Pelvis and Pelvic Wall Flashcards
describe the sacroiliac ligaments
strong and extensive
sacrum driven like a wedge to separate the hip bones
function of sacrotuberous + sacrospinous ligaments
prevent rotation of sacrum/coccyx
w/ hip bone, create the greater and lesser sciatic foramen
forces causing pelvic fractures/breaks (2)
and weak areas (4)
- anterioposterior compression –> fractures of pelvic rami
lateral forces –> squeeze acetabulum and ilia, break both - Pubic rami, acetabulum, SI joints, ala
borders of the lesser/true pelvis
superior: pelvic brim
inferior: muscular pelvic diaphragm
laterally + anterior: lower 1/2 of hip bones
posteriorly by sacrum + coccyx
What is the line demarcating greater/false v. lesser/true pelvis
and what occupies the false pelvis
pelvic brim
abdominal viscera
Differences in M/F pelves, in these categories: general structure false, true pelves inlet, outlet pubic arch, subpubic angle obturator foramen acetabulum greater sciatic notch
M, F (android = M; gynecoid = female)
thick heavy, thin light
deep, shallo
narrow and deep and tapering, wide and shallow cylindrical
heart shaped and narrow, oval and rounded wide (I DO NOT LIKE HEARTS)
small outlet, large
narrow arch angle, wide
round foramen, oval
large acetabulum, small
narrow and inverted V notch, and 90 degree notch
Origin, insertion, innervation, action (thigh) of obturator internus
O: ilium/ischium surface; obturator membrane
insertion: greater trochanter
innervation: obturator n
action: rotate thigh laterally
Origin, insertion, innervation, action (thigh) of piriformis
O: S2-4 surface, superior margin of greater sciatic notch; sacrotuberous ligament
insertion: greater trochanter
innervation: S1-S2
Origin, insertion, innervation, action of coccygeus
O: ischial spine
insertion: inferior end of sacrum and coccyx
innervation: S4-5
action: support pelvic viscera; flex coccyx
4 muscles of the pelvic diaphragm (floor)
named for their origin
and which ones elevate the anal canal (aka are called levator ani)
muscle (origin)
*= levator ani
[ischio] coccygeus (ischial spine)
- iliococcygeus (tendinous arch)
- pubococcygeus (pubis)
- puborectalis (pubis)
tendinous arch of levator ani is what?
thickening of obturator fascia, between ischial spine and body of pubis
Which muscle is key in control of pooping?
puborectalis muscle:
- helps maintain fecal continence
- relaxes w/ urination AND defacation
- DIFFERENT than the sphincters
partially relaxed = kinked colon
fully relaxed = swift emptying of colon
Urogenital/Levator Hiatus:
- passage for what 3 structures?
- formed by an anterior gap in what muscle?
- What two muscles are the most medial and a large part of levator ani?
- rectum, urethra, vagina
- levator ani
- pubococcygeus and puborectalis (and these are most susceptible to tear during birth)
Ischiorectal fossa:
- inferior to what?
- filled with what?
- What are the 2 triangles?
- What movements?
- contains?
- inferior to pelvic floor (and extends anteriorly above the perineal membrane)
- filler with fat
- 2 triangles: anal and urogenital
- movements: of pelvic diaphragm, and expansion of the anal canal
- Contains: neurovasc to the anal canal (and some to the perineum)
Anal canal:
- begins where?
- Structures within? (3)
- begins at the level when the rectum perforates the levator ani
- structures: columns; valves; sinuses
what are the anal sinuses and what is their function?
small recess adjacent valves
exude mucus facilitating defacation
internal anal sphincter
- muscle type
- what kind of contraction?
- responsible for what?
muscle: inner circular smooth (involuntary)
contraction: tonic, except when feces fill the rectum
responsible: 55-85% of resting anal tone
external anal sphincter
- muscle type
- responsible for what?
- 3 parts?
muscle: skeletal (voluntary)
responsible: 15-30% of resting anal tone
3 parts: subQ, superficial, deep (puborectalis)
What are hemorrhoids?
What are they a consequence of?
hemorrhoids: enlarged and collapsed varicosity of normal venous anatomy
consequence of portal htn
What are internal hemorrhoids?
prolapse of rectal mucosa, due to weakened muscularis mucosa
ABOVE the pectinate line
not painful
bleeding is bright red due to abundant arteriovenous anastomoses with internal rectal venous plexus
Describe the basic structure of an external hemorrhoid
external venous plexus covered w/ epidermis
BELOW the pectinate line
painful
Distinctions made by the pectinate line: nerves veins hemorrhoids destination of lymph drainage embryo origin of epithelia
category / ABOVE/ BELOW
Nerves/inferior hypogastric plexus (visceral)/ inferior rectal nn (somatic)
veins/1o to superior rectal vein (portal)/ 1o to inferior rectal veins (systemic)
hemorrhoids/internal/external
lymph/internal iliac and inferior mesenteric/superficial inguinal
embryo/endoderm/ectoderm
