 Good day, ladies and gentlemen. Dr. Sanjay Sanyal here. Welcome to our next section. This time I'm going to demonstrate the structures which are crossing the dorsal aspect of the wrist joint through the extensor retinaculum. If you look carefully, you'll see a band of fibres going obliquely from the radial side to the ulnar side. And you can see the fibres here. This is the extensor retinaculum and my probe as my instrument has gone under that. It is the extensor retinaculum and you can see it has gone in. It starts from the radial side and goes all the way and circles the wrist and it comes back and it gets attached to the radial bone. And in the process, it divides the dorsal aspect of the wrist into six compartments. Let's see what are the structures which go through each of the compartment. By knowing the structures going through, we automatically come to know what are the muscles on the extensor aspect of the arm. So let's start with compartment number 1 on the radial most side. We can see these tendons here. Update your policies longest. Extensor policies grips. That's compartment number 1. Let's jump to compartment number 3. Extensor policies longest. Compartment number 2 is the extensor carbide radial is longest and previous. Compartment number 4. Can we see these tendons here? These are the extensor digitorum tendons. 1, 2, 3, 4. The extensor digitorum tendons and the extensor indices, they go through compartment number 4. Compartment number 5. Can we see this tendon here? Extensor digiti minimi. And compartment number 6, we can see a tendon here. This is the extensor carbide allaris. So these are the six compartments which go under the extensor retinacula. Now I need to show you a very important anatomical landmark which is also got a clinical significance and that is this structure here. This is called the anatomical snuff box. Let's take a look at the boundaries of the anatomical snuff box. It has got a lateral boundary which I mentioned earlier composed of the abductor policies longest and the extensor policies gravis. It has got a medial boundary, extensor policies longest. The floor of the anatomical snuff box is composed of four bones. Going from proximal to distal, proximally we have the radial styloid bones. If I dip my finger, in fact this is something which you can even feel in your own hand. If I dip my finger in, I feel a scapoid bone. Then I feel the trapezium. And if I distally I can feel this bone here, this is the base of the first metacarpal. So this is the depression. Why is this significant? Because passing through the floor of the anatomical snuff box is this important structure which I have lifted up here. This is the radial artery. Let's trace the radial artery from here. If you remember this was our radial artery. The radial artery, it comes here. This is where we feel the radial pulse and then it goes under this tendon. You can see it going under this tendon and it comes here. So the radial artery crosses the anatomical snuff box and we can see it clearly here is the radial artery. And after it passes from here, it gives rise to several major branches. It gives a branch to the thumb called the princeps policies. Then it gives a branch to the index finger called the radialis indices. And after that the same radial artery then pierces the first dorsal introsius muscle here. And it comes on the palmar side and it forms a deep palmar arch. So this is the course of the radial artery. And from there it supplies the metacarpal arteries. So this is the anatomical snuff box and normally it is covered by fascia and it is also crossed over by the superficial branch of the radial nerve. So these are the structures which are seen on the dorsal aspect and the anatomical snuff box. Thank you very much for watching ladies and gentlemen. Dr. Sanjay Sanyal signing out.