L9. Perineum Flashcards
What are the boundaries of the Urogenital triangle vs Anal triangle
Urogenital: pubic symphysis->ischiopubic ramus -> ischial tuberosity
Anal: Coccyx->sacrotuberous lig->Ischial tuberosity
What is Levator ani, origin and innervation
Broad diaphragmatic sheet of skeletal muscle under somatic control in a funnel shape.
Origin is from the sacrum/coccyx.
3 divisions innervated
Internal surface: nerve to levator ani (S3-4)
Ext: pudendal nerve (s2-4)
What is considered the Anal canal, what are the two lines in there separating the pecten
When the rectum pierces through levator ani
This is a transitional region from true gut to outer skin.
- Pectinate line/ anal columns contain terminal radicle of the superior rectal artery and vein.
- pecten- transitional region between endo and ectoderm.
- White line of Hilton
What is the difference between the Int and Ext Anal Sphincter- place, innervation
- Int= continuation of SM coat of the rectum. ANS control, deep to Ext. sphincter (separated by CT)
- Ext: Skeletal muscle from perineal body to anococcygeal ligament which closes the anus (with puborectalis)
Innervated by inferior rectal branch of pudendal nerve.
What is the difference between Ano-rectal varices vs haemorrhoids
Anorectal varices are due to portal hypertension at the anastomoses between superior and middle/inferior rectal veins and can lead to fresh blood in the stool if rupture
Haemorrhoids involve the internal or external plexuses where they become engorged or inflammed due to age, straining etc.
Internal - above the white line of hilton is silent, not painful unless thrombose or prolapse into the anal canal.
External- below the white line is painful if thrombose, itchy because in the somatic region
What is the ischioanal fossa boundaries and what does it contain
Area containing the pudendal canal for pudendal nerve which branches going to innervate the ext anal sphincter, int pudendal artery and vein.
Medial border: Anal canal
Lat border: Obturator internus
Roof: Levator ani
Floor: Skin
Also contains fat which extends superiorly into the urogenital region.
The fat is cushioning which helps the anal canal to expand during defecation.
What part of the ischioanal fossa is important to avoid damaging when draining ulcers
Lateral apex towards the ischial tuberosity because this is where the pudendal canal is originating from so pudendal nerve damage can lead to impotence/sexual dysfunction or urinary/ faecal incontinence. Also int pudendal artery and vein
What is the function of the perineal membrane
It spans between the ischiopubic rami to plug up the urogenital hiatus leaving a vaginal opening, urethral opening and deficit behind the pubic symphysis for the deep dorsal vein of the penis/clit (which drains back to the prostatic/ vesicular plexus).
It is also the site of muscular attachment for deep perineal pouch muscles and superficial perineal pouch.
What is the structure of the urogenital diaphragm - contains deep perineal pouch
- Superior layer of fascia which is deepest- blends with the perineal body and membrane and continuous with the fascia in the scrotum and abdo body wall
- Sphincter urethrae and deep transverse perineal muscles
- Inferior layer of fascia (known superficially as the perineal membrane)
What are the differences between males and females in structures passing through/in the deep perineal pouch
Both have Ext urethral sphincter and Deep transverse perineal muscles
M: Passing through: membranous urethra.- thinnest part surrounded by sphincter urethrae muscle
-Bulbourethral glands within the deep perineal pouch to lubricate urethra.
-Dorsal nerves and arteries of the penis
F: Passing through: Vagina
Within: Compressor urethrae and urethrovaginalis
-Dorsal nerves/arteries of the clitoris
Bartholin’s glands are in the Superficial pouch draining directly in the vaginal orfice
What are the structures in the superficial perineal pouch - Between the perineal membrane and skin
Nerves and vessels
Erectile tissues
Perineal muscles
Bartholin’s glands in females
What is the clinical significance of Scarpa’s fascia of the abdomen being continuous with dartos fascia of the penis/scrotum, colles fascia of the perineum
This is a fascial boundary that separates the urogenital triangle from the anal triangle but if there is perineal trauma, there can be blood, urine into the scrotum or up into the lower abdomen
What are the main branches of the pudendal nerve / internal pudendal artery
Inferior rectal branches (across ischioanal fossa), Perineal (sup pouch) Dorsal artery/nerve of the penis/clitoris (deep pouch)
+ Scrotal/Labial nerve (artery) branch which is sensory and is the fork of Perineal.
What does the pudendal nerve supply and nerve root
S2-4. Supplies the perineal muscles, ext urethral and anal sphincters (conscious control), skin of the genitalia and perineum, erectile muscles: ischiocavernosus and bulbospongiosus
What is saddle anaesthesia and where shouldn’t u look for it
Caused by compression of the cauda equina- numbness in the saddle region.
The area around the anus is S5 therefore will not tell you about the S4 pudendal nerve.
