 This is going to be a demonstration of the hamstring muscles, that's the first shape of part of the thigh and the neuro-muscular structures. So let's identify the hamstring muscles first. This muscle which I have picked up here, this is the biceps femoris. The biceps femoris has got two heads, one is the long head taking origin from the ischial tuberosity and there's a short head which is visible here, which is taking origin from the fever. And the two heads then unite and they form the common tendon which gets inserted out of the head of the fibula, where it is bifurcated by the fibular collateral ligament of the knee joint. So that's the first muscle of the hamstrings, on the lateral aspect. The next muscle that you see of the hamstrings is this one. This cadaver, the muscles were very frable and they were ruptured, so we have held them together. This is the semitendinosis. This also takes origin from the ischial tuberosity and there's a long tendon that's what's called semitendinosis which has brought a very unique insertion onto the upper medial aspect of the tibia. We have lifted it up here. It's a triple insertion of three tendons which is referred to as the pest and serenas and we have lifted up all the three tendons. From the posterior compartment we have the semitendinosis, then from the medial compartment we have the gracilis. This is the gracilis and from the anterior compartment we have the sartorias. So sartorias, gracilis and semitendinosis together are inserted in the pest and serenas on the upper medial aspect of the tibia. So that's about the semitendinosis. This is on the medial side of the posterior espionopathy. The next muscle that we have picked up here which is also quite frable is this one which is just slightly more medial to the semitendinosis and this is semi-membrinosis. We can see that the tendon of origin is slightly membranous and the muscle is more fleshy than the semitendinosis including its insertion. This also takes origin from the ischial diversity and the fibers that come down and they get inserted onto the upper medial aspect of the tibia where they reinforce the capsule of the knee joint posteriorly and they also contribute to the popliteus spacia among many other expansions. So this is the semi-membrinosis. The hamstrings constitute part of the boundaries of the popliteal fossil. Biceps constitutes a supralateral boundary, semi-membrinosis and semitendinosis constitutes the supramedial boundary. And finally last but not the least we have this muscle here. This is the hamstring component of the rector magnets which takes origin also from the ischial diversity. So this is a dual muscle, the rector component belongs to the medial compartment, the hamstring component belongs to the posterior compartment. Having identified the four muscles of the posterior group, the hamstring group, now let us mention something called the rules of hamstrings and the exceptions. So let's start with the origin. Rule, hamstrings take origin from the ischiative velocity except the short head of the biceps. The short head of the biceps takes origin from the posterior aspect of the femur. The insertion, the hamstrings get inserted onto the head of the femur or the upper medial aspect of the tibia except the adductor magnets, hamstring component which gets inserted onto the femur. Rule, hamstrings are two joint muscles. They act on the hip joint and they act on the knee joint. Exception, short head of the biceps, it acts on the knee joint. Another exception, adductor magnets, it does not act on the knee joint. So therefore these two components are one joint muscle. Rule, action, hamstrings collectively are extensors of the hip, flexors of the knee. However, they cannot do both actions to the fullest extent simultaneously. Exception, as we have already mentioned, short head of the biceps cannot extend because it takes origin from the posterior aspect of the femur and the adductor magnets cannot flex the knee because it does not cross the knee joint. Now, supply, rule, hamstrings are supplied by the tibial division of sciatic nerve. The tibial division of sciatic nerve is more obvious in the paupatial fossa. Exception, look, short head of the biceps is supplied by the common fibular division. This is the common fibular division that we can see in the paupatial fossa. So these are the rules and the exceptions of the hamstrings. Now let's go through some clinical correlation pertaining to the hamstring muscles. One notable clinical correlation is a motion fracture or rupture of the hamstring tendon from its origin at the ischial tuberosity. As I mentioned, the prime action of the hamstring is extension of the hip, flexion of the knee. In Olympic hurdle jumpers, at the time of jumping the hurdle, the leg has to be flexed at the hip joint and extended at the knee joint to clear the hurdles. So in that position, the hamstring muscles are put under tremendous traction and it can lead to rupture of the hamstring tendon here where my finger is located. That is one possibility. If it happens to be an adolescent, then the ischial tuberosity epiphysis has not fused with the rest of the bone, then it can also get evolved by the same mechanism. So that is rupture of the hamstring tendon or a motion fracture of the ischial tuberosity produced by extreme degree of flexion of the hip and extension of the knee. This is a plate X-ray of the hip joint to show a motion fracture of the epiphysis of the ischial tuberosity in an adolescent. This is one important clinical correlation pertaining to the hamstrings in the posterior glute. These are the points which I wanted to mention about the hamstrings. That is all for now. Thank you very much for watching. Dr. Sanjay Saria signing out. If you have any questions or comments, please put them in the comment section below. Have a nice day.