 Good day everybody. Dr. Sanjay Asanyal, Provost's Department Chair. This is going to be a demonstration of the sciatic nerve and all its branches right out of the foot. This is the prone cadaver, this is the right side of the cadaver. I'm standing on the right side, camera person is on the right side. So we have to sit out of the gluteal region, the back of the thigh, the perpendicular fossa, back of the leg, right up the ankle. So let's take a look. The sciatic nerve emerges from under the piriformis, and this is the piriformis muscle. Through the infrapiriformis compartment of the greater sciatic foramen. It is formed by two parts, the pre-axial or the tibial and the post-axial or the common fibular, and they unite to form the sciatic nerve, and that is L45S123. In the pelvis it is also united by the posterior femoral cutaneous nerve, which at the opening of the greater sciatic foramen it separates off and it supplies the skin of the back of the thigh and also the skin of the gluteal region. The rest of the sciatic nerve then descends down on the back of the gluteal region on this bed of muscles. Formed respectively by this muscle superior gemulus, this muscle internus, this muscle inferior gemulus and this muscle the quadratus femoris. In this location it is midway between the ischial tuberosity and the greater trochanter. People who are habitual joggers, the sciatic nerve can rub against the ischial tuberosity and produce jogger sciatica. The nerve can get entrapped under the piriformis. In 12% of the cases, one of the divisions can go through the piriformis and in a small percentage it can even come above the piriformis. Any of these situations can compress the sciatic nerve and can produce piriformis syndrome. When the sciatic nerve descends down, it runs in this neurovascular plane. Pustially we have the hamstring muscles and anteriorly we have the adductor component of the adductor magnus and the sciatic nerve runs here and we can see it is giving branches to the hamstring muscles. The tibial division of the sciatic nerve supplies all the hamstring muscles except the short head of the biceps, which recedes from the common fibular division of the sciatic nerve. And we can see somewhere in the back of the thigh, usually at the junction of the upper two thirds and the lower one third, it divides into its two components. The medial one, the tibial component and the lateral one, known as the common fibular component. Now we are going further down and we shall see the course in the paupitial fossa. This is the common fibular component. The common fibular nerve runs infralaterally under cover of the biceps femoris and here it is running like this and it then goes behind the head of the fibula, then it goes lateral to the neck of the fibula and it goes to the leg and supplies the anterior and the lateral compartment. When the common fibular nerve is running behind the head of the fibula and around the neck of the fibula, it is liable to injury in fracture of the neck of the fibula. And if such a thing happens, the patient will lose the ability to dorsiflex his foot and will lead to foot drop, which is a very serious disability. Electronic devices are available for foot drop. Neck is a functional electrical stimulator which is used in foot drop. That is the course of the common fibular nerve. The tibial nerve goes vertically down. It starts from one apex of the paupitial fossa and disappears through the other apex of the paupitial fossa. This is, superior apex is formed by the bicep femoris and the hamstring muscles and the infi apex is formed by the two heads of the gastrocnemius. And we can see the tibial division is the one which is giving numerous branches to the, all the muscles of the leg. I will draw your attention to an important and a very interesting formation of a cutaneous nerve on the back of the leg. So as I mentioned, this is the common fibular nerve and we can see this branch here. This is the main nerve which is going to the leg and this is the branch. This is called the lateral sural cutaneous nerve, which supplies the skin of the posterior lateral aspect of the upper part of the leg. This is a branch coming from the tibial nerve. This is called the medial sural cutaneous nerve. And this is called the sural communicating nerve which also comes from the common fibular. And we can see that they are uniting to form this nerve here. This is called the sural nerve. And this sural nerve supplies the skin of the posterior one-third of the leg. And it is accompanied by this vein here. This is the short subvenous vein which drains the soul and comes on the lateral aspect of the soul and forms a short subvenous vein. And it opens into the popliteal vein by piercing the popliteal fascia and we can see that here. The clinical significance of this is the sural nerve is used for nerve grafting. For example, to replace a lost portion of the facial nerve after pirated surgery. The sural nerve can be sacrificed without any significant disability because it's a cutaneous nerve. And it can be used to replace an important motor nerve like for example the facial nerve. How do we recognize the location of the sural nerve? During surgery we use the short subvenous vein as our landmark. And we know that just located adjacent to that is the sural nerve. So this is an important relationship which I wanted to show to you. Now let's continue with the continuation of the tibial nerve which we can see here. We can see the tibial nerve is disappearing here. And to show the course further we will separate the two halves of the gastrocnemius. And we can see the tibial nerve is accompanied by the popliteal artery and the popliteal vein. And they are disappearing in a passage where my finger is gone in. This place is called the tendinous arch of soleus. And I will show you the tendinous arch of soleus in another view. This is gastrocnemius muscle here. Which are all supplied by branches of the tibial nerve and we can see that here. We have cut the gastrocnemius two heads here. This is the tendocalcaneus which also we have cut. And I have lifted up this is the soleus muscle. And when I look underneath we can see that this is the tibial nerve running between the soleus muscle and the deep posterior muscles of the calf. I am going to put my finger here and I will show it to you. My finger comes here. So this is the tendinous arch of soleus. This is the place where the tibial nerve, the popliteal artery and the vein come from the thigh, from the popliteal fossa into the leg. This tendinous arch of soleus is formed by a fibrous arch bridging from the posterior to the tibial to the fibula to which the soleus muscle is attached. And in this place the popliteal artery can get entrapped. This tibial nerve then runs down and it supplies all the muscles of the back of the leg and then it goes through a tunnel on the medial side of the ankle called the tarsal tunnel under the flexor retiniculum. In the tarsal tunnel it can get entrapped in the condition known as tarsal tunnel syndrome. And then it goes to the foot and divides into a medial and lateral planter nerve. So this is the full course of the tibial nerve and it supplies all the structures right up to the sole of the foot. So that's all that I wanted to show you right 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.