 So this is a quick demonstration of the distinction of the posterior compartment of the thigh, the so-called hamstring compartment. This is the lateral intermuscular septum, which is separating this compartment from the vastus lateralis. And these muscles that we see in front of us, these are the hamstring muscles. In this particular cadaver, these muscles were necrotic and they were already ruptured, so I had to tie them with a tape. This bone that we see here, this is the ischial tuberosity. And a common feature of all these hamstrings is that they take origin from the ischial tuberosity. We will see the insertions as we go along. Let's pick up this muscle on the lateral aspect. This is the long head of the biceps femoris. The next muscle that we see here, this one, this is the semi-tendinosis. And the third muscle that we see here, this is the semi-membrinosis. So the semi-tendinosis is superficial to the semi-membrinosis and they are like this. This is called tendinosis because it is like a tendon. And this is called semi-membrinosis because it is fleshy. So these are the three classical hamstring muscles and their common action is extension of the hip joint by virtue of origin to the ischial tuberosity. The semi-tendinosis is inserted in the pesanserinas along with the gracilis and the sartorius. So I have lifted up these three muscles. So sartorius, gracilis and semi-tendinosis. And the three common insertions is called the pesanserinas which is on the upper middle side of the tibia. This is my hand picking up the three insertions of the sartorius, gracilis and semi-tendinosis from another dissection. The goose boot appearance of the pesanserinas is clearly visible here. And between the insertions of the pesanserinas and the tibia there is a bursa and we can see this bursa here. This is the ancerine, remnant of the ancerine bursa. So this is about the insertion of this semi-tendinosis. Now let us take the insertion of the semi-membrinosis. The semi-membrinosis gets inserted on the upper middle aspect of the tibia and it gives expansion to the posterior capsule of the knee joint. It also gives the archivate and the oblique propitial ligament and it also reinforces the propitius fascia part of which can be seen here. This is the semi-membrinosis. There is a bursa between the semi-membrinosis and the gastrocnemius medial head and this is that bursa. We can see that bursa here. This is the semi-membrinosis bursa. Now let us take a few exceptions to the rule. Hamstrings are extensors of the hip joint and they are flexors of the knee. Though they cannot do both of them to the maximum extent together. But there are exceptions. Let us take the exceptions one by one. This muscle that I have picked up here. This is the short head of the biceps femoris and we can see it is not taking origin from the ischial tuberosity. It is taking origin from the linear asper of the femur. Therefore, this muscle though it unites with the rest of the biceps to form the biceps femoris tendon which gets inserted onto the head of the fibula. But this component of the muscle is incapable of extending the hip joint. So this is one exception. Let us take the next exception and for that I will reflect all these muscles and we see this muscle here. This is the hamstring component of the adductor magnus and we can see that it is also taking origin from the ischial tuberosity. The posterior component of the adductor magnus, anterior component is the adductor component. This though it is taking origin from the ischial tuberosity, its insertion is by means of this tendon that we see here to the adductor tubercle. So therefore, the hamstring component of the adductor magnus can extend the hip joint but it cannot flex the knee joint because it is a one joint muscle. In contrast to the other hamstrings which are two joint muscles, this does not cross the knee joint therefore it cannot cross the knee joint. So these are the two exceptions. Coming to the nerve supply, all the hamstring muscles are supplied by the tibial division of the sciatic nerve which I shall show you just now except the short end of the biceps which is supplied by the common fibula. So these are a few quick words about the hamstring muscles. Now let us take a look at the nerve supply. This nerve that I picked up here this is the sciatic nerve, the largest nerve in the human body and we can see that the sciatic nerve emerges from the gluteal region between the ischial tuberosity and the greater trochanter. It runs on the deep muscles of the gluteal region and it enters the thigh. It runs between the two heads of the biceps femoris, the long head and the short head and then it runs between the hamstrings and the hamstring component of the dr. Magnus. Ideally somewhere in the junction of the upper two-thirds and the lower one-third of the thigh it is supposed to divide into a tibial division and a common fibula. But in this case we see that it is dividing a little lower down in the paupitial fossa into the tibial division and common fibula which I shall describe when I come to the paupitial fossa. So this is about the sciatic nerve. We know that normally whenever there is a big nerve there has to be arteries and veins accompanying it. But in this case we do not see any artery accompanying the sciatic nerve. So how do these muscles receive their nourishment? For that I will draw your attention to what is known as the perforating arteries of the profunda femoris. And we know that the perforating arteries there are four of them. They perforate through the insertion of the adductor magnus at the linea aspera and they go from medial to latrine and they come to the posterior spate. So let us take a look at the four perforators. This is the first perforator which I have picked up here. This is the insertion of the adductor magnus to the linea aspera and we can see this is the first perforator. This is perforator number one and we know that the first perforator participates in the cruciate anastomosis and this is the branch which goes to the cruciate anastomosis. The rest of the perforator it supplies the hand string muscles. This is the second perforator. This is perforating again through the insertion of the adductor magnus at the linea aspera and we can see it is supplying the hand string muscles. The third perforator is this one here. This is the third perforator and I can turn it here to show you the third perforator. This is the third perforator and I have lifted it up here with my instrument. This is perforating through the insertion of the adductor magnus and finally this is the fourth perforator. This is the fourth perforator. It is also perforating through the adductor. This is the terminal perforator and this is the termination of the profunda femoris. These four perforators with their accompanying veins, these are the ones which supply all the muscles of the posterior compartment, all the hand string muscles. That brings me to the next important point. We see this is femoral vein which has become the perforatial vein. This is the femoral artery which has become the perforatial artery. They are emerging through an opening, a hiatus and my finger has gone through the hiatus. This hiatus is referred to as the adductor hiatus. This is an opening between the hamstring component of the adductor magnus and the adductor component of the adductor magnus. This opening in the insertion of the adductor magnus is called the adductor hiatus and this is the place where the femoral artery has become the perforatial artery. This is a location where the femoral artery can get occluded, compressed or entrapped and this is one of the sides of femoral artery entrapment. That brings me to the final point that is about an important clinical correlation. As I told you the common action of hamstring is extension of the hip and flexion of the knee. In Olympic hurdle jumpers when they are doing extreme sports they have to flex the hip to its maximum extent and extend the knee to its maximum extent and in both these situations there is tremendous traction exerted onto the hamstring muscle especially at its origin. In such situation it can rupture here and that is known as hamstring tendon rupture or if the person is an adolescent and the ischial tuberosity has not fused it can evulse the ischial tuberosity and that is known as abortion fracture. This is the next story of the pelvis of an adolescent to show abortion fracture of the epithesis of the ischial tuberosity. So this is one of the important clinical correlations pertaining to the hamstring muscles. So that's all now for the hamstring group of muscles. If you have any questions or comments please put them in the comment section below. Dr. Sanjay Sanyas, Sanyam. Thank you.