Thorax — MCQs
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To which rib does the pleura extend in the mid-axillary line?
Which of the following statements is NOT true?
Which symptoms or signs are typically seen in acute peripheral arterial occlusion?
The suprascapular artery arises from which of the following branches of the subclavian artery?
In a case of chest pain with pericarditis and pericardial effusion, where is the pain referred by?
A 72-year-old patient vomited and then aspirated some of the vomitus while under anesthesia. On bronchoscopic examination, partially digested food is observed blocking the origin of the right superior lobar bronchus. Which of the following groups of bronchopulmonary segments will be affected by this obstruction?
Which artery supplies the mammary gland?
Which of the following is NOT a true rib?
Which of the following is NOT a middle mediastinal mass?
What is the distance from the incisor teeth to the first constriction of the esophagus?
Thorax Indian Medical PG Practice Questions and MCQs
Question 481: To which rib does the pleura extend in the mid-axillary line?
- A. 8th rib
- B. 9th rib
- C. 10th rib (Correct Answer)
- D. 11th rib
Explanation: The extent of the lungs and the pleura follows a predictable anatomical pattern based on surface markings. The parietal pleura always extends lower than the lungs, creating the **costodiaphragmatic recess** [1]. The lower limit of the **pleura** follows the "Rule of Even Numbers" (8, 10, 12): 1. **Mid-clavicular line:** 8th rib 2. **Mid-axillary line:** 10th rib (Correct Answer) 3. **Scapular line/Paravertebral:** 12th rib **Analysis of Options:** * **A. 8th rib:** This is the lower limit of the pleura at the mid-clavicular line. It is also the lower limit of the **lung** at the mid-axillary line. * **B. 9th rib:** This is an intermediate point and does not correspond to the standard surface markings for the lung or pleura in the mid-axillary line [1]. * **C. 10th rib (Correct):** As per the anatomical rule, the pleura reaches its lateral-most inferior extent at the 10th rib in the mid-axillary line. * **D. 11th rib:** This is an incorrect landmark for the pleura in the mid-axillary line. **NEET-PG High-Yield Pearls:** * **The 2-Rib Rule:** The pleura generally sits two ribs lower than the lung at any given vertical line (e.g., at the mid-axillary line, the lung ends at the 8th rib while the pleura ends at the 10th). * **Thoracocentesis (Pleural Tap):** To avoid lung injury, the needle is typically inserted in the 8th or 9th intercostal space in the mid-axillary line, which lies within the costodiaphragmatic recess (below the lung but above the pleural reflection) [2]. * **Spleen Relation:** The left costodiaphragmatic recess (10th rib) is a crucial landmark as it relates to the upper pole of the spleen; trauma here can involve both the pleura and the spleen.
Question 482: Which of the following statements is NOT true?
- A. The coronary sinus is situated in the posterior coronary sulcus.
- B. The coronary sinus is guarded by the Thebesian valve.
- C. The middle cardiac vein runs alongside the posterior interventricular artery.
- D. All cardiac veins are derived from the coronary sinus. (Correct Answer)
Explanation: **Explanation** The correct answer is **D** because it is a false statement. While the coronary sinus is the primary venous channel of the heart, it does **not** receive drainage from all cardiac veins. Specifically, the **anterior cardiac veins** and the **thebesian veins (venae cordis minimae)** drain directly into the chambers of the heart (primarily the right atrium) rather than entering the coronary sinus. [1] **Analysis of Options:** * **Option A (True):** The coronary sinus is a wide venous channel located in the posterior part of the atrioventricular groove (posterior coronary sulcus), situated between the left atrium and left ventricle. * **Option B (True):** The opening of the coronary sinus into the right atrium is guarded by a semicircular endocardial fold known as the **Thebesian valve** (valve of the coronary sinus). [1] * **Option C (True):** The **middle cardiac vein** travels in the posterior interventricular groove alongside the **posterior interventricular artery** (a branch of the right coronary artery in right-dominant hearts). **NEET-PG High-Yield Pearls:** * **Tributaries of the Coronary Sinus:** Great cardiac vein (with anterior interventricular artery), Middle cardiac vein, Small cardiac vein (with marginal artery), Posterior vein of the left ventricle, and Oblique vein of the left atrium (Marshall’s vein). * **Thebesian Veins:** These are the smallest cardiac veins that drain directly into all four heart chambers; they are most numerous in the right atrium and right ventricle. * **Anterior Cardiac Veins:** Usually 2–3 in number, they drain the anterior surface of the right ventricle and open directly into the right atrium.
Question 483: Which symptoms or signs are typically seen in acute peripheral arterial occlusion?
- A. Pain
- B. Pallor
- C. Pulselessness
- D. All the above (Correct Answer)
Explanation: Acute peripheral arterial occlusion is a surgical emergency characterized by the sudden cessation of blood flow to an extremity, most commonly due to an embolism (often from the heart) or local thrombosis. [1] **Explanation of the Correct Answer:** The clinical presentation of acute limb ischemia is classically described by the **"6 Ps."** These signs and symptoms occur because the sudden lack of oxygenated blood leads to tissue ischemia and nerve dysfunction. * **Pain (Option A):** Usually the earliest symptom; it is sudden, severe, and often located distal to the site of occlusion. [1] * **Pallor (Option B):** The affected limb appears pale or "waxy" because the arterial supply is cut off, leaving the capillary beds empty. [1] * **Pulselessness (Option C):** A hallmark sign; pulses are absent distal to the level of the obstruction. [1] Since all three are cardinal features of the condition, **Option D (All the above)** is the correct answer. **Clinical Pearls for NEET-PG:** * **The 6 Ps:** Pain, Pallor, Pulselessness, Paresthesia (numbness/tingling), Poikilothermia (coldness), and Paralysis (a late, ominous sign indicating muscle death). * **Golden Period:** Revascularization should ideally occur within **6 hours** to prevent irreversible muscle necrosis and limb loss. * **Diagnosis:** While the diagnosis is primarily clinical, **Handheld Doppler** is the initial bedside tool, and **CT Angiography** is the gold standard for localization. * **Management:** Immediate anticoagulation with **IV Heparin** is initiated to prevent clot propagation, followed by surgical embolectomy (using a **Fogarty catheter**) or thrombolysis. [1]
Question 484: The suprascapular artery arises from which of the following branches of the subclavian artery?
- A. Internal thoracic artery
- B. Thyrocervical trunk (Correct Answer)
- C. Costocervical trunk
- D. Dorsal scapular artery
Explanation: The **suprascapular artery** is a key vessel involved in the collateral circulation around the scapula. To understand its origin, one must recall the branches of the **subclavian artery**, which is divided into three parts by the scalenus anterior muscle. 1. **Why Thyrocervical Trunk is correct:** The thyrocervical trunk arises from the **first part** of the subclavian artery. It typically gives off four main branches: * Inferior thyroid artery * Ascending cervical artery * **Suprascapular artery** (passes over the superior transverse scapular ligament) * Transverse cervical artery (which divides into superficial and deep/dorsal scapular branches) 2. **Analysis of Incorrect Options:** * **Internal thoracic artery:** Also arises from the first part of the subclavian but descends into the thorax behind the costal cartilages to supply the anterior chest wall and breast. * **Costocervical trunk:** Arises from the **second part** of the subclavian artery (on the right) or the first part (on the left). It divides into the superior intercostal and deep cervical arteries. * **Dorsal scapular artery:** This is often a direct branch of the **third part** of the subclavian artery (though it can sometimes arise from the thyrocervical trunk as the deep branch of the transverse cervical artery). **High-Yield NEET-PG Pearls:** * **Scapular Anastomosis:** The suprascapular artery (from 1st part of subclavian) anastomoses with the circumflex scapular artery (from 3rd part of axillary) and the dorsal scapular artery. This provides a critical bypass if the subclavian or axillary artery is ligated. * **The "Army over Bridge" Mnemonic:** The suprascapular **A**rtery passes **over** the superior transverse scapular ligament, while the suprascapular **N**erve passes **under** (through the notch) the ligament. * **Origin Rule:** Most major branches (Vertebral, Internal Thoracic, Thyrocervical) arise from the **1st part** of the subclavian artery.
Question 485: In a case of chest pain with pericarditis and pericardial effusion, where is the pain referred by?
- A. Phrenic nerve (Correct Answer)
- B. Superficial cardiac plexus
- C. Deep cardiac plexus
- D. Vagus nerve
Explanation: **Explanation:** The correct answer is **Phrenic nerve (A)**. The pericardium consists of two layers: the outer fibrous pericardium and the inner serous pericardium (parietal and visceral layers). The **fibrous pericardium** and the **parietal layer of the serous pericardium** are innervated by the **phrenic nerves (C3–C5)**. These nerves carry somatic sensory fibers. When inflammation occurs (pericarditis) or fluid accumulates (effusion), the phrenic nerve is irritated. Because the phrenic nerve originates from the same spinal cord segments as the supraclavicular nerves, the pain is referred to the **ipsilateral shoulder (C4 dermatome)** or the base of the neck [1]. **Why other options are incorrect:** * **Superficial and Deep Cardiac Plexuses (B & C):** These plexuses are primarily responsible for the autonomic (sympathetic and parasympathetic) innervation of the heart muscle and coronary arteries. While they carry visceral afferents for ischemic pain (like angina), they do not mediate the sharp, localized pain associated with the parietal pericardium [2]. * **Vagus Nerve (D):** The vagus nerve provides parasympathetic supply to the heart (slowing the heart rate) but does not carry sensory fibers from the parietal pericardium that result in referred shoulder pain [3]. **NEET-PG High-Yield Pearls:** * **Visceral Pericardium (Epicardium):** Is insensitive to pain. * **Kehr’s Sign:** Similar referred pain to the left shoulder caused by diaphragmatic irritation (e.g., splenic rupture), also mediated by the phrenic nerve. * **Pericarditis Pain:** Characteristically relieved by sitting up and leaning forward; worsened by lying supine. * **Nerve Course:** The phrenic nerve runs anterior to the lung roots, while the vagus nerve runs posterior to them [3].
Question 486: A 72-year-old patient vomited and then aspirated some of the vomitus while under anesthesia. On bronchoscopic examination, partially digested food is observed blocking the origin of the right superior lobar bronchus. Which of the following groups of bronchopulmonary segments will be affected by this obstruction?
- A. Superior, medial, lateral, medial basal
- B. Apical, anterior, posterior (Correct Answer)
- C. Posterior, anterior, superior, lateral
- D. Apical, lateral, medial, lateral basal
Explanation: ### Explanation The correct answer is **B. Apical, anterior, posterior**. **1. Understanding the Anatomy** The right lung is divided into three lobes: Superior (Upper), Middle, and Inferior (Lower). The **right superior lobar bronchus** (also known as the eparterial bronchus) originates from the right main bronchus and subsequently divides into three segmental bronchi. These bronchi supply the three bronchopulmonary segments of the right upper lobe: * **Apical** (Segment I) * **Posterior** (Segment II) * **Anterior** (Segment III) Since the obstruction is at the origin of the right superior lobar bronchus, all segments distal to it—the apical, posterior, and anterior segments—will be affected by atelectasis or aspiration pneumonia. **2. Analysis of Incorrect Options** * **Option A & D:** These include the **medial** and **lateral** segments, which belong to the **Middle Lobe**, and the **medial/lateral basal** segments, which belong to the **Lower Lobe**. These are supplied by the bronchus intermedius and its branches, not the superior lobar bronchus. * **Option C:** This includes the **superior** segment. While there is a superior segment in the lower lobe (Segment VI), it is supplied by the first branch of the right inferior lobar bronchus. **3. Clinical Pearls for NEET-PG** * **Aspiration Anatomy:** In a supine position (common in anesthesia), aspirated material most commonly lodges in the **superior segment of the right lower lobe** or the **posterior segment of the right upper lobe** due to the verticality of the right main bronchus and gravity [1]. * **Right vs. Left:** The right main bronchus is wider, shorter, and more vertical (25°) than the left (45°), making it the most common site for foreign body aspiration. * **Eparterial Bronchus:** The right superior lobar bronchus is the only bronchus that passes *above* the pulmonary artery, earning it the name "eparterial."
Question 487: Which artery supplies the mammary gland?
- A. Subscapular artery (Correct Answer)
- B. Musculophrenic artery
- C. Inferior epigastric artery
- D. Superior epigastric artery
Explanation: The mammary gland is a highly vascular organ located in the superficial fascia of the pectoral region [2], [3]. Its arterial supply is derived from three main sources: the Axillary artery, the Internal Thoracic artery, and the Posterior Intercostal arteries. **Why Subscapular Artery is Correct:** The **Subscapular artery** is the largest branch of the third part of the axillary artery. While the primary axillary contributors to the breast are the **Lateral Thoracic** and **Superior Thoracic** arteries, the Subscapular artery (and its branches) provides significant collateral supply to the lateral aspect of the gland. In the context of the given options, it is the only artery belonging to the axillary system that contributes to mammary vascularity. **Why the Other Options are Incorrect:** * **Musculophrenic artery:** This is a terminal branch of the internal thoracic artery that supplies the diaphragm and lower intercostal spaces; it does not reach the mammary gland. * **Superior epigastric artery:** Another terminal branch of the internal thoracic artery, it enters the rectus sheath to supply the rectus abdominis muscle [1]. * **Inferior epigastric artery:** A branch of the external iliac artery, it supplies the lower abdominal wall and has no anatomical relation to the thorax or breast [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Primary Supply:** The **Internal Thoracic (Mammary) artery** (via its perforating branches) provides about 60% of the blood supply, mainly to the medial quadrants. * **Lateral Supply:** The **Lateral Thoracic artery** (branch of the 2nd part of the axillary) is the main lateral supplier. * **Venous Drainage:** Venous blood drains into the Axillary, Internal Thoracic, and Posterior Intercostal veins. The latter is clinically significant as it communicates with the **Vertebral Venous Plexus (Batson’s plexus)**, providing a route for breast cancer metastasis to the vertebrae and brain.
Question 488: Which of the following is NOT a true rib?
- A. 5th rib
- B. 6th rib
- C. 7th rib
- D. 8th rib (Correct Answer)
Explanation: ### Explanation The classification of ribs is based on their anterior attachment to the sternum. Ribs are divided into three categories: 1. **True Ribs (Vertebrosternal):** The **1st to 7th pairs**. Their costal cartilages articulate directly with the sternum. 2. **False Ribs (Vertebrochondral):** The **8th, 9th, and 10th pairs**. Their costal cartilages do not reach the sternum directly; instead, they articulate with the costal cartilage of the rib immediately above them. 3. **Floating Ribs (Vertebral):** The **11th and 12th pairs**. They have no anterior attachment and end in the posterior abdominal musculature. **Why Option D is Correct:** The **8th rib** is a **false rib**. It attaches to the 7th costal cartilage to form the costal margin, rather than attaching directly to the sternum. Therefore, it is "not a true rib." **Why Other Options are Incorrect:** * **Options A, B, and C (5th, 6th, and 7th ribs):** These are all **true ribs**. Each possesses its own costal cartilage that articulates directly with the lateral border of the sternum. The 7th rib is the last true rib and the longest rib in the human body. --- ### NEET-PG High-Yield Pearls * **Typical vs. Atypical Ribs:** Ribs 3–9 are "typical" (possess a head, neck, tubercle, and shaft). Ribs 1, 2, 10, 11, and 12 are "atypical." * **Costal Margin:** Formed by the cartilages of the 7th to 10th ribs. * **Weakest Point of a Rib:** The **angle of the rib** is the most common site of fracture. * **First Rib Clinical:** It is the shortest, broadest, and most curved. It has a **scalene tubercle** for the insertion of the Scalenus anterior muscle, which separates the subclavian vein (anterior) from the subclavian artery (posterior).
Question 489: Which of the following is NOT a middle mediastinal mass?
- A. Bronchogenic cyst
- B. Ascending aortic aneurysm
- C. Pericardial cyst
- D. Ganglioneuroma (Correct Answer)
Explanation: The mediastinum is anatomically divided into superior and inferior compartments, with the inferior further subdivided into anterior, middle, and posterior [2]. The **middle mediastinum** contains the heart, pericardium, great vessel origins (ascending aorta, pulmonary trunk), tracheal bifurcation, and lymph nodes [2]. **Why Ganglioneuroma is the correct answer:** A **Ganglioneuroma** is a neurogenic tumor derived from the sympathetic chain or spinal nerves [1]. These structures are located in the paravertebral gutters, which are part of the **posterior mediastinum** [2]. Therefore, neurogenic tumors (including schwannomas and neuroblastomas) are the most common cause of posterior mediastinal masses, not middle [1]. **Analysis of incorrect options:** * **Bronchogenic cyst:** These are congenital anomalies of the primitive foregut, typically located near the tracheal bifurcation or subcarinal region within the middle mediastinum [1]. * **Ascending aortic aneurysm:** Since the ascending aorta originates and resides within the pericardial sac and middle mediastinum, any aneurysmal dilation of this segment presents as a middle mediastinal mass [2]. * **Pericardial cyst:** These are benign lesions usually found at the cardiophrenic angles (more commonly the right). As they arise from the pericardium, they are classic middle mediastinal pathologies. **NEET-PG High-Yield Pearls:** * **Most common middle mediastinal mass:** Lymphadenopathy (Sarcoidosis, Lymphoma, Metastasis) [1]. * **Most common posterior mediastinal mass:** Neurogenic tumors [1]. * **The "4 T’s" of Anterior Mediastinal Masses:** Thymoma, Teratoma (Germ cell tumors), Terrible Lymphoma, and Thyroid (Retrosternal goiter) [1]. * **Neurogenic tumors** in children are more likely to be malignant (Neuroblastoma), while in adults, they are usually benign (Schwannoma).
Question 490: What is the distance from the incisor teeth to the first constriction of the esophagus?
- A. 15 cm (Correct Answer)
- B. 18 cm
- C. 25 cm
- D. 40 cm
Explanation: The esophagus is a muscular tube approximately 25 cm long, extending from the pharynx to the stomach. For clinical procedures like endoscopy or nasogastric intubation, distances are measured from the **upper incisor teeth**. ### **Explanation of the Correct Answer** The esophagus has four anatomical constrictions. The **first constriction** occurs at the **pharyngoesophageal junction**, where the esophagus begins. * **Location:** At the level of the cricoid cartilage (C6 vertebra). * **Mechanism:** Caused by the cricopharyngeus muscle (the upper esophageal sphincter). * **Distance:** It is exactly **15 cm (6 inches)** from the incisor teeth. This is the narrowest part of the entire esophagus. ### **Analysis of Incorrect Options** * **B. 18 cm:** This is not a standard landmark, though the **second constriction** (where the Aortic arch crosses) is located at **22 cm** from the incisors. * **C. 25 cm:** This represents the **third constriction**, where the esophagus is crossed by the **left main bronchus**. It also happens to be the total length of the esophagus itself. * **D. 40 cm:** This represents the **fourth constriction** where the esophagus pierces the **diaphragm** (T10 level) to join the stomach. ### **High-Yield NEET-PG Pearls** * **The "Rule of 15":** Remember the distances as increments: **15 cm** (Cricopharyngeus), **22 cm** (Aorta), **27 cm** (Left bronchus), and **40 cm** (Diaphragm). * **Clinical Significance:** The first constriction (15 cm) is the most common site for **foreign body impaction** and accidental perforation during instrumentation because it is the narrowest point. * **Vertebral Levels:** The esophagus starts at **C6**, passes the tracheal bifurcation at **T4**, and enters the abdomen at **T10**.
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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