大殿筋 （ だいでんきん、英： gluteus maximus muscle ）
The gluteus maximus is the main extensor muscle of the hip. It is the largest and outermost of the three gluteal muscles and makes up a large part of the shape and appearance of each side of the hips. Its thick fleshy mass, in a quadrilateral shape, forms the prominence of the buttocks. The other gluteal muscles are the medius and minimus, and sometimes informally these are collectively referred to as the "glutes".
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 hips and can not sustain standing erectly.
The muscle is made up of muscle fascicles lying parallel with one another, and collected together into larger bundles separated by fibrous septa.
【Structure】
The gluteus maximus is the outermost muscle of the buttocks. It arises from connections to nearby structures in this area. It arises from the posterior gluteal line of the inner upper ilium, a bone of the pelvis, as well as above it to the iliac crest and slightly below it; from the lower part of the sacrum and the side of the coccyx, the tailbone; 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;
The gluteus maximus ends in two main areas:
- those forming the upper 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 inserts into the iliotibial band of the fascia lata;
- the deeper fibers of the lower portion are inserted into the gluteal tuberosity of the linea aspera, between the vastus lateralis and adductor magnus. If present, the third trochanter also serves as an attachment.
【 語 句 】
・extensor muscle：伸筋 ・gluteal muscles：殿筋群 ・fleshy：多肉質の ・quadrilateral：四辺形の ・buttock：臀部 ・erect posture：直立姿勢 ・primates：霊長類 ・erectly：直立に ・muscle fascicle：筋束 ・fibrous septa：線維中隔 ・posterior gluteal line：後殿筋線 ・ilium：腸骨 ・pelvis：骨盤 ・iliac crest：腸骨稜 ・lamina：薄板 ・greater trochanter：大転子 ・iliotibial band：腸脛靭帯 ・fascia lata：大腿筋膜 ・gluteal tuberosity：殿筋粗面 ・linea aspera：骨粗線 ・vastus lateralis：外側広筋 ・adductor magnus：大内転筋
【Bursae】
Three bursae are usually found in relation with the deep surface of this muscle:
- One of these, of large size, separates it from the greater trochanter;
- a second, (often missing), is situated on the tuberosity of the ischium;
- a third is found between the tendon of the muscle and that of the vastus lateralis.
【Function】
The gluteus maximus straighten the leg at the hip; when the leg is flexed at the hip, the gluteus maximus extends it to bring the leg into a straight line with the body.
Taking its fixed point from below, it acts upon the pelvis, supporting it and the trunk upon the head of the femur; this is particularly obvious in standing on one leg.
Its most powerful action is to cause the body to regain the erect position after stooping, by drawing the pelvis backward, being assisted in this action by the biceps femoris (long head), semitendinosus, semimembranosus, and adductor magnus.
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.
The lower part of the muscle also acts as an adductor and external rotator of the limb. The upper fibers act as abductors of the hip joints.
【 語 句 】
・bursae：bursa（滑液包）の複数形 ・ischium：坐骨 ・head of the femur：大腿骨頭 ・stoop：前かがみになる ・biceps femoris：大腿二頭筋 ・semitendinosus：半腱様筋 ・semimembranosus：半膜様筋 ・tibia：脛骨 ・external rotator：外旋
