Tuberosity of the ischium

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Bone: Tuberosity of the ischium
Capsule of hip-joint (distended). Posterior aspect. (Tuberosity of ischium visible at bottom left.)
The superficial branches of the internal pudendal artery. (Tuber. ischial. visible at center left.)
Latin	tuber ischiadicum
Gray's	subject #57 235

Posteriorly, the superior ramus of the ischium forms a large swelling, the tuberosity of the ischium (or ischial tuberosity, also known as the sitz bone^[1], or as a pair the sitting bones).

It marks the lateral boundary of the pelvic outlet.

When sitting, the weight is frequently placed upon the ischial tuberosity.^[2] The gluteus maximus covers it in the upright posture, but leaves it free in the seated position.^[3]

Contents 1 Divisions 2 See also 3 Additional images 4 Notes 5 References 6 External links

[edit] 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.

[edit] See also

• Sitting disability

[edit] Additional images

Muscles of the gluteal and posterior femoral regions, with tuberosity of the ischium highlighted in red.	Right hip bone. External surface.	Right hip bone. Internal surface.	Plan of ossification of the hip bone.
Diameters of inferior aperture of lesser pelvis (female).	Right hip-joint from the front.	The Obturator externus.

[edit] Notes

[edit] References

• Goossens R, Teeuw R, Snijders C (2005). "Sensitivity for pressure difference on the ischial tuberosity". Ergonomics 48 (7): 895–902. doi:10.1080/00140130500123647. PMID 16076744. 
• Platzer, Werner (2004). Color Atlas of Human Anatomy, Vol. 1: Locomotor System (5th ed.). Thieme. ISBN 3-13-533305-1. 

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.

[edit] External links

• SUNY Labs 41:st-0204 - "The Female Perineum: Bones"
• SUNY Labs 17:os-0114 - "Major Joints of the Lower Extremity: Hip bone (lateral view)"
• pelvis at The Anatomy Lesson by Wesley Norman (Georgetown University) (pelvisposterior, pelvislateral, pelvisinside)

v • d • e Bones of pelvis / pelvic cavity (TA A02.5.01-03, GA 2.231-241) General sacrum · coccyx · hip bone Ilium body arcuate line wing gluteal lines (posterior, anterior, inferior) iliac spines (anterior superior, anterior inferior, posterior superior, posterior inferior) other: crest · tuberosity · tubercle · fossa Ischium body ischial spine · lesser sciatic notch superior ramus tuberosity of the ischium inferior ramus no substructures Pubis body pubic crest superior ramus pubic tubercle · obturator crest inferior ramus pectineal line Compound acetabulum (acetabular notch) · iliopubic eminence / iliopectineal line · linea terminalis · ischiopubic ramus / pubic arch obturator foramen · greater sciatic foramen / greater sciatic notch · lesser sciatic foramen lesser pelvis (pelvic inlet, pelvic brim, pelvic outlet) · greater pelvis

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