A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 32-year-old man comes to the emergency department because of a wound in his foot. Four days ago, he stepped on a nail while barefoot at the beach. Examination of the plantar surface of his right foot shows a purulent puncture wound at the base of his second toe with erythema and tenderness of the surrounding skin. The afferent lymphatic vessels from the site of the lesion drain directly into which of the following groups of regional lymph nodes?
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A
Deep inguinalIncorrect. Deep inguinal nodes receive drainage from the superficial inguinals and from the glans penis/clitoris — they don't directly drain the foot.
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B
Superficial inguinalCorrect. the superficial structures of the lower extremity (including the foot) drain via superficial lymphatics directly to the superficial inguinal nodes.
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C
External iliacIncorrect. External iliac nodes are further upstream, receiving drainage from deep inguinals and pelvic viscera — not direct drainage from the foot.
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D
Anterior tibialIncorrect. Anterior tibial/popliteal nodes drain deep structures of the calf; superficial lymphatics from the foot bypass them and go directly to the superficial inguinal nodes.
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E
PoplitealIncorrect. Popliteal nodes drain the deep lymphatics of the lower leg and the lateral foot via the small saphenous route, but superficial structures of the foot bypass the popliteals to drain directly to the superficial inguinal nodes.
↑ Tap an answer to reveal the reasoning
Answer: B. An infected wound on the plantar surface of the foot (below the umbilicus, on the lower extremity) drains via superficial lymphatics to the SUPERFICIAL INGUINAL lymph nodes. The lymphatic drainage of the lower extremity skin and superficial structures up to about the umbilicus all empties into the superficial inguinal nodes, which lie just below the inguinal ligament in the upper anteromedial thigh.
From the superficial inguinal nodes, lymph passes to the deep inguinal nodes (which sit medial to the femoral vein along the femoral canal), then to the external iliac, common iliac, para-aortic chains, and ultimately to the thoracic duct. So the question asks which group receives DIRECT drainage from the foot — superficial inguinal.
Distinguishing other options: deep inguinal nodes receive drainage from the superficial inguinals (one level deeper) and from the glans penis/clitoris — NOT directly from the foot. External iliac nodes receive drainage from deep inguinals and pelvic viscera — even further removed. Anterior tibial nodes are an anatomic anomaly term sometimes used for popliteal nodes that drain the deep structures of the leg — but the superficial structures of the foot bypass these and go directly to the superficial inguinal nodes via superficial lymphatic channels.
Clinical pearl: this anatomy explains why lower extremity skin infections and lower extremity malignancies (like melanoma) commonly cause enlarged inguinal nodes; popliteal nodes can also be enlarged in deep tissue infections.
**Why each option:**
**A.** Deep inguinal nodes receive drainage from the superficial inguinals and from the glans penis/clitoris — they don't directly drain the foot.
**B.** Correct — the superficial structures of the lower extremity (including the foot) drain via superficial lymphatics directly to the superficial inguinal nodes.
**C.** External iliac nodes are further upstream, receiving drainage from deep inguinals and pelvic viscera — not direct drainage from the foot.
**D.** Anterior tibial/popliteal nodes drain deep structures of the calf; superficial lymphatics from the foot bypass them and go directly to the superficial inguinal nodes.