Chapter: Oesophagus & Pharynx; Topic: Upper Oesophageal Sphincter & Swallowing Mechanics; Subtopic: Cricopharyngeus (Cricopharyngeal Sphincter)
Keyword Definitions:
Cricopharyngeal sphincter: The upper oesophageal sphincter formed mainly by the cricopharyngeus muscle at the pharyngoesophageal junction.
Central incisors: The front upper teeth used clinically as a reference point for endoscopic tube insertion distances.
Upper oesophageal sphincter (UOS): Functional zone preventing air entry into the oesophagus and reflux into the pharynx.
Pharyngoesophageal junction: Anatomical transition between the hypopharynx and cervical oesophagus; site of the cricopharyngeal muscle.
Swallowing (deglutition): A coordinated process with oral, pharyngeal and oesophageal phases where the UOS relaxes briefly to permit bolus passage.
1) Lead Question – 2016
The cricopharyngeal sphincter is how far from the central incisor?
A) 15 cm
B) 25 cm
C) 40 cm
D) 50 cm
Answer: A) 15 cm
Explanation (≈100 words): Clinically, the distance from the upper central incisors to the upper oesophageal sphincter — the cricopharyngeal region — is about 15 centimetres in an average adult. This estimate is widely used during endoscopic procedures and nasogastric tube placement as an external reference to identify anatomical levels. The 25 cm and greater values correspond to mid and lower oesophageal levels (e.g., the aortic arch or lower oesophageal sphincter), and are far beyond the cervical UOS. Knowing the ~15 cm benchmark helps clinicians recognise the pharyngoesophageal junction and avoid misplacement or injury during instrumentation.
2) The main muscle forming the cricopharyngeal sphincter is–
A) Thyropharyngeus
B) Cricopharyngeus
C) Superior constrictor
D) Inferior constrictor
Answer: B) Cricopharyngeus
Explanation (≈100 words): The cricopharyngeus is the primary muscle forming the upper oesophageal sphincter (UOS). It is the inferior-most part of the inferior pharyngeal constrictor and wraps circumferentially at the pharyngoesophageal junction. Its tonic contraction prevents air entry into the oesophagus during respiration and transiently relaxes during the pharyngeal phase of swallowing to permit bolus transit. The thyropharyngeus contributes to pharyngeal constriction but does not form the sphincter ring. Recognising the cricopharyngeus as the sphincter muscle is essential for understanding dysphagia causes and for procedures like cricopharyngeal myotomy.
3) Typical location of post-cricoid web causing dysphagia is at–
A) Level of C3–C4 (around 12–14 cm)
B) Level of C5–C6 (around 15–18 cm)
C) Level of T1–T2 (around 25–30 cm)
D) Level of T10 (around 40–45 cm)
Answer: A) Level of C3–C4 (around 12–14 cm)
Explanation (≈100 words): Post-cricoid webs and related hypopharyngeal abnormalities commonly occur just below the cricoid at the C3–C4 level, approximately 12–14 cm from the incisors, producing dysphagia for solids. This region is proximal to the cricopharyngeal sphincter which lies at about 15 cm; subtle differences in centimetre markers aid endoscopists in localising lesions. Lesions at 25–30 cm and deeper correspond to thoracic oesophageal pathology rather than post-cricoid webs. Recognising typical distances assists ENT and GI specialists when correlating symptoms, radiographic barium swallow findings, and endoscopic localisation for interventions.
4) During swallowing the UOS relaxes for approximately–
A) 0.2–0.5 seconds
B) 1–2 seconds
C) 5–10 seconds
D) 20–30 seconds
Answer: B) 1–2 seconds
Explanation (≈100 words): The upper oesophageal sphincter (cricopharyngeus) relaxes transiently during the pharyngeal phase of swallowing for roughly one to two seconds to allow safe passage of the bolus into the cervical oesophagus. This brief relaxation is tightly coordinated with laryngeal elevation and epiglottic closure. A relaxation period shorter than this can cause residue and aspiration risk; prolonged relaxation is uncommon and signifies neuromuscular dysfunction. Recognising the 1–2 second window helps clinicians interpret videofluoroscopic swallow studies and plan interventions for cricopharyngeal dysfunction such as dilation or myotomy.
5) A 55-year-old with oropharyngeal dysphagia and a Zenker’s diverticulum most likely has abnormality at–
A) Lower oesophageal sphincter
B) Cricopharyngeal (UOS) region
C) Mid-oesophagus (aortic arch level)
D) Gastroesophageal junction
Answer: B) Cricopharyngeal (UOS) region
Explanation (≈100 words): Zenker’s diverticulum is a pulsion pouch through Killian’s triangle, just above the cricopharyngeus, and results from increased intraluminal pressure against a non-relaxing upper oesophageal sphincter. Thus pathology is at the cricopharyngeal region (UOS), not the lower oesophageal sphincter or mid-thoracic oesophagus. Patients present with regurgitation, cough, halitosis and oropharyngeal dysphagia. Surgical or endoscopic treatment targets the cricopharyngeal muscle (myotomy) and diverticulum; correctly localising the lesion to the UOS region is therefore central to management.
6) For safe nasogastric tube insertion the tube tip typically passes the UOS at approximately–
A) 12–14 cm from incisors
B) 15–18 cm from incisors
C) 25–30 cm from incisors
D) 40–45 cm from incisors
Answer: B) 15–18 cm from incisors
Explanation (≈100 words): During nasogastric tube placement, the tube traverses the nasopharynx, oropharynx and then the cricopharyngeal region; the tip typically reaches and passes the UOS at roughly 15–18 cm from the central incisors in adults. Confirmatory external markers referencing this range help ensure the tube has entered the oesophagus before advancing toward the stomach (about 40–50 cm). Awareness of the ~15 cm mark prevents coiling in the pharynx and reduces risk of airway misplacement. If resistance is felt at ~15 cm, the UOS may be tight and gentle repositioning or swallowing maneuvers are used.
7) The arterial supply to the region of the cricopharyngeus is primarily from–
A) Superior thyroid artery branches
B) Inferior thyroid artery branches
C) Vertebral artery branches
D) Thyrocervical trunk directly
Answer: A) Superior thyroid artery branches
Explanation (≈100 words): The cervical oesophagus and adjacent cricopharyngeal region receive arterial supply mainly from branches of the superior thyroid artery (a branch of the external carotid) and from smaller branches around the laryngopharyngeal area. The inferior thyroid contributes to lower cervical oesophageal supply, but the dominant arterial input at the pharyngoesophageal junction is typically superior thyroid branches. Knowledge of this vascular anatomy is important during surgical approaches to the cricopharyngeus for myotomy or diverticulectomy to avoid bleeding and preserve laryngeal blood supply.
8) A patient has high-resolution manometry showing a non-relaxing UOS. The best surgical option is–
A) Heller myotomy at LES
B) Cricopharyngeal myotomy
C) Fundoplication
D) Esophagectomy
Answer: B) Cricopharyngeal myotomy
Explanation (≈100 words): Non-relaxing upper oesophageal sphincter (cricopharyngeal dysfunction) causing oropharyngeal dysphagia is often treated with a cricopharyngeal myotomy. This targeted division of the cricopharyngeus reduces outflow obstruction at the UOS and alleviates symptoms such as bolus retention and aspiration risk. Heller myotomy and fundoplication address the lower oesophageal sphincter and gastroesophageal reflux, respectively, and esophagectomy is reserved for severe oesophageal disease. Thus, cricopharyngeal myotomy remains the appropriate surgical option for symptomatic UOS failure confirmed by manometry or videofluoroscopy.
9) On barium swallow the UOS is identified as a high-pressure zone at about–
A) 10–12 cm from incisors
B) 14–16 cm from incisors
C) 30–35 cm from incisors
D) 40–45 cm from incisors
Answer: B) 14–16 cm from incisors
Explanation (≈100 words): Radiologically, the upper oesophageal sphincter/ pharyngoesophageal junction is visualised as a constricted high-pressure zone around 14–16 cm from the upper incisors on barium swallow studies; this corresponds closely to the cricopharyngeal muscle at roughly 15 cm. These barium landmarks aid in diagnosing webs, diverticula, or cricopharyngeal bars. Measurements much deeper into the oesophagus (30–45 cm) represent mid to lower oesophageal structures. Accurate centimetre localisation on swallow studies guides therapeutic decisions such as dilation or myotomy targeted at the UOS level.
10) Neurogenic failure of the UOS relaxation is most commonly due to lesion of–
A) Glossopharyngeal and vagus nerve pathways
B) Phrenic nerve
C) Hypoglossal nerve only
D) Accessory nerve
Answer: A) Glossopharyngeal and vagus nerve pathways
Explanation (≈100 words): Coordination of UOS relaxation during swallowing depends on complex central and peripheral circuits, particularly afferent glossopharyngeal (IX) inputs and efferent vagal (X) motor pathways to pharyngeal constrictors and the cricopharyngeus. Lesions affecting IX/X at the nucleus ambiguus or peripheral branches can produce neurogenic failure of UOS relaxation, resulting in oropharyngeal dysphagia and residue. Phrenic or accessory nerve lesions do not directly impair UOS relaxation. Therefore, investigation of glossopharyngeal and vagal function is essential in patients with suspected neurogenic cricopharyngeal dysfunction.
11) In adults the approximate distance from incisors to lower oesophageal sphincter is–
A) 15 cm
B) 25–40 cm (commonly ~40 cm)
C) 10 cm
D) 5 cm
Answer: B) 25–40 cm (commonly ~40 cm)
Explanation (≈100 words): The lower oesophageal sphincter (LES) typically lies approximately 40 cm from the incisors in adults, though values vary with height and measurement technique and may be cited as 35–45 cm. This contrasts strongly with the upper oesophageal sphincter at about 15 cm. Clinicians use these centimeter markers when placing tubes or interpreting endoscopic/contrast studies: passage beyond ~40 cm suggests the gastric cardia or lower oesophagus, whereas ~15 cm denotes the cricopharyngeal level. Understanding both landmarks prevents misplacement of devices and assists accurate lesion localisation.
Chapter: Oesophagus & Mediastinum; Topic: Oesophageal Relations & Surface Landmarks; Subtopic: Anatomical Constrictions and External References
Keyword Definitions:
Incisors: Upper central teeth used as an external reference point for measuring endoscopic distance to oesophageal landmarks.
Aortic arch relation: The oesophagus is indented by the arch of the aorta where the arch crosses the midline in the superior mediastinum.
Right principal bronchus: The right main bronchus lies inferior to the carina and is related to the lower thoracic oesophagus more distally than the aortic arch.
Thoracic duct: Major lymphatic channel in the posterior mediastinum that typically ascends to cross to the left at the root of the neck near the oesophagus.
Azygos vein: Vein arching into the SVC at T4–T5 posterior to the oesophagus, producing a subtle impression at mid-thoracic levels in some studies.
1) Lead Question – 2016
Which of the following structures is related to the oesophagus 22.5 cm from the incisor teeth?
A) Arch of aorta
B) Right principal bronchus
C) Thoracic duct
D) Azygos vein
Answer: A) Arch of aorta
Explanation (≈100 words): The oesophagus is indented by the arch of the aorta in the upper thorax. Clinically and endoscopically, the aortic arch produces a constriction/impingement of the oesophageal lumen typically observed around 20–25 cm from the incisors; 22.5 cm is a commonly cited landmark for the aortic arch relation. The right main bronchus lies lower (closer to 27–32 cm), the thoracic duct runs posteriorly and is not the dominant external compressing structure at that distance, and the azygos arch typically indents slightly more inferiorly. Therefore, the arch of the aorta is the correct relation at ~22.5 cm.
2) At approximately what distance from the incisors is the upper oesophageal sphincter (cricopharyngeus) encountered?
A) 5 cm
B) 15 cm
C) 30 cm
D) 45 cm
Answer: B) 15 cm
Explanation (≈100 words): The cricopharyngeal sphincter (upper oesophageal sphincter) is located at the pharyngoesophageal junction and is reached endoscopically at roughly 15 cm from the incisors in an average adult. This 15-cm marker is a practical clinical landmark used for tube placement and endoscopic orientation. Distances of ~30–45 cm correspond to mid and lower oesophageal levels (aortic arch to lower oesophageal sphincter). Accurate recognition of the ~15 cm mark helps avoid misplacement during instrumentation and aids in localising proximal oesophageal pathology such as Zenker’s diverticulum or cricopharyngeal bars.
3) Which oesophageal constriction is produced by the left main bronchus or left atrium and is typically felt around 27–30 cm from the incisors?
A) Upper constriction (cricoid)
B) Middle constriction (aortic arch / left main bronchus)
C) Lower constriction (diaphragmatic)
D) Cardio-oesophageal junction
Answer: B) Middle constriction (aortic arch / left main bronchus)
Explanation (≈100 words): The mid-oesophageal constriction is complex: the aortic arch and the left main bronchus (and in some texts the left atrium) can produce impressions. Endoscopically, secondary constrictions around 25–30 cm often reflect the aortic arch followed slightly inferiorly by the left main bronchus. These combined relations are responsible for the "middle" constriction. The upper constriction is at the cricopharyngeus (~15 cm) and the lower at the diaphragmatic hiatus (~40 cm). Clinicians use these landmarks to localise strictures, foreign bodies, or intrinsic masses relative to surrounding mediastinal structures.
4) Which statement is true regarding the thoracic duct relation to the oesophagus?
A) It usually lies anterior to the oesophagus at 10 cm from incisors
B) It ascends posterior to the oesophagus and crosses to the left at the root of the neck
C) It drains directly into the azygos vein at T5
D) It forms the primary mid-oesophageal constriction at 22.5 cm
Answer: B) It ascends posterior to the oesophagus and crosses to the left at the root of the neck
Explanation (≈100 words): The thoracic duct ascends in the posterior mediastinum posterior and right of the oesophagus before crossing to the left at the level of the superior thoracic aperture to drain into the venous angle (left subclavian/internal jugular junction). It does not typically produce a focal oesophageal constriction at 22.5 cm nor drain into the azygos vein. Awareness of its retro-oesophageal course is important during posterior mediastinal surgery and when interpreting mediastinal pathologies, because injury can lead to chyle leak.
5) A patient with progressive solid-food dysphagia has a ring at ~20–22 cm on barium swallow. The most likely external relation causing this indentation is–
A) Lower oesophageal sphincter
B) Arch of aorta
C) Left renal artery
D) Diaphragmatic crura
Answer: B) Arch of aorta
Explanation (≈100 words): A discrete impression or band seen on imaging at about 20–22 cm from the incisors corresponds well with the aortic arch level. Rings or extrinsic indentations here often relate to vascular structures or aortic atherosclerotic impression. Lower oesophageal sphincter and diaphragmatic crura are much more distal (~38–40 cm). The left renal artery is abdominal and unrelated. Thus, when evaluating proximal oesophageal narrowing near 22 cm, an aortic arch relation is high on the differential and warrants correlation with thoracic vascular imaging.
6) In endoscopic practice the right principal (main) bronchus produces an oesophageal impression at approximately what distance from the incisors?
A) 10–15 cm
B) 20–23 cm
C) 27–32 cm
D) 40–45 cm
Answer: C) 27–32 cm
Explanation (≈100 words): The bronchial impressions on the oesophagus are usually encountered more distally than the aortic arch indentation. The right and left main bronchi relate to the oesophagus at roughly 25–32 cm from the incisors, depending on individual anatomy and measurement technique. The right principal bronchus commonly produces a palpable or radiologic impression in the mid-to-lower thoracic oesophagus; this is why foreign bodies often lodge or perforate near these bronchial crossings. Thus, expecting bronchial relations around 27–32 cm assists endoscopists in localisation and risk assessment.
7) Clinically, which structure most commonly compresses the oesophagus to cause dysphagia lusoria when anomalous?
A) Aberrant right subclavian artery (arteria lusoria)
B) Thoracic duct duplication
C) Accessory hemiazygos vein
D) Left gastric artery
Answer: A) Aberrant right subclavian artery (arteria lusoria)
Explanation (≈100 words): Dysphagia lusoria is classically due to an aberrant right subclavian artery that arises distal to the left subclavian and passes posterior (or rarely between) the oesophagus and trachea to reach the right arm, compressing the oesophagus and producing dysphagia, typically in the lower cervical/upper thoracic region. This is an important vascular cause of extrinsic oesophageal compression. Other mediastinal vascular anomalies or enlarged left atrium may also compress the oesophagus, but the aberrant right subclavian artery is the prototypical congenital culprit.
8) The azygos vein commonly produces an oesophageal impression at approximately which vertebral level or distance? (Choose the best match)
A) At the thoracic inlet (~10–12 cm)
B) At T4–T5 level, mid-thoracic (~24–28 cm)
C) At the diaphragm (~38–42 cm)
D) At the lumbar vertebrae (~50–60 cm)
Answer: B) At T4–T5 level, mid-thoracic (~24–28 cm)
Explanation (≈100 words): The azygos vein arches over the right main bronchus to join the superior vena cava at the T4–T5 level and may produce a mild posterior oesophageal impression around the mid-thoracic region, often reported about 24–28 cm from the incisors. Although less prominent than aortic or bronchial impressions, the azygos arch is an important posterior mediastinal landmark. Recognising this helps distinguish vascular from intrinsic oesophageal lesions on radiology and endoscopy. The diaphragm and lumbar vertebrae are far more distal and not relevant to mid-thoracic impressions.
9) Which oesophageal constriction is most relevant when planning cervical oesophageal surgery or cricopharyngeal myotomy?
A) Diaphragmatic constriction (~40 cm)
B) Aortic constriction (~22.5 cm)
C) Cricopharyngeal/upper oesophageal sphincter (~15 cm)
D) Bronchial constriction (~30 cm)
Answer: C) Cricopharyngeal/upper oesophageal sphincter (~15 cm)
Explanation (≈100 words): Cervical oesophageal procedures focus on the upper oesophageal sphincter (cricopharyngeus) located at about 15 cm from the incisors. This sphincter is directly implicated in oropharyngeal dysphagia and Zenker’s diverticulum; thus, accurate localisation is critical for cricopharyngeal myotomy or diverticulectomy. Mid or lower oesophageal constrictions (aortic, bronchial, diaphragmatic) are important for thoracic surgeons or gastroenterologists but are not the primary concern in cervical oesophageal surgery.
10) A foreign body perceived at 22.5 cm on endoscopy is most likely to be lodged at the level of–
A) Cricopharyngeus
B) Aortic arch indentation
C) Lower oesophageal sphincter
D) Gastroesophageal junction
Answer: B) Aortic arch indentation
Explanation (≈100 words): Endoscopic measurement showing an impacted foreign body at ~22.5 cm suggests lodging at the mid-cervical/mid-thoracic junction where the aortic arch indents the oesophagus. This is a common site for entrapment alongside the cricopharyngeus (~15 cm) and the lower oesophageal sphincter (~40 cm). Recognising the aortic arch relationship is essential for predicting potential vascular erosion risk and planning safe removal, often with radiologic correlation to exclude adjacent vascular anomalies or erosion before attempted extraction.
Chapter: Mediastinum & Lymphatic System; Topic: Thoracic Duct – Anatomy & Clinical Relevance; Subtopic: Termination, Course and Relations of Thoracic Duct
Keyword Definitions:
Thoracic duct: The main lymphatic channel draining lymph from most of the body into the venous system.
Venous angle: The junction of the internal jugular and subclavian veins where major lymphatic trunks enter the bloodstream.
Right lymphatic duct: Drains lymph from right upper quadrant (right head, neck, arm, and thorax) into right venous angle.
Chyle: Lipid-rich lymph from the intestines conveyed in the thoracic duct.
Chylothorax: Accumulation of lymph (chyle) in pleural cavity due to thoracic duct injury.
1) Lead Question – 2016
Thoracic duct opens into systemic circulation at?
A) junction of SVC and left brachiocephalic vein
B) Junction of left internal jugular and left subclavian vein
C) Directly into coronary sinus
D) Into azygous vein
Answer: B) Junction of left internal jugular and left subclavian vein
Explanation: The thoracic duct ascends in the posterior mediastinum and typically arches laterally at the root of the neck to terminate at the left venous angle — the junction of the left internal jugular and left subclavian veins. Here it delivers lymph and chyle into the systemic venous circulation, returning protein-rich and lipid-laden lymph to the bloodstream. Variants exist (termination into the left subclavian or left internal jugular separately), but the classic and most common termination is at the left internal jugular–left subclavian junction. Awareness of this anatomy is essential during neck surgery to avoid chyle leak.
2) The thoracic duct begins from–
A) Cisterna chyli
B) Right lymphatic trunk
C) Left lumbar trunk
D) Hepatic lymph trunk
Answer: A) Cisterna chyli
Explanation: The thoracic duct usually originates inferiorly from the cisterna chyli — a dilated sac in the upper abdomen at the level of L1–L2 formed by convergence of the lumbar and intestinal lymph trunks. From there the duct ascends through the aortic hiatus of the diaphragm into the posterior mediastinum. The cisterna chyli collects lymph (including chyle) from the lower limbs, pelvis, and abdominal viscera, making it the classical starting point for the thoracic duct. Not all individuals have a true cisterna chyli; anatomical variations occur, but the functional origin remains the abdominal lymph collectors.
3) Which region does the thoracic duct NOT drain?
A) Left upper limb
B) Right upper limb
C) Lower limbs
D) Abdomen
Answer: B) Right upper limb
Explanation: The thoracic duct drains lymph from the majority of the body: both lower limbs, the pelvis, abdomen, left thorax, left head and neck, and left upper limb. The exception is the right upper quadrant (right side of head and neck, right upper limb and right thorax), which drains into the right lymphatic duct and empties into the right venous angle. Therefore the right upper limb's lymph return is not usually via the thoracic duct. This separation of drainage territories is clinically important when assessing patterns of lymphedema or metastatic spread.
4) Injury to the thoracic duct in the chest most commonly results in–
A) Chylothorax
B) Hemothorax
C) Pneumothorax
D) Empyema
Answer: A) Chylothorax
Explanation: Transection or disruption of the thoracic duct within the thorax commonly leads to chyle leaking into the pleural space — a chylothorax. The fluid is milky and rich in triglycerides and lymphocytes. Causes include thoracic surgery, trauma, malignancy (e.g., lymphoma), or congenital anomalies. Chylothorax can cause respiratory compromise and significant nutritional and immunologic depletion because of loss of lipids and lymphocytes; management ranges from dietary modification (medium-chain triglycerides, nil per os) to thoracic duct ligation depending on severity and persistence.
5) The thoracic duct crosses from right to left at–
A) T8 vertebral level
B) Root of the neck near C7–T1 (superior thoracic aperture)
C) Immediately after the aortic hiatus
D) At the level of the azygos arch
Answer: B) Root of the neck near C7–T1 (superior thoracic aperture)
Explanation: Typically, the thoracic duct ascends on the right side of the vertebral column in the posterior mediastinum and crosses to the left behind the esophagus near the superior thoracic aperture in the lower neck (around the level of C7–T1) before arching laterally to reach the left venous angle. This crossover from right to left explains why injury or pathologic dilation may produce symptoms ipsilateral to the side of its course, and why neck operations near the thoracic inlet risk damaging the duct during left-sided venous procedures.
6) During neck dissection the most likely site for iatrogenic thoracic duct injury is–
A) Right venous angle
B) Left venous angle (junction of internal jugular and subclavian veins)
C) Midline trachea
D) Mandibular ramus
Answer: B) Left venous angle (junction of internal jugular and subclavian veins)
Explanation: The thoracic duct typically terminates at the left venous angle; thus left-sided neck dissections, central line placement in the left subclavian or left internal jugular vein, or lymph node excisions in the lower left neck carry a risk of injuring the duct. Damage here manifests as chyle leak externally from the wound or internally into the pleural space. Surgeons must identify and ligate the duct when seen and manage leaks with pressure, diet alteration, drainage, or surgical repair if needed to prevent prolonged chyle loss.
7) The histological wall of the thoracic duct contains–
A) Smooth muscle and lymphatic valves
B) Hyaline cartilage rings
C) Stratified squamous epithelium
D) Endothelium only without valves
Answer: A) Smooth muscle and lymphatic valves
Explanation: The thoracic duct, like other large lymphatic vessels, has a wall comprised of an endothelial lining, some fibrous connective tissue, and smooth muscle in the tunica media; importantly it contains numerous internal valves that promote unidirectional lymph flow toward the venous system. The presence of valves and segmental smooth muscle allows active propulsion of lymph, particularly during respiration and with adjacent muscular activity. Foreign structures like cartilage or stratified squamous epithelium are not components of lymphatic vessel walls.
8) A patient with lymphoma has dilation of the thoracic duct seen on imaging; the probable mechanism is–
A) Obstruction of lymphatic flow by nodal disease
B) Increased arterial inflow to the duct
C) Direct spread of tumor into the duct lumen only seen in carcinoma
D) Portal hypertension
Answer: A) Obstruction of lymphatic flow by nodal disease
Explanation: Malignant lymphadenopathy in the thorax or abdomen can obstruct lymphatic drainage pathways leading to proximal dilation of the thoracic duct. In lymphoma, bulky nodal disease compresses or invades lymphatic channels causing stasis and dilation, and sometimes chylous effusions. This is different from arterial causes or portal hypertension. Recognition of thoracic duct dilation on imaging in a malignancy patient should prompt evaluation for nodal obstruction and possible intervention if chylous effusion develops.
9) Lymph from the right lung’s lower lobe typically drains into–
A) Right bronchomediastinal trunk → right venous angle
B) Thoracic duct → left venous angle
C) Cisterna chyli directly
D) Internal mammary nodes only
Answer: A) Right bronchomediastinal trunk → right venous angle
Explanation: Lymphatic drainage of the right lung (especially the right upper and middle zones) commonly empties into the right bronchomediastinal trunk which drains into the right venous angle via the right lymphatic duct or directly. The thoracic duct generally services the contralateral (left) thorax and most of the body below. Therefore, lymph from the right lung lower lobe is more likely to follow right-sided bronchomediastinal pathways rather than draining into the thoracic duct; exceptions and anastomoses do occur.
10) Which clinical test or sign suggests thoracic duct injury producing a chylous fistula after neck surgery?
A) Milky drainage from wound increasing with oral fat intake
B) Bright red bleeding from wound on coughing
C) Clear serous drainage unrelated to diet
D) Pus discharge with fever
Answer: A) Milky drainage from wound increasing with oral fat intake
Explanation: Chyle is rich in dietary triglycerides and appears milky; after thoracic duct injury, the wound or drain will often show milky output that becomes more evident after the patient resumes oral feeding, especially with fatty meals. Testing the fluid for triglyceride content (or chylomicrons) confirms chyle. This helps distinguish chyle from serous wound drainage or hemorrhage. Management may begin with dietary fat restriction and drainage, progressing to surgical ligation if conservative measures fail.
11) Which statement about anatomical variation of thoracic duct termination is correct?
A) It always ends at the left venous angle with no variation
B) It may end into the left subclavian vein, left internal jugular vein, or form multiple terminal branches
C) It frequently drains into the right atrium directly
D) It terminates into the pulmonary veins
Answer: B) It may end into the left subclavian vein, left internal jugular vein, or form multiple terminal branches
Explanation: Although the thoracic duct classically terminates at the left venous angle, anatomical variations are common: the duct may empty separately into the left subclavian or left internal jugular veins, or present as a plexus of terminal channels. Rarely it may have duplicated channels or atypical terminations. This variability explains why iatrogenic injury can occur in several ipsilateral venous procedures and why preoperative awareness or imaging can be helpful. Drainage into right-sided heart structures or pulmonary veins does not occur.
Chapter: Thorax; Topic: Cardiac Innervation; Subtopic: Sympathetic & Parasympathetic Supply of Heart
Keyword Definitions:
Sympathetic fibers (T1–T5): Preganglionic neurons from thoracic spinal cord supplying heart via cervical & upper thoracic ganglia.
Vagus nerve: Main parasympathetic supply decreasing heart rate & conduction.
Cardiac plexus: Autonomic plexus formed by sympathetic and parasympathetic fibers at the base of the heart.
Cervical ganglia: Superior, middle & inferior ganglia relaying sympathetic fibers to the heart.
Visceral afferents: Sensory pain fibers running with sympathetic pathways producing referred pain.
1) Lead Question – 2016
Sympathetic supply of the heart is from ?
A) Vagus
B) Thoracic sympathetic fibres (T1 to T5)
C) Lumbar sympathetic fibres
D) Cervical ganglion
Answer: B) Thoracic sympathetic fibres (T1 to T5)
Explanation: Sympathetic innervation to the heart arises from preganglionic neurons in spinal cord segments T1–T5. These fibers synapse in cervical and upper thoracic sympathetic ganglia, sending postganglionic cardiac nerves to form the cardiac plexus. Sympathetic stimulation increases heart rate, contractility and conduction velocity. The vagus nerve supplies parasympathetic fibers, not sympathetic. Lumbar fibers do not participate in cardiac innervation, and although cervical ganglia relay sympathetic impulses, the origin of these fibers is T1–T5. Therefore, thoracic sympathetic fibers (T1–T5) form the primary sympathetic supply of the heart.
2) Parasympathetic supply to the heart is mainly through–
A) Glossopharyngeal nerve
B) Vagus nerve
C) Phrenic nerve
D) Recurrent laryngeal nerve
Answer: B) Vagus nerve
Explanation: The vagus nerve forms the parasympathetic component of the cardiac plexus, slowing heart rate and reducing atrioventricular conduction. Glossopharyngeal and phrenic nerves have no parasympathetic cardiac function; recurrent laryngeal nerve is a branch of vagus but does not supply the heart. Thus, the vagus is the primary parasympathetic nerve to the heart.
3) Pain from myocardial ischemia is referred to the left arm due to involvement of–
A) Parasympathetic fibers
B) Sympathetic afferents T1–T5
C) Glossopharyngeal afferents
D) Cervical plexus
Answer: B) Sympathetic afferents T1–T5
Explanation: Cardiac pain fibers travel with sympathetic pathways entering the spinal cord at T1–T5 segments. These share dermatomal overlap with the medial arm and chest, leading to referred pain. Parasympathetics convey reflex sensations but not ischemic pain. Thus sympathetic afferents T1–T5 mediate cardiac pain referral.
4) Which ganglia send postganglionic sympathetic fibers to the heart?
A) Only superior cervical ganglion
B) Middle and inferior cervical ganglia
C) Cervical and upper thoracic ganglia
D) Stellate ganglion only
Answer: C) Cervical and upper thoracic ganglia
Explanation: Cardiac sympathetic fibers synapse in cervical ganglia (superior, middle, inferior/stellate) and upper thoracic ganglia (T1–T4). These postganglionic fibers form cardiac nerves entering the cardiac plexus. The stellate ganglion alone is not the sole source; all cervical and upper thoracic ganglia contribute.
5) Excess sympathetic stimulation of the heart causes–
A) Bradycardia
B) Positive inotropic and chronotropic effects
C) Atrioventricular block
D) Decreased cardiac output
Answer: B) Positive inotropic and chronotropic effects
Explanation: Sympathetic activation increases heart rate (chronotropy), conduction (dromotropy), and contractility (inotropy). These effects enhance cardiac output. Parasympathetic stimulation causes bradycardia. Thus sympathetic stimulation leads to positive chronotropic and inotropic actions.
6) A patient with stellate ganglion block may show–
A) Increased heart rate
B) Decreased sympathetic supply to the heart
C) Increased AV conduction
D) Severe tachycardia
Answer: B) Decreased sympathetic supply to the heart
Explanation: Stellate ganglion (inferior cervical + T1) provides significant sympathetic cardiac innervation. Its blockade decreases sympathetic outflow, reducing heart rate and contractility. Thus decreased sympathetic supply is expected.
7) The cardiac plexus is located at–
A) Aortic arch and tracheal bifurcation
B) Between diaphragm and stomach
C) Behind esophagus
D) Inside pericardial cavity
Answer: A) Aortic arch and tracheal bifurcation
Explanation: The cardiac plexus lies anterior to the tracheal bifurcation and below the aortic arch. It receives sympathetic and parasympathetic fibers before distributing them to the heart. Thus option A is correct.
8) Stimulation of β1 receptors in the heart by sympathetic fibers causes–
A) Vasoconstriction of coronary arteries
B) Decreased cardiac output
C) Increased heart rate and contractility
D) Complete AV block
Answer: C) Increased heart rate and contractility
Explanation: Sympathetic fibers act via β1 receptors in the myocardium to increase heart rate, conduction and contractile strength. Coronary arteries dilate rather than constrict. Thus stimulation produces enhanced cardiac output.
9) Cardiac visceral afferents responsible for reflex control of blood pressure travel mainly with–
A) Sympathetic nerves
B) Parasympathetic (vagal) nerves
C) Phrenic nerve
D) Spinal accessory nerve
Answer: B) Parasympathetic (vagal) nerves
Explanation: Reflex cardiac sensory fibers (baroreceptor and chemoreceptor inputs) travel with the vagus nerve to mediate cardiovascular reflexes. Sympathetics carry pain, not reflex afferents. Thus vagal afferents regulate cardiovascular reflexes.
10) Which condition is associated with sympathetic overactivity to the heart?
A) Complete heart block
B) Sinus tachycardia
C) Vagal hyperactivity
D) Hypothyroidism
Answer: B) Sinus tachycardia
Explanation: Sympathetic overactivity accelerates SA node automaticity, producing sinus tachycardia. Vagal hyperactivity causes bradycardia. Hypothyroidism slows metabolism and reduces heart rate. Thus sinus tachycardia best represents sympathetic excess.
11) Injury to T1 sympathetic fibers may result in–
A) Horner syndrome
B) Tachycardia
C) Excess sweating
D) Increased heart contractility
Answer: A) Horner syndrome
Explanation: Sympathetic fibers ascending from T1 supply the face via cervical ganglia. Damage results in Horner syndrome (ptosis, miosis, anhidrosis). Cardiac sympathetic effects would be reduced, not increased. Thus T1 injury → Horner syndrome.
Chapter: Heart Anatomy; Topic: Cardiac Valves; Subtopic: Aortic Valve Cusps
Keyword Definitions:
Aortic valve: Semilunar valve located between the left ventricle and aorta.
Semilunar cusps: Thin crescent-shaped valve leaflets preventing backflow.
Right coronary cusp: Aortic cusp giving rise to the right coronary artery.
Left coronary cusp: Aortic cusp giving rise to the left coronary artery.
Posterior (non-coronary) cusp: Aortic cusp not associated with any coronary artery.
1) Lead Question – 2016
Which of the following are cusps of the aortic valves?
a) Left, right and Anterior
b) Anterior, Right and Posterior
c) Posterior, Left and Right
d) Anterior, Posterior and Left
Answer: c) Posterior, Left and Right
Explanation: The aortic valve contains three semilunar cusps: the right coronary cusp, the left coronary cusp, and the posterior (non-coronary) cusp. The right and left cusps give rise to the corresponding coronary arteries, while the posterior cusp does not. These cusps prevent regurgitation of blood into the left ventricle during diastole. There is no anterior cusp in the aortic valve (anterior cusp belongs to the pulmonary valve). Therefore, the correct combination is Posterior, Left and Right cusps. This anatomical arrangement is consistent across normal cardiac anatomy and forms the basis for coronary ostia location.
2) How many cusps does the pulmonary valve have?
a) Two
b) Three
c) Four
d) One
Answer: b) Three
Explanation: The pulmonary valve, like the aortic valve, is a semilunar valve composed of three cusps: anterior, left, and right. These cusps prevent backflow from the pulmonary trunk into the right ventricle. The pulmonary valve’s anterior cusp differentiates it from the aortic valve, which possesses a posterior (non-coronary) cusp instead. The presence of three cusps ensures even pressure distribution and efficient closure during diastole. A bicuspid (two-cusped) pulmonary valve is extremely rare compared to the more common congenital bicuspid aortic valve. Thus, the correct number of pulmonary valve cusps is three.
3) The coronary arteries arise from which aortic sinuses?
a) Posterior only
b) Right and left aortic sinuses
c) Right sinus only
d) None of the sinuses
Answer: b) Right and left aortic sinuses
Explanation: The right coronary artery originates from the right coronary sinus, whereas the left coronary artery arises from the left coronary sinus. The posterior sinus is a non-coronary sinus with no arterial origin. These sinuses are dilated spaces located above the aortic valve cusps and play an essential role in smooth valve function by preventing cusp adhesion to the aortic wall. Their anatomical relationship ensures that coronary perfusion begins during diastole when the aortic valve is closed. Therefore, the coronary arteries arise specifically from the left and right sinuses.
4) A patient with aortic regurgitation most likely has dysfunction of which valve component?
a) Chordae tendineae
b) Aortic cusps
c) Papillary muscles
d) Mitral annulus
Answer: b) Aortic cusps
Explanation: Aortic regurgitation results from incomplete closure of the aortic valve, leading to backflow into the left ventricle during diastole. Since the aortic valve has no chordae tendineae or papillary muscles, pathology is usually in the cusps or aortic root. Degenerative changes, bicuspid morphology, or inflammatory destruction affect coaptation of the cusps. Mitral annulus involvement does not contribute to aortic regurgitation. Thus dysfunction of the aortic cusps is the primary cause in most cases.
5) Which of the following valves is most commonly bicuspid congenitally?
a) Pulmonary valve
b) Aortic valve
c) Mitral valve
d) Tricuspid valve
Answer: b) Aortic valve
Explanation: Bicuspid aortic valve (BAV) is the most common congenital cardiac anomaly, occurring in about 1% of the population. Instead of three cusps, the valve has two, predisposing it to early calcification, stenosis, and regurgitation. Other valves are rarely bicuspid congenitally. The mitral valve is normally bicuspid, but that is not a congenital abnormality. Thus the aortic valve is the most common congenital bicuspid valve.
6) Which cusp of the aortic valve is non-coronary?
a) Right
b) Left
c) Posterior
d) Anterior
Answer: c) Posterior
Explanation: The posterior cusp of the aortic valve is known as the **non-coronary cusp** because no coronary artery arises from its sinus. The right and left cusps are associated with corresponding right and left coronary arteries. There is no anterior cusp in the aortic valve; this term is used for the pulmonary valve. Thus, the posterior cusp is designated as the non-coronary cusp.
7) The aortic valve opens during which phase of the cardiac cycle?
a) Late diastole
b) Early systole
c) Mid diastole
d) Late systole
Answer: b) Early systole
Explanation: At the beginning of systole, rising left ventricular pressure exceeds aortic pressure, forcing the aortic valve open. This permits ejection of blood into the aorta. As systole ends and ventricular pressure falls, the cusps close to prevent regurgitation. The valve plays no role in diastolic filling. Hence, the aortic valve opens specifically during early systole.
8) Aortic stenosis affects which part of the valve most commonly?
a) Commissures
b) Annulus
c) Cusps
d) Aortic wall
Answer: c) Cusps
Explanation: Aortic stenosis usually results from calcification and thickening of the cusps, limiting their mobility. Rheumatic disease leads to commissural fusion, but degenerative disease—most common—primarily stiffens the cusps. Annular calcification affects the mitral valve more frequently. Therefore, cusp pathology is the hallmark feature of aortic stenosis.
9) Which valve lacks chordae tendineae?
a) Mitral valve
b) Tricuspid valve
c) Aortic valve
d) Bicuspid valve
Answer: c) Aortic valve
Explanation: Semilunar valves (aortic and pulmonary) do not have chordae tendineae or papillary muscles; their cusps function independently and attach directly to the arterial wall. Only atrioventricular valves (mitral and tricuspid) use chordae tendineae to prevent prolapse into the atria. Thus the aortic valve lacks chordae tendineae.
10) In infective endocarditis, vegetations on the aortic valve typically occur on–
a) Atrial surface of cusps
b) Ventricular surface of cusps
c) Aortic surface of cusps
d) Commissures only
Answer: b) Ventricular surface of cusps
Explanation: High-pressure gradients across the aortic valve cause turbulent blood flow, leading vegetations to form on the **ventricular (outflow) surface** of the aortic cusps. In contrast, AV valves show vegetations on the atrial surfaces. The location helps differentiate the affected valve. Thus vegetations on the aortic valve are classically on the ventricular surface.
11) Which valve prevents backflow into the left ventricle?
a) Mitral valve
b) Pulmonary valve
c) Tricuspid valve
d) Aortic valve
Answer: d) Aortic valve
Explanation: The aortic valve closes during diastole to prevent blood from flowing back into the left ventricle. Its three cusps create a tight seal when closed. The mitral valve prevents backflow into the left atrium, not the ventricle. Thus, the valve responsible for preventing regurgitation into the left ventricle is the aortic valve.
Chapter: Cardiovascular System; Topic: Coronary Circulation; Subtopic: LAD & Myocardial Infarction
Keyword Definitions:
LAD (Left Anterior Descending artery): Major coronary artery supplying anterior wall, septum, and apex.
Coronary dominance: Determined by the artery giving posterior interventricular branch.
Anterior MI: Infarction due to LAD occlusion affecting left ventricle.
Coronary perfusion: Coronary arteries fill during diastole, not systole.
Septal branches: LAD branches supplying interventricular septum.
1) Lead Question – 2016
Which is the widow's artery in myocardial infarction?
a) Left anterior descending artery
b) Right coronary artery
c) Posterior interventricular artery
d) Left circumflex artery
Answer: a) Left anterior descending artery
Explanation: The LAD (Left Anterior Descending artery), also called the “widow-maker,” supplies a large portion of the anterior wall of the left ventricle, the anterior two-thirds of the interventricular septum, and the cardiac apex. Occlusion of the LAD leads to extensive myocardial damage, resulting in high mortality if not treated promptly. It is the most commonly affected artery in acute myocardial infarction. Because of the large territory it supplies, an LAD blockage severely compromises cardiac output, contributing to its high lethality. Therefore, the LAD is widely referred to as the widow’s artery.
2) Which artery supplies the SA node most commonly?
a) Right coronary artery
b) Left circumflex artery
c) LAD
d) Posterior interventricular artery
Answer: a) Right coronary artery
Explanation: In nearly 60% of individuals, the SA node receives its blood supply from the right coronary artery. The remaining cases are supplied by the left circumflex artery. The LAD does not directly supply the SA node. Proper SA node perfusion is essential for maintaining normal sinus rhythm. Thus, the RCA most commonly supplies the SA node.
3) A blockage of the LAD most likely causes which ECG change?
a) Inferior wall ST elevation
b) Anterior wall ST elevation
c) Lateral wall ST depression
d) No significant ECG change
Answer: b) Anterior wall ST elevation
Explanation: LAD occlusion affects the anterior surface of the left ventricle, leading to ST elevation in V1–V4 on ECG. Inferior changes would occur with RCA occlusion. LAD occlusion is critical because it affects the main pumping chamber of the heart.
4) Coronary arteries fill primarily during–
a) Early systole
b) Late systole
c) Diastole
d) Throughout the entire cardiac cycle
Answer: c) Diastole
Explanation: Coronary perfusion occurs mainly during diastole when ventricular relaxation reduces compression of coronary vessels. During systole, myocardial contraction restricts coronary flow. This principle is important in conditions like tachycardia, where shortened diastole reduces coronary perfusion.
5) The posterior interventricular artery arises from RCA in which type of circulation?
a) Left dominant
b) Codominant
c) Right dominant
d) Mixed
Answer: c) Right dominant
Explanation: In right-dominant circulation (most common), the posterior interventricular artery arises from the RCA. In left dominance, it originates from the circumflex artery. Dominance describes the artery supplying the posterior descending branch.
6) A patient with a posterior MI most likely has an obstruction of which vessel?
a) LAD
b) RCA
c) Left main coronary artery
d) Diagonal branches
Answer: b) RCA
Explanation: In right-dominant hearts, RCA gives rise to the posterior descending artery, supplying the inferior and posterior ventricular walls. Occlusion results in posterior or inferior MI. LAD and diagonal branches supply the anterior wall.
7) Which artery supplies the AV node most commonly?
a) LAD
b) Left circumflex
c) RCA
d) Marginal artery
Answer: c) RCA
Explanation: The AV node receives its primary blood supply from the RCA in nearly 90% of individuals. Loss of this blood supply can lead to AV block. The LCx supplies the AV node in left-dominant circulation.
8) The circumflex artery supplies which area mainly?
a) Interventricular septum
b) Lateral wall of left ventricle
c) Right ventricle
d) Apex of the heart
Answer: b) Lateral wall of left ventricle
Explanation: The LCx artery provides blood to the lateral surface of the left ventricle via obtuse marginal branches. It does not supply the interventricular septum, which is supplied by the LAD.
9) Which of the following arteries is most commonly affected in sudden cardiac death?
a) Diagonal artery
b) LAD
c) RCA
d) Obtuse marginal artery
Answer: b) LAD
Explanation: LAD occlusion leads to major anterior infarctions and can interrupt blood supply to a large portion of the myocardium, contributing to sudden cardiac death. Its territory includes critical conduction tissue.
10) A clot in the left main coronary artery affects which regions?
a) Entire left ventricle
b) Anterior and lateral walls
c) Right ventricle only
d) Apex only
Answer: b) Anterior and lateral walls
Explanation: The left main coronary artery divides into the LAD and LCx. Thus, blockage compromises both anterior (LAD territory) and lateral (LCx territory) walls. This type of occlusion carries very high mortality.
11) A patient with chest pain showing ST elevation in leads II, III, aVF likely has occlusion of–
a) LAD
b) RCA
c) LCx
d) Diagonal branch
Answer: b) RCA
Explanation: ST elevation in II, III, and aVF corresponds to an inferior wall MI, typically due to RCA occlusion in right-dominant circulation. LAD changes appear in V1–V4.
Chapter: Thorax; Topic: Lung Hilum Relations; Subtopic: Posterior & Anterior Structures of Lung Hilum
Keyword Definitions:
Lung hilum: Region on mediastinal lung surface where bronchi, vessels, and nerves enter/leave.
Vagus nerve: Parasympathetic nerve passing posterior to lung root.
Phrenic nerve: Motor nerve to diaphragm passing anterior to lung hilum.
Pulmonary ligament: Fold of pleura extending inferiorly from hilum.
Root of lung: Collection of bronchus, pulmonary artery, pulmonary veins, and nerves.
1) Lead Question – 2016
Which of the following passes posterior to the hilum of the lung?
a) Vagus
b) Phrenic nerve
c) SVC
d) Right atrium
Answer: a) Vagus
Explanation: The vagus nerve is the major parasympathetic nerve supplying thoracic and abdominal organs. In relation to the lung hilum, the vagus nerve characteristically passes **posterior** to the root of the lung on both sides before forming the pulmonary plexus. The phrenic nerve, in contrast, always runs **anterior** to the lung hilum. The superior vena cava and right atrium lie anterior or right-sided and do not pass posterior to the hilum. Therefore, the structure passing posterior to the lung hilum is the vagus nerve, an important anatomic relationship relevant in thoracic surgeries.
2) Which of the following passes anterior to the root of the lung?
a) Azygos vein
b) Vagus nerve
c) Phrenic nerve
d) Esophagus
Answer: c) Phrenic nerve
Explanation: The phrenic nerve runs anterior to the lung hilum, supplying the diaphragm. The vagus passes posteriorly, and the azygos vein arches over the right lung root. The esophagus is positioned posterior to the left atrium and lung root, not anterior. Hence, phrenic nerve is the anterior relation.
3) The azygos vein arches over which lung hilum?
a) Left
b) Right
c) Both sides
d) Neither
Answer: b) Right
Explanation: The azygos vein ascends along the right side of the vertebral column and arches over the right lung hilum to drain into the superior vena cava. It does not cross the left side. Thus, it is a characteristic posterior-superior relation of the right lung hilum.
4) Which structure is most posterior in the right lung root?
a) Pulmonary vein
b) Pulmonary artery
c) Right main bronchus
d) Phrenic nerve
Answer: c) Right main bronchus
Explanation: At the hilum, bronchus lies posterior, pulmonary artery is superior, and pulmonary veins are inferior/anterior. The phrenic nerve is anterior. Thus the most posterior structure in the right lung root is the right main bronchus.
5) Which nerve forms the posterior pulmonary plexus?
a) Phrenic
b) Spinal accessory
c) Vagus
d) Intercostal nerves
Answer: c) Vagus
Explanation: The vagus nerve contributes parasympathetic fibers to the posterior pulmonary plexus. The phrenic is primarily motor to diaphragm with sensory branches. Intercostal nerves supply parietal pleura and thoracic wall.
6) Enlargement of which structure may compress the left recurrent laryngeal nerve?
a) Right lung root
b) Left pulmonary artery
c) Ligamentum arteriosum area
d) Thoracic duct
Answer: c) Ligamentum arteriosum area
Explanation: The left recurrent laryngeal nerve loops under the aortic arch near the ligamentum arteriosum. Enlargement of structures here (aneurysm, lymph nodes) can compress it. It does not loop around pulmonary vessels or lung roots.
7) Which lung has a bronchus lying superior to the pulmonary artery ("eparterial")?
a) Right
b) Left
c) Both
d) Neither
Answer: a) Right
Explanation: The right upper lobe bronchus arises above the right pulmonary artery, making it “eparterial.” The left bronchus always lies inferior to its pulmonary artery.
8) The pulmonary veins at the lung hilum are located–
a) Superiorly
b) Anterior and inferior
c) Posteriorly
d) Medially
Answer: b) Anterior and inferior
Explanation: Pulmonary veins are consistently found anterior and inferior to the pulmonary artery and bronchus. This is important during lung surgeries and hilar dissections.
9) The esophagus is closely related to which lung posteriorly?
a) Right lung
b) Left lung
c) Both lungs
d) Neither lung
Answer: b) Left lung
Explanation: The esophagus passes posterior to the left lung root and left atrium, creating an important relationship for transesophageal echocardiography and surgical approaches.
10) On the left side, which artery arches over the root of the lung?
a) Azygos vein
b) Left subclavian artery
c) Aortic arch
d) Internal thoracic artery
Answer: c) Aortic arch
Explanation: The aortic arch forms a superior relation to the left lung hilum, unlike the azygos arch on the right. Subclavian and internal thoracic arteries are more superior and anterior.
11) Which structure runs within the pulmonary ligament?
a) Inferior pulmonary vein
b) Pulmonary artery
c) Lymph vessels
d) Bronchial arteries
Answer: c) Lymph vessels
Explanation: The pulmonary ligament is a pleural fold extending from the hilum downward, containing lymphatics and loose connective tissue. It stabilizes the lung root while allowing movement during respiration.
Chapter: Thorax; Topic: Heart and Great Vessels; Subtopic: Levels of Cardiac Valves
Keyword Definitions:
Pulmonary valve: Semilunar valve between right ventricle and pulmonary trunk; located at level of 3rd costal cartilage.
Cardiac valve levels: Surface anatomy landmarks used for auscultation and clinical examination.
Costal cartilage: Bars of hyaline cartilage connecting ribs to sternum.
Intercostal spaces: Spaces between ribs used as clinical reference points.
Surface marking: External anatomical point corresponding to internal heart structures.
1) Lead Question – 2016
What is the level of the pulmonary valve?
a) 3rd intercostal space
b) 4th costal cartilage
c) 3rd costal cartilage
d) 2nd intercostal space
Answer: c) 3rd costal cartilage
Explanation: The pulmonary valve is located posterior to the left side of the sternum at the level of the **3rd left costal cartilage**. Although its auscultatory area is at the 2nd left intercostal space, its anatomic location differs. The pulmonary valve lies superior to the aortic valve and is part of the outflow tract of the right ventricle. The 3rd intercostal space and 4th costal cartilage do not correspond anatomically to this valve. Therefore, the correct anatomical level of the pulmonary valve is the 3rd costal cartilage.
2) The aortic valve is located at which level?
a) 2nd right intercostal space
b) 3rd right costal cartilage
c) 2nd left intercostal space
d) 4th costal cartilage
Answer: b) 3rd right costal cartilage
Explanation: Anatomically, the aortic valve lies behind the left side of the sternum at the level of the 3rd right costal cartilage. Its auscultation point is different (2nd right intercostal space). Hence, the correct anatomical landmark is the 3rd right costal cartilage.
3) The tricuspid valve is located at–
a) 4th left intercostal space
b) 4th–5th intercostal space behind sternum
c) 3rd costal cartilage
d) 2nd intercostal space
Answer: b) 4th–5th intercostal space behind sternum
Explanation: The tricuspid valve lies behind the sternum opposite the 4th–5th intercostal spaces. This corresponds anatomically to the right AV junction. It is auscultated at the lower left sternal border.
4) The mitral valve is best heard at which surface point?
a) Left 5th intercostal space midclavicular line
b) 2nd right intercostal space
c) 3rd costal cartilage
d) 1st intercostal space
Answer: a) Left 5th intercostal space midclavicular line
Explanation: The mitral valve is auscultated at the cardiac apex, located in the left 5th intercostal space at the midclavicular line. This corresponds to the left ventricular apex.
5) Which valve lies most superior in anatomical position?
a) Mitral valve
b) Pulmonary valve
c) Tricuspid valve
d) Aortic valve
Answer: b) Pulmonary valve
Explanation: Among all cardiac valves, the pulmonary valve lies highest anatomically, located at the 3rd costal cartilage level. The aortic valve is slightly inferior and medial to it.
6) Which structure lies directly posterior to the sternum at the level of 2nd costal cartilage?
a) Aortic arch
b) Pulmonary trunk
c) Superior vena cava
d) Right atrium
Answer: b) Pulmonary trunk
Explanation: The pulmonary trunk arises from the right ventricle and lies behind the sternum at the level of the 2nd costal cartilage before bifurcating beneath the aortic arch.
7) Which valve is most commonly affected in rheumatic heart disease?
a) Aortic
b) Tricuspid
c) Mitral
d) Pulmonary
Answer: c) Mitral
Explanation: The mitral valve is the most common site of rheumatic involvement, leading to stenosis or regurgitation. It lies at the left 4th costal cartilage level.
8) Pain from pericarditis is referred to which dermatome due to phrenic nerve involvement?
a) C4
b) C5
c) C3–C5
d) T1
Answer: c) C3–C5
Explanation: The phrenic nerve originates from C3–C5 and supplies sensory fibers to pericardium, causing referred pain to shoulder (C4 dermatome).
9) Which landmark corresponds to the beginning of the ascending aorta?
a) 2nd right costal cartilage
b) 3rd costal cartilage
c) Sternal angle
d) Xiphoid process
Answer: a) 2nd right costal cartilage
Explanation: The ascending aorta begins at the level of the 2nd right costal cartilage, superior to the aortic valve origin.
10) The pulmonary trunk bifurcates at which level?
a) T3
b) Sternal angle
c) T8
d) C7
Answer: b) Sternal angle
Explanation: The pulmonary trunk divides into right and left pulmonary arteries at the level of the sternal angle (T4–T5 vertebral level).
11) Which valve lies most posteriorly within the heart?
a) Mitral
b) Pulmonary
c) Aortic
d) Tricuspid
Answer: a) Mitral
Explanation: The mitral valve is the most posterior cardiac valve, situated between the left atrium and left ventricle, closely related to the esophagus and important in TEE imaging.
Chapter: Thorax; Topic: Lungs and Pleura; Subtopic: Surface Markings of Lungs
Keyword Definitions:
Inferior border of lung: The lowest extent of the lung during quiet respiration.
Pleural reflections: Folds of pleura marking changes in direction between parietal pleura surfaces.
Midaxillary line: Vertical line used as a surface landmark for thoracic anatomy.
Costodiaphragmatic recess: Lowest pleural recess, important for fluid accumulation.
Rib levels: Surface anatomical points used to determine pleural and lung boundaries.
1) Lead Question – 2016
Lower limit of the inferior border of the lung in the midaxillary line is ?
a) 6th rib
b) 8th rib
c) 10th rib
d) 12th rib
Answer: b) 8th rib
Explanation: The inferior border of the lung varies according to anatomical location. At the midclavicular line, it reaches the 6th rib; at the midaxillary line, it reaches the **8th rib**, and posteriorly near the vertebral column, it reaches the 10th rib. These levels correspond to the functional expansion of the lung during respiration. In contrast, the pleura extends two ribs below (6–8–10 for lungs and 8–10–12 for pleura). Therefore, the correct lower level of the lung in the midaxillary line is the **8th rib**, an essential landmark for thoracocentesis safety.
2) The pleural reflection in the midclavicular line reaches which rib?
a) 6th rib
b) 8th rib
c) 4th rib
d) 2nd rib
Answer: a) 6th rib
Explanation: The parietal pleura descends to the 6th rib in the midclavicular line. It always lies two ribs lower than the lung border at each anatomical point.
3) The costodiaphragmatic recess reaches which rib in the midaxillary line?
a) 6th rib
b) 8th rib
c) 10th rib
d) 12th rib
Answer: c) 10th rib
Explanation: The pleural reflection reaches the 10th rib in the midaxillary line, creating the costodiaphragmatic recess—the lowest recess of the pleura.
4) Thoracocentesis in midaxillary line is safely performed at–
a) 5th intercostal space
b) 7th–9th intercostal space
c) 2nd intercostal space
d) 10th intercostal space
Answer: b) 7th–9th intercostal space
Explanation: To avoid lung injury, thoracocentesis is performed below lung border (8th rib) but above pleural recess (10th rib). Thus 7th–9th spaces are ideal.
5) Posteriorly, the lung extends down to which rib level during quiet breathing?
a) 6th
b) 8th
c) 10th
d) 12th
Answer: c) 10th
Explanation: Posteriorly, the lung descends to the 10th rib, while pleura reaches the 12th rib. This difference is important during posterior thoracentesis.
6) In forced expiration, the inferior lung border moves–
a) Upward
b) Downward
c) No change
d) Flattens
Answer: a) Upward
Explanation: During forced expiration, the diaphragm ascends, pushing the lung borders upward, reducing lung volume.
7) Which area is most likely to accumulate fluid first in pleural effusion?
a) Costodiaphragmatic recess
b) Costomediastinal recess
c) Apex of lung
d) Hilum
Answer: a) Costodiaphragmatic recess
Explanation: Being the most dependent pleural area, the costodiaphragmatic recess collects fluid earliest in effusions.
8) The lung apex rises above which structure?
a) 1st rib
b) Clavicle
c) 2nd rib
d) Scapula
Answer: b) Clavicle
Explanation: The lung apex extends 2–3 cm above the medial clavicle; hence, injury to the neck may damage it.
9) The inferior border of the pleura at midclavicular line lies at–
a) 6th rib
b) 8th rib
c) 10th rib
d) 12th rib
Answer: b) 8th rib
Explanation: Pleural lower limits are 8th rib (midclavicular), 10th (midaxillary), and 12th (paravertebral).
10) Which structure lies closest to the right lung apex?
a) Right subclavian artery
b) Azygos vein arch
c) Esophagus
d) Tracheal bifurcation
Answer: a) Right subclavian artery
Explanation: The right subclavian artery arches behind the lung apex, making it clinically significant in thoracic outlet injuries.
11) Which rib does the horizontal fissure correspond to anteriorly?
a) 2nd
b) 3rd
c) 4th
d) 5th
Answer: c) 4th
Explanation: The horizontal fissure of the right lung aligns with the 4th costal cartilage anteriorly and runs laterally to meet the oblique fissure.
Chapter: Thorax; Topic: Intercostal Nerves; Subtopic: Typical and Atypical Intercostal Nerves
Keyword Definitions:
Intercostal nerve: Ventral rami of thoracic spinal nerves supplying thoracic wall.
Typical intercostal nerve: A nerve that follows the standard course and branches (T3–T6).
Atypical intercostal nerve: Nerves with special courses or distributions (T1, T2, T7–T12).
Lateral cutaneous branch: Sensory branch supplying lateral thoracic wall.
Collateral branch: Branch running below the main intercostal nerve.
1) Lead Question – 2016
Which is a typical intercostal nerve?
a) First
b) Second
c) Third
d) Seventh
Answer: c) Third
Explanation: Typical intercostal nerves are those that follow the standard course between the internal and innermost intercostal muscles, giving rise to lateral cutaneous, muscular, and collateral branches. These include **T3 to T6**. They supply the thoracic wall without taking part in plexus formation or supplying abdominal structures. In contrast, T1 contributes to the brachial plexus, T2 gives rise to the intercostobrachial nerve, and T7–T12 extend into the abdominal wall. Therefore, the **3rd intercostal nerve** is a typical intercostal nerve.
2) Which intercostal nerve gives rise to the intercostobrachial nerve?
a) T1
b) T2
c) T3
d) T4
Answer: b) T2
Explanation: The T2 intercostal nerve becomes atypical because it gives off the intercostobrachial nerve to the axilla and medial upper arm.
3) Which intercostal nerve contributes to the brachial plexus?
a) T1
b) T3
c) T4
d) T6
Answer: a) T1
Explanation: The T1 nerve root joins the brachial plexus and thus is not considered a typical intercostal nerve.
4) Intercostal nerves run between–
a) External and internal intercostals
b) Internal and innermost intercostals
c) Innermost and pleura
d) Endothoracic fascia and pleura
Answer: b) Internal and innermost intercostals
Explanation: The neurovascular bundle (vein-artery-nerve) lies in the costal groove between internal and innermost intercostals.
5) Pain from the intercostal muscles is transmitted via–
a) Dorsal rami
b) Ventral rami
c) Sympathetic fibers
d) Parasympathetic fibers
Answer: b) Ventral rami
Explanation: Intercostal nerves are ventral rami of thoracic spinal nerves T1–T11.
6) T7–T11 intercostal nerves become–
a) Lumbar nerves
b) Abdominothoracic nerves
c) Phrenic nerves
d) Cervical nerves
Answer: b) Abdominothoracic nerves
Explanation: These nerves continue beyond the costal margin to supply abdominal muscles.
7) The dermatome of the nipple corresponds to–
a) T2
b) T3
c) T4
d) T6
Answer: c) T4
Explanation: T4 dermatome marks the nipple level and is clinically important for thoracic sensory mapping.
8) Which branch of a typical intercostal nerve supplies the skin of the thorax laterally?
a) Anterior cutaneous
b) Muscular
c) Lateral cutaneous
d) Collateral
Answer: c) Lateral cutaneous
Explanation: The lateral cutaneous branch divides into anterior and posterior branches supplying lateral thorax skin.
9) Intercostal nerve block is given in relation to–
a) Superior border of rib
b) Inferior border of rib
c) Mid-shaft of rib
d) Costochondral junction
Answer: a) Superior border of rib
Explanation: The neurovascular bundle lies inferior to the rib; hence injection is given near the superior border of the rib below.
10) Which nerve supplies the skin over the umbilicus?
a) T6
b) T10
c) T12
d) L1
Answer: b) T10
Explanation: T10 dermatome corresponds to the umbilicus, used clinically for spinal cord lesion localization.
11) Which intercostal nerve is important in angina pain referral?
a) T1
b) T2
c) T4
d) T5
Answer: c) T4
Explanation: Cardiac pain is referred mainly through T1–T4 dermatomes, making T4 significant in precordial pain pathways.