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The ischial tuberosity (or tuberosity of the ischium, tuber ischiadicum), also known informally as the sitz bone, or as a pair the sitting bones) is a large swelling posteriorly on the superior ramus of the ischium. It marks the lateral boundary of the pelvic outlet. When sitting, the weight is frequently placed upon the ischial tuberosity.〔Goossens (2005), pp 895–982〕 The gluteus maximus provides cover in the upright posture, but leaves it free in the seated position.〔Platzer (2004), p 236〕 ==Divisions== The tuberosity is divided into two portions: a lower, rough, somewhat triangular part, and an upper, smooth, quadrilateral portion. * The ''lower portion'' is subdivided by a prominent longitudinal ridge, passing from base to apex, into two parts: * * The outer gives attachment to the adductor magnus * * The inner to the sacrotuberous ligament * The ''upper portion'' is subdivided into two areas by an oblique ridge, which runs downward and outward: * * From the upper and outer area the semimembranosus arises * * From the lower and inner, the long head of the biceps femoris and the semitendinosus 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ischial tuberosity」の詳細全文を読む スポンサード リンク
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