Topic: Lumbar Plexus
Subtopic: Nerve Branches
Keyword Definitions:
Lumbar plexus: A network of nerves in the posterior abdominal wall formed by ventral rami of L1–L4 spinal nerves.
Iliohypogastric nerve: Branch of lumbar plexus supplying abdominal wall and skin above pubis.
Ilioinguinal nerve: Branch of lumbar plexus supplying groin and upper medial thigh skin.
Obturator nerve: Nerve from lumbar plexus supplying medial thigh muscles.
Subcostal nerve: A branch of T12 nerve, not part of the lumbar plexus.
Lead Question - 2014
All are branches of lumbar plexus except?
a) Iliohypogastric nerve
b) Ilioinguinal nerve
c) Obturator nerve
d) Subcostal nerve
Explanation: The lumbar plexus arises from L1–L4 spinal nerves. It gives branches such as iliohypogastric, ilioinguinal, genitofemoral, femoral, and obturator nerves. The subcostal nerve is from T12 and not part of the lumbar plexus. Hence, the correct answer is d) Subcostal nerve.
1. The lumbar plexus is formed by which spinal segments?
a) L1–L3
b) L1–L4
c) L2–L5
d) T12–L3
Explanation: The lumbar plexus is formed by ventral rami of L1–L4, with a contribution from T12 in some cases. It supplies abdominal wall, thigh, and pelvic regions. Correct answer: b) L1–L4.
2. Which nerve of the lumbar plexus supplies the skin of the lateral thigh?
a) Genitofemoral
b) Lateral femoral cutaneous
c) Ilioinguinal
d) Obturator
Explanation: The lateral femoral cutaneous nerve, a branch of the lumbar plexus (L2–L3), supplies sensation to the lateral thigh. Lesion causes meralgia paresthetica. Correct answer: b) Lateral femoral cutaneous.
3. A patient presents with difficulty adducting the thigh. Which nerve is affected?
a) Obturator nerve
b) Femoral nerve
c) Sciatic nerve
d) Iliohypogastric nerve
Explanation: The obturator nerve supplies adductor muscles of the medial thigh. Injury leads to loss of thigh adduction and sensory loss in medial thigh. Correct answer: a) Obturator nerve.
4. The femoral nerve arises from which roots?
a) L2–L4
b) L1–L3
c) L3–L5
d) T12–L2
Explanation: The femoral nerve is the largest branch of the lumbar plexus and arises from L2–L4 roots. It supplies anterior thigh muscles and skin over anterior thigh and medial leg. Correct answer: a) L2–L4.
5. During hernia repair, which nerve is most at risk of injury in the inguinal canal?
a) Femoral
b) Ilioinguinal
c) Obturator
d) Genitofemoral
Explanation: The ilioinguinal nerve passes through the inguinal canal and is commonly at risk during hernia surgeries. Its injury causes numbness over groin and upper medial thigh. Correct answer: b) Ilioinguinal.
6. Which lumbar plexus nerve supplies the cremaster muscle in males?
a) Ilioinguinal
b) Genitofemoral
c) Obturator
d) Femoral
Explanation: The genital branch of the genitofemoral nerve supplies the cremaster muscle and scrotal skin in males. It is tested by the cremasteric reflex. Correct answer: b) Genitofemoral.
7. A patient has anesthesia over the anterior thigh and medial leg. Which nerve is most likely damaged?
a) Obturator
b) Femoral
c) Ilioinguinal
d) Genitofemoral
Explanation: The femoral nerve supplies sensation to the anterior thigh and via the saphenous branch to medial leg. Damage results in anesthesia and weakness of knee extension. Correct answer: b) Femoral nerve.
8. Which nerve is NOT a branch of the lumbar plexus?
a) Genitofemoral
b) Pudendal
c) Iliohypogastric
d) Lateral femoral cutaneous
Explanation: The pudendal nerve arises from the sacral plexus (S2–S4) and is not a branch of the lumbar plexus. Correct answer: b) Pudendal.
9. A patient develops burning pain over the lateral thigh after tight clothing. Which nerve is compressed?
a) Obturator
b) Lateral femoral cutaneous
c) Genitofemoral
d) Femoral
Explanation: Compression of the lateral femoral cutaneous nerve (L2–L3) causes meralgia paresthetica, presenting with burning pain and numbness over lateral thigh. Correct answer: b) Lateral femoral cutaneous.
10. Which of the following supplies the quadriceps femoris muscle?
a) Femoral nerve
b) Obturator nerve
c) Lateral femoral cutaneous
d) Genitofemoral
Explanation: The quadriceps femoris is the chief extensor of the knee, innervated by the femoral nerve (L2–L4). Correct answer: a) Femoral nerve.
11. A pelvic fracture injures the obturator nerve. Which action is lost?
a) Hip flexion
b) Hip extension
c) Hip adduction
d) Knee extension
Explanation: The obturator nerve supplies adductor muscles. Injury results in loss of thigh adduction with sensory deficit over medial thigh. Correct answer: c) Hip adduction.
Topic: Vertebral Column
Subtopic: Sacrum Articular Surface
Keyword Definitions:
Sacrum: A large triangular bone at the base of the spine formed by fusion of five sacral vertebrae.
Articular surface: The surface of a bone that forms a joint with another bone.
Ilium: The broad upper part of the hip bone that articulates with the sacrum.
Sacroiliac joint: A synovial joint between sacrum and ilium providing stability to pelvis.
Vertebrae: Series of small bones forming the spinal column, classified into cervical, thoracic, lumbar, sacral, and coccygeal regions.
Lead Question - 2014
Articular surface of the sacrum extends upto how many vertebrae in males?
a) 1 to 1½
b) 2 to 2½
c) 3 to 3½
d) 4 to 4½
Explanation: The auricular (articular) surface of the sacrum articulates with the ilium forming the sacroiliac joint. In males, this surface typically extends from the level of the first sacral vertebra down to the middle of the third sacral vertebra, i.e., about 3 to 3½ vertebrae. Correct answer: c).
1. Which type of joint is formed between sacrum and ilium?
a) Synovial joint
b) Fibrous joint
d) Symphysis
Explanation: The sacroiliac joint is a synovial joint between the auricular surface of sacrum and ilium, providing stability and transmitting body weight. Correct answer: a) Synovial joint.
2. The sacrum is formed by fusion of how many vertebrae?
a) 3
b) 4
c) 5
d) 6
Explanation: The sacrum is a triangular bone formed by fusion of five sacral vertebrae, usually completed by adulthood. It contributes to the posterior wall of pelvis. Correct answer: c) 5.
3. A patient presents with pain localized to the sacroiliac joint after trauma. Which surface of sacrum is involved?
a) Auricular surface
b) Sacral canal
c) Spinous tubercles
d) Median crest
Explanation: The auricular surface of sacrum articulates with the ilium at the sacroiliac joint. Trauma here causes joint pain and instability. Correct answer: a) Auricular surface.
4. Which vertebral level corresponds to the sacral promontory?
a) L3
b) L4
c) S1
d) S2
Explanation: The sacral promontory is the anterior projecting edge of the first sacral vertebra (S1), important in pelvic measurements. Correct answer: c) S1.
5. A fracture involving the alae of sacrum will affect articulation with?
a) Coccyx
b) Lumbar vertebrae
c) Ilium
d) Pubis
Explanation: The lateral alae of the sacrum form articulation with the ilium at the sacroiliac joint. Injury disrupts pelvic stability. Correct answer: c) Ilium.
6. Which structure passes through the anterior sacral foramina?
a) Spinal cord
b) Sacral spinal nerves
c) Vertebral artery
d) Iliolumbar artery
Explanation: The anterior sacral foramina transmit anterior divisions of sacral spinal nerves and blood vessels. Correct answer: b) Sacral spinal nerves.
7. A patient with ankylosing spondylitis shows fusion at which joint first?
a) Pubic symphysis
b) Sacroiliac joint
c) Intervertebral joint
d) Hip joint
Explanation: Ankylosing spondylitis initially affects the sacroiliac joints, leading to pain and eventual fusion, then progresses to spine. Correct answer: b) Sacroiliac joint.
8. Which ligament strengthens the sacroiliac joint?
a) Anterior sacroiliac ligament
b) Interosseous sacroiliac ligament
c) Posterior sacroiliac ligament
d) All of the above
Explanation: The sacroiliac joint is stabilized by anterior, posterior, and interosseous sacroiliac ligaments. Correct answer: d) All of the above.
9. Which structure forms the continuation of the sacral canal?
a) Vertebral canal
b) Coccygeal canal
c) Neural tube
d) Intervertebral foramen
Explanation: The sacral canal is the continuation of the vertebral canal, ending at the sacral hiatus and transmitting sacral nerves. Correct answer: a) Vertebral canal.
10. In caudal epidural anesthesia, the needle is inserted at which landmark?
a) Sacral hiatus
b) Sacral promontory
c) Auricular surface
d) Sacral crest
Explanation: The sacral hiatus at the lower end of sacrum allows access for caudal epidural anesthesia. It is bounded by sacral cornua. Correct answer: a) Sacral hiatus.
11. A patient has compression of S1 nerve root. Which symptom is expected?
a) Loss of ankle jerk
b) Loss of knee jerk
c) Weak elbow extension
d) Weak shoulder abduction
Explanation: S1 nerve root compression leads to absent ankle jerk, weakness of plantar flexion, and pain radiating down posterior leg. Correct answer: a) Loss of ankle jerk.
Topic: Pelvis and Vertebral Column
Subtopic: Sacroiliac Joint
Keyword Definitions:
Sacroiliac joint: Synovial joint between auricular surface of sacrum and ilium, transmitting body weight to pelvis.
Sacrum: A triangular bone formed by fusion of five sacral vertebrae, articulating with ilium, coccyx, and L5 vertebra.
Auricular surface: Ear-shaped surface of sacrum that articulates with ilium to form sacroiliac joint.
Vertebral level: A reference point using vertebrae to locate anatomical structures.
Pelvic stability: Strength provided by joints, ligaments, and muscles to support body weight and locomotion.
Lead Question - 2014
Lower limit of sacroiliac joint lies upto which level in females?
a) 1 to 1½
b) 2 to 2½
c) 3 to 3½
d) 4 to 4½
Explanation: In females, the sacroiliac joint extends from the auricular surface of sacrum, usually from the upper part of S1 to about the middle of S3. Thus, its lower limit corresponds to approximately the level of 3 to 3½ vertebrae. Correct answer: c) 3 to 3½.
1. The sacroiliac joint is classified as?
a) Fibrous joint
b) Primary cartilaginous
c) Synovial plane
d) Symphysis
Explanation: The sacroiliac joint is a synovial plane joint, stabilized by strong ligaments, allowing limited movement but providing stability for weight transmission. Correct answer: c) Synovial plane.
2. Which ligament is strongest in stabilizing the sacroiliac joint?
a) Anterior sacroiliac
b) Posterior sacroiliac
c) Interosseous sacroiliac
d) Iliolumbar
Explanation: The interosseous sacroiliac ligament is the strongest stabilizer, lying deep between sacrum and ilium, transmitting weight and limiting joint mobility. Correct answer: c) Interosseous sacroiliac.
3. A 30-year-old woman presents with low back pain, tenderness over sacroiliac joint, worsened by standing. Which pathology is likely?
a) Osteoarthritis
b) Sacroiliitis
c) Disc prolapse
d) Hip arthritis
Explanation: Sacroiliitis is inflammation of the sacroiliac joint, presenting with localized pain and tenderness, common in autoimmune diseases like ankylosing spondylitis. Correct answer: b) Sacroiliitis.
4. Which gender has a shorter sacroiliac joint surface?
a) Male
b) Female
c) Both equal
d) None
Explanation: Females have a shorter but wider sacroiliac joint surface compared to males, allowing greater pelvic flexibility for childbirth. Correct answer: b) Female.
5. The sacral promontory is part of?
a) Ilium
b) Coccyx
c) First sacral vertebra
d) Pubis
Explanation: The sacral promontory is the anterior projecting margin of the body of the first sacral vertebra, forming part of the pelvic brim. Correct answer: c) First sacral vertebra.
6. A woman with pelvic instability after delivery may have injury to?
a) Pubic symphysis
b) Sacroiliac joint
c) Acetabulum
d) Iliolumbar ligament
Explanation: During childbirth, the sacroiliac joint can be strained due to relaxation of ligaments under hormonal influence, leading to instability and back pain. Correct answer: b) Sacroiliac joint.
7. Which muscle inserts near the auricular surface of sacrum?
a) Piriformis
b) Gluteus maximus
c) Iliacus
d) Quadratus lumborum
Explanation: The piriformis arises from the anterior sacrum, near the auricular surface, and exits via greater sciatic foramen to attach on femur. Correct answer: a) Piriformis.
8. Which imaging is best for diagnosing sacroiliitis?
a) X-ray
b) Ultrasound
c) MRI
d) CT
Explanation: MRI is the most sensitive imaging for early detection of sacroiliitis, as it identifies marrow edema and inflammation before radiographic changes. Correct answer: c) MRI.
9. Which joint transmits body weight from spine to pelvis?
a) Pubic symphysis
b) Hip joint
c) Sacroiliac joint
d) Sacrococcygeal joint
Explanation: The sacroiliac joint connects the sacrum with ilium, transmitting weight from axial skeleton to pelvis and lower limbs. Correct answer: c) Sacroiliac joint.
10. A patient with ankylosing spondylitis develops fusion of which joint earliest?
a) Hip
b) Knee
c) Sacroiliac
d) Lumbar
Explanation: In ankylosing spondylitis, the sacroiliac joint is first affected, progressing to spinal joints and causing “bamboo spine.” Correct answer: c) Sacroiliac.
11. Which structure forms the posterior boundary of sacroiliac joint?
a) Iliac crest
b) Sacral canal
c) Posterior sacroiliac ligament
d) Sacral promontory
Explanation: The posterior sacroiliac ligament lies behind the sacroiliac joint, forming its posterior boundary and reinforcing its stability. Correct answer: c) Posterior sacroiliac ligament.
Topic: Lungs and Bronchi
Subtopic: Right Principal Bronchus
Keyword Definitions:
Principal bronchus: Primary bronchus arising from trachea, supplying each lung.
Right principal bronchus: Wider, shorter, and more vertical than left; directs aspirated foreign bodies.
Left principal bronchus: Longer, narrower, and more horizontal, passing under arch of aorta.
Trachea: Airway tube dividing at carina into right and left bronchi.
Lobar bronchus: Secondary bronchus supplying each lobe of the lung.
Lead Question - 2014
True about right principal bronchus ?
a) Narrower
b) Horizontal
c) Shorter
d) All are true
Explanation: The right principal bronchus is wider, shorter, and more vertical compared to left. This explains why inhaled foreign bodies often lodge in right lung. It is not narrower or horizontal. Correct answer is c) Shorter. Knowledge of bronchial anatomy is crucial for bronchoscopy and foreign body removal. (50 words)
1. Which bronchus is more prone to foreign body aspiration?
a) Right
b) Left
c) Both equally
d) Neither
Explanation: Right principal bronchus is wider, shorter, and vertical, creating a direct path for foreign bodies. Left is narrower and oblique. Correct answer is a) Right. This anatomical difference explains clinical findings in children and adults with accidental aspiration. Prompt bronchoscopy is needed for removal. (50 words)
2. Left principal bronchus passes beneath which structure?
a) Arch of aorta
b) Superior vena cava
c) Right pulmonary artery
d) Right atrium
Explanation: The left bronchus is longer and runs beneath the arch of aorta and anterior to esophagus. Correct answer is a) Arch of aorta. Its oblique path protects it from direct entry of foreign bodies. Important in imaging and thoracic surgeries involving mediastinum. (50 words)
3. Carina corresponds to which vertebral level?
a) T2
b) T4
c) T6
d) T8
Explanation: Carina, the ridge where trachea bifurcates into principal bronchi, lies at the level of T4/T5 intervertebral disc and sternal angle. Correct answer is b) T4. The carina is a sensitive structure; irritation triggers cough reflex, important in bronchoscopy. (50 words)
4. During bronchoscopy, foreign body is seen lodged in right middle lobe bronchus. This is branch of:
a) Left bronchus
b) Right principal bronchus
c) Trachea directly
d) Posterior mediastinum
Explanation: Right principal bronchus divides into three lobar bronchi—upper, middle, and lower—supplying corresponding lobes. A foreign body in right middle lobe bronchus originates from right principal bronchus. Correct answer is b) Right principal bronchus. Knowledge of lobar divisions is crucial for targeted bronchoscopy and segmentectomy. (50 words)
5. Which artery crosses anterior to right principal bronchus?
a) Right pulmonary artery
b) Left pulmonary artery
c) Ascending aorta
d) Subclavian artery
Explanation: The right pulmonary artery crosses anterior to the right principal bronchus. On the left, pulmonary artery passes superior to left bronchus. Correct answer is a) Right pulmonary artery. These relationships are important during pulmonary angiography, mediastinal surgery, and CT interpretation. (50 words)
6. Which bronchus is longer and narrower?
a) Right
b) Left
c) Both equal
d) Neither
Explanation: Left principal bronchus is longer (5 cm) and narrower, with a more oblique course compared to right. Correct answer is b) Left. This makes aspiration less common on the left side. Anatomical difference is important in intubation and pathology interpretation. (50 words)
7. A 3-year-old child aspirates a peanut. It is most likely found in:
a) Left upper lobe bronchus
b) Right lower lobe bronchus
c) Left lower lobe bronchus
d) Trachea
Explanation: Due to vertical orientation, right lower lobe bronchus is the most common site for foreign body aspiration. Correct answer is b) Right lower lobe bronchus. Radiological confirmation and prompt bronchoscopy are essential for removal. This is a frequent pediatric emergency. (50 words)
8. The angle between right principal bronchus and trachea is:
a) 25°
b) 45°
c) 60°
d) 90°
Explanation: Right principal bronchus forms an angle of about 25° with trachea, making it more in line with tracheal axis. Left forms an angle of about 45°. Correct answer is a) 25°. This anatomical angle explains clinical predisposition for right-sided aspiration. (50 words)
9. Which structure lies posterior to left principal bronchus?
a) Azygos vein
b) Descending thoracic aorta
c) Superior vena cava
d) Right atrium
Explanation: The descending thoracic aorta lies posterior to the left principal bronchus. Correct answer is b) Descending thoracic aorta. This anatomical relation is significant in mediastinal imaging and during surgeries involving aortic aneurysms. (50 words)
10. In case of bronchogenic carcinoma of right main bronchus, which symptom is most expected?
a) Hoarseness
b) Cough with aspiration
c) Hematuria
d) Dysphagia
Explanation: Tumors involving right principal bronchus commonly present with cough and recurrent aspiration pneumonia due to obstruction. Correct answer is b) Cough with aspiration. Other symptoms may include wheezing, hemoptysis, and dyspnea. Clinical correlation with imaging and bronchoscopy is essential for diagnosis. (50 words)
Subtopic: Thoracic Duct Formation
Keyword Definitions:
Thoracic duct: The largest lymphatic vessel in the human body draining lymph from most areas.
Cisterna chyli: Dilated sac at the lower end of thoracic duct collecting lymph from abdomen.
Subclavian vein: Vein that drains blood from upper limb into brachiocephalic vein.
Jugular vein: Vein draining blood from head and neck.
Brachiocephalic vein: Large vein formed by subclavian and internal jugular veins.
Lead Question - 2014
Thoracic duct is formed by?
a) Union of left subclavian and left internal jugular vein.
b) Union of brachiocephalic vein and internal jugular vein
c) Continuation of upper end of cisterna chyli
d) None of the above
Explanation: The thoracic duct originates as the continuation of the cisterna chyli at the level of L1-L2 vertebrae, ascending through the thorax. It drains into the venous system at the junction of the left internal jugular and left subclavian veins. Correct answer: c) Continuation of upper end of cisterna chyli.
Guessed Questions for NEET PG:
1) Length of thoracic duct is approximately?
a) 10 cm
b) 20 cm
c) 40 cm
d) 50 cm
Explanation: The thoracic duct measures about 40 cm in adults. It starts from cisterna chyli in the abdomen and ascends to the venous angle. Its long course makes it prone to injury during surgery. Correct answer: c) 40 cm.
2) Thoracic duct pierces diaphragm through?
a) Aortic hiatus
b) Caval opening
c) Esophageal hiatus
d) None
Explanation: The thoracic duct passes through the diaphragm along with the aorta at the aortic hiatus at the level of T12 vertebra. This is a key anatomical relation during abdominal and thoracic surgeries. Correct answer: a) Aortic hiatus.
3) Which vein receives terminal drainage of thoracic duct?
a) Right subclavian vein
b) Left brachiocephalic vein
c) At junction of left internal jugular and left subclavian vein
d) Superior vena cava
Explanation: The thoracic duct terminates into the venous system at the left venous angle, i.e., the junction of the left subclavian vein and left internal jugular vein. This is a key anatomical landmark. Correct answer: c) Junction of left internal jugular and subclavian vein.
4) Thoracic duct drains all except?
a) Left upper limb
b) Right thorax
c) Left abdomen
d) Left thorax
Explanation: The thoracic duct drains lymph from entire body except the right upper limb, right thorax, right side of head and neck, which are drained by the right lymphatic duct. Correct answer: b) Right thorax.
5) In a neck surgery, thoracic duct injury leads to leakage of?
a) Blood
b) Bile
c) Chyle
d) Lymphocyte-depleted fluid
Explanation: Injury to thoracic duct leads to chylous fistula, with leakage of milky chyle rich in triglycerides. This complication is common during left neck dissections near the venous angle. Correct answer: c) Chyle.
6) Cisterna chyli is located at?
a) T8-T9
b) L1-L2
c) S1-S2
d) T12
Explanation: The cisterna chyli is located anterior to the bodies of L1 and L2 vertebrae, behind the right crus of diaphragm. It acts as the reservoir for intestinal and lumbar lymph trunks. Correct answer: b) L1-L2.
7) In chylothorax, fluid accumulates in?
a) Pleural cavity
b) Peritoneal cavity
c) Pericardial cavity
d) Subarachnoid space
Explanation: Chylothorax occurs when the thoracic duct is injured, leading to leakage of chyle into the pleural cavity. It is a serious surgical complication, requiring drainage and repair. Correct answer: a) Pleural cavity.
8) Right lymphatic duct drains lymph from?
a) Right upper limb
b) Right thorax
c) Right side of head and neck
d) All of the above
Explanation: The right lymphatic duct drains lymph from right upper limb, right thorax, and right side of head and neck. It terminates into the right venous angle. Correct answer: d) All of the above.
9) In case of lymphoma, thoracic duct obstruction may cause?
a) Ascites
b) Chylothorax
c) Chylous ascites
d) Edema
Explanation: Thoracic duct obstruction due to malignancy such as lymphoma may cause chylous ascites, characterized by milky fluid in peritoneum. This is a clinical indicator of lymphatic obstruction. Correct answer: c) Chylous ascites.
10) During oesophageal carcinoma surgery, thoracic duct is at risk at level of?
a) T2
b) T4
c) T8
d) T12
Explanation: Thoracic duct runs posterior to oesophagus in thorax, closely related at T4 to T8 levels. Surgical manipulation in esophagectomy carries risk of injury. Correct answer: c) T8.
Topic: Lymphatic System
Subtopic: Termination of Thoracic Duct
Keyword Definitions:
Thoracic duct: Largest lymphatic channel, draining lymph from most of the body except right upper quadrant.
Venous angle: Junction of internal jugular vein and subclavian vein.
Subclavian vein: Major vein draining blood from the upper limb.
Internal jugular vein: Vein draining blood from brain, face, and neck.
Brachiocephalic vein: Large vein formed by union of subclavian and internal jugular veins.
Lead Question - 2014
Thoracic duct opens into ?
a) Subclavian vein
b) Internal jugular vein
c) Right brachiocephalic vein
d) Left brachiocephalic vein
Explanation: The thoracic duct terminates at the left venous angle, i.e., the junction of the left subclavian and left internal jugular veins. This anatomical site is critical in surgeries of the neck and mediastinum. Correct answer: a) Subclavian vein (at its junction with internal jugular vein).
Guessed Questions for NEET PG:
1) Which side of the venous angle receives thoracic duct?
a) Right
b) Left
c) Both sides
d) Variable
Explanation: The thoracic duct consistently terminates at the left venous angle, formed by left internal jugular and left subclavian veins. This is a fixed anatomical feature with great surgical relevance. Correct answer: b) Left.
2) Right lymphatic duct opens into?
a) Left venous angle
b) Right venous angle
c) Superior vena cava
d) Azygos vein
Explanation: The right lymphatic duct drains lymph from right upper limb, right thorax, and right side of head and neck. It opens into the right venous angle, i.e., junction of right internal jugular and subclavian veins. Correct answer: b) Right venous angle.
3) Length of thoracic duct is?
a) 10 cm
b) 20 cm
c) 40 cm
d) 60 cm
Explanation: The thoracic duct measures approximately 40 cm in adults. It extends from cisterna chyli at L1-L2 vertebrae to the left venous angle in the root of the neck. Correct answer: c) 40 cm.
4) Thoracic duct crosses from right to left at the level of?
a) T2
b) T4
c) T6
d) T8
Explanation: The thoracic duct ascends on the right side of vertebral column and crosses to the left side at the level of T4-T6 vertebrae, continuing upward to terminate in the left venous angle. Correct answer: b) T4.
5) A 45-year-old man develops chylothorax after oesophagectomy. Which structure is injured?
a) Azygos vein
b) Thoracic duct
c) Hemiazygos vein
d) Vagus nerve
Explanation: Chylothorax results from thoracic duct injury during mediastinal or esophageal surgery. Milky fluid rich in triglycerides accumulates in the pleural cavity, requiring drainage. Correct answer: b) Thoracic duct.
6) Cisterna chyli is located at?
a) T10
b) T12
c) L1-L2
d) S1
Explanation: The cisterna chyli is located anterior to the bodies of L1 and L2 vertebrae. It collects lymph from lumbar and intestinal trunks and continues as thoracic duct. Correct answer: c) L1-L2.
7) Thoracic duct drains all except?
a) Right lower limb
b) Left upper limb
c) Right thorax
d) Left thorax
Explanation: The thoracic duct drains both lower limbs, abdomen, left thorax, left upper limb, and left head and neck. The right thorax, right upper limb, and right head and neck are drained by the right lymphatic duct. Correct answer: c) Right thorax.
8) In a left neck dissection, accidental thoracic duct injury causes leakage of?
a) Blood
b) Serous fluid
c) Chyle
d) Bile
Explanation: Injury to thoracic duct causes leakage of chyle, a milky lymph rich in fats. Chylous fistula is a known complication in neck surgeries, particularly near left venous angle. Correct answer: c) Chyle.
9) In lymphoma, obstruction of thoracic duct may cause?
a) Pleural effusion
b) Ascites
c) Chylous ascites
d) Pericardial effusion
Explanation: Thoracic duct obstruction by lymphoma or tumor can cause chylous ascites, characterized by milky fluid in the peritoneal cavity due to blocked lymphatic flow. Correct answer: c) Chylous ascites.
10) During ligation of thoracic duct, surgeon aims to prevent?
a) Air embolism
b) Chylothorax
c) Pneumothorax
d) Pulmonary embolism
Explanation: Ligation of thoracic duct is done to prevent persistent chylothorax, which results from continuous leakage of chyle into pleural cavity. This is life-threatening due to nutritional loss. Correct answer: b) Chylothorax.
Topic: Thorax
Subtopic: Relations of Lung Hilum
Keyword Definitions:
Hilum of lung: Area on the medial surface of lung where bronchi, vessels, and nerves enter or leave.
Vagus nerve: Cranial nerve X, provides parasympathetic supply to thoracic and abdominal organs.
Azygos vein: Vein draining posterior thoracic wall, arches over right lung root.
SVC: Large vein returning venous blood from upper body to right atrium.
Arch of aorta: Major arterial curve from ascending to descending aorta, giving major branches.
Lead Question - 2014
Posterior relation of hilum of lung ?
a) Azygous vein
b) SVC
c) Vagus nerve
d) Arch of aorta
Explanation: The posterior relation of the lung hilum is the vagus nerve, which passes behind the root of both lungs. Azygos vein arches over right lung root anteriorly, and arch of aorta lies superiorly. Correct answer: c) Vagus nerve.
Guessed Questions for NEET PG:
1) Which nerve lies anterior to the lung hilum?
a) Vagus
b) Phrenic
c) Sympathetic trunk
d) Intercostal
Explanation: The phrenic nerve passes anterior to the root of the lung, while the vagus nerve lies posterior. This relationship is crucial during thoracic surgeries. Correct answer: b) Phrenic.
2) Which vessel arches over the right lung hilum?
a) Hemiazygos vein
b) Azygos vein
c) Superior vena cava
d) Internal thoracic vein
Explanation: The azygos vein arches over the root of the right lung to drain into the superior vena cava. This is a classical radiological landmark in chest imaging. Correct answer: b) Azygos vein.
3) Which structure crosses the arch of aorta anteriorly?
a) Left phrenic nerve
b) Left vagus nerve
c) Left recurrent laryngeal nerve
d) Left subclavian vein
Explanation: The left phrenic nerve crosses the arch of aorta anteriorly, while the left recurrent laryngeal nerve hooks around ligamentum arteriosum posteriorly. Correct answer: a) Left phrenic nerve.
4) A patient with left lung tumor compresses the posterior relation of hilum. Which nerve is likely affected?
a) Left phrenic
b) Left vagus
c) Sympathetic chain
d) Intercostal nerve
Explanation: Tumors at the left lung hilum posteriorly may compress the vagus nerve, leading to parasympathetic dysfunction, hoarseness, or cardiac reflex changes. Correct answer: b) Left vagus.
5) In right lung hilum, which lies superior among structures?
a) Pulmonary vein
b) Pulmonary artery
c) Main bronchus
d) Azygos vein
Explanation: At the right hilum, the bronchus lies posterior, pulmonary artery superior, and pulmonary veins anterior-inferior. This arrangement is remembered as "B-A-V" (Back to front). Correct answer: b) Pulmonary artery.
6) Left recurrent laryngeal nerve hooks around?
a) Right subclavian artery
b) Arch of aorta
c) Left pulmonary artery
d) Superior vena cava
Explanation: The left recurrent laryngeal nerve, branch of vagus, hooks around the arch of aorta near ligamentum arteriosum. Correct answer: b) Arch of aorta.
7) Which bronchus is more prone to foreign body aspiration?
a) Left main bronchus
b) Right main bronchus
c) Both equal
d) Depends on position
Explanation: The right main bronchus is shorter, wider, and more vertical, making it more prone to aspiration of foreign bodies. Correct answer: b) Right main bronchus.
8) During hilar lymph node dissection, which nerve injury can cause hoarseness of voice?
a) Phrenic
b) Sympathetic
c) Recurrent laryngeal
d) Intercostal
Explanation: Injury to recurrent laryngeal nerve during lymph node dissection causes vocal cord paralysis and hoarseness. Correct answer: c) Recurrent laryngeal.
9) In chest radiograph, hilar shadow mainly represents?
a) Bronchi
b) Pulmonary arteries
c) Lymph nodes
d) Pulmonary veins
Explanation: On radiographs, hilar shadows are predominantly formed by pulmonary arteries. Bronchi are air-filled and less visible. Correct answer: b) Pulmonary arteries.
10) A 60-year-old smoker has left hilar mass compressing anterior relation of hilum. Which nerve is affected?
a) Left vagus
b) Left phrenic
c) Left recurrent laryngeal
d) Sympathetic chain
Explanation: The anterior relation of the lung hilum is the phrenic nerve. Compression leads to diaphragmatic palsy, breathlessness, and raised hemidiaphragm. Correct answer: b) Left phrenic.
Topic: Lungs and Mediastinum
Subtopic: Hilum of Lungs
Keyword Definitions:
Hilum of lung: Depression on the mediastinal surface where bronchi, vessels, and nerves enter.
Azygous vein: Drains thoracic wall, arches over root of right lung into SVC.
Vagus nerve: Provides parasympathetic fibers to lungs.
SVC: Superior vena cava, drains blood from upper body to heart.
Arch of aorta: Curved portion of aorta, related to left lung hilum.
Lead Question - 2014
Not related to hilum of right lung?
a) Azygous vein
b) Vagus nerve
c) SVC
d) Arch of aorta
Explanation: The hilum of the right lung is related to the azygous vein, superior vena cava, and vagus nerve. However, the arch of the aorta is a relation of the left lung hilum, not the right. Thus, the correct answer is Arch of aorta. This distinction is important in thoracic anatomy.
Guessed Questions for NEET PG:
1) Structure most commonly arching over the root of the right lung?
a) Pulmonary trunk
b) Azygous vein
c) Right phrenic nerve
d) Right brachiocephalic vein
Explanation: The azygous vein arches over the root of the right lung before draining into the superior vena cava. This anatomical landmark is unique to the right side. The correct answer is Azygous vein. This relation is crucial during mediastinal dissections and radiological imaging for diagnosis.
2) In a patient undergoing lung surgery, which nerve must be preserved near hilum of right lung?
a) Phrenic nerve
b) Vagus nerve
c) Hypoglossal nerve
d) Sympathetic trunk
Explanation: The vagus nerve passes posterior to the hilum of the right lung and provides parasympathetic innervation. Injury to it can cause impaired bronchoconstriction and secretory reflexes. Thus, the correct answer is Vagus nerve. Preservation is critical during lung resections and mediastinal lymph node dissections.
3) Which vessel lies anterior to the right lung hilum?
a) Superior vena cava
b) Azygous vein
c) Pulmonary artery
d) Arch of aorta
Explanation: The superior vena cava lies anterior to the hilum of the right lung, draining venous blood into the right atrium. This relation helps surgeons and radiologists distinguish normal vascular landmarks. The correct answer is Superior vena cava. Its injury can cause rapid hemodynamic compromise during thoracic procedures.
4) Clinical case: A 50-year-old with carcinoma lung has enlarged lymph nodes compressing the structure arching over right hilum. Which is affected?
a) Aortic arch
b) Left subclavian artery
c) Azygous vein
d) Right pulmonary artery
Explanation: Lymphadenopathy around the right lung hilum often compresses the azygous vein, which arches over it. Compression may cause venous congestion. The correct answer is Azygous vein. Recognition of this relation helps in staging lung carcinoma and planning surgery or radiotherapy.
5) Right pulmonary artery in relation to hilum lies:
a) Superior to right bronchus
b) Inferior to right bronchus
c) Anterior to right bronchus
d) Posterior to right bronchus
Explanation: In the right lung, the pulmonary artery lies anterior to the bronchus at the hilum. This arrangement differs from the left lung, where the artery is superior to bronchus. The correct answer is Anterior to right bronchus. This anatomical difference is remembered by “RALS” (Right Anterior, Left Superior).
6) Clinical case: During mediastinoscopy, the surgeon encounters a nerve behind right lung hilum. Likely identity?
a) Phrenic nerve
b) Vagus nerve
c) Intercostal nerve
d) Accessory nerve
Explanation: The vagus nerve runs posterior to the root of the lung, unlike the phrenic nerve, which runs anterior. Identifying this during thoracic procedures prevents iatrogenic injury. The correct answer is Vagus nerve. Injury may cause autonomic dysfunction of bronchi and impaired airway regulation.
7) Which structure is not found in hilum of lungs?
a) Pulmonary artery
b) Pulmonary veins
c) Main bronchus
d) Thoracic duct
Explanation: The hilum transmits bronchi, pulmonary arteries, and pulmonary veins. Thoracic duct does not pass through the hilum, instead ascends in the posterior mediastinum. Therefore, the correct answer is Thoracic duct. Differentiating contents is key for interpreting chest radiographs and CT scans.
8) Clinical scenario: A stab wound injures a structure anterior to right hilum. Which is likely damaged?
a) Superior vena cava
b) Aortic arch
c) Azygous vein
d) Descending thoracic aorta
Explanation: Anterior to the right lung hilum lies the superior vena cava. A penetrating injury here may cause fatal venous hemorrhage. The correct answer is Superior vena cava. Identifying this anatomical relation helps trauma surgeons anticipate bleeding sources in thoracic injuries.
9) Which structure is posterior to both lung hila?
a) Azygous vein
b) Descending aorta
c) Vagus nerve
d) Pulmonary veins
Explanation: The vagus nerve is consistently posterior to the hilum of both lungs. This relation is surgically important in thoracic approaches. Thus, the correct answer is Vagus nerve. Damage may result in autonomic dysfunction including impaired bronchial tone regulation.
10) Clinical case: CT chest shows a mass compressing right hilum. Which vessel arching above hilum must be checked?
a) Aortic arch
b) Azygous vein
c) Pulmonary artery
d) Superior vena cava
Explanation: The azygous vein arches above the right lung hilum. On CT scans, compression of this vein may indicate mediastinal pathology or hilar mass. The correct answer is Azygous vein. Recognizing this landmark helps radiologists in staging lung cancers and evaluating mediastinal syndromes.