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Department of Neurobiology and Developmental Sciences: Human Structure Module
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  9. Bones of the Pelvis and Perineum

Bones of the Pelvis and Perineum

BoneStructureDescriptionNotes
os coxae one of three bones that form the pelvispaired; 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
acetabuluma 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 notcha notch in the inferior margin of the acetabulumit 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 fossaa roughened depression in the center of the acetabulumthe ligament of the head of the femur occupies the acetabular fossa
lunate surface of the acetabulumthe smooth articular surface of the acetabulumthe lunate surface surrounds the acetabular fossa and the acetabular notch
obturator foramena large foramen formed by the pubic and ischial ramiobturator 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.
pubisan angulated bone the forms the anterior part of the pelvisone 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
bodysuperolateral portion of the pubis the body of the pubis forms about 1/5 of the acetabulum
pubic crestridge on the superior border of the superior ramusattachment of rectus abdominis & pyramidalis mm.
pubic tubercleprocess at the lateral end of pubic crestattachment point of the medial end of the inguinal ligament
superior ramussuperior "limb" that passes medially from the body of the pubisarticulates with the superior ramus of the opposite side at the pubic symphysis
pectenridge on superior surface of the superior pubic ramusattachment point of the pectineal ligament
inferior ramusinferior "limb" that passes inferolaterally from the pubic symphysisarticulates with the ischial ramus to form the ischiopubic ramus; attachment
site for the root of the penis (clitoris)
obturator groovegroove on the inferior surface of the superior pubic ramusmarks 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 ramusthe limb of the ischium that passes anteriorly and superomedially toward
the pubis
it articulates with the inferior ramus of the pubis
bodythe part of the ischium that participates in the formation of the acetabulumit articulates with the ilium and the pubis at the acetabulum; the body
of the ischium forms 2/5 of the acetabulum
ischial tuberositythe 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 notchthe notch located between the ischial tuberosity and the ischial spinethe lesser sciatic notch is converted to the lesser sciatic foramen by the
sacrospinous ligament and the sacrotuberous ligament
ischial spinethe spine that arises just superior to the lesser sciatic notchit is the site of attachment of the sacrospinous ligament and the site of
origin of the superior gemellus m.
iliumfan-shaped bone that forms the lateral prominence of the pelvisone of three bones that form the os coxae: ilium, ischium, pubis
bodythe portion of the ilium that participates in the formation of the acetabulumthe body of the ilium forms 2/5 of the acetabulum
iliac crestarching superior edge the ilium that forms the rim of the "fan"attachment for abdominal wall muscles
iliac tubercleroughened area along the outer edge of the iliac crest
anterior superior iliac spinespine at the anterior end of the iliac crestlateral attachment of the inguinal ligament
posterior superior iliac spinespine at the posterior end of the iliac crestposition marked by a dimpling of the skin
arcuate lineridge 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 pelvisit is formed by 5 fused vertebrae; the sacrum and two os coxae bones form
the pelvis
basethe superior part of the sacrumthe base of the sacrum includes the articular surface for the fifth lumbar
vertebra and the superior portion of the two ala
promontorya projection of the superior part of the sacrum in an anterior directionthe body of the fifth lumbar vertebra sits on the sacral promontory and
articulates with it through a symphysis
alathe lateral portion of the sacrumpaired; 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 sacrumthere 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 foraminaan opening in the posterior surface of the sacrumthere are four pairs; each transmits the dorsal primary ramus of the respective
sacral spinal nerve
sacral canalthe opening in the center of the sacrumit is the continuation of the vertebral canal at sacral vertebral levels
sacral hiatusan opening in the posterior surface of the sacrum in the midlineit 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
articular surfacethe roughened area located on the lateral surface of the sacrumthis surface articulates with the ilium in the sacroiliac articulation
bodythe central portion of the sacrumthe body is equivalent to the bodies of the other vertebra
basethe superior surface of the sacrumthe base of the sacrum articulates with the fifth lumbar vertebra through
an intervertebral disk
coccyx the most inferior portion of the vertebral columnthe 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
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