Thorax Practice Questions

Q: Which of the following ducts commences in the abdomen as an elongated lymph sac superior to the cisterna chyli?

Thoracic duct. The **Thoracic duct** is the largest lymphatic vessel in the body. It typically commences in the abdomen at the level of the **L1-L2 vertebrae** as a dilated, sac-like structure called the **cisterna chyli** [1]. It then ascends through the aortic opening of the diaphragm to enter the posterior mediastinum [2]. It drains lymph from the entire body except for the right upper quadrant (which is drained by the right lymphatic duct). **Analysis of Options:** * **Thoracic duct (Correct):** It begins as the cisterna chyli (or just superior to it) in the abdomen. It is a high-yield structure in anatomy due to its unique course: it starts on the right side, crosses to the left at the level of **T5**, and eventually empties into the junction of the left internal jugular and left subclavian veins. * **Gartner’s duct:** This is a vestigial remnant of the mesonephric (Wolffian) duct in females, found in the broad ligament of the uterus. It is unrelated to the lymphatic system. * **Bile duct & Hepatic duct:** These are parts of the biliary system responsible for transporting bile from the liver/gallbladder to the duodenum. They do not originate from a lymph sac. **High-Yield NEET-PG Pearls:** * **Length:** Approximately 45 cm (18 inches). * **Relations at Aortic Hiatus:** The thoracic duct lies between the **Azygos vein** (on the right) and the **Aorta** (on the left). * **Clinical Significance:** Injury to the duct during thoracic surgery leads to **Chylothorax** (accumulation of milky lymph in the pleural cavity). * **Virchow’s Node:** Enlargement of the left supraclavicular lymph node (Troisier’s sign) often indicates abdominal malignancy (e.g., gastric cancer) because the thoracic duct carries malignant cells to this site.

Q: All are true about the branches of the aorta except?

Coronary arteries arise from the arch of the aorta.. The aorta is the largest artery in the body, divided into the ascending aorta, the arch of the aorta, and the descending aorta. Understanding its branching pattern is crucial for NEET-PG. ### **Explanation of the Correct Answer (D)** The **coronary arteries** (Right and Left) do **not** arise from the arch of the aorta. Instead, they arise from the **ascending aorta**, specifically from the right and left aortic sinuses (Sinuses of Valsalva) just above the aortic valve. This is a high-yield distinction: the ascending aorta has only two branches (the coronaries), while the arch typically has three. ### **Analysis of Other Options** * **Option A:** The arch of the aorta begins and ends at the **sternal angle (Angle of Louis)**, which corresponds to the lower border of the **T4 vertebra**. It starts as a continuation of the ascending aorta and ends by becoming the descending thoracic aorta. * **Option B:** The three major branches—the **Brachiocephalic trunk, Left Common Carotid, and Left Subclavian artery**—all arise from the **convexity** (superior aspect) of the arch. * **Option C:** The **left recurrent laryngeal nerve** hooks around the concavity of the aortic arch, specifically lateral to the **ligamentum arteriosum** [1], before ascending in the tracheoesophageal groove [1]. (Note: The right recurrent laryngeal nerve hooks around the right subclavian artery). ### **High-Yield Clinical Pearls** * **Aortic Arch Level:** T4 is the "magical level" where the arch starts, ends, and where the trachea bifurcates. * **Anomalous Origin:** The most common variation of the arch is a "Bovine Arch," where the left common carotid arises from the brachiocephalic trunk. * **Coarctation of Aorta:** Usually occurs just distal to the origin of the left subclavian artery (near the ductus arteriosus).

Q: During cardiac catheterization of a 6-year-old child, contrast medium released into the arch of the aorta is immediately visible in the left pulmonary artery. What is the most likely explanation for this finding?

Patent ductus arteriosus. The clinical scenario describes a **left-to-right shunt** occurring specifically between the aorta and the pulmonary circulation [1]. **1. Why Patent Ductus Arteriosus (PDA) is correct:** The ductus arteriosus is a fetal vessel connecting the **arch of the aorta** (distal to the left subclavian artery) to the **left pulmonary artery** [1]. In normal development, it closes shortly after birth to become the *ligamentum arteriosum*. If it remains patent, the higher pressure in the aorta forces blood (and contrast medium) directly into the pulmonary artery [2]. This explains why contrast injected into the aortic arch is immediately visible in the left pulmonary artery. **2. Why the other options are incorrect:** * **Atrial Septal Defect (ASD):** This involves a shunt between the left and right atria. Contrast in the aorta would have already passed the atria; it would not flow "backward" from the aorta to the pulmonary artery through an ASD. * **Mitral Stenosis:** This is a valvular narrowing between the left atrium and left ventricle. While it causes pulmonary congestion, it does not create an anatomical communication between the aorta and the pulmonary artery. * **Patent Ductus Venosus:** This is a fetal shunt that bypasses the liver, connecting the umbilical vein to the inferior vena cava. It has no direct connection to the aorta or pulmonary arteries. **High-Yield NEET-PG Pearls:** * **Embryology:** The ductus arteriosus is derived from the **left 6th aortic arch**. * **Clinical Sign:** PDA is characterized by a **"machinery-type" continuous murmur**, loudest at the left infraclavicular area. * **Management:** **Indomethacin** (NSAID) is used to close a PDA in premature infants (by inhibiting prostaglandins), while **Prostaglandin E1** is used to keep it open in cyanotic heart disease.

Q: The arch of aorta lies in which mediastinum?

Superior. **Explanation:** The mediastinum is divided into **superior** and **inferior** compartments by an imaginary horizontal plane (the **Transverse Thoracic Plane of Ludwig**) passing from the sternal angle (Angle of Louis) to the lower border of the T4 vertebra [2]. 1. **Why Superior Mediastinum is Correct:** The arch of aorta begins and ends at the level of the sternal angle. However, its entire course loops upward into the **superior mediastinum**. It starts as a continuation of the ascending aorta at the T4/T5 level, arches superiorly and posteriorly to the left of the trachea, and then descends to become the thoracic aorta at the same T4/T5 level [1]. 2. **Why other options are incorrect:** * **Middle Mediastinum:** This contains the heart, the pericardium, and the **ascending aorta** [1]. Once the aorta leaves the pericardial sac and begins to arch, it enters the superior mediastinum. * **Posterior Mediastinum:** This contains the **descending thoracic aorta**, which begins after the arch ends at the level of T4 [1]. * **Anterior Mediastinum:** This is a narrow space between the sternum and pericardium, containing mainly the thymus (in children), lymph nodes, and connective tissue [1]. It does not contain the aorta. **High-Yield Clinical Pearls for NEET-PG:** * **The "T4" Level:** This is the most important landmark in thoracic anatomy. At this level: the Arch of Aorta begins and ends, the Trachea bifurcates (Carina), and the Azygos vein drains into the SVC. * **Branches of the Arch:** From right to left—Brachiocephalic trunk, Left Common Carotid, and Left Subclavian artery. * **Aortic Knuckle:** On a PA view chest X-ray, the arch of the aorta is visible as the "aortic knuckle" or "aortic bud."

Q: The number of lactiferous ducts that open into the nipple is

15-20. The mammary gland (breast) is a modified sweat gland composed of glandular tissue and supporting stroma. The glandular portion is organized into **15 to 20 independent lobes** [1]. Each lobe is drained by a single **lactiferous duct**. These ducts converge toward the nipple, where each undergoes a localized dilation called the **lactiferous sinus** (which acts as a milk reservoir during lactation) before narrowing again to open independently on the surface of the nipple [1]. Therefore, there are 15–20 ductal openings on the nipple. **Analysis of Options:** * **Option B (15-20):** Correct. This corresponds to the anatomical number of lobes and their respective primary drainage ducts [1]. * **Option A (0-5):** Incorrect. This number is too low to represent the complex lobular architecture of the human breast. * **Options C & D (35-75):** Incorrect. While there are hundreds of terminal duct lobular units (TDLUs) within the breast, they all coalesce into the 15–20 major lactiferous ducts before reaching the nipple [1, 3]. **High-Yield Facts for NEET-PG:** * **Lymphatic Drainage:** Approximately 75% of the lymph from the breast drains into the **axillary nodes** (primarily the pectoral/anterior group). * **Suspensory Ligaments of Cooper:** These fibrous bands connect the dermis to the deep fascia and provide structural support; their contraction by a tumor causes **skin dimpling** [3, 4]. * **Nerve Supply:** The breast is supplied by the anterior and lateral cutaneous branches of the **4th to 6th intercostal nerves**. * **Etiology:** Most breast cancers (Carcinoma) arise from the epithelium of the **terminal duct lobular unit (TDLU)**.

Q: A patient presents with carcinoma in the upper and outer quadrant of the breast. To which of the following lymph nodes does this metastasis typically occur, EXCEPT:

Parasternal lymph nodes. **Explanation:** The lymphatic drainage of the breast is a high-yield topic for NEET-PG. Approximately **75% of the lymph** from the breast, particularly from the **lateral quadrants** (including the upper outer quadrant), drains into the **Axillary Lymph Nodes** [1]. **Why Parasternal Lymph Nodes is the correct answer (The "Except"):** The **Parasternal (Internal Mammary) lymph nodes** primarily receive drainage from the **medial quadrants** of the breast. While some deep drainage from any part of the breast can reach these nodes, the classic pathway for the upper outer quadrant is strictly through the axillary chain. In the context of a "typical" metastasis from the upper outer quadrant, the axillary nodes are the primary destination, making the parasternal nodes the outlier in this list. [2] **Analysis of Incorrect Options:** * **Anterior (Pectoral) Nodes:** These are the primary "Level I" nodes that receive the bulk of the drainage from the lateral quadrants [1]. They are usually the first to be involved. * **Central Nodes:** Lymph flows from the anterior, posterior, and lateral groups into the central nodes (Level II) [1]. These are commonly involved as the disease progresses. * **Lateral (Brachial) Nodes:** While these primarily drain the upper limb, they are part of the axillary chain and can be involved in the retrograde or contiguous spread of breast carcinoma. **Clinical Pearls for NEET-PG:** * **Sentinel Lymph Node:** The first node to receive drainage from a tumor site (usually an anterior axillary node for the upper outer quadrant) [2]. * **Rotter’s Nodes:** These are interpectoral nodes located between the pectoralis major and minor muscles. * **Staging:** Axillary node involvement is the most important prognostic factor in breast cancer [1]. * **Drainage Pattern:** Lateral quadrants → Axillary nodes; Medial quadrants → Parasternal nodes; Inferior quadrants → Subdiaphragmatic/Rectus sheath nodes.

Q: The anterior interventricular artery is a branch of which of the following?

Left coronary artery. The **Left Coronary Artery (LCA)** arises from the left aortic sinus of the ascending aorta. After a short course between the pulmonary trunk and the left auricle, it divides into two primary terminal branches: the **Anterior Interventricular Artery** (also known as the Left Anterior Descending or LAD) and the **Circumflex Artery**. The anterior interventricular artery runs in the anterior interventricular groove toward the apex of the heart, supplying the anterior parts of both ventricles and the anterior two-thirds of the interventricular septum [1]. **Analysis of Options:** * **Option A (Right coronary artery):** The RCA typically gives off the *Posterior* Interventricular Artery (in 67% of cases, defining right dominance), not the anterior one. * **Option C (Circumflex artery):** This is a sister branch of the LCA [1]. It winds around the left margin of the heart in the atrioventricular groove but does not give rise to the anterior interventricular artery. * **Option D (Left anterior descending artery):** This is simply another name for the anterior interventricular artery itself. A vessel cannot be a branch of itself. **High-Yield Clinical Pearls for NEET-PG:** * **"The Widow Maker":** The anterior interventricular artery (LAD) is the most common site of coronary artery occlusion. * **Blood Supply to Conducting System:** The LAD supplies the **Right Bundle Branch** and the anterior fascicle of the Left Bundle Branch via its septal branches. * **Cardiac Dominance:** Determined by which artery gives rise to the *Posterior* Interventricular Artery (usually the RCA).

Q: At which anatomical site is a sternal puncture typically performed?

Upper part of the manubrium of the sternum. **Explanation:** Sternal puncture is a common clinical procedure used to obtain bone marrow for diagnostic purposes (e.g., evaluating leukemias or anemias). **Why Option B is correct:** The **upper part of the manubrium sterni** is the preferred site for sternal puncture in adults. This is because the manubrium is the thickest part of the sternum and is composed of robust cancellous bone containing active red marrow. Its superficial location makes it easily accessible, and its thickness provides a safety margin to prevent the needle from penetrating the posterior table [1]. **Analysis of Incorrect Options:** * **Option A:** The body of the sternum is thinner than the manubrium. Puncturing the lower half increases the risk of accidental penetration into the mediastinum [1]. * **Option C:** The lower part of the manubrium is closer to the **sternal angle (Angle of Louis)**. At this level, the bone is relatively thinner, and the great vessels (like the arch of the aorta) lie immediately posterior, increasing the risk of fatal injury. * **Option D:** The xiphoid process is often cartilaginous or thin and irregular. It lacks sufficient marrow and is located too close to the liver and diaphragm. **High-Yield Clinical Pearls for NEET-PG:** * **Safety:** The most feared complication of sternal puncture is injury to the **arch of the aorta** or the **right atrium**, which lie posterior to the sternum. * **Pediatric Note:** In children, sternal puncture is generally avoided because the bone is too thin; the **upper end of the tibia** or the **iliac crest** is preferred. * **Landmark:** The manubrium lies at the level of the **T3 and T4** vertebrae. * **Contraindication:** Never perform a sternal puncture if a midline sternotomy is planned or if the patient has suspected multiple myeloma with significant lytic lesions in the sternum.

Q: A 58-year-old woman is admitted to the emergency department with severe dyspnea. Bronchoscopy reveals that the carina is distorted and widened. Enlargement of which group of lymph nodes is most likely responsible for altering the carina?

Inferior tracheobronchial. **Explanation:** The **carina** is a cartilaginous ridge located at the bifurcation of the trachea into the right and left primary bronchi (at the level of the T4-T5 vertebrae). Because of its central location directly beneath the tracheal split, it is highly sensitive to pressure from surrounding structures. **1. Why Inferior Tracheobronchial nodes are correct:** The **inferior tracheobronchial lymph nodes** (also known as **subcarinal nodes**) are situated in the angle formed by the bifurcation of the trachea. When these nodes enlarge—often due to bronchogenic carcinoma or granulomatous diseases—they push upward against the carina [1]. On bronchoscopy, this manifests as a **widening, blunting, or distortion** of the normally sharp carinal ridge. This is a classic clinical sign of lymphadenopathy in the subcarinal space. **2. Why other options are incorrect:** * **Pulmonary (Intrapulmonary) nodes:** These are located within the lung parenchyma along the secondary bronchi and do not contact the tracheal bifurcation. * **Bronchopulmonary (Hilar) nodes:** Located at the hilum of the lung where the primary bronchi enter. While they can cause hilar masses, they are too lateral to distort the carina. * **Superior tracheobronchial nodes:** These are located in the tracheoesophageal grooves, superior to the primary bronchi. Their enlargement typically affects the lateral walls of the trachea rather than the carina itself. **Clinical Pearls for NEET-PG:** * **Carinal Reflex:** The carina is the most sensitive area of the tracheobronchial tree for triggering the cough reflex. * **Surface Anatomy:** The carina corresponds to the **Sternal Angle (Angle of Louis)** anteriorly. * **Cancer Staging:** Distortion of the carina is a significant finding in lung cancer staging, often indicating inoperability due to mediastinal node involvement.

Question 1

Which of the following ducts commences in the abdomen as an elongated lymph sac superior to the cisterna chyli?

Accepted Answer

Thoracic duct

Answer

Gartner's duct

Answer

Bile duct

Answer

Hepatic duct

Question 2

All are true about the branches of the aorta except?

Accepted Answer

Coronary arteries arise from the arch of the aorta.

Answer

The beginning and end of the arch of the aorta are at the same level.

Answer

Branches arise from the convexity.

Answer

The left recurrent laryngeal nerve winds around the arch.

Question 3

During cardiac catheterization of a 6-year-old child, contrast medium released into the arch of the aorta is immediately visible in the left pulmonary artery. What is the most likely explanation for this finding?

Accepted Answer

Patent ductus arteriosus

Answer

Atrial septal defect

Answer

Mitral stenosis

Answer

Patent ductus venosus

Question 4

The arch of aorta lies in which mediastinum?

Accepted Answer

Superior

Answer

Posterior

Answer

Answer

Middle

Question 5

The number of lactiferous ducts that open into the nipple is

Accepted Answer

15-20

Answer

0-5

Answer

35-50

Answer

50-75

Question 6

A patient presents with carcinoma in the upper and outer quadrant of the breast. To which of the following lymph nodes does this metastasis typically occur, EXCEPT:

Accepted Answer

Parasternal lymph nodes

Answer

Anterior axillary lymph nodes

Answer

Central axillary lymph nodes

Answer

Lateral axillary lymph nodes

Question 7

The anterior interventricular artery is a branch of which of the following?

Accepted Answer

Left coronary artery

Answer

Right coronary artery

Answer

Circumflex artery

Answer

Left anterior descending artery

Question 8

At which anatomical site is a sternal puncture typically performed?

Accepted Answer

Upper part of the manubrium of the sternum

Answer

Junction of the upper and lower half of the body of the sternum

Answer

Lower part of the manubrium of the sternum

Answer

Area just above the xiphisternum

Question 9

Which of the following statements is true regarding the left phrenic nerve?

Accepted Answer

Supplies the mediastinal and diaphragmatic pleura on the left side and the diaphragmatic peritoneum

Answer

Arises from the ventral rami of C2, C3, and C4

Answer

Descends lateral to the left lung

Answer

Passes through the aortic opening in the diaphragm

Question 10

A 58-year-old woman is admitted to the emergency department with severe dyspnea. Bronchoscopy reveals that the carina is distorted and widened. Enlargement of which group of lymph nodes is most likely responsible for altering the carina?

Accepted Answer

Inferior tracheobronchial

Answer

Pulmonary

Answer

Bronchopulmonary

Answer

Superior tracheobronchial

Thorax — MCQs

Thorax — MCQs

On this page

Practice by Chapter

Want unlimited practice?