Pelvic Walls & Floor

what are the functions of the pelvic girdle?

bear the weight of the upper body when sitting or standing

transfer weight from the axial to the lower appendicular skeleton for standing and walking

provide attachment for the powerful muscles of locomotion and posture as well as the abdominal wall

contain and protect the pelvic viscera (urinary tract, reproductive organs)

provide attachments for muscles and membranes that form the pelvic floor

what are the bones of the pelvic girdle?

right & left pelvic bones (innominate)

ilium, ischium, pubis

sacrum & coccyx

what are the characteristics of the male pelvis?

thick & heavy structure

deeper greater pelvis

lesser pelvis is narrow, deep, and tapering

pelvic inlet is heartshaped and narrow

pelvic outlet is comparatively small

pubic arch & suprapubic angle is narrow (less than 70 degrees)

obturator foramen is round

acetabulum is large

greater sciatic notch is narrow (less than 70 degrees) and inverted V

what are the characteristics of the female pelvis?

thin and light structure

greater pelvis is shallow

lesser pelvis is wide, shallow, cylindrical

pelvic inlet is oval and rounded; wide

pelvic outlet is comparatively large

pubic arch & suprapubic angle is wide (greater than 80 degrees)

obturator foramen is oval-shaped

acetabulum is small

greater sciatic notch is almost 90 degrees

what are the three joints of the pelvic girdle?

sacroiliac joint

pubic symphysis

sacrococcygeal joint

what are the characteristics of the sacroiliac joint?

auricular surface of ilium with auricular surface of sacrum - “little movement”

joint under relatively constant pressure to rotate anteriorly based on anatomical design

upper/dorsal part of joint is not synovial, is fibrous held in place by tough interosseous S-I ligaments, helps limit anterior motion

lower/ventral part of the joint is synovial

what are the major ligaments of the SI joint?

*mostly designed to prevent anterior motion

posterior SI: runs down and medially from ilium to sacrum

iliolumbar: L4 and L5 transverse processes to posterior iliac crest

anterior SI: ilium to sacrum

sacrotuberous: iliac tuberosity and posterior surface of lower sacrum to ischial tuberosity

sacrospinous: lateral borders of lower sacrum and coccyx to attach to the spine of ischium

what are the characteristics of the pubic symphysis?

anterior connection of pelvis

fibrocartilaginous joint

limited motion

motion increases dramatically during pregnancy, especially at the time of birth

similar increase in SI joint mobility during pregnancy and birth

superior and inferior pubic ligaments

interpubic disc lies between the two bones

what are the characteristics of the sacrococcygeal joint?

secondary fibrocartilaginous joint with an IV disc

formed between the oval surface at the apex of the sacrum, and the base of the coccyx

slightly moveable joint

anterior & posterior sacrococcygeal ligaments

what are the walls of the pelvic cavity?

anteroinferior wall

two lateral walls

posterior wall (posterolateral wall - roof)

floor

what are the characteristics and functions of the anteroinferior wall?

a weight-bearing floor rather than wall

formed via the bodies and rami of the pubic bones and the pubic symphysis

bears the weight of the urinary bladder

what are the characteristics of the lateral walls of the pelvis?

formed by the right and left innominate bones

obturator fascia - thickened centrally as the tendinous arch for the attachment of the pelvic diaphragm (ATLA)

obturator internus muscle

obturator nerves and vessels

branches of the internal iliac vessels

what are the components of the posterior (posteriolateral) wall?

obturator membrane

ligaments: sacrospinous, sacrotuberous

piriformis

where is the pelvic floor located?

formed by the funnel-shaped pelvic diaphragm - consists of the levator ani and coccygeus muscles and their fascia

stretches between the pubis anteriorly and the coccyx posteriorly and from one lateral pelvic wall to the other

what are the three parts of the levator ani?

puborectalis

pubococcygeous

iliococcygeus

where is the levator ani located?

collectively they run from the body of the pubis, the tendinous arch of the obturator fascia and the ischial spine to the perineal body, the coccyx, the anococcygeal ligament, the walls of the prostate or vagina, the rectum and the anal canal

what are the functions of the levator ani?

help to support the pelvic viscera; acting together, they raise the pelvic floor and assist the abdominal muscles in forced expiration activities

what are the characteristics of the male pelvic peritoneum?

continuous with peritoneum of abdomen

drapes over pelvic viscera to form pouches: folds between viscera and pelvic walls, pouches protect viscera from rectum

what are the characteristics of the pelvic peritoneum in females?

continuous with peritoneum of abdomen

drapes over pelvic viscera in the midline to form pouches: folds between viscera and pelvic walls (more in females due to more viscera), pouches protect viscera from rectum