Anatomy of perineum

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2. MOB TCD
Perineum
Professor Emeritus Moira O’Brien
FRCPI, FFSEM, FFSEM (UK), FTCD
Trinity College
Dublin

3. Perineum
•Area below the levator ani
•Boundaries
•Pubic arch
•Ischial tuberosities
•Sacrotuberous ligament
•Coccyx
MOB TCD

4. Perineal Triangles
MOB TCD

5. •Divided into two triangles
•Urogenital triangle
•Anal triangle
•Perineal body central point
of perineum
Perineum
MOB TCD

6. Urogenital Triangle
•Deep pouch
•Superficial pouch
•Perineal membrane
separates the two
•Deep is superior to
perineal membrane
•Roof is pelvic fascia
MOB TCD

7. Deep Pouch in Male
•Membranous portion of
the urethra
•Sphincter urethra or
external sphincter of
bladder
•Perineal nerve
•Deep transverse perineal
muscle
MOB TCD

8. •Bulbourethreal glands
•Internal pudendal artery and
branches
•Artery to bulb
•Dorsal nerve of penis
•Branches of perineal nerve
Deep Pouch in Male
MOB TCD

9. •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

10. Sphincter Urethrae (Female)
•Sphincter urethrae
in the deep pouch
•Also called external
sphincter of bladder
•Perineal branch of
pudendal S 2,3
MOB TCD

11. 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
MOB TCD

12. Superficial Pouch (Male)
MOB TCD

13. Superficial Pouch (Male)
MOB TCD

14. Superficial Pouch (Male)
MOB TCD

15. 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
MOB TCD

16. 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
MOB TCD

17. •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

18. •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

19. •Root of penis
•Corpus spongiosum
•Bulb, body and glans
•Spongy portion of urethrae
•Crura and corpora cavernosa
Contents Superficial Pouch (Male)
MOB TCD

20. Penis
MOB TCD

21. Penis
MOB TCD

22. •Corpus spongiosum
•Corpora cavernosa
•Consists of erectile
cavernous tissue
•Each enclosed in a fibrous
membrane, tunica albuginea
•Surrounded by Colles’
Fascia
Penis
MOB TCD

23. •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

24. •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

25. 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
MOB TCD

26. Spongy Urethra
MOB TCD

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

28. 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
MOB TCD

29. Vessels and Nerves
•Deep and dorsal arteries of
penis
•Deep dorsal vein
•Scrotal nerves
•Perineal nerve
•Dorsal nerve of penis
MOB TCD

30. Lymphatics
•Skin of scrotum to medial
superficial inguinal glands
•Testes to para aortic glands
at L2
MOB TCD

31. Nerve Supply
•Preganglionic of sympathetic
from L1 and L2 cause
ejaculation
•Parasympathetic
preganglionic from S2,3,4
cause erection
MOB TCD

32. Female Pelvis and Perineum
MOB TCD

33. Superficial Pouch (Female)
•Mons pubis
•Labia majora
•Labia minora
•Dorsal prepuce
•Frenulum of glans
•Vestibule
MOB TCD

34. Superficial Pouch (Female)
MOB TCD

35. •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

36. •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

37. Superficial Pouch (Female)
MOB TCD

38. •Cutaneous anteriorly
•Ilioinguinal nerve
•Labial vessels and nerve
posteriorly
•Motor
•Perineal branches of pudendal
Superficial Pouch (Female)
MOB TCD

39. 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
MOB TCD

40. 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
MOB TCD

41. •Upper portion of the vagina is
clasped
•By the pubovaginalis portion of
the levator ani
•Bulbospongiosus muscles
surrounds outlet
•Hymen
Vagina
MOB TCD

42. •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

43. •Anal canal
•Ischiorectal fossa
Anal Triangle
MOB TCD

44. •Anorectal junction: below
ampulla of rectum
•Anus: 4 cm
•Anterior: perineal body
•Posterior: anococcygeal body
•Lateral: ischiorectal fossae
Anal Canal
MOB TCD

45. •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

46. 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
MOB TCD

47. •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

48. Blood and Nerve Supply
•Mucosa upper two thirds
•Superior rectal artery
•Autonomic nerves
•Lower third
•Inferior rectal
•Somatic nerves
MOB TCD

49. 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
MOB TCD

50. 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
MOB TCD

51. Embryology of Anal Canal
•Upper two thirds
•Cloaca
•Lower third
•Proctodeum
MOB TCD

52. 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
MOB TCD
MOB TCD

53. •Anterior: posterior border
perineal membrane
•Posterior: sacrotuberous
ligament, gluteus maximus
Ischiorectal Fossa (Female)
MOB TCD

54. •Lateral: fascia on medial aspect
of obturator internus ani
•Pudendal canal
•Ischial tuberosity
Ischiorectal Fossa (Male)
MOB TCD

55. •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

56. Pudendal Canal
•Runs posterior to anterior
•Contents
•Pudendal nerve
•Inferior rectal nerve
•Dorsal nerve of penis or clitoris
•Perineal nerve
•Scrotal or labial nerves
MOB TCD

57. Pudendal Block
MOB TCD

58. Dermatomes
MOB TCD

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