 So, this is going to be a demonstration of the deep compartment on the posterior aspect of the leg. This is the prone cadaver, this is the right side, I am standing on the right side and the camera person is on the left side. To show the deep muscles, we will first reflect the gastrocnemius and that we have done. Now that we have reflected out the structures from the knee, posterior aspect of the knee is this muscle here covered by its fascia. This is the popliteus muscle. The popliteus muscle is an oblique muscle. It is situated above the solial line on the posterior aspect of the tibia and my finger is tracing along the solial line. Below the solial line is the attachment of the solius and above the solial line is the insertion of the popliteus. The popliteus muscle then goes up like this and the origin of the popliteus is from the lateral condyle of the femur and from the lateral meniscus of the knee. So from these two origins it gets inserted here and there is a bursa between the tendon of the popliteus and the posterior aspect of the condyle which communicates with the knee joint. The popliteus helps to lock and unlock the knee. It helps to rotate the tibia five degrees medially and it also helps to rotate the femur five degrees laterally depending on whether the tibia is weight bearing or non-weight bearing. It rotates the knee by five degrees only in the extended position. Apart from that the popliteus also forms the lower part of the floor of the popliteal fursus. The popliteus fascia gets reinforcement from insertion of this muscle. This is the semi-membrinosus. The semi-membrinosus muscle gives an expansion which reinforces the popliteus fascia. So these are some quick words about the popliteus. Then we will reflect the tendocalcaneus and the solius which also we have done and in so doing we see the deep muscles. However, we will be moving back and forth between the popliteus region and the deep. First let's identify the muscles that we can see in the deep compartment or the posterior aspect of the leg. So let's start off with the medial most muscle that we can see here. This muscle and I'm going to trace my finger all along from behind the tibia and go along down and I'm going down and we can see this. This is the flexor digitorum longus. Now let's come a little laterally. We see the next muscle here, this one where my finger is tracing and I'm going to trace my finger further down and we can see that lower down it becomes tendinous and this tendon then moves in front of the flexor digitorum longus and it comes in front. This muscle is the tibialis posterior and the third muscle that we see in the posterior aspect of the leg is this muscle which is arising from the lower end of the fibula and the interocious membrane and it's coming down and I'm tracing with my finger and this is that other muscle I've lifted up here with my finger. This is the flexor halusus longus. So therefore the three muscles that we can see the deep compartment are the flexor digitorum longus, tibialis posterior and flexor halusus longus. So from medial to lateral in the back of the leg it is DTH. However in the region of the ankle when the tendons are moving under the flexor retinaculum of the ankle the flexor digitorum longus tendon moves behind and the tibialis posterior tendon comes in front and we can see that here. So here the relationship becomes tibialis posterior, flexor digitorum longus and flexor halusus longus. Tibialis posterior is the second most powerful plantar flexor after the tendocalcanius and the flexor halusus longus flexes the great toe, flexor digitorum longus flexes the other toes. Now let's take a look at the neuro vascular bundle. This structure which I have lifted up here, this is the tibial nerve. To trace the tibial nerve let's come back to the pocretial fossa. This was the shatting nerve and the shatting nerve we can see in this particular case is dividing in the pocretial fossa into a common fibular here and the tibial nerve here. So this is the tibial nerve when I exert traction here we can see the tibial nerve is moving. The tibial nerve then runs under the tendinous arch of soleus and this is the tendinous arch of soleus where my finger has gone in and it has come out here. This is where the tibial nerve enters into the leg and it supplies all the muscles in the posterior compartment both superficial and deep. The next structure that we can see here is this neuro vascular bundle. This is the posterior tibial artery and it's accompanying venaecomitantes. The posterior tibial artery is the continuation of the pocretial artery and before I go to the pocretial fossa let me pick up the next structure here. This is the other component from the posterior tibial this is the fibular artery. So therefore again let's come back to the pocretial fossa. In the pocretial fossa we can see this is the pocretial artery which I have lifted up here and again I am going to put my hand inside this is the tendinous arch of soleus. And here the pocretial artery divides into what we cannot see here is that the anterior tibial which goes in front it goes in front of the intrusions membrane and the posterior tibial then divides into a common fibular artery and a posterior tibial artery and they are accompanied by their respective venaecomitantes. Both this common fibular and the posterior tibial they give three sets of branches one we can see this is the nutrient artery of the fibula here and this is the nutrient artery of the tibia here. Then they give respectively the lateral and medial malular branches and lateral and medial calcaneal branches. Apart from that we can see one more branch here running on the lateral aspect of the neck of the fibula. This is referred to as the circumfrix fibular artery which accompanies the common fibular nerve around the neck of the fibula. So these are the vascular structures that we can see in the posterior compartment. Now I shall tell you one mnemonic in the ankle under the fixer etniculum going from front to back the structures are tibial is posterior then we have fixer digitorum longus td the vascular structure tibial nerve and fixer halusus longus. So therefore the mnemonic is tom dick bloody nervous Harry these five structures run under the fixer etniculum between the calcaneus and the medial malindus and into the foot. We can see this multiple perforating vessels here and we can see the cut portions of them here and we can see them here also we can see multiple these are all the perforators which perforate from the superficial to the deep compartment the veins that brings me to some important functional and clinical correlations pertaining to the deep veins of the calf. These are under extremely low pressure and therefore they are assisted in their venous blood flow up by means of contraction of the calf muscles within the tight osteoficial compartment and this is referred to as the calf pump also referred to as the peripheral heart without this it would have been very difficult for the blood to move up because the blood in the venous system in the leg is extremely low pressure zero to two millimeters of mercury and it's to move up against gravity. So that brings me to the next concept if there's a failure of the calf pump there'll be pooling of blood also referred as venous stasis and that can lead to deep pain thrombosis and it can also lead to pulmonary embolism so these are two important clinical functional aspects that we need to remember. The next point is I just now refer to the nutrient artery of the fibula here we can use a segment of the fibula vascularized segment of the fibula for grafting to replace a lost portion of the bone of the tibia on the other leg so we cut here with the vascular supply and we anastomose to a vascular anastomosis and we grafted to the lost segment of tibia especially in compound fracture of the tibia so that is another important clinical surgical application of this. If there is a blood trauma to the back of the leg then these muscles as I mentioned are enclosed in a tight osteoficial compartment and they cannot expand outwards so therefore they swell and they push the vascular structures inside and they can lead to what is known as compartment syndrome in which case the treatment should be immediate fasciautomy to cut open the deep fascia the cruel fascia so as to allow the muscles to expand. I mentioned the tendinous arch of soleus and I'm going to put my finger again under the tendinous arch of soleus this is the tendinous arch of soleus where my finger has gone in and we can see the structures are coming from the pulmonary artery to the leg under the tendinous arch of soleus here and this is the potential site of entrapment of the pulmonary artery. That's all for now thank you very much for watching Dr. Sanjosh and you're signing out David over with the camera person if you have any questions or comments please put them in the comment section below have a nice day.