Extensor indicis muscle

Extensor indicis proprius
Transverse section across distal ends of radius and ulna. (Label "Ext. indic. prop." visible at bottom center.)
Posterior surface of the forearm. Deep muscles. Extensor indicis muscle is labeled in purple.
Details
Latin	musculus extensor indicis
Origin	posterior distal third of ulna and interosseous membrane
Insertion	index finger (extensor hood)
Artery	posterior interosseous artery
Nerve	posterior interosseous nerve
Actions	extends index finger, wrist
Identifiers
Gray's	p.456
Dorlands /Elsevier	m_22/12548933
TA	A04.6.02.052
FMA	38524
Anatomical terms of muscle

In human anatomy, the extensor indicis [proprius] is a narrow, elongated skeletal muscle in the deep layer of the dorsal forearm, placed medial to, and parallel with, the extensor pollicis longus. Its tendon goes to the index finger, which it extends.

Origin and insertion

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. ^[1]

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 always runs on the ulnar side of the tendon of the common extensor digitorum. Both these extensors lack the oblique bands (connexus intertendinei) interlinking the tendons of the extensor digitorum on the dorsal side of the hand. ^[2]

Action

The extensor indicis extends the index finger, and by its continued action assists in extending (dorsiflexion) the wrist and the midcarpal joints.^[1]

Because the index finger and little finger have separate extensors, these fingers can be moved more independently than the other fingers. ^[2]

Additional images

The mucous sheaths of the tendons on the back of the wrist. (Extensor indicis proprius visible going into second digit.)  Bones of left forearm. Posterior aspect.  Posterior surface of the forearm. Deep muscles.  Transverse section across the wrist and digits.  Extensor indicis muscle  Extensor indicis muscle  Extensor indicis muscle  Extensor indicis muscle  Extensor indicis muscle  Muscles of hand. Posterior view.  Muscles of hand. Posterior view.

Notes

References

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)

• Platzer, Werner (2004). Color Atlas of Human Anatomy, Vol. 1: Locomotor System (5th ed.). Thieme. ISBN 3-13-533305-1. 
• Ross, Lawrence M. (ed.); Lamperti, Edward D. (ed.) (2006). Thieme Atlas of Anatomy: General Anatomy and Musculoskeletal System. Thieme. ISBN 1-58890-419-9. 

External links

• Anatomy photo:09:05-0106 at the SUNY Downstate Medical Center - "Extensor Region of Forearm and Dorsum of Hand: Deep Muscles of Extensor Region"
• lesson5musofpostforearm at The Anatomy Lesson by Wesley Norman (Georgetown University)
• Extensor_indicis at the Duke University Health System's Orthopedics program
• Ritter, Merrill A.; Inglis, Allen E. (1969). "The Extensor Indicis Proprius Syndrome" (PDF). J Bone Joint Surg Am. (51): 1645–1648.