The extensor digitorum longus inserts into the middle and distal phalanges of the 2nd to 5th toes. Which of the following describes its insertion?

The extensor digitorum longus inserts into the middle and distal phalanges of the 2nd to 5th toes. Which of the following describes its insertion?

• A. It inserts into the proximal phalanges of the 2nd to 5th toes
• B. It inserts into the middle and distal phalanges of the 2nd to 5th toes
• C. It inserts into the base of the metatarsals 2-5
• D. It inserts into the distal phalanges of the great toe

Answer: (B)

The key idea is where the muscle’s tendon actually attaches, because that determines what joints it can move. The extensor digitorum longus sends tendons to the middle and distal phalanges of the toes 2 through 5, via the extensor expansions. This arrangement lets it extend those toes at both the metatarsophalangeal joints and the interphalangeal joints. It doesn’t attach to the proximal phalanges, the bases of the metatarsals, or the distal phalanx of the great toe—that would point to different muscles or different insertions. So describing its insertion as the middle and distal phalanges of the 2nd to 5th toes is the correct fit.

The key idea is where the muscle’s tendon actually attaches, because that determines what joints it can move. The extensor digitorum longus sends tendons to the middle and distal phalanges of the toes 2 through 5, via the extensor expansions. This arrangement lets it extend those toes at both the metatarsophalangeal joints and the interphalangeal joints. It doesn’t attach to the proximal phalanges, the bases of the metatarsals, or the distal phalanx of the great toe—that would point to different muscles or different insertions. So describing its insertion as the middle and distal phalanges of the 2nd to 5th toes is the correct fit.