Pelvis & Abdominal Muscles .docx

8 Pages

Anatomy and Cell Biology
Course Code
Anatomy and Cell Biology 3319
Kem Rogers

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Bony Pelvis & Muscles of Abdomen Pelvic Girdle • Attaches lower limps to spine and supports visceral organs of the pelvis • Full weight of upper body passes through girdle to lower limbs • Attaches to axial skeleton by very strong ligaments • Pelvic girdle socket is a deep cup that firmly secures the head of the femur • Lower limbs have less freedom of movement but are much more stable • Consists of o Paired hip bones o Sacrum (part of the axial skeleton) • Each hip bone (also called coxal or pelvic bone) units with its partner anteriorly & sacrum posteriorly • Deep structure formed by hip bones, sacrum & coccyx is the pelvis • Hip bone is large & irregular in shape • During childhood, it consists of 3 separate bones: ilium, ischium, & pubis • In adults, 3 bones are fused and boundaries are indistinguishable • At Y-shaped junction of ilium, ischium & pubis - deep hemispherical socket: acetabulum on lateral pelvic surface o Receives ball-shaped head of femur Ilium • Large, flaring bone that forms superior region of hip bone • Consists of: inferior body & superior winglike ala • Thicked superior margin of ala is iliac crest • Many muscles attach to crest – thickest at tubercle of iliac crest • Each iliac crest ends anteriorly in a blunt anterior superior iliac spine & posteriorly in a sharp posterior superior iliac spine • Tomical landmark is easily felt through skin • Position of posterior superior iliac spines is indicated by dimples in the skin that lie approx. 5 cm lateral to midline of the back at the junction of lumbar and gluteal regions • Located inferior to superior iliac spines are anterior & posterior inferior iliac spines • Posteriorly, just inferior to the posterior inferior iliac spine – ilium is deeply indented to form greater sciatic notch • Sciatic nerve, largest nerve in the body, passes through to enter posterior thigh • Broad posterolateral surface of ilium: gluteal surface - crossed by 3 ridges: posterior, anterior & inferior gluteal lines o Define attachment sites of gluteal muscles • Internal surface of iliac ala is concave – iliac fossa • Posterior to fossa lies roughened auricular surface - articulates with sacrum, forming sacroiliac joint • Weight of the body is transmitted from vertebral column to pelvis through this joint • Running anteriorly & inferiorly from auricular surface is robust ridge: arcuate line o Defines superior boundary of true pelvis o Inferior part of ilium joins with ischium posteriorly Ischium • Forms posteroinferior region of hip bone • Shaped like an arc, it has a thicker, superior body & thinner, inferior ramus • Anteriorly ischial ramus joins pubis • Triangular ischial spine lies posterior to acetabulum and projects medially o Attachment point for a ligament from sacrum & coccyx: sacrospinous ligament • Just inferior to ischial spine is lesser sciatic notch o Nerves pass & vessels that serve perineum (area around anus & external genitalia) • Inferior surface of ischial body is rough & thickened ischial tuberosity – strongest part of hip bone o Bears all the weight of body when individual is sitting o Massive sacrotuberous ligament runs from sacrum to each ischial tuberosity & holds pelvis together o Area of attachment of hamstring muscles Pubis • Forms anterior region of hip bone • Lies nearly horizontal & bladder rests upon it • V-shaped, with superior & inferior rami extending from flat body • Body of pubis lies medially, & its anterior border is thickened to form pubic crest • At lateral end of each crest is knoblike pubic tubercle – attachment point for inguinal ligament • Two rami of the pubic bone – extend laterally o Inferior pubic ramus jons ischial ramus o Superior pubic ramus joins with bodies of ischium & ilium • Thin ridge: pectineal line – lies along superior pubic ramus – forming anterior portion of pelvic brim • Large hole: obturator formaen o Occurs between pubis & ischium o Few nerves & vessels pass through it o Almost completely closed by fibrous membrane: obturator membrane • In midline – bodies of two pubic bones are joined by disc of fibrocartilage – joint: pubic symphysis • Inferior to joint – inferior pubic rami & ischial rami from arch shaped like inverted V – pubic arch or subpubic angle o Angle of this arch helps to distinguish male pelvis from female pelvis Pelvic Structure & Childbearing • Body pelvis is divided into two parts: false (greater) pelvis & true (lesser) pelvis • Parts are separated by pelvic brim – continuous oval ridge that runs form pubic crest through arcuate line – rounded inferior edges of sacral ala & the sacral promontory • False pelvis o Superior to pelvic brim o Bound by alae of iliac bones o Part of the abdomen & contains abdominal organs • True pelvis o Lies inferior to pelvic brim o Forms deep bowl containing pelvic organs • Female pelvis is adapted for childbearing: wider, shallower & lighter • Pelvic inlet o Delineated by pelvic brim o Largest diameter is from right to left in the frontal plane o As labor begins, infants head enters inlet & forehead faces one ilium & back of head faces other o If mother’s sacral promontory is too large – can block the entry of infant into true pelvis • Pelvic ou
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