Pelvis Flashcards
Inferior hypogastric plexus
Recieves pre-ganglionic parasympathetic fibres from
S2 - S4
Inferior hypogastric plexus form on posterior abdominal wall as extensions of abdominal pre-vertebral plexus
Post-ganglionic fibres penetrate pelvic floor –>
Innervate erectile tissue in males and females
Sacrum
Five sacral vertebrae fused
Has 4 anterior sacral foramina
Has 4 posterior sacral foramina
Sacral canal posteriorly which is a continuation of vertebral canal
Zygapophysial joints
Joints between adjacent inferior and superior articular processes of L5 and S1
Ligaments of the sacro-iliac joints
Anterior sacro-iliac ligaments
-thickening of the fibrous memrbane of the joint capsule
Interosseous sacro-iliac ligament
- largest, strongest
- posteriosuperior to joint and attach on roughended areas on ilium and sacrum
Posterior sacro-iliac ligament
-covers the interossesous sacro-iliac ligament
Ligaments between L5 –> ilium/sacrum
Lumbosacral ligament
-Transverse process L5 –> sacrum
Ileolumbar ligament
-Iliac crest –> transverse process of L5
Ligaments of pubic symphysis joint
Superior pubic ligament
-located above the joint
Inferior pubic ligament
-located below joint
Female vs male pelvis
Female pelvis
- circular inlet
- pubic arch 80-85
- ischial spines don’t project
Male pelvis
- heart-shaped inley
- pubic arch 50-60
- pojecting ischial spines + prominent sacral promonotory
Sacrospinous ligament
Smaller of the two ligaments
Triangular, apex attached to ischial spine
Base attached to margins of sacrum and coccyx
More anterior vs sacrotuberous ligament
Sacrotuberous ligament
Larger of the two, sits posterior to sacrospinous
Triangular
Base has broad attachment that extends from posterior superior iliac spine –> coccyx
Attaches to medial margin of ischial tuberosity
Innervation of obturator internus
Innervated by nerve to obturator internus
L5 S1
O: deep surface of obturator membrane and surrounding bone
I: Medial surface of greater trochanter of femur
-tendon leaves pelvic cavity through lesser sciatic foramen, makes a 90 bend around ischium –> posterior to hip –> greater trochanter
F: Lateral rotation of extended hip
Abduction of flexed hip
Innervation of piriformis
Innervated by branches from (L5) S1 + S2
O: Anterior surface of sacrum between the four anterior sacral foramina
I: Medial side of superior border of greater trochanter of femur
F: Lateral rotation of extended hip
Abduction of flexed hip
Obturator canal
Supeior defect in obturator membrane
Borders:
- Superior pubic ramus
- Obturator internus, externus, and membrane
Contants
- Obturator nerve
- Obturator vessels
Greater sciatic foramen
Borders:
- greater sciatic notch
- sacrspinous ligament (posterior)
- sacrotuberous ligament (inferior)
- spine of ischium
Piriformis divides into two compartments
Superior to piriformis
- Superior gluteal nerve
- Superior gluteal vessels
Inferior to piriformis
- Inferior gluteal nerve
- Inferior gluteal vessels
- Internal pudendal vessels
- posterior femoral cutaenous nerve
- nevre to obturator internus
- nerve to quadrate femoris
Innervation of levator ani
Innervated by:
- inferior rectal branch of internal pudendal nerve
- direct branches from ventral ramus of S4
O: line around pelvic wall
- ischial spine
- tendinous arch
- obturator internus
- pubic bone
I:
- anterior: superior surface of perineal mambrane
- posterior: meets partner on perineal body, around anal canal and along anococcygeal ligament
F: reinforces pelvic floor, reinforces sphincters
Innervation of coccyges
Innervated by direct branches from ventral rami of S3 and S4
O: ischial spine and pelvic surface of sacrospinous ligament
I: lateral margin of coccyx and related border of sacrum
F: contributes to formation of pelvic floor which support viscera and pulls coccyx forward after defecation
Anococcygeal ligament
Posterior to the anal aperture the two sides of levator ani form raphe = anococcygeal ligament
This forms structural connection with external anal sphincter and coccyx
Parts of levator ani
Pubococcygeus
- originates body of pubis
- -> midline as far back as coccyx
Puborectalis
- Originates form pubis
- -> forms sling around inferior anal aperture
Iliococcygeus
- Originates from fascia surrounding obturator internus
- -> forms anococcygeal ligament / raphe
Perineal membrane
Thick facial triangular structure
- attached to bony framework of pub arch
- free posterior border
Anterior gap: between inferior pubic ligament and fascia
Covers deep perineal pouch
Hiatus for urethra and vagina
Deep perineal pouch
Covered by perineal membrane
Skeletal muscle tha functions as a sphincter
Anteriorly: external urethral sphincter
+/-spinchter urethrovaginalis (surrounds urethra and vagina)
+/- compressor urethrae pm each side: originate from ischiopubic rami and meet anterior to urethra
Deep transverse perineal muscle
Two muscles that parallel free edge of perineal membrane
-joins with partner in midline
Act to stabilise position of perineal body
Structures connecting to perineal body
Positioned on posterior border of perineal membrane
Structures connecting to it:
- posterior end of urogenital hiatus in levator ani
- deep transverse perineal muscles meet at it
- females: urethrovaginalis
- external anal sphincter
- superficial transverse perineal muscles
- bulbospongiosus muscles of perineum
Innervation of external urethral sphincter
Innervated by perineal branches of pudendal nerve S2 - S4
O: inferior ramus of pubis and adjacent walls of deep perineal pouch
I: surrounds membranous part of urethra
F: compresses membranousus urethra
Innervation of deep transverse perineal muscle
Innervated by perineal branches of pudendal nerve S2 - S4
O: medial aspect of ischial ramus
I: perineal body
F: stabilises position of perineal body
Level of start of retcum
S3
