In which layer is the flexor hallucis brevis located?

In which layer is the flexor hallucis brevis located?

• A. 2nd layer
• B. 1st layer
• C. 3rd layer
• D. 4th layer

Answer: (C)

Understanding how the intrinsic muscles of the sole are arranged in layers helps explain why the flexor hallucis brevis is in the third layer. The third layer contains muscles that mainly control the big toe and its joints, including the flexor hallucis brevis along with the adductor hallucis and the flexor digiti minimi brevis. This sits deeper than the superficial first layer (which has abductor hallucis, flexor digitorum brevis, and abductor digiti minimi) and above the fourth layer (which houses the interossei). The flexor hallucis brevis has two heads and inserts on the proximal phalanx of the big toe, enabling flexion at the metatarsophalangeal joint. That functional role and its deeper position relative to the superficial muscles explain why it belongs to the third layer.

Understanding how the intrinsic muscles of the sole are arranged in layers helps explain why the flexor hallucis brevis is in the third layer. The third layer contains muscles that mainly control the big toe and its joints, including the flexor hallucis brevis along with the adductor hallucis and the flexor digiti minimi brevis. This sits deeper than the superficial first layer (which has abductor hallucis, flexor digitorum brevis, and abductor digiti minimi) and above the fourth layer (which houses the interossei). The flexor hallucis brevis has two heads and inserts on the proximal phalanx of the big toe, enabling flexion at the metatarsophalangeal joint. That functional role and its deeper position relative to the superficial muscles explain why it belongs to the third layer.