Lecture 14: Pelvis: Contents, Vessels and Nerves Flashcards
Fusion of pelvic bones to other structures
Fuse to sacrum posteriorly
Fuse together anteriorly (16/18 years old)
Ischial tuberosity = “sit bones”
Bones of the sacrum
Ala: wings of S1 vertebrae
Sacral body
Sacral (untervertebral) foreamen (Anterior): 4x paired. anterior rami/ cauda equina
Coccyx: separate bone w. own joint to the sacrum
Sacral canal: spinal cord nerves run through
Sacral foreamen (Posterior): 4x paired. posterior rami- back muscles
Sacral hiatus: little fusion. is covered by little membrane.
Cornu
Clinical relevance of Sacral hiatus
Cordal nerve blocks
Can insert needles into sacral hiatus as contain spaghetti nerves, which are easily pushed out of the way when you insert a needle
True vs False Pelvis
Above the pelvic inlet: Abdominal cavity/ False Pelvis
Below pelvic inlet: Pelvic cavity/ True Pelvis
- good judgement point during trauma to see if pelvic contents have shifted
Components of the Pelvic inlet
Distinguishes b/w False and True Pelvis
Sacral promontory –> Margin of Ala –> Arcuate line –> Pectineal line –> Pubic tubercle, crest and symphysis (Linea Terminalis)
Linea Terminalis
Pubic Tubercle, Crest and Symphysis
Pelvic Tilt
- Pelvis ~60 degrees Anteriorly –> ASIS inline with Pubic Tubercle
- Sacrum is also tilted ~40 degrees Posteriorly and Inferiorly
Pelvic Boundaries
Bone: Anterior (Pubic bones), Posterior (sacrum, coccyx, piriformis) and Lateral (illium, ishcium and pubis) walls
Muscular: Floor (pelvic Diaphragm)
- Below is Perineum
Roof: None. Peritoneal cavity
Female Gender differences b/w pelvis
Pelvis: most sexually dimorphic bone in the body
Female Pelvis:
1. Illia spread wider
2. Sub-pubic angle generally greater than 90 degrees.
3. Larger and more circular pelvic inlet.
4. Ischial spine more attached to the side.
5. Sacrum Tilted backwards
6. Big Pelvic Outlet (Larger and less obstructed)
Male Gender difference b/w pelvis
Male Pelvis:
- Illia spread wider
- Sub-pubic angle generally greater than 90 degrees.
- Larger and more circular pelvic inlet.
- Ischial spine more attached to the side.
- Sacrum Tilted backwards
- Big Pelvic Outlet (Larger and less obstructed)
Sacral ligaments location and function
- Sacrospinous ligament
- Sacrotuberous ligament
- -> Form Greater and Lesser Sciatic formation - Anterior Sacro-Illiac Ligament –> allows flexion/mechanical transfer of forces when walking
- Posterior Sacro-Illiac Ligament –> stronger and larger fibrous ligament
- > strong INTEROSSEOUS ligaments
- visible when remove iliac blades
Pubic Symphysis
Fibrocartilage
Relaxes during childbirth –> relaxes/opens up pelvic bones/cavity for child birth
Muscles of the Pelvic Wall
- Piriformis: Travels through greater sciatic foreamen
- Obturator Internus:
- covers majority of obturator foreamen (obturator canal deficet)
- Leaves lesser sciatic foreamen –> 90 degree flip backwards –> heads towards hip –> functions as a lateral rotator
Pelvic Vessel passages
- Greater sciatic foreaman Superior to Piriformis:
Superior gluteal vessels and nerves - Greater sciatic foreamen Inferior to Piriformis:
Sciatic n., Inferior gluteal, Posterior femoral cutaneous, quadratus femoris nerves + vessels - Lesser Sciatic foreamen: Pudendal nerves + Internal Pudendal nerves and vessels to Obturator internus
- Obturator Canal : Obturator nerves and vessels (supply adductors and medial thigh)
Pudendal nerves
Most posterior medial
hooks around and back in
Which nerves associated with the sciatic foreamen is at greatest risk during surgery?
- Superior Gluteal nerve: Laterally and superior approaches hip –> Risk of cutting during surgery
- Sciatic nerve: innervates hamstrings and all the muscles below the knee. Risk of hitting during intramuscular injection
Therefore: operate on ventromedial side (Not upper quad)
Sciatic nerve
Largest pelvis nerve
Runs down and innervates hamstring and all the muscles below the knee
At risk of hitting during Intramuscular injection
What are the arterial divisions off the common illiacs?
Common illiac –>
- External Illiac –> Leg
- Internal Illiac (pelivs and gluteal) –>
a) Anterior b) Posterior
What are the arterial divisions of the Anterior Internal Iliac?
- Superior Vesicular (2-3) (VE) –> Umbilical (VE)
- Obturator Internus (P)
- Inferior Vesicular (VE)/Uterine (VI) –> Vaginal/Prostatic (VI)
- Middle Rectal (VI)
–>
a) Internal Pudendal (P) –> Inferior Rectal
b) Inferior Gluteal (P)
(3x Vesicular, 3x Visceral, 3x parietal)
Branches of Anterior Division Male specific
Prostate, Seminal vesicles + Ductus deferens: supplied by Inferior vesicular a. and middle rectal a.
Note: Inferior vesicular (bladder and structures below (prostate, seminal vesicles, ductus deferens)
Note: Superior vesicular supplies majority of bladder
TESTICULAR artery comes from ABDOMINAL AORTA (different system)
Gonadal artery in comparison to other pelvic arterial supply
General Pelvic arterial supply: Anterior division of Internal Iliac
Males: Testes: Testicular artery from ABDOMINAL AORTA L2 (Different division)
Females: Ovaries: Ovarian artery from ABDOMINAL AORTA as well
Branches of Anterior Division Female specific
Uterine artery –> Vaginal artery –> supplies female genitalia
OVARIAN artery comes from ABDOMINAL AORTA L2(different system)
Pelvic venous drainage
Bladder, Prostate, rectum, Uterus, Vagina = Perineum = all drain through a rich venous plexus –> Internal Pudendal vein –> Internal Iliac vein
Exception: Deep dorsal vein fo the penis/clitoris –> through Anterior deficiency in perineal membrane –> Vesical/Prostatic Plexus –>
Same end source but different pathway
Sacral plexus
Anterior sacral Foramina S1-4
- Lumbosacral trunk joins at L4-5
Internal pelvis is mainly Autonomic innervation –> Sacral plexus innervates structures that are External to pelvis
Some important nerves to pelvis and peritoneum
1. Gluteal nerves
2.
