The structure indicated is the gluteus maximus.
The gluteus maximus muscle is one of the muscles of the gluteal region. The muscles in the gluteal region are divided into a superficial and deep group. There are four muscles of the superficial group:
- Gluteus maximus
- Gluteus medius
- Gluteus minimus
- Tensor fasciae latae
There are 5 muscles in the deep group:
- Gemellus superior
- Gemellus inferior
- Quadratus femoris
- Obturator internus
The gluteus maximus muscle is the largest of the gluteal muscles, and is also the largest muscle in the human body.
Origin: Posterior surface of ilium, posterior superior iliac crest, posterior surface of sacrum and coccyx
Insertion: Primarily to fascia lata at iliotibial tract. Upper posterior surface of femur at gluteal tuberosity.
Action: Hip extension, lateral (external) rotation, abduction (middle and upper fibres)
Innervation: Inferior gluteal nerve
Learn more about the anatomy of the gluteal muscles in this tutorial.