 Good day everybody. Welcome to a dissection of the deep muscles of the gluteal region. I'm Dr. Sanjay Sanyal, Professor and Department Chair of Anatomical Sciences. We are going to demonstrate the deep muscles of the gluteal region and in order to do that, we have reflected the gluteus maximus and this is the gluteus medius, which also we have reflected and this is the gluteus minimus. But let's focus on the deep muscles. The first muscle which comes to our notice is this muscle here, which has been lifted by my instrument. This is the piriformis muscle, a pear-shaped muscle. This muscle takes origin from anterior surface of the sacrum that is inside the pelvis and it emerges outside into the gluteal region through this space here. This is the greater sciatic foremen and in so doing it converts the greater sciatic foremen into a suprapiriformis compartment and an infrapiriformis compartment. Okay. After that the great the piriformis muscle gets inserted onto the tip of the greater trochanter. The piriformis muscle along with all the other deep group of muscles are responsible for lateral rotation of the femur. That is the lateral rotation of the hip joint. The nerve supply is what is known as the nerve to piriformis, which is S1 to anterior MI. The piriformis muscle can compress the sciatic nerve in the condition known as piriformis syndrome. The suprapiriformis compartment gives passage to the superior gluteal vessels and nerve and the infrapiriformis compartment gives rise to, among other things, the inferior gluteal vessels and nerves. Let's take the other deep muscles. In order to do that, let's retract all these structures here and when we do that, we see three small muscles which come to our view. This is the first muscle here, this one. The second one is this muscle. So this is the superior gemulus. This is the inferior gemulus and in between we see a small tendon and part of a muscle, a third muscle, which I have lifted up with my instrument. This is the operator internus. The superior gemulus takes attachment origin from the ischial spine and the inferior gemulus takes attachment from the ischial tuberosity and both of them get inserted onto the tendon of the operator internus. What about the operator internus itself? The operator internus, the muscle which I have lifted up here, a little bit of the muscle is visible here and the tendon is visible here. The operator internus tendon gets inserted onto the trochanteric fossa. Where does the operator internus take origin from? This also takes origin from inside the pelvis, from the margins of the operator foramen and the operator membrane. And when it comes out through the lesser sciatic foramen, it makes a 90-degree bend and there is a persa between the operator internus tendon and the ischial spine which is located where my probe is pointing. So these three muscles together constitute what is known as the triceps coccy. The superior gemulus and the operator internus are supplied by the nerve to the operator internus. The inferior gemulus and the fourth muscle of the deep group, namely the quadratus femoris, are supplied by the nerve to the quadratus femoris. All of them are L5S1 and that brings me to the last muscle of the deep group and that is this muscle here. This is a quadrangular-shaped muscle, hence the name quadratus femoris. It takes origin from the ischial tuberosity here and it gets inserted onto a tubercle on the posterior surface of the femur, the trichocentric crest of the femur, which is called the quadrate tubercle and this is the quadratus femoris. Before I conclude, I wanted to bring to your notice one important point. These deep group of muscles, except the piriformis, namely the superior gemulus, operator internus, inferior gemulus and the quadratus femoris, they provide the bed on which the sciatic nerve runs, on the posterior surface of the gluteal region between the greater trichocenter and the ischial tuberosity. And finally, this tough ligament that you see here, this is the sacro tuberous ligament. This is the sacro tuberous ligament, which is arising from the ischial tuberosity and it as you do the sacrum, that's why it is called the sacro tuberous ligament. Thank you very much for watching, ladies and gentlemen. Dr. Sanjay Sanyal signing out. Have a nice day. If you have any questions or comments, put them in the comment section below. Guys, make sure you give this video a big thumbs up and click on the subscribe button.