Medical Gross Anatomy
Anatomy Tables - Bones of the Pelvis and Perineum
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Medical Gross Anatomy |
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| Bone | Structure | Description | Notes |
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| os coxae | one of three bones that form the pelvis | paired; the os coxae forms the lateral part of the pelvis; it is formed by three fused bones: ischium, ilium & pubis; also known as the innominate bone | |
| acetabulum | a cup-shaped depression in the lateral surface of the os coxae bone | acetabulum means vinegar cup; it is the socket for the head of the femur; it is formed by the: ilium (1/5), ischium (2/5) and pubis (2/5); the acetabular fossa lies in the floor of the acetabulum | |
| acetabular notch | a notch in the inferior margin of the acetabulum | it is spanned by the transverse acetabular ligament; the acetabular br. of the obturator a. enters the hip joint by passing through the acetabular notch | |
| acetabular fossa | a roughened depression in the center of the acetabulum | the ligament of the head of the femur occupies the acetabular fossa | |
| lunate surface of the acetabulum | the smooth articular surface of the acetabulum | the lunate surface surrounds the acetabular fossa and the acetabular notch | |
| obturator foramen | a large foramen formed by the pubic and ischial rami | obturator means to occlude or stop up, a reference to the fact that the obturator membrane closes the obturator foramen almost completely; a site of attachment for the obturator externus m. and the obturator internus m. | |
| pubis | an angulated bone the forms the anterior part of the pelvis | one of three bones that form the os coxae: ilium, ischium, pubis; its body forms 1/5 of the acetabulum; its symphyseal surface unites with the pubis of the opposite side to form the pubic symphysis; the superior and inferior pubic rami participate in the formation of the obturator foramen | |
| body | superolateral portion of the pubis | the body of the pubis forms about 1/5 of the acetabulum | |
| pubic crest | ridge on the superior border of the superior ramus | attachment of rectus abdominis & pyramidalis mm. | |
| pubic tubercle | process at the lateral end of pubic crest | attachment point of the medial end of the inguinal ligament | |
| superior ramus | superior "limb" that passes medially from the body of the pubis | articulates with the superior ramus of the opposite side at the pubic symphysis | |
| pecten | ridge on superior surface of the superior pubic ramus | attachment point of the pectineal ligament | |
| inferior ramus | inferior "limb" that passes inferolaterally from the pubic symphysis | articulates with the ischial ramus to form the ischiopubic ramus; attachment site for the root of the penis (clitoris) | |
| obturator groove | groove on the inferior surface of the superior pubic ramus | marks the area of passage of the obturator vessels and n. in the obturator canal | |
| ischium | the "V"- shaped bone that forms the posteroinferior part of the pelvis | one of the three bones that form the os coxae: ilium, ischium, pubis | |
| ischial ramus | the limb of the ischium that passes anteriorly and superomedially toward the pubis | it articulates with the inferior ramus of the pubis | |
| body | the part of the ischium that participates in the formation of the acetabulum | it articulates with the ilium and the pubis at the acetabulum; the body of the ischium forms 2/5 of the acetabulum | |
| ischial tuberosity | the roughened projection that protrudes posteroinferiorly from the body of the ischium | it is the site of attachment of the sacrotuberous ligament; it is the site of origin of the inferior gemellus m., quadratus femoris m. and the hamstring mm. (semitendinosus, semimembranosus, long head of biceps femoris, ischiocondylar portion of the adductor magnus) | |
| lesser sciatic notch | the notch located between the ischial tuberosity and the ischial spine | the lesser sciatic notch is converted to the lesser sciatic foramen by the sacrospinous ligament and the sacrotuberous ligament | |
| greater sciatic notch | the notch on the inferior portion of ischium located medial to the ischial spine | the greater sciatic notch is converted to the greater sciatic foramen by the sacrospinous ligament and the sacrotuberous ligament | |
| ischial spine | the spine that arises just superior to the lesser sciatic notch | it is the site of attachment of the sacrospinous ligament and the site of origin of the superior gemellus m. | |
| ilium | fan-shaped bone that forms the lateral prominence of the pelvis | one of three bones that form the os coxae: ilium, ischium, pubis | |
| body | the portion of the ilium that participates in the formation of the acetabulum | the body of the ilium forms 2/5 of the acetabulum | |
| iliac crest | arching superior edge the ilium that forms the rim of the "fan" | attachment for abdominal wall muscles | |
| iliac tubercle | roughened area along the outer edge of the iliac crest | ||
| anterior superior iliac spine | spine at the anterior end of the iliac crest | lateral attachment of the inguinal ligament | |
| posterior superior iliac spine | spine at the posterior end of the iliac crest | position marked by a dimpling of the skin | |
| arcuate line | ridge running from anteroinferior to posterosuperior on the inner surface of the ilium | inferior boundary of the iliac fossa; marks the plane of transition from abdominal cavity to pelvic cavity | |
| sacrum | a triangular bone that is the posterior skeletal element forming the pelvis | it is formed by 5 fused vertebrae; the sacrum and two os coxae bones form the pelvis | |
| base | the superior part of the sacrum | the base of the sacrum includes the articular surface for the fifth lumbar vertebra (through an intervertebral disk) and the superior portion of the two ala | |
| promontory | a projection of the superior part of the sacrum in an anterior direction | the body of the fifth lumbar vertebra sits on the sacral promontory and articulates with it through a symphysis | |
| ala | the lateral portion of the sacrum | paired; it projects laterally from the body of the sacrum; it represents the fused costal and transverse processes of the first sacral vertebra | |
| anterior sacral foramina | an opening in the anterior surface of the sacrum | there are four pairs; each transmits the ventral primary ramus of the respective sacral spinal nerve; branches of the lateral sacral aa. Enter the sacral canal through these openings | |
| posterior sacral foramina | an opening in the posterior surface of the sacrum | there are four pairs; each transmits the dorsal primary ramus of the respective sacral spinal nerve | |
| sacral canal | the opening in the center of the sacrum | it is the continuation of the vertebral canal at sacral vertebral levels | |
| sacral hiatus | an opening in the posterior surface of the sacrum in the midline | it is a normal feature that results from the failure of fusion of the laminae of the fifth sacral segment (and sometimes the fourth) during development | |
| auricular surface | the roughened area located on the lateral surface of the sacrum | this surface articulates with the ilium in the sacroiliac articulation | |
| body | the central portion of the sacrum | the body is equivalent to the bodies of the other vertebra | |
| coccyx | the most inferior portion of the vertebral column | the coccyx results from the fusion of the four coccygeal vertebrae; it may be a single bone or the first coccygeal vertebra may be separated from the other three; it articulates with the fifth sacral segment; coccygeal vertebrae are reduced in complexity, having no pedicles, laminae or spines |
| The material presented in these tables is
contained in the book: MedCharts Anatomy by Thomas R. Gest & Jaye Schlesinger Published by ILOC, Inc., New York Copyright © 1995, unauthorized use prohibited. |
The excellent editorial assistance of Dr. Pat Tank, UAMS is gratefully acknowledged. |
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| Copyright© 2000 The University of Michigan. Unauthorized use prohibited. |
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