Nerves and blood supply of lower limb — MCQs

10 questions

Seven hours after undergoing left hip arthroplasty for chronic hip pain, a 67-year-old woman reports a prickling sensation in her left anteromedial thigh and lower leg. Neurologic examination shows left leg strength 3/5 on hip flexion and 2/5 on knee extension. Patellar reflex is decreased on the left. Sensation to pinprick and light touch are decreased on the anteromedial left thigh as well as medial lower leg. Which of the following is the most likely underlying cause of this patient's symptoms?

A 76-year-old hypertensive man who used to smoke 20 cigarettes a day for 40 years but quit 5 years ago presents to his family physician with a painless ulcer on the sole of his left foot, located at the base of his 1st toe. He has a history of pain in his left leg that awakens him at night and is relieved by dangling his foot off the side of the bed. His wife discovered the ulcer last week while doing his usual monthly toenail trimming. On physical exam, palpation of the patient’s pulses reveals the following: Right foot Femoral 4+ Popliteal 3+ Dorsalis Pedis 2+ Posterior Tibial 1+ Left foot Femoral 4+ Popliteal 2+ Dorsalis Pedis 0 Posterior Tibial 0 Pulse detection by Doppler ultrasound revealed decreased flow in the left posterior tibial artery, but no flow could be detected in the dorsalis pedis. What is the most likely principal cause of this patient’s ulcer?

A 38-year-old man is brought to the emergency department after suffering a motor vehicle accident as the passenger. He had no obvious injuries, but he complains of excruciating right hip pain. His right leg is externally rotated, abducted, and extended at the hip and the femoral head can be palpated anterior to the pelvis. Plain radiographs of the pelvis reveal a right anterior hip dislocation and femoral head fracture. Which sensory and motor deficits are most likely in this patient's right lower extremity?

A 34-year-old man is brought to the emergency department 3 hours after being bitten by a rattlesnake. He was hiking in the Arizona desert when he accidentally stepped on the snake and it bit his right leg. His pulse is 135/min and blood pressure is 104/81 mm Hg. Examination shows right lower leg swelling, ecchymosis, and blistering. Right ankle dorsiflexion elicits severe pain. A manometer inserted in the lateral compartment of the lower leg shows an intracompartmental pressure of 67 mm Hg. In addition to administration of the antivenom, the patient undergoes fasciotomy. Two weeks later, he reports difficulty in walking. Neurologic examination shows a loss of sensation over the lower part of the lateral side of the right leg and the dorsum of the right foot. Right foot eversion is 1/5. There is no weakness in dorsiflexion. Which of the following nerves is most likely injured in this patient?

A 31-year-old woman presents with difficulty walking and climbing stairs for the last 3 weeks. She has no history of trauma. The physical examination reveals a waddling gait with the trunk swaying from side-to-side towards the weight-bearing limb. When she stands on her right leg, the pelvis on the left side falls. When she stands on her left leg, the pelvis remains level. Which of the following nerves is most likely injured in this patient?

A 25-year-old woman presents with shooting pain along the lateral aspect of her right thigh. The pain is exacerbated by standing or walking for long periods. Physical examination reveals tenderness at the anterior superior iliac spine. Which of the following nerves is most likely affected?

One day after undergoing surgery for a traumatic right pelvic fracture, a 73-year-old man has pain over his buttocks and scrotum and urinary incontinence. Physical examination shows right-sided perineal hypesthesia and absence of anal sphincter contraction when the skin around the anus is touched. This patient is most likely to have which of the following additional neurological deficits?

A 26-year-old woman presents to the obstetrics ward to deliver her baby. The obstetrician establishes a pudendal nerve block via intravaginal injection of lidocaine near the tip of the ischial spine. From which of the following nerve roots does the pudendal nerve originate?

An 80-year-old woman is brought to the emergency department for left hip pain 30 minutes after she fell while walking around in her room. Examination shows left groin tenderness. The range of motion of the left hip is limited because of pain. An x-ray of the hip shows a linear fracture of the left femoral neck with slight posterior displacement of the femur. Which of the following arteries was most likely damaged in the patient's fall?

Q10

A newborn boy born vaginally to a healthy 37-year-old G3P1 from a pregnancy complicated by hydramnios fails to pass meconium after 24 hours of life. The vital signs are within normal limits for his age. The abdomen is distended, the anus is patent, and the rectal examination reveals pale mucous with non-pigmented meconium. Based on a barium enema, the boy is diagnosed with sigmoid colonic atresia. Disruption of which structure during fetal development could lead to this anomaly?

Nerves and blood supply of lower limb US Medical PG Practice Questions and MCQs

Question 1: Seven hours after undergoing left hip arthroplasty for chronic hip pain, a 67-year-old woman reports a prickling sensation in her left anteromedial thigh and lower leg. Neurologic examination shows left leg strength 3/5 on hip flexion and 2/5 on knee extension. Patellar reflex is decreased on the left. Sensation to pinprick and light touch are decreased on the anteromedial left thigh as well as medial lower leg. Which of the following is the most likely underlying cause of this patient's symptoms?

A. Femoral nerve injury (Correct Answer)
B. L5 radiculopathy
C. Sural nerve injury
D. S1 radiculopathy
E. Fibular nerve injury

Explanation: ***Femoral nerve injury*** - The patient's symptoms—weakness in **hip flexion** (iliopsoas via femoral nerve) and **knee extension** (quadriceps via femoral nerve), decreased **patellar reflex** (femoral nerve), and sensory loss in the **anteromedial thigh** (femoral nerve) and **medial lower leg** (saphenous nerve, a branch of the femoral nerve)—are all consistent with femoral nerve dysfunction. - **Hip arthroplasty procedures** can sometimes lead to iatrogenic femoral nerve damage due to retraction, compression, or direct injury during surgery, especially when positioning or using surgical instruments. *L5 radiculopathy* - L5 radiculopathy typically causes weakness in **foot dorsiflexion**, **eversion**, and **toe extension**, along with sensory loss over the **dorsum of the foot** and lateral lower leg, which does not match the patient's presentation. - While it can cause hip abductor weakness, it would not explain the prominent **quadriceps weakness** and **decreased patellar reflex**. *Sural nerve injury* - The sural nerve provides sensation to the **posterolateral aspect of the lower leg** and lateral malleolus, and has no motor function to the hip or knee. - Injury to this nerve would not account for the patient's **proximal weakness** or sensory loss in the anteromedial thigh. *S1 radiculopathy* - S1 radiculopathy typically leads to weakness in **plantarflexion**, **hip extension**, and an absent **Achilles reflex**, along with sensory loss over the lateral foot and sole. - It would not explain the significant **quadriceps weakness**, **decreased patellar reflex**, or sensory changes in the anteromedial thigh. *Fibular nerve injury* - Fibular (peroneal) nerve injury primarily results in **foot drop** (weakness in dorsiflexion and eversion of the foot) and sensory loss over the **dorsum of the foot** and anterolateral lower leg. - It does not affect hip flexion, knee extension, or the patellar reflex, nor does it cause sensory loss in the anteromedial thigh.

Question 2: A 76-year-old hypertensive man who used to smoke 20 cigarettes a day for 40 years but quit 5 years ago presents to his family physician with a painless ulcer on the sole of his left foot, located at the base of his 1st toe. He has a history of pain in his left leg that awakens him at night and is relieved by dangling his foot off the side of the bed. His wife discovered the ulcer last week while doing his usual monthly toenail trimming. On physical exam, palpation of the patient’s pulses reveals the following: Right foot Femoral 4+ Popliteal 3+ Dorsalis Pedis 2+ Posterior Tibial 1+ Left foot Femoral 4+ Popliteal 2+ Dorsalis Pedis 0 Posterior Tibial 0 Pulse detection by Doppler ultrasound revealed decreased flow in the left posterior tibial artery, but no flow could be detected in the dorsalis pedis. What is the most likely principal cause of this patient’s ulcer?

A. An occluded posterior tibial artery on the left foot
B. An occlusion of the first dorsal metatarsal artery
C. A narrowing of the superficial femoral artery (Correct Answer)
D. An occlusion of the deep plantar artery
E. An absent dorsalis pedis pulse with an absent posterior tibial pulse in the left foot

Explanation: ***A narrowing of the superficial femoral artery*** - The patient's history of **claudication** (pain relieved by dangling the foot) and severely diminished pulses (0 in dorsalis pedis and posterior tibial) in the left foot indicates significant **peripheral artery disease (PAD)**. - The superficial femoral artery is a common site for atherosclerotic narrowing, which would impede blood flow to the lower leg and foot, leading to **ischemic ulcers**. *An occluded posterior tibial artery on the left foot* - While there is diminished flow in the posterior tibial artery, the symptoms like **claudication** and the presence of a **painless ulcer** on the sole of the foot suggest a more proximal and significant arterial obstruction. - An isolated posterior tibial artery occlusion usually doesn't cause such widespread distal ischemia without involvement of other major arteries. *An occlusion of the first dorsal metatarsal artery* - An occlusion here would primarily affect the dorsal aspect of the foot or possibly the first toe, but it is unlikely to cause a **painless ulcer on the sole** of the foot or the described **claudication symptoms**. - While contributing to local ischemia, it's generally a more distal and less significant cause of such pervasive symptoms. *An occlusion of the deep plantar artery* - The deep plantar artery is a branch of the **dorsalis pedis artery** and primarily supplies the plantar arch and toes. - Its occlusion alone would not explain the severe **claudication** and diffuse absence of pulses in both the dorsalis pedis and posterior tibial arteries. *An absent dorsalis pedis pulse with an absent posterior tibial pulse in the left foot* - While this finding is present and crucial, it describes the *result* of significant ischemia in the foot, not the *principal cause*. - The underlying cause of these absent pulses and the resulting ulcer is a more proximal obstruction in the arterial supply to the lower limb.

Question 3: A 38-year-old man is brought to the emergency department after suffering a motor vehicle accident as the passenger. He had no obvious injuries, but he complains of excruciating right hip pain. His right leg is externally rotated, abducted, and extended at the hip and the femoral head can be palpated anterior to the pelvis. Plain radiographs of the pelvis reveal a right anterior hip dislocation and femoral head fracture. Which sensory and motor deficits are most likely in this patient's right lower extremity?

A. Loss of sensation laterally below the knee, weak thigh extension and knee flexion
B. Numbness of the ipsilateral scrotum and upper medial thigh
C. Sensory loss to the dorsal surface of the foot and part of the anterior lower and lateral leg and foot drop
D. Paresis and numbness of the medial thigh and medial side of the calf, weak hip flexion and knee extension
E. Numbness of the medial side of the thigh and inability to adduct the thigh (Correct Answer)

Explanation: ***Numbness of the medial side of the thigh and inability to adduct the thigh*** - An **anterior hip dislocation** is caused by forced **abduction** and **external rotation**, putting the **obturator nerve** at risk due to its anatomical course through the **obturator foramen** and proximity to the hip joint. - Damage to the **obturator nerve** (L2-L4) results in **sensory loss** over the **medial thigh** and paralysis of the **adductor muscles** (adductor longus, brevis, magnus, gracilis), leading to an inability to adduct the thigh. *Loss of sensation laterally below the knee, weak thigh extension and knee flexion* - **Sensory loss laterally below the knee** and **weak thigh extension/knee flexion** are characteristic of **sciatic nerve** or common **peroneal nerve injury**, which is more common in **posterior hip dislocations**. - The presented case describes an **anterior dislocation**, making **obturator nerve** injury more likely than sciatic nerve injury. *Numbness of the ipsilateral scrotum and upper medial thigh* - **Numbness of the ipsilateral scrotum** and **upper medial thigh** is associated with injury to the **ilioinguinal nerve** or **genitofemoral nerve**. - While these nerves supply portions of the **medial thigh** and **genitalia**, they are not typically injured in **anterior hip dislocations** which primarily affect deeper structures like the **obturator nerve**. *Sensory loss to the dorsal surface of the foot and part of the anterior lower and lateral leg and foot drop* - **Sensory loss to the dorsal surface of the foot**, **anterior lower and lateral leg**, and **foot drop** are classic signs of **common peroneal nerve** injury due to its superficial course around the fibular head. - Although the common peroneal nerve is a branch of the **sciatic nerve**, direct injury specifically to the **common peroneal nerve** in an anterior hip dislocation is less probable than obturator nerve injury, and foot drop is characteristic of more severe neural compromise, typically seen in **posterior dislocations or direct trauma**. *Paresis and numbness of the medial thigh and medial side of the calf, weak hip flexion and knee extension* - **Paresis and numbness of the medial thigh** are consistent with **obturator nerve** injury. However, **numbness of the medial side of the calf** and **weak hip flexion/knee extension** point towards **femoral nerve** injury. - While the **femoral nerve** can be injured, the prominent clinical picture of **anterior hip dislocation** points more directly to the **obturator nerve** findings of medial thigh numbness and adduction weakness, rather than primarily femoral nerve symptoms.

Question 4: A 34-year-old man is brought to the emergency department 3 hours after being bitten by a rattlesnake. He was hiking in the Arizona desert when he accidentally stepped on the snake and it bit his right leg. His pulse is 135/min and blood pressure is 104/81 mm Hg. Examination shows right lower leg swelling, ecchymosis, and blistering. Right ankle dorsiflexion elicits severe pain. A manometer inserted in the lateral compartment of the lower leg shows an intracompartmental pressure of 67 mm Hg. In addition to administration of the antivenom, the patient undergoes fasciotomy. Two weeks later, he reports difficulty in walking. Neurologic examination shows a loss of sensation over the lower part of the lateral side of the right leg and the dorsum of the right foot. Right foot eversion is 1/5. There is no weakness in dorsiflexion. Which of the following nerves is most likely injured in this patient?

A. Sural nerve
B. Tibial nerve
C. Saphenous nerve
D. Superficial peroneal nerve (Correct Answer)
E. Deep peroneal nerve

Explanation: ***Superficial peroneal nerve*** - The **superficial peroneal nerve** (also known as the superficial fibular nerve) is responsible for **foot eversion** (peroneus longus and brevis muscles) and provides sensory innervation to the **dorsum of the foot**, except for the web space between the first and second toes. - The patient's inability to evert the foot and sensory loss on the dorsum of the foot, combined with a history of **compartment syndrome** and fasciotomy in the lateral compartment, strongly indicates injury to the superficial peroneal nerve. *Sural nerve* - The **sural nerve** provides sensory innervation to the **posterolateral aspect of the lower leg** and the lateral aspect of the foot. - It does not innervate muscles involved in foot eversion or dorsiflexion, so its injury would not lead to the motor deficits described. *Tibial nerve* - The **tibial nerve** innervates the muscles of the posterior compartment of the leg, responsible for **plantarflexion** and inversion of the foot, and provides sensation to the sole of the foot. - Its injury would lead to weakness in plantarflexion and sensory loss on the sole, not the symptoms described. *Saphenous nerve* - The **saphenous nerve** is a pure sensory nerve, supplying sensation to the **medial aspect of the lower leg and foot**. - Its injury would result in sensory loss in this distribution but no motor deficits affecting foot eversion or dorsiflexion. *Deep peroneal nerve* - The **deep peroneal nerve** (also known as the deep fibular nerve) innervates the muscles of the anterior compartment of the leg, primarily responsible for **foot dorsiflexion** and toe extension, and provides sensation to the web space between the first and second toes. - The patient has no weakness in dorsiflexion, ruling out significant injury to the deep peroneal nerve.

Question 5: A 31-year-old woman presents with difficulty walking and climbing stairs for the last 3 weeks. She has no history of trauma. The physical examination reveals a waddling gait with the trunk swaying from side-to-side towards the weight-bearing limb. When she stands on her right leg, the pelvis on the left side falls. When she stands on her left leg, the pelvis remains level. Which of the following nerves is most likely injured in this patient?

A. Right inferior gluteal nerve
B. Right obturator nerve
C. Right superior gluteal nerve (Correct Answer)
D. Right femoral nerve
E. Left femoral nerve

Explanation: ***Right superior gluteal nerve*** - The presentation of a **waddling gait** and the **Trendelenburg sign** (pelvis dropping on the unsupported side) is characteristic of **gluteus medius** and **minimus** weakness. - These muscles are innervated by the **superior gluteal nerve**. In this case, when the patient stands on her right leg, the left pelvis falls, indicating weakness of the right gluteus medius/minimus. *Right inferior gluteal nerve* - The **inferior gluteal nerve** innervates the **gluteus maximus**, which is primarily responsible for hip extension. - Damage to this nerve would primarily lead to difficulty with **climbing stairs** and rising from a seated position, but not typically the specific pelvic drop described. *Right obturator nerve* - The **obturator nerve** innervates the **adductor muscles** of the thigh. - Damage would result in weakness of hip adduction and **medial thigh sensory deficits**, which are not the primary symptoms here. *Right femoral nerve* - The **femoral nerve** innervates the **quadriceps femoris** and the **sartorius**, responsible for knee extension and hip flexion. - Injury would cause difficulty with **knee extension** and **hip flexion**, potentially leading to knee buckling or instability, which is not consistent with the Trendelenburg sign observed. *Left femoral nerve* - Injury to the left femoral nerve would affect the **left quadriceps** and **sartorius** muscles. - This would cause weakness in extending the left knee and flexing the left hip, which is not consistent with the observed **right-sided gluteal weakness** indicated by the Trendelenburg sign on the right.

Question 6: A 25-year-old woman presents with shooting pain along the lateral aspect of her right thigh. The pain is exacerbated by standing or walking for long periods. Physical examination reveals tenderness at the anterior superior iliac spine. Which of the following nerves is most likely affected?

A. Common peroneal nerve
B. Obturator nerve
C. Sciatic nerve
D. Lateral femoral cutaneous nerve (Correct Answer)

Explanation: ***Lateral femoral cutaneous nerve*** - This presentation is classic for **meralgia paresthetica**, caused by compression of the **lateral femoral cutaneous nerve** as it passes under the inguinal ligament, leading to pain and numbness on the **lateral thigh**. - Tenderness at the **anterior superior iliac spine** points to the inguinal ligament region where this nerve is most vulnerable to compression. *Common peroneal nerve* - Injury to the common peroneal nerve typically causes **foot drop** and sensory deficits over the **dorsum of the foot** and **lateral leg**, not the lateral thigh. - It is often compressed at the **fibular head**, which is anatomically distinct from the anterior superior iliac spine. *Obturator nerve* - The obturator nerve innervates the **medial thigh muscles** and provides sensation to the medial thigh; its compression would cause pain in this region, not the lateral thigh. - Injury often leads to **adductor weakness** and is typically associated with pelvic trauma or surgery. *Sciatic nerve* - Sciatic nerve pain typically radiates down the **posterior aspect of the leg** into the foot (**sciatica**), often associated with lumbar disc herniation. - Sensory deficits would follow the dermatomal distribution of its branches (**tibial** and **common peroneal nerves**).

Question 7: One day after undergoing surgery for a traumatic right pelvic fracture, a 73-year-old man has pain over his buttocks and scrotum and urinary incontinence. Physical examination shows right-sided perineal hypesthesia and absence of anal sphincter contraction when the skin around the anus is touched. This patient is most likely to have which of the following additional neurological deficits?

A. Impaired hip flexion
B. Paralysis of hip adductors
C. Absent cremasteric reflex
D. Impaired psychogenic erection
E. Absent reflex erection (Correct Answer)

Explanation: ***Absent reflex erection*** - The patient's symptoms (buttock/scrotal pain, perineal hypesthesia, urinary incontinence, absent anal sphincter contraction) suggest **damage to the sacral plexus and pudendal nerve**, consistent with a **cauda equina syndrome**. - **Reflex erections** are primarily mediated by the **sacral parasympathetic outflow (S2-S4)**, which are likely compromised given the other sacral nerve deficits. *Impaired hip flexion* - **Hip flexion** is primarily controlled by the **L1-L3 nerve roots** (e.g., iliopsoas muscle), and while a severe pelvic fracture could cause widespread nerve damage, the current symptoms localize more strongly to the sacral region. - The described symptoms are more indicative of **sacral nerve involvement** rather than higher lumbar segments that govern hip flexion. *Paralysis of hip adductors* - **Hip adduction** is mainly innervated by the **obturator nerve (L2-L4)**. - The patient's symptoms point to **S2-S4 nerve dysfunction** (perineal sensation, anal sphincter, bladder), which are distinct from the obturator nerve's primary innervations. *Absent cremasteric reflex* - The **cremasteric reflex** is mediated by the **genitofemoral nerve (L1-L2)**. - The symptoms presented are more consistent with **sacral nerve damage**, specifically S2-S4, rather than the higher lumbar segments responsible for the cremasteric reflex. *Impaired psychogenic erection* - **Psychogenic erections** are initiated by **supraspinal input** descending through the thoracolumbar spinal cord (T10-L2) to activate sympathetic pathways. - While sacral nerve damage can affect the final efferent pathway for all erections, the direct impairment of psychogenic initiation is linked to higher centers and **thoracolumbar sympathetic outflow**, not purely sacral damage.

Question 8: A 26-year-old woman presents to the obstetrics ward to deliver her baby. The obstetrician establishes a pudendal nerve block via intravaginal injection of lidocaine near the tip of the ischial spine. From which of the following nerve roots does the pudendal nerve originate?

A. L4-L5
B. S2-S4 (Correct Answer)
C. L3-L4
D. L5-S2
E. L5-S1

Explanation: ***S2-S4*** - The **pudendal nerve** originates from the **sacral plexus**, specifically from the ventral rami of spinal nerves **S2, S3, and S4**. - Its origin from these segments is crucial for its function in innervating structures of the **perineum**, **external genitalia**, and the **anal and urethral sphincters**, making it highly relevant for procedures like **pudendal nerve blocks** during childbirth. *L4-L5* - Nerve roots **L4-L5** contribute significantly to the **lumbar plexus** and subsequently to nerves like the **femoral nerve** and portions of the **sciatic nerve**. - These roots are primarily involved in innervating the **lower limbs** (e.g., quadriceps, tibialis anterior) and are not the primary origin of the pudendal nerve. *L3-L4* - The **L3-L4** nerve roots are also part of the **lumbar plexus**, chiefly contributing to the **femoral nerve**. - They are essential for motor innervation of the **anterior thigh muscles** and sensation in this area, distinct from the pudendal nerve's role in the perineum. *L5-S2* - While **S2** is part of the pudendal nerve's origin, the inclusion of **L5** and **S1** primarily characterizes the origin of the **sciatic nerve** (which is formed by L4-S3) and its branches, such as the common fibular and tibial nerves. - These roots are primarily concerned with the **posterior thigh** and **leg innervation**, not the perineum, which differentiates it from the pudendal nerve. *L5-S1* - The nerve roots **L5-S1** are key components of the **lumbosacral plexus** and contribute significantly to the **sciatic nerve**, particularly its innervation of the **hamstrings** and certain lower leg muscles. - This origin does not align with the known roots of the **pudendal nerve** which stems from S2-S4.

Question 9: An 80-year-old woman is brought to the emergency department for left hip pain 30 minutes after she fell while walking around in her room. Examination shows left groin tenderness. The range of motion of the left hip is limited because of pain. An x-ray of the hip shows a linear fracture of the left femoral neck with slight posterior displacement of the femur. Which of the following arteries was most likely damaged in the patient's fall?

A. Superior gluteal artery
B. Deep circumflex iliac
C. Deep femoral artery
D. Obturator
E. Medial circumflex femoral (Correct Answer)

Explanation: ***Medial circumflex femoral*** - This artery is the **primary blood supply** to the femoral head and neck, making it highly vulnerable to injury in cases of femoral neck fractures. - Damage to the medial circumflex femoral artery significantly increases the risk of **avascular necrosis** of the femoral head. *Superior gluteal artery* - The superior gluteal artery primarily supplies the **gluteus medius** and **minimus muscles**. - It is **not directly involved** in the primary blood supply to the femoral head and neck. *Deep circumflex iliac* - This artery mainly supplies the **iliac fossa** and the **abdominal wall muscles**. - It does not contribute significantly to the blood supply of the femoral neck. *Deep femoral artery* - The deep femoral artery, also known as the **profunda femoris artery**, is the main supply to the **thigh muscles**. - While it gives rise to the circumflex arteries, it is not the artery directly compromised in a femoral neck fracture. *Obturator* - The obturator artery primarily supplies the **adductor muscles** of the thigh and contributes a small branch to the femoral head via the **ligamentum teres**. - This contribution is **insufficient** to maintain viability of the femoral head, especially in trauma to the femoral neck.

Question 10: A newborn boy born vaginally to a healthy 37-year-old G3P1 from a pregnancy complicated by hydramnios fails to pass meconium after 24 hours of life. The vital signs are within normal limits for his age. The abdomen is distended, the anus is patent, and the rectal examination reveals pale mucous with non-pigmented meconium. Based on a barium enema, the boy is diagnosed with sigmoid colonic atresia. Disruption of which structure during fetal development could lead to this anomaly?

A. Inferior mesenteric artery (Correct Answer)
B. Superior mesenteric artery
C. Vitelline duct
D. Cloaca
E. Celiac artery

Explanation: ***Inferior mesenteric artery*** - **Sigmoid colonic atresia**, as observed in this case, results from an ischemic event affecting the segment of the bowel supplied by the **inferior mesenteric artery** during fetal development. - Interruption of blood flow to this region can lead to subsequent **atresia** as the affected part of the intestine necroses and is reabsorbed. *Superior mesenteric artery* - The **superior mesenteric artery** primarily supplies the midgut structures, including the small intestine and parts of the large intestine up to the transverse colon. - Disruption of the superior mesenteric artery would typically lead to atresias higher up in the **gastrointestinal tract**, such as jejunal or ileal atresias, not sigmoid colonic atresia. *Vitelline duct* - The **vitelline duct** (also known as the omphalomesenteric duct) connects the midgut to the yolk sac during early fetal development. - Persistent patency or partial obliteration of the vitelline duct can lead to anomalies like **Meckel's diverticulum** or vitelline cysts, which are distinct from colonic atresia. *Cloaca* - The **cloaca** is a common cavity for the digestive, urinary, and reproductive tracts during early embryonic development. - Defects in cloacal development lead to complex malformations involving these systems, such as **imperforate anus** or persistent cloaca, rather than isolated colonic atresia with a patent anus. *Celiac artery* - The **celiac artery** supplies the foregut structures, including the stomach, duodenum, liver, and spleen. - Disruption of the celiac artery during fetal development would result in malformations of these upper gastrointestinal organs, not the sigmoid colon.

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