[Music] in this lesson we will review the extensor group of muscles that extend from the forearm into the fingers let's start by looking an anterior view of the right elbow region to understand the attachment of the extensor muscles at this site to orient ourselves this is the distal end of the humerus which has a prominent structure bony projection on as the medial epicondyle seen here on the other side on the lateral side is the lateral epicondyle which is seen over here this distal end of the humerus articulates with the radius and the ulna this is
the radius which is seen over here and the ulna which is seen over here and the attachment of the extensor muscles is in the region of the lateral epicondyle and the bony Ridge just superior to it known as the supracondylar range it's a general attachment for most of the extensor muscles the clinical significance of this common extensor attachment at the lateral epicondyle area is that it is often inflamed and becomes painful a condition known as tennis elbow it often occurs in tennis players but not exclusively and hence the name tennis elbow the similar condition can
be found at the common flexor attachment on the medial epicondyle and that is known as golfer's elbow these conditions typically occur in sports persons who play these games but can happen in individuals because of repetitive stress injury in a variety of different activities let's now look at the sites and the relationships of these various extensor muscles as they become tenderness at the wrist and at the in the level of the hand the first one of these group of muscles is the brachioradialis and it attaches onto the distal radius as here this muscle does not cross
the wrist joint and therefore has no action at the wrist joint it has action at the elbow only the next muscle which is immediately adjacent to it and on the other side of this muscle is a muscle that has a long name it's called the extensor carpi radialis longus or EC RL for short and it runs down the radius crossing the carpals or the wrist bones and attaches onto the base of the second metacarpal this name the extensor carpi radialis longus is very descriptive of this muscle it's an extensor muscle because it crosses on the
dorsum of the wrist and it extends the wrist hence the name carpi it's on the radial side of the wrist and hence the name radialis and it is the longer of the two muscles then hence the name longus and you've guessed right there is another muscle immediately adjacent to it known as extensor carpi radialis brevis or EC RB and that is seen here going down to the base of the third metacarpal these two muscles form strong extensors of the wrist joint and have a slight action of radial deviation as well and therefore will have a
balancing muscle that we will look at momentarily the next muscle in this group is a muscle that goes to the index finger and it is known as extensor indices Pro Prius or AIP for short and it is seen here going to the distal failings of the index finger this is the EIP there's another muscle which is somewhat like the flexor digitorum muscles known as extensor digitorum and it is seen here going down to the various digits the four digits extensor digitorum communis or the common extensor digitorum the common extensor of the digits and sometimes abbreviated
as EDC this is the tendon of the EDC in the index finger similarly we have this tendon going in the middle ring and little fingers as well seen in blue color the EDC is a muscle that has a common belly more approximately and then splits into these four segments one for each of the digits and in that respect it is not unlike the long flexors that are on seen on the Palmer side there's one other muscle which goes into the little finger known as extensors digitally EDM for short and it is seen right here in
red note that the index finger and the little finger have two extensor digits they have an independent extensor in addition to the common extensor the EIP for the index finger and the EDM for the little finger this allows for a level of independent extension of these two individual fingers which is not so easily seen in the middle finger or in the ring finger there's one other muscle in this group known as the extensor carpi ulnaris which is the most owner of these muscles and it is seen here going to the base of the fifth metacarpal
this is a strong extensor of the wrist and it has a balancing action with the extensors on the radial side and like the EC RL and EC RB the extensor carpi ulnaris or ECU it does cross the wrist joint but does not go into the digits all of these muscles are supplied by the radial nerve let's now look at these tendons in a superficial dissection of the right hand as seen in this photograph well put the first tendon that is visible here the EC RL this is the extensor carpi radialis longus tendon seen here on
the radial side and it does cross the wrist joint going to the base of the second metacarpal immediately adjacent to it is the ECR be the extensor carpi radialis brevis seen here these two tendons are on the radial side and there are strong extensors of the wrist joint next we see the extensor indices propria CIP seen here going to the index finger we then have the four tendons from the EDC extensor digitorum communists' seen going down here there's a tendon going to each of the digits as seen here and then on the other side we
have the extensor digital mini-me the EDM which is seen going down here into the little finger and finally we have the extensor carpi ulnaris which is going down the other side and attaches onto the base of the fifth metacarpal the ECU and the EC RL and EC RB only have their action on the wrist joint note also the specific relationship in the index finger and the little finger between the common extensor as well as their individual extensors the EIP is seen on the ulnar side of the EDC tendon to the index finger this is a
consistent relationship similarly the EDM extensor digital mini-me is on the other side of the extensor digitorum communis tendon going to the little finger this is also a consistent relationship all of these tendons are kept in place by fibers membrane known as the extensor retinaculum it is removed in this diagram the extensor retinaculum is over the dorsum of the wrist joint [Music] you
