Gluteus maximus muscle/عضلة ألوية كبرى/臀大肌(Tún dà jī)

The gluteus maximus (also known as glutæus maximus or, collectively with the gluteus medius and minimus, the glutes) is the largest and most superficial of the three gluteal muscles. It makes up a large portion of the shape and appearance of the buttocks.

It is a broad and thick fleshy mass of a quadrilateral shape, and forms the prominence of the nates.

Its large size is one of the most characteristic features of the muscular system in humans,connected as it is with the power of maintaining the trunk in the erect posture. Other primates have much flatter buttocks.

The muscle is remarkably coarse in structure, being made up of fasciculi lying parallel with one another and collected together into large bundles separated by fibrous septa.

Origin and insertion

Muscles of the gluteal and posterior femoral regions, showing origin and insertion of gluteus maximus muscle.

It arises from the posterior gluteal line of the inner upper ilium, and the rough portion of bone including the crest, immediately above and behind it; from the posterior surface of the lower part of the sacrum and the side of the coccyx; from the aponeurosis of the erector spinae (lumbodorsal fascia), the sacrotuberous ligament, and the fascia covering the gluteus medius (gluteal aponeurosis).

The fibers are directed obliquely downward and lateralward;

those forming the lower and larger portion of the muscle, together with the superficial fibers of the lower portion, end in a thick tendinous lamina, which passes across the greater trochanter, and is inserted into the iliotibial band of the fascia lata;

the deeper fibers of the lower portion of the muscle are inserted into the gluteal tuberosity between the vastus lateralis and adductor magnus.

Bursae

Three bursae are usually found in relation with the deep surface of this muscle:

One of these, of large size, and generally multilocular, separates it from the greater trochanter;

a second, often wanting, is situated on the tuberosity of the ischium;

a third is found between the tendon of the muscle and that of the vastus lateralis.

Actions

When the gluteus maximus takes its fixed point from the pelvis, it extends the femur and brings the bent thigh into a line with the body.

Deep-Gluteal-Buttock-Stretch-

Taking its fixed point from below, it acts upon the pelvis, supporting it and the trunk upon the head of the femur; this is especially obvious in standing on one leg.

Gluteal-Buttock-Stretch-Lying-

Its most powerful action is to cause the body to regain the erect position after stoping, by drawing the pelvis backward, being assisted in this action by the biceps femoris, semitendinosus, semimembranosus, and adductor magnus.

Lateral-Hip-Stretch-WEB

The gluteus maximus is a tensor of the fascia lata, and by its connection with the iliotibial band steadies the femur on the articular surfaces of the tibia during standing, when the extensor muscles are relaxed.