Muscle that Extend the index finger

 MCQ 43 @ MN FB page

Q. Muscle that can extend the index finger at interphalangeal joint include all except ?

a. The first dorsal inerosseous

b. The first lumberical

c. The second palmar interosseous

d. Extensor carpi radialis longus.

Wrongly answered at various places as option C.

Option C is NOT the answer here.

We had already answered this with proper explanation on our facebook notes.

On request of our readers - we are reposting the question with explanation here.

ANSWER:

Ans: D

Explanation from Gray's Anatomy -- Compiled and edited by DrShiviMudgal (Director/Admin @MedicoNotebook)

The interossei are muscles between and attached to the metacarpals.

They insert into the proximal phalanx of each digit and into the extensor hood and are divided into two groups, the dorsal interossei and the palmar interossei. All of the interossei are innervated by the deep branch of the ulnar nerve. Collectively, the interossei abduct and adduct the digits and contribute to the complex flexion and extension movements generated by the extensor hoods.

 Dorsal interossei

 Dorsal interossei are the most dorsally situated of all of the intrinsic muscles and can be palpated through the skin on the dorsal aspect of the hand (Fig. 7.99). There are four bipennate dorsal interosseous muscles between, and attached to, the shafts of adjacent metacarpal bones (Fig. 7.99). Each muscle inserts both into the base of the proximal phalanx and into the extensor hood of its related digit.

The tendons of the dorsal interossei pass dorsal to the deep transverse metacarpal ligaments:

• the first dorsal interosseous muscle is the largest and inserts into the lateral side of theindex finger;
• the second and third dorsal interossei insert into the lateral and medial sides, respectively, of the middle finger;
• the fourth dorsal interosseous muscle inserts into the medial side of the ring finger. 

Palmar interossei

The first palmar interosseous muscle originates from the medial side of the palmar surface of metacarpal I and inserts into both the base of the proximal phalanx of the thumb and into the extensor hood. A sesamoid bone often occurs in the tendon attached to the base of the phalanx.

The second palmar interosseous muscle originates from the medial surface of metacarpal II and inserts into the medial side of the dorsal expansion of the index finger.

The third and fourth palmar interossei originate from the lateral surfaces of metacarpals IV and V and insert into the lateral sides of the respective dorsal hoods.

 Like the tendons of the dorsal interossei, the tendons of the palmar interossei pass dorsal to the deep transverse metacarpal ligaments.

The palmar interossei adduct the thumb, index, ring, and little fingers with respect to a long axis through the middle finger. The movements occur at the metacarpophalangeal joints. Because the muscles insert into the dorsal hoods, they also produce complex flexion and extension movements of the digits

Extensor carpi radialis longus -- Extends and abducts the wrist

Extensor indicis -- Extends index finger