Which muscle is unipennate?

Which muscle is unipennate?

• A. Dorsal Interosseous Muscle
• B. Flexor Digitorum Longus
• C. Plantar Interosseous Muscle
• D. Abductor Hallucis

Answer: (C)

Unipennate muscles have fibers arranged on one side of a single tendon, like a single feather anchored at one edge. The plantar interosseous muscles fit this pattern: they originate from the plantar aspects of the metatarsals and insert on the medial sides of the proximal phalanges of toes 3–5, with the muscle fibers pulling toward a single tendinous line. This arrangement gives a strong, concentrated pull to adduct the toes toward the second toe. In contrast, the dorsal interosseous muscles are bipennate (fibers on both sides of a central tendon) and abduct the toes, while the flexor digitorum longus is a long, mostly parallel-fibered flexor running along the leg, not pennate. The abductor hallucis is a broad, fan-shaped muscle with fibers radiating toward the big toe, not organized on one side of a tendon. So the plantar interosseous muscle is the one that is unipennate.

Unipennate muscles have fibers arranged on one side of a single tendon, like a single feather anchored at one edge. The plantar interosseous muscles fit this pattern: they originate from the plantar aspects of the metatarsals and insert on the medial sides of the proximal phalanges of toes 3–5, with the muscle fibers pulling toward a single tendinous line. This arrangement gives a strong, concentrated pull to adduct the toes toward the second toe.

In contrast, the dorsal interosseous muscles are bipennate (fibers on both sides of a central tendon) and abduct the toes, while the flexor digitorum longus is a long, mostly parallel-fibered flexor running along the leg, not pennate. The abductor hallucis is a broad, fan-shaped muscle with fibers radiating toward the big toe, not organized on one side of a tendon. So the plantar interosseous muscle is the one that is unipennate.