Extensor digiti minimi

Where is the muscle located and how is it structured?

The extensor digiti minimi (m. extensor digiti minimi) is a muscle located in the superficial layer of the posterior forearm compartment.

• Origin (Origo) — lateral epicondyle of the humerus (epicondylus lateralis). The muscle originates in this area as part of the common extensor tendon.
• Insertion (Insertio) — dorsal aponeurosis (dorsal expansion) of the 5th digit. Heading toward the little finger, the tendon of this muscle joins the tendon of the extensor digitorum (m. extensor digitorum).

Topography and adjacent structures

The extensor digiti minimi lies in the superficial layer of the posterior muscle group of the forearm. The same muscle layer contains:

• Brachioradialis muscle (m. brachioradialis);
• Extensor carpi radialis longus and brevis muscles (m. extensor carpi radialis longus and m. extensor carpi radialis brevis);
• Extensor digitorum (m. extensor digitorum), whose tendons extend to all digits of the hand except the thumb;
• Extensor carpi ulnaris muscle (m. extensor carpi ulnaris);
• Anconeus muscle (m. anconeus).

What passes through the extensor digiti minimi compartment?

Upon passing to the hand, the tendon of the extensor digiti minimi passes beneath the extensor retinaculum (retinaculum musculorum extensorum).

• Extensor digiti minimi compartment — the tendon passes through its own separate 5th compartment beneath the retinaculum.
• Compartment contents — the synovial sheath of the extensor digiti minimi is located inside.
• Boundaries of the synovial sheath — the proximal boundary of the sheath is at the level of the radioulnar joint. The distal boundary is located below the middle of the 5th metacarpal bone.

Blood Supply, Innervation, and Function

• Function — the main task of the muscle is to extend the little finger (5th digit). Additionally, it participates in the extension of the entire hand.
• Blood supply — the muscle is supplied by the posterior interosseous artery (a. interossea posterior).
• Innervation — motor impulses are supplied by the radial nerve (n. radialis). Spinal segments C7–C8 are involved in innervation.

For comparison, other movements of the little finger are provided by the following segments: abduction of the little finger — C8–Th1, opposition of the little finger to the thumb — C7–Th1, flexion of the proximal phalanx of the little finger — C7–Th1.

Class and exam questions

What else to study on this topic

• Extensor digitorum (m. extensor digitorum)
• Extensor retinaculum (retinaculum musculorum extensorum)
• Radial nerve (n. radialis)
• Extensor carpi ulnaris (m. extensor carpi ulnaris)

Other topics in the "Anatomical Structures" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.