Perineum Flashcards
What is the ischiorectal fossa?
The area around the anal opening, in between the pelvic floor and skin of the perineum
Is the urethral sphincter in the deep or superficial perineal pouch?
The deep perineal pouch
How is the external anal canal divided?
It is divided into deep, superficial (middle) and subcutaneous components
What are the borders of the perineum?
The pubic symphysis and coccyx, anterior and posterior
The ischial tuberosities laterally
What makes up the internal anal sphincter?
A thickening of the smooth muscle wall
What are the names of the two triangles of the perineum?
Urogenital triangle
Anal triangle
What is the origin of the perineal membrane?
The ischiopubic rami on either side of the urogenital triangle
What part of the pelvic floor does the external anal sphincter complex with?
The sling of puborectalis muscle
Why are episiotomies performed?
To control the tearing sphincters during childbirth
What are the corpus caverosum of the penis anchored to?
Ischiopubic rami
Where does the pudendal nerve arised from and which nerve roots contribute to it?
The sacral plexus
S2-S4
What constitutes the lateral walls of the ischiorectal fossa?
Obturator internus
The ischial tuberosity
What is the structure of the clitoris?
Two corpus cavanosa with a small erectile mass
Which part of the anal canal is anchored? To what is it anchored?
The superficial (middle) part
- Anteriorly it is anchored to the perineal body
- Posteriorly it is anchored to the tip of the coccyx
What is the neurovascular supply of the lower 1/3 of the anal canal?
The inferior rectal artery
Drains into the systemic venous system
Somatic nerve supply - the pudendal nerve
What lines the anal canal?
Upper 2/3s is mucosa
Lower 1/3 is skin
Where does the pudendal canal lie?
In a split in the fascia overlying obturator internus as it runs in the ischiorectal fossa
What are the branches of the pudendal nerve and what do they supply?
The inferior rectal nerve for the anal canal
Splits into deep and superficial branches to supply all the structures in the urogenital triangle
Terminal branch - dorsal nerve of penis or clitoris
Describe the course of the pudendal nerve
It starts in the pelvis >
Exits with piriformis via the greater sciatic foramen >
Winds around the back of the ischial spine (above to below the pelvic floor) >
Back through the lesser sciatic foramen >
Into perineum and runs in the pudendal canal
The pudendal nerve carries all but one type of sensory information, what is it?
Parasympathetic
Which nerve supplies the perineum?
The pudendal nerve
Describe the structure of the perineal membrane
It is a thick, dense fascial layer with extra thickening on the posterior margin called the central tendon of the perineum
What supports the central tendon of the perineum?
The transverse perineal muscles - there are four, with a pair above and below the tendon
Where is the membraneous part of the urethra?
Associated with the external urethral sphincter
What is the name of the structure that splits the urogenital triangle into the superficial and deep perineal pouch
The perineal membrane
What is important about the venous drainage of the anal canal?
It is a sight of anastomoses of the portal and systemic circulation
What is the central tendon of the perineum?
A thickening on the posterior margin of the perineal membrane
Where is the perineum located?
Beneath the pelvic floor
Between the thighs
What is the neurovascular supply of the upper 2/3s of the anal canal?
Superior rectal artery
Drains into the portal system
Innervated by autonomic nerves
