 of the gluteal region. This muscle that we can see here in front of us, we have already split it. This is the gluteus maximus. A quick word about its origin. It takes origin from the ilium behind the posterior gluteal line. Sacrum coccyx and the fibers then converge. It's a big muscle of the gluteal region, the largest muscle and the most superficial. And then the fibers after converging, they get two insertions. The superficial three fours of the fibers get inserted onto this tough structure that we can see here. This is the iliotibial tract. The iliotibial tract goes all the way down, crosses the knee joint and gets inserted onto the tibial in a tubercle called the anterolateral tubercle of journey. That is the superficial three fourths. The deeps can be seen once I reflect the gluteus maximus and I have reflected it now. And we can see the deeps are getting inserted here. And I'll put my finger and you can see it is stopping here. And this is onto the gluteal tuberosity on the back of the femur. So this is the insertion. The action of the gluteus maximus. It is an extension of the hip and it is a lateral rotator. But more important than that, this is a muscle which is responsible for standing up from a sitting position, sitting down from a standing position, climbing upstairs, climbing uphill. In fact, this works in both isometric contraction, isotonic concentric and isotonic eccentric contraction, especially when sitting and standing. So this is a very important action of the gluteus maximus. Nerve supply of the gluteus maximus. It is supplied by this nerve here that we can see in front of us and we can see the nerves on the inner surface of the gluteus, the fibres, the inferior gluteal nerve. This is the other cut end of the inferior gluteal nerve we can see here. This is the nerve supply of the gluteus maximus. If the gluteus maximus is paralyzed, the patient will not be able to extend and laterally rotate his hip. But more important, he will not be able to sit and stand and he will not be able to climb up. And there's a clinical condition called epiconus syndrome, which involves the S12 segment of the spinal cord where gluteus maximus is paralyzed. There are some verses in relation to the gluteus maximus and one of that we can see here. It is in relation to between the gluteus maximus and the greater trochanter. This is the greater trochanter lateral surface where my finger is located. This is known as the trochantering bursa. This is to prevent friction between this muscle and the greater trochanter. The other is remnant of that we can see here between the gluteus maximus and the ischial tuberosity and this is the ischial bursa. Normally when the person is standing, the gluteus maximus covers the ischial tuberosity. When the person sits down, it moves away and then the ischial tuberosity is directly in contact with the sitting surface and that's when this bursa prevents friction. And there's a third bursa between the iliotibial tract where my finger is located and a muscle on the thigh. You can see it here. The vastus lateralis. So that is called the gluteus femoral bursa. So these are the three bursa in relation to the gluteus maximus. Now let's reflect the gluteus maximus once more and let's see the next deep muscles, deep to the gluteus. This muscle that we see in front of us. This is the gluteus medius and we can see that the fibers are arising from the ilium again between the posterior and the anterior gluteal lines. Most of the fibers are coming down vertically and they get inserted onto the greater trochanter. In continuity, let us now reflect the gluteus medius. And once we reflect the gluteus medius, we can see yet another muscle in the depths of it. This is the gluteus minimus. This also takes origin from the ilium between the inferior and the anterior gluteal lines and here also the fibers are coming down vertically and they get also inserted onto the greater trochanter. So both gluteus medius and gluteus minimus, they have similar actions. Their action is to stabilize the pelvis. They are also abductors and medial rotators of the hip. And the nerve supply of the gluteus medius and minimus, we can see clearly here. Once I reflect the gluteus medius, we can see this nerve here. This is the superior gluteal nerve. The superior gluteal nerve emerges from the pelvis through the greater sciatic form and above the pyriformis. And we can clearly see it is supplying the deep surface of the gluteus medius. It is giving branches to the gluteus minimus and it will also give branches to the tensor facial area. That brings me to the next last muscle of the superficial group of the gluteal region. For that, let me put back the gluteus maximus again in its place. This is the tensor facial area which is the last muscle of the superficial group of the gluteal muscles. It takes origin from the outer surface of the iliac crest. It's a V-shaped muscle and the fibers then converge and they get inserted between the two leaves of this iliotibia tract. This nerve supply and action are the same as the gluteus medius and the gluteus minimus. This is also a site of intramuscular injection. There's a very important clinical correlation pertaining to the gluteus medius. If there's an injury to the superior gluteal nerve, like for example a stab injury to the buttock, then the gluteus medius is paralyzed. Of course, other muscles are also paralyzed, but the most important manifestation is because of this. As I told you, one of the job of the gluteus medius is to stabilize the pelvis, especially when we are standing on one leg. Gluteus medius of that leg prevents the pelvis from sagging down to the opposite side. If this muscle is paralyzed, then when the person is standing on the leg of the paralyzed side, the pelvis will sag down on the opposite side. And that condition is known as Frendlenberg sign. And because the leg will then drag on the ground, the person will develop one of the three gates, either a gluteal gate or a high stepping gate or an out swinging gate. So that's a very important clinical manifestation pertaining to injury or paralysis of the gluteus medius muscle and the superior gluteal nerve, L5S1. Thank you very much for watching. Dr. Sanjasan is signing out. If you have any questions or comments, please put them in the comment section below. Have a nice day.