 So this is a supine cadaver the right hand is pronated. I'm narrating from the right side camera person is also the right side Let's take a look at the neuro vascular structures that we can see supplying the muscles of the extensor compartment So for that I'm going to come a little approximately and this is the radial nerve The radial nerve comes in front of the common extensor origin That is the lateral epicondyle lateral epicondyle is referred as a common extensor origin Where my finger is located because it gives origin to all the extensor muscles just in front of the lateral epicondyle That the radial nerve it divides into a superficial and a deep branch. This is the superficial branch Which runs as I mentioned under the bricure radialis and the deep branch is the muscular branch This supplies initially the extensor carbide radialis longers and the extensor carbide radialis brevis Which are the two most important extensors of the wrist. These are the two Muscles which I mentioned and after that it pierces through the supinator and it comes on to the extensor aspect And we can see it continuing here and it supplies all the muscles of the extensor compartment and the continuation of this nerve Which passes deep to the fourth tunnel and this is the continuation of the radial nerve here And if the radial nerve is injured here like for example dislocation of the elbow or fracture dislocation of the proximal Radial nerve joint then it can cause paralysis of the extensors of the wrist especially and that will lead to a very serious condition known as wrist drop This is an x-ray of the forearm showing multi-year fracture dislocation Caressed by proximal ulnar fracture and proximal radial nerve joint dislocation And this is a second picture showing the same thing these situations radial nerve injury is quite likely Now let's take a look at the structures on the dorsum of the finger We have opened up the middle finger dorsal aspect and the same structure will be present in all other fingers So we can see that on the dorsum of the finger There's an expansion here which I have lifted up on one side and this is the other side of that expansion This is known as the dorsal digital expansion or the dorsal aponeurosis of the digits If you notice sides of the expansions are thickened the long extensor tendon It gets attached to this on the sides the thickened portion gives attachment to the lumbarical muscles And to the entraceous muscles on either side and after that the deponeurosis then continues and in this region It breaks up into three slips a medium slip which gets attached to the base of the middle phalanx and the two lateral slips This is one of that and this is the other one These two go on either side of the digit and then they unite and they get inserted onto the base of the distal phalanx So this is the dorsal digital expansion to summarize this dorsal digital expansion contains the main extensor tendon It contains the lumbaricals. It contains the insertion of the Intraceous muscles Approximately it is held onto the finger by means of an aponeurotic hood It is because of this unique arrangement of this dorsal expansion that these Intraceous and the lumbarical muscles together can perform what is known as the Zee movement as shown by my hand here The Zee movement is flexion of the metacarpal phalangeal joints and extension of the intra phalangeal joints This movement is possible by virtue of this unique dorsal digital expansion of the digits This same arrangement will apply in all the digits in this correction We can mention a few clinical correlations in baseball players or in Housewives or those who are arranging the bedsheets if the finger is held stiff and it gets hit against hard surface The distal phalanx can forcibly flex and it can produce tear of this Expansion on the base of the distal phalanx in which case the distal phalanx will become Flaxet and that is referred to as mallet finger The next thing is if there is paralysis of the allure nerve which supplies the intrinsic muscles of the head namely the Intraceous muscles and the lumbaricals then the Zee movement will not be possible and Therefore the opposite movement will take place and this is referred to as a claw hand So the basis of the Zee movement and its opposite that is a claw hand are because of this extensor expansion So these are some of the points which I want to mention pertaining to the structures on the extensor aspect and the dorsal of the wrist Thank you very much for watching. Dr. Sanjay Sanyal signing out. Please like and subscribe if you have any questions or comments Please put them in the comment section below. Have a nice day