Question

question 70

which of the following best describes the insertion of the extensor digitorum?

a it indirectly inserts on all digits of the hand.
b it indirectlyinserts on all digits of the hand except the thumb.
c it directly inserts on all digits of the hand.
d it directly inserts on all digits of the hand except the thumb.
e it directly inserts on the index finger only.

Explanation:

Identify the muscle and target digits

The question asks for the insertion of the extensor digitorum muscle. The extensor digitorum is a superficial muscle of the posterior compartment of the forearm. It divides into four tendons that travel to the medial four digits of the hand (digits 2 through 5: index, middle, ring, and little fingers). It does not send a tendon to the thumb (digit 1), which has its own dedicated extensor muscles (extensor pollicis longus and brevis).

Analyze the mechanism of insertion

Rather than inserting directly into the bone as a simple tendon, the tendons of the extensor digitorum flatten out over the dorsal aspect of the phalanges to form a specialized connective tissue structure called the extensor expansion (or extensor hood). Because the muscle inserts into these broad aponeurotic expansions rather than attaching directly to the phalanges, the insertion is described as indirect.

Evaluate the given options

• A: Incorrect. It does not insert on the thumb (digit 1).
• B: Correct. It inserts indirectly (via the extensor expansions) on digits 2 through 5 (all digits except the thumb).
• C: Incorrect. It does not insert on the thumb, and the insertion is indirect.
• D: Incorrect. While it targets all digits except the thumb, the insertion is indirect via extensor expansions, not direct.
• E: Incorrect. It inserts on digits 2 through 5, not just the index finger.

Answer:

• (A) It indirectly inserts on all digits of the hand.
• (B) It indirectly inserts on all digits of the hand except the thumb. (Correct answer)
• (C) It directly inserts on all digits of the hand.
• (D) It directly inserts on all digits of the hand except the thumb.
• (E) It directly inserts on the index finger only.