midaxillary line. - This level is too high for the lung border in the midaxillary plane. *10th rib* - The **10th rib** in the midaxillary line corresponds to the inferior border of the **pleura** during normal expiration, not the lung. - The lung itself is always superior to the pleural reflection at any given point. *12th rib* - The **12th rib** in the midaxillary line is significantly below the typical inferior border of the lung and even the pleura during normal expiration. - This level is much too low and would relate to the kidney or other abdominal structures.
Question 625: Which of the following is not included in the chest wall?
- A. Ribs
- B. Thoracic Vertebrae
- C. Sternum
- D. Lumbar vertebrae (Correct Answer)
Explanation: The lumbar vertebrae are located in the lower back, inferior to the thoracic vertebrae, and are not part of the bony framework of the chest wall [1]. The chest wall is defined by structures that enclose the thoracic cavity, which extends from the neck to the diaphragm [1]. The ribs form the lateral and anterior boundaries of the chest wall, providing protection for the internal organs. They articulate posteriorly with the thoracic vertebrae and anteriorly with the sternum (directly or indirectly). The thoracic vertebrae form the posterior boundary of the chest wall, articulating with the ribs [1]. There are 12 thoracic vertebrae (T1-T12), all of which contribute to the structural integrity of the thorax. The sternum, or breastbone, forms the anterior boundary of the chest wall, articulating with the ribs via costal cartilages [1]. It consists of the manubrium, body, and xiphoid process, all crucial components of the thoracic cage [1].
Question 626: What is the level of the pulmonary valve?
- A. 3rd costal cartilage (Correct Answer)
- B. 2nd intercostal space
- C. 3rd intercostal space
- D. 4th costal cartilage
Explanation: ***3rd costal cartilage*** - The **pulmonary valve** is anatomically located at the **upper border of the 3rd left costal cartilage** at the left sternal border. - This represents the actual anatomical level where the valve structure sits within the thorax. - It is important to distinguish between the **anatomical level** (where the valve actually is) and the **surface marking for auscultation** (where it is best heard - 2nd intercostal space). *2nd intercostal space* - The **left 2nd intercostal space** at the sternal border is the **surface marking for auscultation** of the pulmonary valve. - This is where the pulmonary valve sounds are best heard during clinical examination. - However, this is NOT the anatomical level of the valve itself - sound travels and is best heard at this superficial location. *3rd intercostal space* - The **left 3rd intercostal space** is the location of **Erb's point**, where multiple cardiac sounds can be auscultated. - This is inferior to the auscultation point and not the anatomical level of the pulmonary valve. *4th costal cartilage* - The **4th costal cartilage** level corresponds more closely to the **tricuspid valve** area. - This is too inferior to represent the anatomical level of the pulmonary valve.
Question 627: What is the source of preganglionic sympathetic supply to the heart?
- A. Sympathetic fibers from the lumbar region
- B. Parasympathetic nerve (Vagus nerve)
- C. Thoracic sympathetic fibers (T1 to T5) (Correct Answer)
- D. Sympathetic ganglia from the cervical region
Explanation: ***Thoracic sympathetic fibers (T1 to T5)*** - The **preganglionic sympathetic neurons** supplying the heart originate in the **intermediolateral cell column of the spinal cord** from segments T1 to T5 [1]. - These fibers then synapse in the **cervical and upper thoracic sympathetic ganglia**, from which postganglionic fibers directly innervate the heart [1]. *Parasympathetic nerve (Vagus nerve)* - The **vagus nerve (cranial nerve X)** provides **parasympathetic innervation** to the heart, which generally **decreases heart rate and contractility** [3]. - It does not supply sympathetic innervation [3]; its effects are typically opposite to those of the sympathetic system. *Sympathetic fibers from the lumbar region* - Sympathetic fibers from the **lumbar region** primarily innervate structures in the **abdomen and lower limbs**. - They do not directly contribute to the sympathetic supply of the heart. *Sympathetic ganglia from the cervical region* - While **cervical sympathetic ganglia** (superior, middle, and inferior/stellate) contain postganglionic neurons that innervate the heart, their preganglionic input still originates from the **thoracic spinal cord (T1-T5)** [2]. - These ganglia are a relay point for sympathetic signals to the heart, but the ultimate source of the preganglionic sympathetic outflow is the thoracic spinal cord.
Question 628: Which anatomical structure is located posterior to the transverse pericardial sinus?
- A. Aorta
- B. Pulmonary trunk
- C. SVC
- D. Left atrium (Correct Answer)
Explanation: Left atrium - The **transverse pericardial sinus** is a passage posterior to the great arteries (aorta and pulmonary trunk) and anterior to the great veins and **left atrium**. [1] - Therefore, the **left atrium** is situated directly *posterior* to this sinus, receiving its venous return from the lungs. *Aorta* - The **aorta** is located *anterior* to the transverse pericardial sinus, along with the pulmonary trunk. - These great vessels form the anterior boundary of the transverse pericardial sinus. *Pulmonary trunk* - Similar to the aorta, the **pulmonary trunk** is found *anterior* to the transverse pericardial sinus. - It arises from the right ventricle and makes up the other part of the anterior boundary of the sinus. *SVC* - The **superior vena cava (SVC)** is located *posterior* to the ascending aorta but is positioned laterally to the transverse pericardial sinus. - It drains into the **right atrium** and forms the superior aspect of the heart.
Question 629: 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 630: 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.
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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