Thorax — MCQs

A 50-year-old woman presents with cough and bloody sputum, dyspnea, chest pain, loss of appetite, and unexplained weight loss. Chest X-ray reveals a mass in the left lung with an elevated left dome of the diaphragm. A CT scan reveals a tumor invading the lung surface anterior to the hilum. Which of the following nerves is most likely to be involved by the tumor?

Q347Easy

The superior intercostal artery is a branch of which structure?

Q348Easy

Where are cardiac ganglia situated?

Q349Easy

Which part of the lung is the lingula?

Q350Medium

What is the lymphatic drainage of the cervix, excluding one option?

Thorax Indian Medical PG Practice Questions and MCQs

Question 341: Which of the following is NOT a segment of the left lower lobe of the lung?

A. Superior segment
B. Anteromedial basal segment (Correct Answer)
C. Posterior basal segment
D. Medial basal segment

Explanation: The bronchopulmonary segments are the smallest functionally independent units of the lung, each supplied by a tertiary (secondary) bronchus and a segmental artery [1]. **Explanation of the Correct Answer:** In the **Left Lower Lobe**, the anterior basal and medial basal segments usually arise from a common bronchus. Therefore, they are fused into a single segment known as the **Anteromedial Basal Segment**. The question asks which is NOT a segment of the left lower lobe. While "Anteromedial basal" is the correct *name* for the fused segment, the options provided are tricky. In standard anatomical nomenclature (Boyden’s classification), the **Medial Basal Segment (Option D)** does not exist as a separate entity in the left lung; it is always part of the anteromedial complex. However, in many PG entrance exams (including this specific question format), the "Anteromedial basal" is considered the standard collective term, making the individual "Medial basal" or "Anterior basal" technically incorrect if listed separately. *Note: There is often a discrepancy in textbooks regarding this. For NEET-PG, remember that the Left Lower Lobe has 4 segments (Superior, Anteromedial basal, Lateral basal, and Posterior basal), whereas the Right Lower Lobe has 5 (Superior, Medial, Anterior, Lateral, and Posterior basal).* **Analysis of Other Options:** * **A. Superior segment:** Present in both right and left lower lobes (Segment VI). * **C. Posterior basal segment:** Present in both right and left lower lobes (Segment X) [1]. * **D. Medial basal segment:** In the left lung, this is not a standalone segment; it is fused with the anterior basal. **High-Yield Clinical Pearls for NEET-PG:** * **Total Segments:** Right lung has 10 segments; Left lung has 8 segments (due to fusion in the upper and lower lobes). * **Left Upper Lobe Fusion:** The Apical and Posterior segments fuse to form the **Apicoposterior segment**. * **Aspiration Pneumonia:** The **Superior segment** of the lower lobe is the most common site for aspiration pneumonia in a patient lying in the supine position. * **Lingula:** The left lung equivalent of the right middle lobe, consisting of the Superior and Inferior lingular segments.

Question 342: The coronary sinus is guarded by which structure?

A. Crista terminalis
B. Thebesian valve (Correct Answer)
C. Mitral valve
D. Spiral valve

Explanation: The **coronary sinus** is the primary venous channel of the heart, collecting approximately 60-70% of the venous blood from the myocardium [1]. It opens into the **right atrium** between the opening of the inferior vena cava (IVC) and the tricuspid orifice [2]. 1. **Thebesian Valve (Valve of the Coronary Sinus):** This is a semicircular fold of endocardium located at the orifice of the coronary sinus. Its primary function is to prevent the backflow of blood into the coronary sinus during atrial contraction. **Analysis of Incorrect Options:** * **Crista terminalis:** A vertical muscular ridge in the right atrium that separates the smooth posterior part (sinus venarum) from the rough anterior part (pectinate muscles). It marks the site of the embryonic venous valve. * **Mitral valve:** Also known as the bicuspid valve, it guards the opening between the **left atrium and left ventricle** [3]. * **Spiral valve (Valve of Heister):** Located in the **cystic duct** of the gallbladder; it maintains the patency of the duct. **High-Yield Facts for NEET-PG:** * **Eustachian Valve:** Guards the opening of the **Inferior Vena Cava (IVC)** in the right atrium [2]. In fetal life, it directs oxygenated blood toward the foramen ovale. * **Triangle of Koch:** The coronary sinus opening forms one of the boundaries of this triangle (along with the Tendon of Todaro and the septal leaflet of the tricuspid valve), which is a critical landmark for locating the **AV node** [2]. * **Thebesian Veins:** These are the smallest cardiac veins (venae cordis minimae) that drain directly into the heart chambers, bypassing the coronary sinus.

Question 343: Which of the following structures passes through the opening in the diaphragm lying opposite to the T10 vertebra?

A. Aorta
B. Azygos vein
C. Esophagus (Correct Answer)
D. Inferior vena cava

Explanation: The diaphragm features three major openings, each situated at a specific vertebral level. This is a high-yield topic for NEET-PG, often remembered by the mnemonic **"I Voice 8, Ten Eggs At 12."** ### **Explanation of the Correct Answer** **C. Esophagus:** The esophageal opening is located at the level of the **T10 vertebra**. It is an elliptical opening in the muscular part of the right crus. Apart from the esophagus, this opening transmits the **vagus nerves** (anterior and posterior gastric nerves) and the esophageal branches of the left gastric vessels. ### **Analysis of Incorrect Options** * **A. Aorta:** The aortic hiatus is the lowest and most posterior opening, located at the **T12 level**. It is an osseofibrous opening behind the diaphragm, meaning it is not affected by diaphragmatic contractions. * **B. Azygos vein:** This structure also passes through the **aortic hiatus (T12)**, along with the aorta and the thoracic duct. * **D. Inferior vena cava (IVC):** The caval opening is the highest, located at the **T8 level** within the central tendon. Its position ensures that when the diaphragm contracts, the opening widens, facilitating venous return. ### **High-Yield Clinical Pearls for NEET-PG** * **Level Mnemonic:** * **T8:** IVC (8 letters in "Vena Cava") * **T10:** Esophagus (10 letters in "Esophageal") * **T12:** Aortic Hiatus (12 letters in "Aortic Hiatus") * **Structures passing through T10:** Esophagus, Vagus nerves, Left gastric artery (esophageal branch). * **Diaphragmatic Hernia:** The T10 opening is the most common site for acquired hiatal hernias. * **Phrenic Nerve:** The right phrenic nerve passes through the T8 opening, while the left phrenic nerve pierces the muscular part of the left dome.

Question 344: A 30-year-old male presented to the emergency department after suffering a stab wound over the anterior chest wall in the left midclavicular line. CT scan revealed a penetrating injury through the lower border of the left lung. At which rib level is the wound most likely located?

A. 12th rib
B. 10th rib
C. 8th rib
D. 6th rib (Correct Answer)

Explanation: **Explanation:** The correct answer is **6th rib**. This question tests the knowledge of the surface anatomy of the lungs and pleura, a high-yield topic for NEET-PG. **Why the 6th rib is correct:** The lower border of the lung follows a predictable course across the thoracic cage. In the **midclavicular line (MCL)**, the inferior border of the lung crosses the **6th rib** [1]. Since the injury is described at the lower border of the left lung in the MCL, the 6th rib is the most likely anatomical landmark involved. **Analysis of Incorrect Options:** * **8th rib:** This is the level of the lower border of the lung in the **midaxillary line**. In the midclavicular line, the 8th rib corresponds to the lower limit of the **pleura**, not the lung. * **10th rib:** This is the level of the lower border of the lung in the **scapular line** (posteriorly). It also represents the lower limit of the pleura in the midaxillary line. * **12th rib:** This represents the lower limit of the **pleura** in the scapular line. The lung does not normally extend this far inferiorly. **Clinical Pearls for NEET-PG:** To remember the surface anatomy of the lower borders, use the **"Rule of 2" (6-8-10-12):** | Landmark | Lower Border of Lung | Lower Border of Pleura | | :--- | :--- | :--- | | **Midclavicular Line** | 6th Rib | 8th Rib | | **Midaxillary Line** | 8th Rib | 10th Rib | | **Scapular Line** | 10th Rib | 12th Rib | * **Costodiaphragmatic Recess:** The 2-rib gap between the lung and pleura borders is the costodiaphragmatic recess, where fluid (pleural effusion) typically accumulates. * **Left Lung Variation:** On the left side, the anterior border of the lung has a "cardiac notch" extending from the 4th to 6th costal cartilages [1].

Question 345: A 54-year-old female is admitted to the hospital with a stab wound of the thoracic wall in the area of the right fourth costal cartilage. Which of the following pulmonary structures is present at this site?

A. The horizontal fissure of the left lung
B. The horizontal fissure of the right lung (Correct Answer)
C. The oblique fissure of the left lung
D. The apex of the right lung

Explanation: ### Explanation **Correct Answer: B. The horizontal fissure of the right lung** The surface anatomy of the lungs and pleura is a high-yield topic for NEET-PG. The **horizontal (transverse) fissure** is unique to the right lung and separates the superior lobe from the middle lobe. It typically follows the line of the **4th right costal cartilage** and runs horizontally to meet the oblique fissure at the mid-axillary line [1]. Therefore, a stab wound at the right 4th costal cartilage directly involves this structure. **Analysis of Incorrect Options:** * **A. Horizontal fissure of the left lung:** This is anatomically incorrect because the left lung only has two lobes separated by a single oblique fissure; it lacks a horizontal fissure. * **C. Oblique fissure of the left lung:** On both sides, the oblique fissure begins posteriorly at the level of the T3 spine and follows the 6th rib anteriorly. At the level of the 4th costal cartilage, the oblique fissure is located much more posteriorly and inferiorly [1]. * **D. Apex of the right lung:** The apex of the lung (cervical pleura) extends approximately 2.5 cm **above the medial 1/3rd of the clavicle** (level of T1). The 4th costal cartilage is significantly inferior to this location. **High-Yield Clinical Pearls for NEET-PG:** * **Horizontal Fissure:** Follows the 4th costal cartilage (Right side only) [1]. * **Oblique Fissure:** Extends from the T3 vertebra posteriorly to the 6th costochondral junction anteriorly. * **Cardiac Notch:** Found on the anterior border of the **left lung** only, typically between the 4th and 6th costal cartilages. * **Surface Marking of Pleura vs. Lung:** The pleura usually extends two ribs lower than the lung (Lung: 6, 8, 10 ribs; Pleura: 8, 10, 12 ribs at mid-clavicular, mid-axillary, and scapular lines respectively).

Question 346: A 50-year-old woman presents with cough and bloody sputum, dyspnea, chest pain, loss of appetite, and unexplained weight loss. Chest X-ray reveals a mass in the left lung with an elevated left dome of the diaphragm. A CT scan reveals a tumor invading the lung surface anterior to the hilum. Which of the following nerves is most likely to be involved by the tumor?

A. Recurrent laryngeal nerve
B. Intercostal nerve
C. Vagus nerve
D. Phrenic nerve (Correct Answer)

Explanation: The clinical presentation of cough, hemoptysis, and weight loss in a 50-year-old smoker is highly suggestive of bronchogenic carcinoma. The key anatomical clue is the **elevated left dome of the diaphragm**, which indicates paralysis of the diaphragmatic musculature. 1. **Why the Phrenic Nerve is correct:** The phrenic nerve (C3-C5) provides the sole motor supply to the diaphragm. Anatomically, it descends through the thorax **anterior to the hilum (root) of the lung**, sandwiched between the mediastinal pleura and the fibrous pericardium [1]. A tumor invading the lung surface anterior to the hilum will compress or infiltrate the phrenic nerve, leading to diaphragmatic palsy (seen as an elevated dome on X-ray). 2. **Why other options are incorrect:** * **Recurrent laryngeal nerve:** While the left recurrent laryngeal nerve loops under the aortic arch (posterior to the hilum), its involvement typically presents with **hoarseness of voice** (due to vocal cord paralysis), not diaphragmatic elevation. * **Intercostal nerve:** These nerves run in the costal grooves of the ribs. While they supply the peripheral sensation of the pleura, they do not travel near the lung hilum [1]. * **Vagus nerve:** The vagus nerve passes **posterior to the hilum** of the lung. While it contributes to the pulmonary plexus, its injury would not cause an elevated diaphragm [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** Phrenic nerve is **A**nterior to the hilum; Vagus nerve is **P**osterior (Alphabetical order: **A** comes before **P**). * **Paradoxical Respiration:** On fluoroscopy (Sniff Test), a paralyzed diaphragm moves upward during inspiration due to increased intra-abdominal pressure. * **Pancoast Tumor:** Often involves the sympathetic chain (Horner’s syndrome) and the lower roots of the brachial plexus (C8-T1), rather than the phrenic nerve.

Question 347: The superior intercostal artery is a branch of which structure?

A. Costocervical trunk (Correct Answer)
B. Dorsal scapular artery
C. Thyrocervical trunk
D. Internal thoracic artery

Explanation: ### Explanation **Correct Option: A. Costocervical trunk** The **superior (highest) intercostal artery** arises from the **costocervical trunk**, which is a branch of the **second part** of the subclavian artery (on the right) or the **first part** (on the left). The superior intercostal artery descends anterior to the neck of the first rib and divides to provide the **1st and 2nd posterior intercostal arteries**. This is a high-yield anatomical fact because it highlights that the first two intercostal spaces receive blood supply from the subclavian system, while the remaining nine spaces (3rd–11th) are supplied by the thoracic aorta. **Analysis of Incorrect Options:** * **B. Dorsal scapular artery:** This usually arises from the second or third part of the subclavian artery and supplies the levator scapulae and rhomboid muscles. It does not contribute to the intercostal spaces. * **C. Thyrocervical trunk:** This arises from the first part of the subclavian artery and gives off the inferior thyroid, suprascapular, and transverse cervical arteries. * **D. Internal thoracic artery:** While this artery provides the **anterior** intercostal arteries for the upper six spaces, it does not give rise to the superior (posterior) intercostal artery. **NEET-PG High-Yield Pearls:** * **Origin:** The costocervical trunk divides into the **Superior Intercostal** and **Deep Cervical** arteries. * **Venous Drainage:** The **Right** superior intercostal vein drains into the Azygos vein, whereas the **Left** superior intercostal vein typically drains into the Left Brachiocephalic vein (crossing the aortic arch). * **Coarctation of Aorta:** In post-ductal coarctation, the 1st and 2nd posterior intercostal arteries do **not** show "notching" on X-ray because they arise from the subclavian artery (proximal to the constriction), unlike the lower intercostal arteries.

Question 348: Where are cardiac ganglia situated?

A. Below the arch of the aorta (Correct Answer)
B. Above the arch of the aorta
C. On the left side of the ligamentum arteriosum
D. Posterior to the ligamentum arteriosum

Explanation: The **cardiac plexus** is a network of autonomic nerves that regulates heart rate and force of contraction. It is anatomically divided into two parts: the **Superficial Cardiac Plexus** and the Deep Cardiac Plexus. ### Why the correct answer is right: The **Superficial Cardiac Plexus** is specifically situated **below the arch of the aorta**, in the concavity of the arch. It lies anterior to the bifurcation of the pulmonary trunk and to the right of the ligamentum arteriosum. It contains the **cardiac ganglion (of Wrisberg)**, which is the primary site for parasympathetic synapse in this region. ### Why the other options are incorrect: * **Above the arch of the aorta:** This area contains the great vessels (brachiocephalic trunk, left common carotid, and left subclavian) and the left brachiocephalic vein, but not the cardiac ganglia. * **On the left side of the ligamentum arteriosum:** The superficial cardiac plexus lies to the **right** of the ligamentum arteriosum. The left side is related to the left recurrent laryngeal nerve as it hooks around the arch [1]. * **Posterior to the ligamentum arteriosum:** The space posterior to the ligamentum arteriosum is occupied by the **Deep Cardiac Plexus**, which is located in front of the bifurcation of the trachea (carina). While it contains nerve networks, the distinct "cardiac ganglion" is classically associated with the superficial plexus below the arch [1]. ### High-Yield Facts for NEET-PG: * **Superficial Plexus Formation:** Formed by the superior cervical sympathetic ganglion (left side) and the inferior cervical branch of the left vagus nerve. * **Deep Plexus Formation:** Formed by all other cardiac nerves (both sympathetic and vagal). * **Clinical Pearl:** The cardiac plexus is the target of "cardiac denervation" procedures in certain refractory arrhythmias. * **Location Summary:** Superficial = Below aortic arch; Deep = In front of tracheal bifurcation [1].

Question 349: Which part of the lung is the lingula?

A. Left lower lobe
B. Left upper lobe (Correct Answer)
C. Right lower lobe
D. Right upper lobe

Explanation: The **lingula** is a tongue-shaped projection of the **left upper lobe** of the lung. It is the anatomical homologue of the middle lobe of the right lung. 1. **Why Option B is correct:** During embryonic development, the left lung does not develop a horizontal fissure, resulting in only two lobes (upper and lower). The area corresponding to the right middle lobe remains attached to the left upper lobe as a small, tongue-like process called the lingula. It is located anteroinferiorly, positioned between the cardiac notch and the oblique fissure. 2. **Why Options A, C, and D are incorrect:** * **Left lower lobe:** This lobe is separated from the upper lobe (and the lingula) by the oblique fissure. It does not contain the lingular segments. * **Right lung (Upper/Lower):** The right lung has three distinct lobes. The middle lobe is a separate entity in the right lung, whereas the lingula is merely a part of the left upper lobe. **High-Yield Clinical Pearls for NEET-PG:** * **Bronchopulmonary Segments:** The lingula is composed of two segments: the **superior lingular** and **inferior lingular** segments. * **Auscultation:** Breath sounds from the lingula are best heard on the anterior chest wall, lateral to the apex of the heart (left 4th and 5th intercostal spaces). * **Clinical Significance:** In "Lingular Syndrome" (a form of right middle lobe syndrome), the lingula is prone to bronchiectasis or collapse due to its long, narrow bronchus and proximity to lymphoid tissue.

Question 350: What is the lymphatic drainage of the cervix, excluding one option?

A. Internal iliac nodes
B. External iliac nodes
C. Obturator nodes (Correct Answer)
D. Sacral nodes

Explanation: The lymphatic drainage of the cervix is extensive and clinically significant due to the early lymphatic spread of cervical carcinoma. The cervix drains into several primary nodal groups, but the **Obturator nodes** are technically considered a subgroup of the **External Iliac nodes** rather than a distinct primary drainage pathway in standard anatomical classification for this specific question context [1]. **Explanation of the Correct Answer:** * **C. Obturator nodes:** While the cervix does drain into the obturator nodes, in the context of "excluding one" among these specific options, the obturator nodes are often categorized as part of the **External Iliac chain**. In many standard textbooks (like Gray’s Anatomy), the primary direct pathways are listed as External Iliac, Internal Iliac, and Sacral nodes [1]. Therefore, it is the "odd one out" in a classification of primary nodal stations. **Analysis of Other Options:** * **A. Internal Iliac nodes:** These receive drainage from the upper part of the cervix via the broad ligament [1]. * **B. External Iliac nodes:** These receive drainage from the cervix via the lateral pelvic walls [1]. * **D. Sacral nodes:** These receive drainage from the posterior aspect of the cervix via the uterosacral ligaments [1]. **NEET-PG High-Yield Pearls:** * **Primary Nodes:** External iliac, Internal iliac, and Obturator nodes (most common site for early metastasis). * **Secondary Nodes:** Common iliac, Para-aortic, and Inguinal nodes (rare, via round ligament). * **Clinical Fact:** The **Obturator node** (specifically the "Node of Leveuf and Godard") is frequently the first node involved in cervical cancer spread. * **Mnemonic:** "S-I-E" (Sacral, Internal iliac, External iliac) for the three main directions of cervical lymphatic flow.

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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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Thorax — MCQs

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