 So just to bring up to speed, this is the flexor retinogulum that we see in front of us. And I have retracted the superficial palmar arch which came from the ulnar artery here to show you the flexor retinogulum in more detail. And we can see immediately it is attached to the PC-Pompon and to the hook of Hammett. Laterally it is attached to the tubicle of the scaphoid and the tubicle of the trapezium. And this flexor retinogulum bridges over the carpal tunnel. We have already split open the flexor retinogulum and we can see the cut margin here. We can see the cut margin is very thick. Flexor retinogulum is a very tough structure and once we split it open, we see the carpal tunnel with the contents passing through the carpal tunnel. So what are the contents of the carpal tunnel? We have these four tendons. These are the tendons of the flexor digital superficialis which I have eviscerated out of the carpal tunnel. And under that, we have these four tendons of the flexor digital profundus which also we have eviscerated out. Apart from these eight tendons, we also have this tendon. This is the flexor policies longest tendon. So these are the nine tendons of the carpal tunnel. Last but definitely not the least, the most important content of the carpal tunnel is the median nerve. This is the median nerve. This median nerve is the one which is responsible for the carpal tunnel syndrome that we hear about. This median nerve can get compressed in the carpal tunnel because the carpal tunnel is already over crowded with nine tendons with their sandalware sheets. And compression of the median nerve is how the carpal tunnel produces the carpal tunnel syndrome. So let's mention a few quick words about these tendons. If we were to pick up these four tendons of the flexor digital superficialis and we trace them, we find that this is the tendon which is going to the little finger. This is the tendon going to the ring finger, this to the middle finger and this to the index finger. And under that, we have this flexor digital profundus which are also going to the same four fingers. We will trace the tendons right up to the digits and we can see them here. We find that the tendons first run in a fibrous flexor sheath which we have split open. And if you look closely, we see that the superficialis tendon splits into two parts. And through the split portion, the profundus tendon is passing. Same thing we will see in this finger also. We can see the superficialis tendon has split into two parts and through the split portion, the profundus is passing. The same thing is seen here also and the same thing is seen here also. The superficialis tendon gets inserted onto the fetal phalanx and the profundus tendon gets inserted onto the tip of the fetal phalanx. So, therefore, the superficialis is responsible for flexing the proximal interphalangio joint. The profundus tendon is responsible for flexing the distal interphalangio joint. All of them are enclosed in the synavir sheath. The synavir sheath of the little finger is continuous with the synavir sheath of all these combined eight tendons while the synavir sheath of the ring, middle and the index finger stop here. This is referred to as the ulnar person. If a person gets an infected thorn prick in the little finger, the infection can spread all the way up to here and can involve this portion of the person. And that infection is referred to as suppurative tino-sinovitis. Of course, the same thing can happen to these other fingers also, but the infection will stop here because these do not communicate with the ulnar person. Now, let's take a look at this flexor-polisis-longus tendon. This is the flexor-polisis-longus tendon, which is also a content of the carpard tunnel. This flexor-polisis-longus tendon has got its own synavir sheath. And this synavir sheath is referred to as the radial person. And infection of the thumb of the synavir sheath will produce radial suppurative tino-sinovitis. When these superficialis and the profundus tendons are passing through to the digits, they pass through a fibrous flexor sheath, which we have straight open here. And that fibrous flexor sheath can sometimes become very tight. And in which case, they can compress and prevent free movement of the tendon here, even though the tendons are enclosed in the synavir sheath. In such a situation, the person, if he flexes his finger, after that he has difficulty extending his finger. That's because the fibrous flexor sheath has gripped the tendons tightly and it's preventing full release of the tendon. And that condition is referred to as trigger finger. Now, let's take a look at these muscles that we can see here in this dissection. We can see one muscle small, worm-like, thin muscle going to the radial side. Second one going to the radial side. Then we have a third muscle here and we have a fourth muscle here. These are the lumbrical muscles. The lateral two lumbricals, they arise from the profundus tendon to the second and the third digit. And they are unipenated and they get inserted onto the radial side of the dorsal extensor expansion. The medial two lumbricals are bipenated. They get inserted onto the dorsal expansion of the ring and the little finger respectively. The function of the lumbricals is to perform the Z movement, namely flexion of the metacarpophalogen joint and extension of the IP joints. The lateral two lumbricals are supplied by the same nerve which supplies the lateral half of the profundus, namely the medial nerve. The medial two lumbricals are supplied by the same nerve which supplies the medial half of the profundus, that is the ulnar nerve. This is the ulnar nerve which I have lifted up here, accompanied by the ulnar artery. It is passing through a canal here. This is referred to as the guion canal. And the ulnar nerve can get compressed in the guion canal or it can also be injured in fracture of the hook of hamate here. Or it can be injured in a condition known as handle bar neuropathy. Ulnar nerve gives a communicating branch to the medial nerve. It gives a superficial branch, which we can see going to this little finger and the medial part of the ring finger. And it gives a deep branch which supplies all the intrinsic muscles of the hand, except the lateral two lumbricals. Injury to the ulnar nerve here will produce paralysis of the hypothera muscles and it will also produce paralysis of the medial two lumbricals. And the person will get what is known as ulnar claw hand. Now let us come to the medial nerve, which I mentioned to you in the beginning. This is the medial nerve. The medial nerve, it passes through the copper tunnel and we can see it is giving rise to these branches in the palm. It is giving a branch to the radial side of the ring finger. It is giving a branch to the entire middle finger. It is giving a branch to the entire index finger. It's giving a branch to the thumb. These are all the branches of the medial nerve and I have picked up the whole stem of the medial nerve here. Additionally, we can see this is a communicating branch from the medial nerve to the ulnar nerve. And finally, we can also see this branch of the medial nerve. This is called the recurrent branch of the medial nerve which supplies the three nerve muscles. This is a very superficial branch and this can be injured if a person gets a superficial laceration of the palm here. If a person falls on his palm and it strikes a sharp object. In which case, the person can get paralysis of the three nerve muscles if this nerve is injured. This medial nerve is the main culprit which is compressed in the copper tunnel syndrome. In which case, the person will have tingling, numbness and peristhesia of this half of the ring finger, middle finger, index finger and the thumb. Additionally, the person will have weakness of the three nerve muscles and weakness of the lateral two lubricants because they are also supplied by the medial nerve. In this connection, I need to mention that the branch of the medial nerve which supplies the Palmer skin, the lateral three force of the Palmer skin does not arise from the copper tunnel. It arises from a branch of the medial nerve which goes above the copper tunnel. So therefore, in copper tunnel syndrome, the Palmer skin is spared. So this is the important clinical significance of the medial nerve. That brings me to the point which I had started with in the dissection when we made an incision of the flexor retinaculum to relieve a pressure of the copper tunnel. This incision that I made is the exact incision that is done in surgical practice. Earlier days, we used to do it by means of an open surgery. Nowadays, this incision in copper tunnel syndrome is done by means of an endoscope. In either situation, if you notice, I have made the incision slightly towards the ulnar side. The purpose of doing this incision is to safeguard three structures. Number one, we have to safeguard the recurrent branch of the medial nerve. Otherwise, if we got this, then we can produce paralysis of the theramoses. The second structure to be safeguarded is this, the communication between the ulnar nerve and the medial nerve. And the third structure to be safeguarded is this one, which is the superficial Palmer arch which is coming from the ulnar arch. So these are the three structures that we need to safeguard when we are doing a release of the copper tunnel in copper tunnel syndrome by cutting open the flexor retinaculum. Now, what I have done, I have lifted up the superficialis and the profundus tendons. And my finger has got under all of these tendons and you can see my finger here. This space where my finger is located now, this is called mid Palmer space. This mid Palmer space is a space under the profundus tendons. Just to bring you up to speed, covering all of this was the Palmer aponeurosis. We have removed that. Just under the Palmer aponeurosis was the superficial Palmer arch which we have reflected to one side. These long tendons, they are in the central compartment with the corresponding numericals. And under that, this space where my finger now is located, this is called the mid Palmer space. If a patient sustains an infection of the mid Palmer space and you can see it is quite a big space, the infection can track down. It can track through the copper tunnel, as you can see here. And it can come into this space on the flexor aspect of the wrist. This is called the space of Parona. So therefore, the space of Parona is bounded by, anteriorly by the flexor, digital profundus tendon muscles. Postially, it is bounded by this muscle here, which is called the pronated quadratus. Medially, it is bounded by the attachment of the anti-brickle fasciate. And laterally, it is attached the anti-brickle fasciate radius. And approximately, it is bounded by the attachment of the flexors of the palm to the radius. So this whole thing is called the space of Parona, which communicates with the mid Palmer space. Additionally, we have another space in the palm, and that also we can see here. These are the thinner muscles, as I mentioned. This is in the compartment called the thinner compartment. And this is the adductor policies muscle, which is in a separate compartment called the adductor compartment. Between the thinner muscles and the adductor compartment, this space that we see here, this is called the thinner space. So this is also a potential space of infection. And these are the two spaces that we can see in the palm. And finally, to conclude, we have hypothenol compartment, the thinner compartment, adductor compartment, central compartment, and dorsal to the mid Palmer space, we have the interosseous compartment. So these are the various compartments, each of which contain the various muscles. So these are the structures, which I wanted to show you in the dissection, deep dissection of the hand. That's all for now. Thank you very much for watching Dr. Sanjay Sanyal. Sanyal, please like and subscribe. If you have any questions or comments, please put them in the comment section below. Have a nice day.