Lecture 15: Perineum Flashcards
Urogenital and Anal Triangles
V shape. 2x triangles at an angle with eachother
Pelvic triangle:
1. Urogenital triangle: Anterior and horizontal
2. Anal triangle: Posterior and Inferior
- Perineal body inb/w at centre
Components of the Pelvic outlet
Pubic Symphysis Ischiopubic Ramus Ischial Tuberosity ST ligament Coccyx
Perineal body
Fibrous CT (tough and palpable landmark) The attachment and anchor point for 4x muscles: 1. Levator ani 2. Bulbospongiosus 3. External Anal sphincter 4. Perineal muscles
Pelvic Floor
Levator Ani + Coccyges = continuous muscle sheet
Pelvic Floor is a diaphragm –> separates abdominal and pelvic cavity –> opposite archs (funnel shape bowl)
Function: stop pelvic viscera from prolapsing (keep pelvic contents inside pelvis)
Divisions of Levator Ani
- Pubococcygeus: slings around midline where urogenital structures come out. Deficiet b/w. (3x components)
- Illiococygeus
- Ischiococygeus: remnant muscle not used for same function
- Perineal body is anchor point for levator ani muscles
- supplied by Pudendal nerve (S2-4) and Nerve to Levator Ani (S4)
Note: Levator Ani S4 nerve located ontop of pelvic cavity –> damage results in prolapse of levator ani and pelvic contents
- All used to stop prolapse
Pubococcygeus Divisions within Levator Ani
- Levator prostatae/pubovaginalis
- Pubococcygyeus
- Puborectalis: 1. Sling around rectum 2. Creates angulation -> both helping maintain faecal continence
- relaxes when you deficate
Illiococcygeus of the Levator Ani
1/2 Attaches to the fascia of obturator internus
Prevents prolapse of the pelvic viscera
Pudendal nerve and nerve to levator ani
External Anal sphincter
External anal sphincter runs from PB (perineal body) –> ACL (anococcygeal ligament)
Skeletal muscle –> conscious control
Different fibre direction (wraps around itself) –> helps to close off anus (pubic control aided by puborectalis)
Pudendal nerve (S2-4) (part of peritneum) + INFERIOR rectal branch
Internal Anal sphincter
Smooth muscle –> Autonomic control
Deep to External Anal sphincter (separated by CT)
Ischioanal Fossa Diagram
**
Ischioanal Fossa
Fossa= fat
Medially: sphincters
Laterally: obturator internus + ischial tuberosity
- Inferiolaterally: Pudendal nerve + Internal Pudendal a&v
Superior: Levator Ani muscle/Pelvic diaphragm
Floor: skin and fascia
Clinical relevance of Ischioanal Fossa
Pudendal nerve bloocks
Access to anal canal
Ischioanal Ulcers
Hitting pudendal vessels may lead to impotence or incontenence
Palpable landmarks of Ischioanal fossa
Laterally: Ischial tuberosity
Posteriorly: Coccyx
Midline (b/w anus and vagina/scrotum): Perineal Body
- Avoid Lateral apex: Pudendal vessels enter perineum here. Supply Sexual, sensation, continence function at risk
Anal canal
Rectum pierces pelvic floor
Anal columns: contain a terminal radicle of Superior Rectal vessels (some glands)
Below Pectinate line: Mesothelium/mucous membrane –> skin
Puborectalis forming sling around rectum (**spot in diagram)
Rectal/Anal Arterial Supply
- Superior Rectal Artery (Inferior Mesenteric) - run length of anal column
- Middle Rectal Artery (Int. Illiac) - variable size
- Inferior Rectal Artery (Int. Pudendal)
Rectal/Anal Lymphatic Drainage
Lymphatics follow Arterial system
- Superior: Pre-aortic nodes L3
- Middle: Internal Illiac
- Inferior: Internal Illiac
- Anal canal Inferior to Pectinate line: Superficial Inguinal nodes - is skin –> lymphatics follows venous
Rectal/Anal Venous Drainage
- Superior Rectal vein
- Inferior Rectal vein
- quite superficial structures
Join at Internal and External Venous plexuses
Complications of Rectal/Anal Venous Drainage
- Porto-systemic anastomosis (High pressure –> distended vessels —> valves not working –> backflow –> varices)
- Haemorrhoids: Superificial structures –> at risk of haemorrhage re infections and inflammation
Perineal membrane
= Urogenital diaphragm = Deep Perineal Pouch
Function: another boundary stopping most of the deficiet –> stops urogenital structure herniating through
Muscle attachment site
Midline deficiet
Anterior deficit in Perineal membrane
Deep dorsal vein of penis/clitoris bypasses pudendal system –> entering straight into the vesicular plexus (pelvis’ venous plexus)
Layers of the Urogenital Diaphragm/Perineal Membrane
- Superior Fascial Layer: deep, blends w. perineal body + membrane (thin membranous layer)
- Muscles: Sphincter urethrae + Deep transverse perineal muscles
- **Inferior Fascial Layer: superficial, perineal membrane
Fascia and communication around Urogenital Diaphragm/Perineal membrane/Deep Perineal Pouch
Scarpa’s membranous fascia of the abdomen
= continuous with Dartos fascia of penis/scrotum = continuous with Colle’s fascia of perineum
ALL attach to the Perineal body
Trauma around Perineal membrane/ Deep perineal pouch/ Urogenital Diaphragm
Trauma –> Bowl of penis bleeds –> blood pours into Superficial pouch –> fascia continuous so blood can fill up into Lower abdomen (and dorsal artery, vein and nerve)
Deep Perineal Pouch/Membranous Urethra muscles
Visceral structures and Perineal membrane creates the deep perineal pouch
Muscles surrounding urethral and vaginal openings
1. External Urethral Opening
2. Sphincter Urethrovaginalis
3. Compressor Urethra = required more in men due to the bend in their urethra
4. Deep Transverse Peroneal muscle
Urethra of men and woman
Mens urethra= bends
Woman’s urethra = straight = requires less help of the compressor urethra
Features of Male Perineum
Membranous urethra Bulbourethral glands (in deep perineal pouch. secretes mucous) Neurovascular stuff (dorsal nerve of penis)
Features of Female Perineum
Vagina
Compressor urethrae muscle
Dorsal nerve of the Clitoris
Bartholin’s glands in Superficial pouch
Superficial perineal pouch
Structures b/w Peroneal membrane and Skin Contains: 1. Nerve and vessels 2. Erectile tissue 3. Perineal muscles 4. Bartholin's glands (females) 5. Everything more superifical is fat
Internal Pudendal Artery
Main male branches: Inferior Rectal, Perineal, Deep artery of penis (+ scrotal, artery of bulb of penis + deep artery of penis)
Main female branches: Inferior Rectal, Perineal, Deep artery of clitoris (+ labial, artery of bulb of vestibule + deep artery of clitoris)
Diagrams *
Schematic*
Pudendal Nerve
S2-4 Supplies: 1. Perineal muscles 2. External Urethral Sphincter 3. Skin of Genitalia and Perineum 4. Erectile muscles (ischial cavernosus and bulbospongiosum)
Pudenal Nerve clinically
risk of damage if insert needle in lateral apex of ischioanal fossa
