9. Pelvic diaphragm. Nerves and arteries of the pelvic cavity Flashcards
What is the false pelvis?
The posterior abdominal wall, iliacus covering the iliac bones
What is the true pelvis?
aka lesser pelvis, pelvic cavity
Inferior to arcuate lines on the iliac bones (equivalent to pelvic brim or pelvic inlet)
____ _____ lines the pelvic lateral wall, while _________ ___ forms the muscular pelvic floor
Obturator Internus lines the pelvic lateral wall, while Levator Ani forms the muscular pelvic floor
What is the perineum?
The diamond-shaped perineum is the (pudendal) region below the pelvic floor
Contains the genitalia and urethra anteriorly, and the anal canal and ischio-anal fossae posteriorly
Which two structures rest on the elevator ani (the pelvic floor)?
The bladder and prostate
Perineal membrane seperates what?
Deep and Superficial compartments of the Perineum anteriorly
Inlet / brim of pelvis formed by?
Pubic symphysis and crest Superior pubic ramus / pectineal line Arcuate line of ileum SI join Sacral ala Promontory (S1)
Pelvic outlet formed by…
Pubic symphysis and ischiopubic rams
Ischial tuberosity
To sacrotuberous ligament
Sacrum and coccyx
Changes to female pelvis?
Must accommodate childbirth
- -> Lighter
- -> More rounded
- -> Wider
- -> Oval inlet
Changes to male pelvis
Heavier
Heart shaped inlet
Narrowed outlet (due to more acute sub-pubic angle and encroached upon by the ischial spines)
Ligaments of the pelvis?
Sacrospinous
- From ischial spine to adjacent sacrum and coccyx
- Triangular shape
Sacrotuberous
- Broader
- From ileum, sacrum and coccyx to ischial tuberosity
Both enclose the greater and lesser sciatic foramina
What are the 3 passages through the pelvis floor?
Greater sciatic foremen
-Superior gluteal nerve and vessels
Lesser sciatic foramen
- Sciatic nerve + Inferior gluteal vesels
- Pudendal nerve + internal pudendal vessels
Obturator canal
-Obturator nerve and vessels
Muscles that make up the pelvic walls?
Piriformis
Obturator interns
Piriformis, attachments?
2 roles?
From sacrum to greater trochanter
Forms the posterior pelvic wall
Divides the greater sciatic foreman
Obturator internus, attachments?
2 roles?
From obturator membrane and adjacent bone, passing to greater trochanter
Forms
- the lateral pelvic wall
- its overlying obturator fascia gives origin to the pelvic floor muscle – levator ani
What forms the pelvic floor?
Coccygeus
Levator ani
Divisions of elevator ani?
- Iliococcygeus
- Pubo-coccygeus, divided into pubo:
- Rectalis (posteriorly)
- Vaginalis or prostaticus
- Urethralis (anteriorly around the urogenital opening)
Nerve supply of iliococcygues and pubo-urethralis?
By direct branches from S3,4
Function of the tendinous arch of the obturator internus?
Origin for levator ani
Position of coccygeus muscle?
Overlies the sacrospinous ligament and blends with levator ani posteriorly
Importance of the levator ani as a bowl of the pelvic floor?
For the support of the viscera and maintenance of the urinary + faecal continence.
Weakness may result in incontinence and prolapse
Where does each side of the levator ani meet?
In the midline to form the:
- anococcygeal raphe (boday and ligament)
- perineal body (/Central tendon of the perineum) just anterior to the anal canal and posterior to the vagina in the female
What forms a sling around the recto-anal junction?
Puborectalis
Levator ani:
Attachments?
Nerve supply?
Function?
Nerve supply: S3 and 4
Attachments:
- Posterior aspect of the pubic bone
- Tendinous arch of the obturator fascia
- -> Ischial spine
Function:
Supports the pelvic viscera
Makes the recto-anal angle more acute aiding rectal continence
Augments the external anal and urethral spincters
Forms a vaginal sphincter
Name the pelvic lymph nodes?
Lumbar (caval/aortic) Inferior mesenteric Common iliac Internal iliac External iliac Superficial inguinal Deep inguinal Sacral Pararectal Obturator
What makes up the somatic pelvic nerve supply?
Lumbosacral plexus: Made up of ventral rami of L 4,5 and S1,2,3,4.
Gives of the pudendal nerve (S2,3,4) to the pelvic floor and voluntary sphincters
PLUS direct branches from S3 and S4 to pelvic floor muscles
What makes up the autonomic pelvic nerve supply?
Sympathetic trunk, bilateral and extending into the pelvis give:
- Sacral Splanchnics
- Superior hypogastric plexus, which sends branches to the pelvic plexuses
Parasympathetic pelvic splanchics from S2,3,4
These are lateral and posterior to rectum and mesorectum
The thoracic sympathetic trunk gives which splanchnics?
The thoracic sympathetic trunk gives:
Greater splanchnic nerve derived from T 5 to 9 (Foregut)
Lesser splanchnic nerve derived from T 10 and 11 (Midgut)
Least splanchnic nerve derived from T 12 (Hindgut)
Relationship between splanchinc nerves and pelvis?
The splanchnic nerves form the pre-aortic (vertebral) plexus and synapse in ganglia at the coeliac trunk, SMA and IMA
The pre-aortic plexus passes into the pelvis as the superior hypogastric plexus that divides to become the (inf hypogastric) pelvic plexus.
This pelvic plexus is augmented by sacral splanchnics from the sympathetic trunk in the pelvis
What happens to the sympathetic trunks are they reach the pelvis?
Pass anteior to the sacrum and fuse as the ganglion impar opposite the coccyx
They carry pre-ganglionic nerves that arise in spinal cord segments T10-L2 and emerge that withe equivalent spinal nerves to pass as white rami communicantes to the sympathetic trunks which then give sacral splanchnic nerves to the pelvic plexus
Other name for pelvic plexus?
Inferior hypogastric
Which splanchnic nerves contribute to the pre-aortic plexus?
Lesser and least splanchnic (T10-12)
What “boosts” the pelvic plexus?
Sacral splanchincs
What is the position of the pelvic plexus?
In fascia lateral to:
- Rectum
- Seminal vesicles
- Prostate
- (Cervix and vaginal fornices)
- Posterior aspect of bladder
In angle between internal iliac and inferior vesical arteries
So is at risk of surgical injury
Branches and supply of the internal iliac artery?
Branch of the common iliac opposite the SI joint at the level of the L5
Divisions: Into anterior and posterior trunks to supply…
- The buttock
- The medial thigh
- The posterior pelvic and abdominal walls
- The pelvic viscera (reuctum, anal canal, uturus, vagina, bladder, urethra) **
- The perineum
**The ovary and testis are supplied by gonadal arteries from the Ao at L2
Collateral circulation of the internal iliac artery?
Its gluteal branches contribute to important anastomoses around the hip that may form a collateral circulation for the lower limb
