MOB TCD

Perineum

Professor Emeritus Moira O’Brien

FRCPI, FFSEM, FFSEM (UK), FTCD

Trinity College

Dublin

Perineum

• Area below the levator ani• Boundaries• Pubic arch• Ischial tuberosities• Sacrotuberous ligament• Coccyx

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Perineal Triangles MOB TCD

• Divided into two triangles• Urogenital triangle• Anal triangle• Perineal body central point

of perineum

Perineum MOB TCD

Urogenital Triangle

• Deep pouch• Superficial pouch• Perineal membrane

separates the two• Deep is superior to

perineal membrane• Roof is pelvic fascia

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Deep Pouch in Male

• Membranous portion of the urethra

• Sphincter urethra or external sphincter of bladder

• Perineal nerve• Deep transverse perineal

muscle

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• Bulbourethreal glands• Internal pudendal artery and

branches • Artery to bulb• Dorsal nerve of penis• Branches of perineal nerve

Deep Pouch in Male MOB TCD

• Vagina• Urethra• Sphincter urethra or external

sphincter of bladder• Perineal nerve• Deep transverse perineal muscle • Internal pudendal artery • Artery to bulb• Dorsal nerve of clitoris

Deep Pouch in Female MOB TCD

Sphincter Urethrae (Female)

• Sphincter urethrae in the deep pouch

• Also called external sphincter of bladder

• Perineal branch of pudendal S 2,3

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Perineal Membrane (Male)

• Piercing membrane• Spongy urethrae• Ducts of bulbourethral glands• Artery to bulb• Internal pudendal artery• Deep and dorsal arteries of

penis• Dorsal nerve of penis• Deep dorsal vein passes above

membrane• Enters prostatic venous plexus

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Superficial Pouch (Male) MOB TCD

Superficial Pouch (Male) MOB TCD

Superficial Pouch (Male) MOB TCD

Colles’ Fascia

• Attached posteriorly to

perineal membrane• Sides of pubic arch laterally• Deep fascia of thigh along a line

drawn from pubic tubercle • Anterior floor of pouch • Layer of scrotum • Surrounds penis as far as glans• Passes up on to anterior

abdominal wall

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Membranous Layer of Superficial or Colles’ Fascia

• Posterior attached to posterior border of perineal membrane

• Anterior it forms floor of superficial pouch and forms layer of the scrotum

• Surrounds penis as far as glans• Then on to anterior abdominal wall• Attached to fascia lata from a

horizontal line from pubic tubercle• Rupture of spongy urethra is limited

by the attachment of Colles’ fascia

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• Roof• Perineal membrane• Floor• Colles’ or membranous layer of

superficial fascia• Ruptured urethra in male• Urine limited by the attachments

of Colles’ fascia in superficial pouch

Superficial Pouch (Male) MOB TCD

• Penis corpus spongiosum• Corpora cavernosa• Spongy urethra• Bulbospongiosus muscle• Ischiocavernosus muscle• Superficial transverse perinei muscle• Internal pudendal artery• Deep and dorsal arteries of penis• Dorsal nerves of penis • Scrotal vessels and nerves

Superficial Pouch (Male) MOB TCD

• Root of penis• Corpus spongiosum• Bulb, body and glans• Spongy portion of urethrae• Crura and corpora cavernosa

Contents Superficial Pouch (Male) MOB TCD

Penis MOB TCD

Penis MOB TCD

• Corpus spongiosum• Corpora cavernosa• Consists of erectile

cavernous tissue• Each enclosed in a fibrous

membrane, tunica albuginea• Surrounded by Colles’

Fascia

Penis MOB TCD

• Deep artery enters crura of corpora cavernosa

• Dorsal nerve of penis• Dorsal artery of penis• Deep dorsal vein lies on

dorsum between Colles’s fascia and tunica albuginea

• Passes above perineal membrane

• Enters prostatic venous plexus

Penis MOB TCD

• Erectile tissue• Helicine arteries• Fibrous saccules arterioles

enter directly• Dorsal vein open• Parasympathetic causes

erection L2,3,4• Ejaculation is via the

sympathetic impulses from L1-L2

Penis MOB TCD

Corpus Spongiosum

• Bulb posterior dilatation• Body (horizontal)• Glans dilated anteriorly• Spongy urethra• Dilated posteriorly in the bulb• Uniform in body• Dilated in the glans• Fossa navicularis• Meatus vertical slit

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Spongy Urethra MOB TCD

• Urethra unprotected • Before it enters bulb• Ducts of bulbo-urethral glands • Enter intrabulbar fossa• Littre’ glands end in navicular

fossa

Spongy Urethra MOB TCD

Muscles in Superficial Pouch (Male)

• Bulbospongiosus muscle• Ischiocavernosus muscle• Superficial transverse perinei

muscle• Supplied by perineal

branches of pudendal nerve• Enter pouch by piercing

Colles’ fascia

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Vessels and Nerves

• Deep and dorsal arteries of penis

• Deep dorsal vein• Scrotal nerves• Perineal nerve• Dorsal nerve of penis

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Lymphatics

• Skin of scrotum to medial superficial inguinal glands

• Testes to para aortic glands at L2

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Nerve Supply

• Preganglionic of sympathetic from L1 and L2 cause ejaculation

• Parasympathetic preganglionic from S2,3,4 cause erection

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Female Pelvis and Perineum MOB TCD

Superficial Pouch (Female)

• Mons pubis• Labia majora• Labia minora• Dorsal prepuce • Frenulum of glans• Vestibule

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Superficial Pouch (Female) MOB TCD

• Urethra• Vagina• Clitoris• Crura of clitoris• Ischiocavernosa• Bulbs of vestibule join, pass

to glans • Bulbospongiosus• Bartholin’s or vestibular glands

Superficial Pouch (Female) MOB TCD

• Crura and glans of clitoris • Covered by

ischiocavernosus muscle• Bulbs of vestibule• Inferior greater vestibular

or Bartholin’s glands beside vagina

• Covered by bulbospongiosus muscle

Superficial Pouch (Female) MOB TCD

Superficial Pouch (Female) MOB TCD

• Cutaneous anteriorly• Ilioinguinal nerve• Labial vessels and nerve

posteriorly• Motor• Perineal branches of pudendal

Superficial Pouch (Female) MOB TCD

Structure of Female Urethra

• Muscular layer continuous with bladder• Spongy erectile tissue • Plexus of veins• Mucous membrane transitional• Distal non-keratinising stratified squamous • No fascia between lower two thirds of urethra

and vagina

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Vagina

• Fornices, gutters which surround the cervix

• Anterior shallow• Posterior deeper• Superior covered with

peritoneum of the pouch of Douglas

• Lateral: uterine artery above ureter

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• Upper portion of the vagina is clasped

• By the pubovaginalis portion of the levator ani

• Bulbospongiosus muscles surrounds outlet

• Hymen

Vagina MOB TCD

• Erectile tissue• Muscular wall• Pelvic fascia• Non-keratinised stratified squamous

epithelium• Urethra lower third anterior wall• No fascia between lower two thirds

of urethra and vagina

Vagina MOB TCD

• Anal canal• Ischiorectal fossa

Anal Triangle MOB TCD

• Anorectal junction: below ampulla of rectum

• Anus: 4 cm• Anterior: perineal body• Posterior: anococcygeal body• Lateral: ischiorectal fossae

Anal Canal MOB TCD

• Upper two thirds• Columnar epithelium• Anal columns contain radicles

of superior rectal artery and veins

• 4, 7, 11 o’clock position• Anal valves along pectinate line• Anal sinus, Hilton white line;

internal sphincter• Subcutaneous deep• Lower third skin

Anal Canal MOB TCD

Muscles of Anal Canal

• Anorectal ring• Internal sphincter• Puborectalis• Puborectal fascia• External sphincter• Deep; true sphincter• Inferior rectal nerve • Superficial S4• Subcutaneous; true sphincter• Inferior rectal nerve

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• Anorectal ring• Puborectalis• Internal sphincter• Upper two thirds• Perianal fascia is medial to

deep and superficial sphincter• Passes to lateral wall forms

pudendal canal • Above subcutaneous sphincter

Muscles of Anal Canal MOB TCD

Blood and Nerve Supply

• Mucosa upper two thirds• Superior rectal artery• Autonomic nerves• Lower third• Inferior rectal• Somatic nerves

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Venous Drainage

• Mucosa upper two thirds• Superior rectal vein• Portal system• Lower third• Inferior rectal vein• Vein into systemic system• Portal systemic anastomosis

4,7,11 o’clock

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Lymphatic Drainage

• Upper third• Pre-aortic inferior mesenteric• Waldeyer’s fascia passes from

sacrum to the ampulla of rectum• Encloses superior rectal vessels

and lymphatics• Internal iliac• Lower third• Inferior rectal cross ischiorectal fossa• Medial superficial inguinal glands

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Embryology of Anal Canal

• Upper two thirds• Cloaca• Lower third • Proctodeum

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Ischiorectal Fossa

• Wedge shaped fossa• Apex: origin of levator ani

from obturator internus• Lunate fascia • Base: perianal fascia and

subcutaneous fat• Medial: levator ani• External anal sphincters

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• Anterior: posterior border perineal membrane

• Posterior: sacrotuberous ligament, gluteus maximus

Ischiorectal Fossa (Female) MOB TCD

• Lateral: fascia on medial aspect of obturator internus ani

• Pudendal canal • Ischial tuberosity

Ischiorectal Fossa (Male) MOB TCD

• Soft ischiorectal fat• Lunate fascia above the fat• Inferior rectal vessels pass

above the fat to reach medial wall

• Perineal branch of S4

Ischiorectal fossa

Ischiorectal Fossa MOB TCD

Pudendal Canal

• Runs posterior to anterior• Contents• Pudendal nerve• Inferior rectal nerve• Dorsal nerve of penis or clitoris• Perineal nerve• Scrotal or labial nerves

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Pudendal Block MOB TCD

Dermatomes MOB TCD

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