In human anatomy, the extensor indicis roprius'' is a narrow, elongated

skeletal muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of m ...

in the deep layer of the dorsal

forearm The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in ...

, placed medial to, and parallel with, the

extensor pollicis longus In human anatomy, the extensor pollicis longus muscle (EPL) is a skeletal muscle located dorsally on the forearm. It is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together wi ...

. Its tendon goes to the index finger, which it extends.

Structure

It arises from the distal third of the dorsal part of the body of ulna and from the interosseous membrane. It runs through the fourth tendon compartment together with the extensor digitorum, from where it projects into the dorsal aponeurosis of the index finger. Opposite the head of the second metacarpal bone, it joins the ulnar side of the tendon of the extensor digitorum which belongs to the index finger. Like the extensor digiti minimi (i.e. the extensor of the little finger), the tendon of the extensor indicis runs and inserts on the ulnar side of the tendon of the common extensor digitorum. The extensor indicis lacks the juncturae tendinum interlinking the tendons of the extensor digitorum on the dorsal side of the hand.

Variation

The extensor indicis proprius does not show much variation. It exists as a single tendon most of the time. Double tendons of the extensor indicis proprius was also reported. It is known that the extensor indicis proprius inserts to the index finger on the ulnar side of the extensor digitorum. However, the insertion on the radial side of the common extensor digitorum infrequently seen, namely the ''extensor indicis radialis''. Split tendons of the muscle inserting on both ulnar and the radial side of the common extensor digitorum was also reported. Anomalous hand extensors including the extensor medii proprius and the extensor indicis et medii communis are often seen as variations of the extensor indicis due to the shared characteristics and embryonic origin.

Function

The extensor indicis extends the index finger, and by its continued action assists in extending ( dorsiflexion) the wrist and the midcarpal joints. Because the index finger and little finger have separate extensors, these fingers can be moved more independently than the other fingers.

Additional images

Notes

References

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External links

* - "Extensor Region of Forearm and Dorsum of Hand: Deep Muscles of Extensor Region" * * * {{Authority control Muscles of the upper limb