 Good day everybody, Dr. Sanjay Sanyal, Professor Department Chair. This is a demonstration of the deep muscles of the calf region. So this is the prone caravans, this is the left side. The direction is from the left side, the camera person is on the left side. So we have the gastrochemist in front of us and I'm reflecting the gastrochemist. And I have also made an initiation on the tendocalcaneus and I'm reflecting the soleus. And in so doing, we see the deep muscles of the calf. This muscle that we see here on the medial side, this is the flexor digitorum longus. The flexor digitorum longus takes origin from the posterior aspect of the tibia. Then we have this next muscle here, this is the tibialis posterior, this tendinous structure here and this muscle. And the third muscle that we see here is this one here, this is the flexor halosus longus. The flexor digitorum longus, tibialis posterior and the flexor halosus longus. These three tendons, they pass through this area here, this is referred to as the torso tunnel and then they go to the foot. The flexor digitorum longus, it gets inserted onto the tips of the lateral foretoes and therefore they are plantar flexors of the toes. The tibialis posterior is the most powerful plantar flexor among these three and it is also responsible for maintaining the transverse arch of the foot by means of it, intricate insertion in layer four of the sole of the foot. The flexor halosus longus is a flexor of the great toe. Now let's take a look at the neurovascular bundle. And we can see that the neurovascular bundle is coming from the pubidial region here and I put back the soleus in place and my finger has gone under this. This is referred to as the tendinous arch of soleus and I put my instrument under the tendinous arch and we can see it has come to the other side. The neurovascular structures, they pass from the pubidial region under the tendinous arch of soleus which is a fibrous arch extending from the back of the tibia to the fibula from which the soleus takes origin. And then it comes to the leg and this is one of the sites of entrapment of the pubidial artery under the tendinous arch of soleus. At the point of the tendinous arch of soleus, the pubidial artery divides into a posterior division which is seen here. This is the posterior tibial artery with its accompanying venecomitantes. This is the artery with its two venecomitantes and it also gives the anterior tibial artery which we cannot see which goes in front of the anterior intracereous membrane. This posterior tibial artery as it runs down, it runs between the soleus and the deep muscles of the calf. And we can see it is accompanied by the venecomitantes. And we can also see that these venecomitantes are receiving these communicating veins or these perforating veins which pierce the deep fascia and covering blood from the superficial to the deep. This is one perforating vein. We can see a remnant of another one and there are remnants of this one and there is yet one more. So these venecomitantes, they receive perforating veins which drain blood from superficial to deep. And these veins are the ones which are responsible for what is known as deep vein thrombosis. This artery then continues in the tarsal tunnel here and it then goes to the fork where it divides into a medial and a lateral plantar artery. This posterior tibial artery also gives a branch called the circumflex fibular which we cannot see because it is high up which winds around the neck of the fibular. Then it gives rise to this branch here. This is the fibular artery with its name venecomitante. This fibular artery runs on the lateral aspect of the back of the leg and it supplies the structure of the fibular. So that brings me to the branches of the posterior tibial artery and the fibular artery. Both of them have similar branches. Both of them give a nutrient artery each to the tibia and to the fibular. Both of them give a branch to the malleolus respectively to the medial malleolus and to the lateral malleolus. And both of them give calcaneal branches, medial side and lateral side. The fibular artery also establishes communication through the intrusions membrane with the anterior tibial artery. The next structure that we can see here is this nerve here. This nerve which continues from the pubricial fossa and this is the tibial nerve. It supplies all the muscles of the posterior compartment with both superficial and deep. And the tibial nerve also runs in the same neurovascular plane and it enters the tarsal tunnel. This tibial nerve can get entrapped in the tarsal tunnel which I am going to describe just now and can produce what is known as the tarsal tunnel syndrome. Now let's take a look at the structures in the tarsal tunnel. Before I go to the tarsal tunnel proper, I would like to draw your attention to something. As I mentioned in the beginning, on the top, this muscle, the medial most muscle is the flexor digiterum longus. After that is the tibialis posterior and after that is the flexor halosus longus. But as we go down, the tibialis posterior moves under the flexor digiterum longus and we can see that this tibialis posterior is going under. Therefore in the tarsal tunnel, the relationship is as follows. From anterior to posterior, we have this tendon here. This is the tibialis posterior. Then we have flexor digiterum longus. Then we have the posterior tibial artery and vein. Then we have the tibial nerve and then we have the flexor halosus longus. So therefore here we have a mnemonic. Tom, Dick, Bloody, Nervous, Harry from anterior to posterior. So what bridges the tarsal tunnel? The tarsal tunnel is bridged over by this tough facial structure which we have slit open. This is the flexor knuckle. It extends from the calcaneus to the medial malleolus and it forms a tunnel, osteopibrous tunnel under these structures pass from the back of the leg to the foot. And as I mentioned a little while back, the tibial nerve can get entrapped here in the condition known as tarsal tunnel syndrome. To complete the story about the deep muscles in the posterior aspect of the calf, let me mention the popridius muscle. This muscle that we see in front of us, this is the popridius muscle. The popridius forms part of the flow of the popridius muscle and the popridius muscle is covered by a fascia called the popridius fascia, which is a deep fascia and it is also reinforced by these white fibers that we can see here. This reinforcement is achieved by aponeurotic expansions from this muscle and this muscle is the semi-membranosis and we can see the semi-membranosis is reinforcing the popridius fascia. The popridius has got two origins. One origin is outside the knee joint from the lateral femoral condyle where my finger is located and this is the origin which separates lateral fibular collateral ligament from the knee capsule. The second origin is from inside the knee joint and that is from the lateral meniscus and this comes out through an opening in the posterior capsule of the knee joint and that opening is bridged over by a ligament called the arcuate popridial ligament and it is under the arcuate popridial ligament that the internal head of the popridius which comes from the lateral meniscus passes out. So therefore part of the popridius is inside the knee joint and these two origins then unite to form the main popridius and this is where my finger is located. The popridius muscle then descends down obliquely and medially and it gets inserted onto the back of the tibia as you can see here in this plane and it is inserted along this line here. This is called the solial line. So above the solial line is inserted the popridius and below the solial line at the solial line is the solius muscle which is this one. That brings me to the nerve supply of the popridius. The popridius is supplied by the tibial nerve and we can see the branch of the tibial nerve coming here. The classical textbook description is that the nerve goes across the popridius and then it enters the popridius from its deep aspect. However various research have shown that there are considerable variations of the nerve supply but all of them are branches of the tibial nerve which is here. Coming to the action of the popridius. The popridius acts only when the knee is fully extended. Now when the knee is fully extended either it can be either in contact with the ground when it is known as a weight bearing extension or it can be without contact with the ground when it is known as non-weight bearing extension. When it is in a non-weight bearing extension then the popridius when it contracts it rotates the tibia five degrees medially to unlock the knee. In contrast when it's weight bearing extension then obviously the tibia cannot rotate then it rotates the femur five degrees laterally to unlock the knee. So therefore by this action the popridius is responsible for unlocking the knee before flexion. The popridius also helps to lock the knee along with the cruciate ligaments. Additionally because it takes partial origin from the lateral meniscus when the knee is rotating it moves the lateral meniscus away and prevents it from getting injured. So therefore these are some of the important functions and actions of the popridius muscle. Finally when the popridius is taking origin from the lateral femoral condyle and as it descends down there is a bursa under the popridius between the popridius tendon and the posterior aspect of the tibia and that is referred to as the popridius bursa which is located deep inside and that bursa can communicate with the knee joint synovial capsule. So these are some of the points which I wanted to mention about the popridius muscle which is the deepest muscle of the posterior compartment of the leg. Before I close I need to mention something about the concept of calf pump. In order to understand the calf pump let's take a look at some superficial veins that we have observed here. This is the short syphilis vein along with its accompanying nerve that is the sural nerve and we can see that here. And on this side this is the long syphilis vein. So these are the two superficial veins of the leg which come from the medial and the lateral side of the foot respectively. The superficial venous system they give multiple perforating veins which pierce through the deep fascia and I mentioned it, showed it a little while back. These are the perforating veins and these perforating veins then open into the deep veins of the calf. The blood normally flows from superficial to deep and after that it goes up. How does the blood move up against gravity? It is by virtue of this osteofibrous compartment. There are tough transverse intermuscular septum separating the soleus muscle from the deep muscles and these muscles they contract within the tight osteofibrous compartment and when they contract they squeeze the blood up and that is the concept of the calf pump and the valves direct the blood upwards and not downwards. This calf pump is very important in moving the blood up and if this calf pump were to fail it will lead to stasis of blood here and can lead to deep vein thrombosis. So therefore deep vein thrombosis is predisposed by incompetence of the valves, number one, non-usage of the leg, weakness of the calf muscles and prolonged immobilization like for example long flights or invalidity when the patient is bedridden. In these situations deep vein thrombosis is a very major and real possibility and that can lead to pulmonary embolism and can lead to even to sudden death. Therefore after surgery it is mandatory to put the patient on low dose herbarin and mobilize the patient as quickly as possible. So that is the concept of the deep veins of the calf and the calf pump. So that's all for now. Thank you very much for watching. Dr. Sanjay Sanyal signing out. David who is the camera person. If you have any questions or comments please put them in the comment section below. Have a nice day.