Monday, 2 June 2014

Extensor Indicis

Today We're talking about everyone's favourite 'pointer muscle' Extensor Indicis!

Extensor: a clue that this muscle does the action of extension
Indicis: I used to think it was latin for 'index' as in index finger...but turns out it's latin for 'one who points' (!)
This muscle is deep to (underneath) extensor digitorum and extensor carpi ulnaris
assists digitorum  to specifically extend the index finger (aka pointer finger)

Muscle Attachment Points

 Origin: Posterior surface of distal shaft of ulna and interosseous membrane
Insertion:   Tendon of the extensor digitorum at the level of the second metacarpal

Let's break that down...

Origin:  the Ulna is one of two forearm bones (the one on the pinky side!) The distal end of the ulna is at the wrist, and the posterior surface of this bone is the same side of the back of the hand  (anterior surface would be the palm side) The interosseous membrane is a sheath of connective tissue that stretches between the ulna and the radius (the other forearm bone -thumbside)

( whewf! if this makes some sense look at the picture of muscle (above) again! It may make more sense)

Insertion: metacarpal referring to the knuckle area.

Muscle Action (s) :
 1) extends the second finger (at the metacarpophalangeal joint - where finger meets knuckle)

2) Also assists to adduct the second fingy

It's tendon runs diagonally across the wrist and hand
right along side extensor digitorum's tendon:

 Try extending your index finger at the MCP (knuckle) you may see two side by side tendons passing the knuckle  - the medial one (closer to middle finger) is the extensor indicis tendon

 Oh, and just because...

 The 'Pointer' Sisters are all about Extensor Indicis - am I right?  ;)