PELVIS Flashcards
what does the pelvis consist of?
bony pelvis + pelvic cavity
what is the pelvic girdle and what 4 bones does it consist of?
a basin-shaped ring of bones that connect the vertebral column to the two femurs. surrounds the pelvis. composed of sacrum, coccyx, 2 x os coxae (hip bone).
what are the primary functions of the pelvic girdle? (2)
1) transfer the weight from the axial to the lower appendicular skeleton for standing and walking.
2) bear the weight of the upper body when sitting and standing.
how is weight transferred from axial skeleton to the ilia?
via sacro-iliac ligaments
what 3 bones make up the hip bone after they fuse in puberty and where do they meet?
ilium, ischium, pubis - meet at the acetabulum
what is the sacrum composed of and where do they articulate with the hip bones?
formed by the fusion of 5, originally separate, sacral vertebrae. articulate with os coxae at sacroiliac joints.
what does the pelvic inlet do?
divides the pelvis into the greater (false) and lesser (true) pelves
male vs. female pelvis
male = thick and heavy, female = thin and light
GREATER PELVIS: male = deep, female = shallow
LESSER PELVIS: male = narrow and deep and tapering, female = wide and shallow and cylindrical
PELVIC INLET: male = heart-shaped and narrow, female = oval and rounded and wide
PELVIC OUTLET: male = comparatively small, female = comparatively large
PUBIC ARCH AND SUBPUBIC ANGLE: male = narrow (< 70), female = wide (>80)
ACETABULUM: male = large, female = small
GREATER SCIATIC NOTCH: male = narrow (<70) inverted V, female = almost 90
sacro-iliac joints purpose and characteristics
= link the axial skeleton and the inferior appendicular skeleton.
= synovial joints
- strong, weight-bearing compound joints
- limited mobility
- permits weight transfer from the vertebral column to the pelvis
- allows slight but significant movement during childbirth, when the pubis symphysis and the ligaments are softened by hormones
what are the secondary functions of the pelvic girdle?
protection and support of a domino pelvic viscera and housing + attachment for structures of the genital and urinary systems.
false (greater) pelvis
= greater, expanded blade-like portions of each ilium superior to the pelvic brim. bounded on each side by the ilium. situated above and in front of the pelvic brim.
true (lesser) pelvis
- bounded in front and below by the pubic symphysis and the superior rami of the pubis. bounded above and behind by the sacrum and coccyx
- encloses pelvic cavity
- provides the skeletal framework for both the pelvic cavity and the perineum, which are separated by the pelvic diaphragm
- contains the pelvic colon, rectum, bladder, and some of the sex organs
which ligaments help to support and immobilise the sacrum as it carries the weight of the body?
sacrospinous and sacrotuberous ligaments
position of the pelvic cavity
- extends superiorly into the thoracic cage
- extends inferiorly into the pelvis
- lined with peritoneum
- drapes over the superior aspects of the pelvic viscera, but in most regions does not reach the pelvic floor
- bladder is anterior
- rectum is posterior
- funnel-shaped
- continuous with the abdominal cavity at the pelvic inlet
what forms the floor of the pelvic cavity and what muscles does it consist of?
pelvic diaphragm - levator ani and coccygeus
what muscles is the levator ani composed of?
iliococcygeus (outside)
pubococcygeus (inside)
puborectalis (underneath)
main action, innervation, proximal and distal attachment of levator ani
main action: forms most of pelvic diaphragm that helps support pelvic viscera.
innervation: nerve to levator ani (branches of S4), inferior anal nerve, and coccygeal plexus
proximal attachment: body of pubis, ischial spine, tendinous chord of obturator fascia
distal attachment: perineal body, coccyx, anococcygeal ligament, walls of prostate/vagina, rectum and anal canal
coccygeus main function, innervation, proximal and distal attachment
main function - forms small part of pelvic diaphragm that supports pelvic viscera. flexes coccyx
innervation - branches of S4 and S5 spinal nerves
proximal attachment - ischial spine
distal attachment - inferior end of sacrum and coccyx
Arises from the lateral border of the sacrum and coccyx, the fibres cross on the deep surface of the sacrospinous ligament and insert into the ischial spine.
what muscles make up the lateral and posterosuperior walls of the pelvic cavity?
lateral - obturator internus
posterosuperior wall - piriformis
obturator internus and piriformis function, where they arise from and pass through
both hip rotator muscles, arise within the pelvis and pass outward through the sciatic foramina.
Piriformis muscles pass through the greater sciatic foramina in order to enter the gluteal area
function of parietal peritoneum and how is it separated from pelvic floor
linens the abdominal cavity, remains separated from the pelvic floor by the pelvic viscera and surrounding pelvic fascia.
what is parietal pelvic fascia?
a membranous layer of variable thickness that lines the inner aspect of the muscles forming the walls and floor of the pelvis
what is visceral pelvic fascia?
includes the membranous fascia that directly ensheathes the pelvic organs, forming the adventitial layer of each.
adventitia definition
the outer layer of surrounding connective tissue surrounding an organ
what is the Tendinous Arch of Levator Ani and where does it extend from/to?
a thickened portion of the obturator fascia on the medial aspect of the obturator internus that extends in an arching line from the pubis posteriorly to the ischial spine
what is the Tendinous Arch of Pelvic Fascia?
a continuous bilateral band running from the pubis to the ischial spine
anococcygeal ligament
the fibres of the levator ani which arise more posteriorly unite in this midline at this fibrous band
what is the anterior wall of the pelvis formed from?
symphysis pubis, body of pubis, pubic rami
what is the posterior wall of the pelvis formed from?
sacrum, coccyx, piriformis muscle
what does the obturator canal do?
transmits the obturator nerve and vessels
where does the obturator internus originate and insert?
originates at the pelvic surface of the ilium and ischium and the obturator membrane. inserts itself into the greater trochanter of the femur
what bears the weight of the urinary bladder?
the anterior wall of the pelvis
iliococcygeus location
Arises from ischial spine and the tendinous arch of levator ani and blends with the fibres of the anococcygeal body
pubococcygeus
Arises from the lateral aspect of the posterior surface of the body of the pubis and inserts into the coccyx and the anococcygeal body.
puborectalis location and function
The muscle fibres arise from the posterior aspect of the body of one pubic bone, wrap around the posterior aspect of the anorectal junction and insert on the posterior aspect of the other pubic bone. It is involved in maintaining faecal continence.
what is the anococcygeal body?
a mass of fibrous tissue which lies between the anus and the coccyx
