 So, this is a prone cadaver. This is the left side. The narration is from the left side. The camera person is also on the left side. So, this muscle that we see in the posterior aspect of the thigh is the hamstring muscles. Let's take a quick look at the general aspects of the hamstring muscles. In general, the hamstring muscles take origin from the ischial tuberosity and we can see that. And in general, again, the hamstring muscles, they get inserted either onto the head of the fibula or onto the upper aspect of the tibia. The hamstrings are two joint muscles. They cross the hip joint, they cross the knee joint. Because of this reason, the hamstrings, they act on the hip joint and the knee joint. They are extensors of the hip and they are flexors of the knee. However, they cannot do both of these actions to the fullest extent simultaneously. And you can try that yourself also. You'll find that you can extend your hip, but you cannot flex your knee to the fullest extent at the same time. The last general rule is that all the hamstrings are supplied by the tibial division of sciatic nerve. Having mentioned the general rules, let's mention the few exceptions. The first exception is this muscle that we see here. This is the shorted of the biceps, femoris. The shorted of the biceps, femoris takes origin from the linea aspera of the femur. Therefore, it does not cross the hip joint. Therefore, it is not a two joint muscle. Therefore, it cannot act on the hip joint. The other exception is this muscle here. This is the hamstring component of the dr. magnus. This does not cross the knee joint. It gets inserted onto the adductor tubercle of the femur. And therefore, it cannot act on the knee joint. It cannot flex the knee. So these are the two exceptions of the hamstring general rule. Now let's take the hamstring muscles one by one. This muscle that we see here, this is the biceps femoris. The biceps femoris has got two heads. The long head takes origin from the ischial tuberosity. And the short head, as I mentioned just now, it takes origin from the linea aspera. And the two heads then unite. And they found the biceps femoris. And the biceps femoris then gets inserted onto the head of the fibula. And as it gets inserted onto the head of the fibula, it is partially split like this by the fibular collateral ligament. And in this region, common fibular nerve winds behind and lateral to the head and the neck of the fibula. Then we have this muscle here. This is the semitendinosis. This also takes origin from the ischial tuberosity. And this runs on the medial aspect. It becomes a long, thin tendon. And it gets inserted onto the upper middle aspect of the tibia as the best ad serenus. I shall mention the details of the best ad serenus shortly. The next hamstring component is this one here. This is the semitendinosis. And we can see that the origin is membranous. It takes origin from the ischial tuberosity. It runs just below. And it's more fleshy than the semitendinosis. And this gets inserted onto the upper medial aspect of the tibia. This semitendinosis gives multiple expansions. One of them, it reinforces the capsule posteriorly of the knee joint. It forms the oblique and brittle ligament on the back of the knee. It also reinforces the perpendicular spacia. So that is about the semitendinosis. And at the point of insertion, there is a bursa between the semitendinosis and the medial head of the gastropamias. That is known as the semitendinosis bursa. And then we have this muscle here. This is the hamstring component of the adductor magnus. The adductor magnus is a dual muscle. The adductor component gets inserted onto the linear aspera. The hamstring component of it takes origin from the ischial tuberosity and the tendon goes down, which is known as the adductor tendon and gets inserted onto the adductor tubercle, which we cannot see in this dissection. So these are the hamstring muscles individually that we have mentioned. And I've already mentioned the action. They extend the hip joint and they flex the knee joint. Now let's take a look at the nerve. This is the sciatic nerve that we can see here. The sciatic nerve, after it comes out from the gluteal region, it runs in the hamstring compartment of the thigh between the main hamstring muscles and the adductor component of the adductor magnus. And we can see it is running here. And when I separate this, we can see the rest of the sciatic nerve is running here. And it continues down and then it goes into the popliteal fossa. Approximately at the junction between the upper two thirds and the lower one third of the thigh, it divides into a tibial division and a common fibular division. And we can see the division here. The tibial component of the sciatic nerve gives branches to all the hamstring muscles except the short head of the visus femoris, which receives branch from the common fibular nerve. Then I would like to draw your attention to what I had mentioned earlier, the so-called pesanserinas. The pesanserinas is a combined triple insertion of three muscles, one each from each of the compartments of the thigh. The first one I had already mentioned, the semitendinosis. The next muscle is this one here. This is the muscle of the medial compartment and this is the gracilis. The gracilis takes origin from the pubic bone and it runs on the medial compartment and it becomes a narrow tendon and this also unites as the pesanserinas along with the semitendinosis. And the third muscle is this one here. This is a muscle of the anterior compartment. It comes from the anterior spine and runs down and gets inserted onto the pesanserinas. This is the sartorius. So therefore the three muscles of the pesanserinas are the sartorius, the gracilis and the semitendinosis. And the three insertions, they form a goose foot-like insertion on the upper medial aspect of the tibia and that is referred to as the pesanserinas. And this pesanserinas insertion is a functional counterpart of this long aponeurotic band that we see here. This is the iliotibia tract, which gets inserted onto the anterolateral tubercle of Gerdi. The next structure which I would like to draw your attention to are these neurovascular structures. For that, I have separated the hamstring muscles, I have separated the visus femoris, the semimembranosus and we can see these neurovascular structures here. These are the perforators. What are the perforating arteries? The perforating arteries are the branches from the profundum femoris artery which runs on the anterior surface of the adductor magnus. The profundum femoris artery gives four perforating arteries and they are called perforating because they perforate through the adductor magnus near its insertion to the lineaspera and they come to the posterior aspect of the thigh and they supply all the structures in the posterior aspect of the thigh because the posterior aspect of the thigh does not have any separate blood supply of its own. So let's take a look at the perforators. This is the fourth perforator. The fourth perforator is the termination of the profundum femoris and this is very close to the adductor hiatus. The adductor hiatus is an opening between the adductor and the hamstring component of the adductor magnus through which the femoral vessels become the perforatial vessels. So the fourth perforator perforates very close to that and we can see it is ramifying on the posterior compartment. Then we have this perforator. This is the third perforator. Then we have this perforator. And this one, this is the first perforator. To repeat again, first perforator, second perforator, third perforator, and the fourth perforator. And we can see that they're extensively ramifying and they're anastomosing and it is also giving a communication which went outside the back of the thigh. The first perforator, which I showed just now, this first perforator, this participates in a cruciate anastomosis around the greater trochanter. Contributed by the branch of the inferior gluteal artery, the first perforator and the medial and the lateral circumflex femoral arteries which are also branches with the profound femoris. This cruciate anastomosis provides a collateral circulation in iliofemoral occlusion. At this juncture, let me mention an important clinical correlation pertaining to the hamstring muscles. This is seen in Olympic hurdlers. Olympic hurdlers, when they're jumping over the hurdles, they flex their hip to the extreme extent and simultaneously they extend their knee to the fullest extent to cross the hurdle. And if you look at the action and the position of the hip and the knee, it is exactly the opposite of the action of the hamstring. Hamstrings are supposed to extend the hip and flex the knee. While the Olympic hurdlers, they flex the hip and extend the knee. In such a situation, there is extreme tension exerted here where my finger is located. And in such situations, there may be rupture of the common hamstring tendon at its origin from the ischial tuberosity. If the hurdler is an adolescent, then the ischial tuberosity epithesis had not fused with the rest of the bone, and it can get evolved from the rest of the ischial tuberosity. That is known as abortion fracture of the ischial tuberosity, which also has same clinical significance. This is an x-ray, the right hip of an adolescent showing abortion fracture of the ischial tuberosity at its epithesis. So that is abortion fracture or rupture of the hamstring tendon at the ischial tuberosity, which is seen in hurdlers. And that carries a significant disability. These are the points which I wanted to mention to you about the posterior aspect of the thigh. That's all for now. Thank you very much for watching. Please like and subscribe. Dr. Sanjay Sanyal, Sunny out. If you have any questions or comments, please put them in the comment section below. Have a nice day.