5x vertebrae fused
4x paired foramen (nerve passage)
Label posterior sacrum
What makes up the pelvic inlet. What is this the boundary of?
- Sacral promontory
- Alae of sacrum
- Arcuate line
- Pectineal line
- Pubic tubercle
- Pubic Crest
- Pubic symphysis
Above this= false pelvis
Below this= true pelvis
Describe the 'Pelvic Tilt'
~60 degree tilt anteriorly.
ASIS in line with Pubic tubercle
(sacrum also tilted)
What are the pelvic boundaries?
Ant, Post and Lat = bone
Floor = muscular (pelvic diaphragm)
Male/female variation of the pelvis
What forms the greater and lesser sciatic foramen?
Sacrospinous and sacrotuberous ligaments
Other ligaments of the pelvis?
Posterior sacroiliac ligament: fibrous (for strength)
Anterior sacroiliac ligament: synovial
Muscles of the pelvic wall
Piriformus and Obturator Internus
OI: fills entire obturator foramen except obturator canal, has 90 degree bend
Draw out the vessel passages through the greater and lesser sciatic foramen.
Journey of Pudendal Nerve and vessel
Leave through Greater sciatic foramen, loop under and around sacrospinous ligament and re-enter below pelvic floor into perineum
Label nerves. Why do we need to know where these are?
Superior Gluteal Nerve: at risk during lateral approach to surgery
Sciatic Nerve: at risk during intramuscular injection
Draw the branching of the anterior division!
Don't learn the pattern!!
Male/female differences of the anterior division of the internal iliac
Male: inferior vesical + middle rectal supply prostatem seminal vesicles and ductus deferens.
Testicular arteries from abdo aorta @L2
Female: uterine artery gives off vaginal artery (supplies femal genitalia)
Draw branches of the posterior division
To superior gluteal → GSF above piriformis
Venous drainage of the pelvis (EASY)
ALL draining to the Internal Iliac Veins
Exception: Deep dorsal vein of the penis/clitoris, drsins through deficiency in perineal membrane → vesical/prostatic plexuses
The sacral plexus
S1-4 is joined by L4-5 (lumbrosacral trunk), although it's mostly going to structures external of the pelvis, some are important!
- Gluteal Nerves
- Sciatic Nerves
- Nerves to Levator Ani and Coccygeus
- Pudendal Nerves
Superior Gluteal (L4,L5,S1): to gluteus medius and minimus
Inferior Gluteal (L5,S1,S2): to gluteus maximus
Passing above and below piriformis
Tibial always leaves below piriformis
Common peroneal can be above, below or thorugh
Nerves to Levator Ani (direct S3-4) and Coccygeus
- Direct branches of sacral plexus
- Lie atop muscle → risk of damage → risk of prolapse
"S2,3,4 keeps the penis off the floor
- Supplies everything in perineum (M and S)
Branches of the Pudendal Nerve
- Inferior rectal
- DOrsal nere to clitoris/penis
2 Plexuses of the ANS to the pelvic Viscera
- Superior Hypogastric : Sits on anterior body of L5 and sacral
- Inferior Hypogastric: on pelvic Floor (compression risk!)
Sympathetic supply to pelvic viscera
L1/2 fibres descends into pelvis via Sup. hypogastric and sacral splanchnic. Splits to form two big right and left hypogastric nerves
- Contract int urethral and anal sphincters (continence)
- Moves secretions along epididymis
Parasympathetic supply via pelvic viscera
S2-4, ascend via HG nerves → sup. hypogastric plexus → abdomen
Direct into Inf. HG
- Vasodilation (for erection)
- Bladder contraction