Posterior Compartment of the Thigh

00:01 Now let's have a look at these muscles in a bit more detail.

00:03 So let's have a look at the posterior thigh muscles.

00:07 Here we can see a number of muscles that form in this location.

00:10 We have semimembranosus, and we have a similarly named muscle known as semitendinosis.

00:16 The difference between these two apart from their positioning is that the semitendinosis has a very thick tendon that actually starts quite more proximately than semimembranosus, which has a slightly flatter muscle helpings, give them their two names.

00:30 So running on the medial aspect, we have semimembranosus, semi tendinosis, and then running more on the lateral aspect, we have biceps femoris.

00:39 As its name implies, like biceps brachii, it has two heads.

00:43 Let's have a look at semibranosus, the origin and insertion of semimembranosus.

00:49 The origin is it comes down from the ischial tuberosity and it goes and attaches to the posterior surface of the medial tibial condyle.

00:58 So we see it runs distally down towards the leg.

01:02 Semi tendinosis, this also comes from the ischial tuberosity.

01:05 It lies more superficial than semimembranosus.

01:08 But it also goes and attaches to the tibia.

01:11 This time is attaching to the medial surface of the proximal tibia.

01:16 So it's attaching just medial to the tibial tuberosity.

01:21 Biceps femoris is the more laterally positioned muscle in the posterior thigh.

01:25 And here we can see it's long head, remember biceps means it has two head, its long head is coming from the ischial tuberosity.

01:33 It also has a shorter head and this is coming from the linear aspera.

01:37 Remember that line on the posterior aspect of the femur.

01:41 So the two heads, long head, short head, coming from the ischial of tuberosity and the linea aspera respectively.

01:48 And then passes down and attaches to the head of the fibular.

01:53 These muscles are supplied by the sciatic nerve, but primarily they also have an important function in movement of the knee.

02:02 So here we can see the position of the hamstring muscles is sitting very much posterior to the femur.

02:09 Now what this means is, as it runs posterior to the femur, it runs posterior to the knee joint.

02:15 And as it actually runs posterior to the knee joint, it is going to flex the knee as it moves the knee backwards.

02:22 So here we see flexion of the knee joint as the hamstring muscles cross the knee joint and attach to the neck.

02:28 So that's going to flex the knee.

02:30 As they also cross the hip joint as they're attaching to the ischial tuberosity, contraction of these muscles will also lead to extension of the hip joint.

02:40 So the hamstrings are important in flexing the knee and also extending the hip joint.

02:46 If we have a look at the neurovasculature of the posterior thigh, here we can remove biceps to see clearly sciatic nerve and we can see a number of various perforating arteries that are coming from the deep femoral artery and these are running down and how many to supply the deep substance of these muscles.