Urethra anatomy 1

Urethra anatomy 1

1. ANATOMY OF URETHRA

Dept of Urology
Govt Royapettah Hospital and Kilpauk Medical College
Chennai

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2. Moderators:
Professors:
•Prof. Dr. G. Sivasankar, M.S., M.Ch.,
•Prof. Dr. A. Senthilvel, M.S., M.Ch.,

Asst Professors:
•Dr. J. Sivabalan, M.S., M.Ch.,
•Dr. R. Bhargavi, M.S., M.Ch.,
•Dr. S. Raju, M.S., M.Ch.,
•Dr. K. Muthurathinam, M.S., M.Ch.,
•Dr. D. Tamilselvan, M.S., M.Ch.,
•Dr. K. Senthilkumar, M.S., M.Ch.
Dept Of Urology, KMC and GRH, Chennai 2

3. Embryology
Dept Of Urology, KMC and GRH, Chennai 3

4. •Prostatic Urethra .Prox.-mesonephric duct
Distal –urogenital sinus

•Membranous U. & prox. Penile U - urogenital sinus

•Distal penile U.-ingrowth of ectodermal cells of glans.

Dept Of Urology, KMC and GRH, Chennai 4

5. •epithelialized tube for the passage of urine and semen

• “anterior” urethra extends from the meatus to the proximal
bulbar urethra

•“posterior” urethra extends from the bladder neck to the
distal membranous urethra
Dept Of Urology, KMC and GRH, Chennai 5

6. Male urethra
•18–20 cm long

• from internal orifice in the urinary bladder to the meatus

THE ANTERIOR URETHRA ( 16 cm long)
proximally - lies within the perineum
distally - within the penis , surrounded by the corpus-
- spongiosum.

THE POSTERIOR URETHRA ( 4 cm long)
lies in the pelvis proximal to the corpus spongiosum
where it is acted upon by the urogenital sphincter mechanism

Dept Of Urology, KMC and GRH, Chennai 6

7. Parts of urethra
Parts of anetrior urethra
•Fossa navicularis: lined with stratified squamous epithelium

•Pendulous urethra: at the centre of c.spongiosum and lined by lined simple
squamous epithelium

•Bulbous urethra: closer to dorsal aspect of the c.spongiosum, lined distally
with squamous epithelium & transitional epithelium .
Dept Of Urology, KMC and GRH, Chennai 7

8. Parts of distal urethra
•Membranous urethra :traverses the perineal pouch and surrounded
by external urethral sphincter


•Prostatic urethra :proximal to the membranous urethra and is mostly
surrounded by the prostate


•Bladder neck is the location of the bladder neck musculature,
surrounded by intravesical protrusion of the prostate
Dept Of Urology, KMC and GRH, Chennai 8

9. Dept Of Urology, KMC and GRH, Chennai 9

10. Gross structure

Dept Of Urology, KMC and GRH, Chennai 10

11. Pre-prostatic urethra
•1-1.5cm in length

•Circular smooth M.is thickened to form invol.int.sphincter

•Small periurethral glands, extend between smooth M.to be enclosed
by preprostatic sphincter. They form <1% secretary element &
contribute significant prostatic volume in old age

• Smooth M. of this part prevents retrograde ejaculation.
Dept Of Urology, KMC and GRH, Chennai 11

12. Prostatic urethra
•3–4 cm in length

•closer to the anterior than the posterior surface of the gland.

•It is continuous above with the preprostatic part and emerges from the
prostate slightly anterior to its apex

•Throughout its length the posterior wall possesses a midline ridge, THE
URETHRAL CREST.

•On each side of the crest there is a shallow depression, the PROSTATIC
SINUS, the floor of which is perforated by the orifices of 15–20
PROSTATIC DUCTS.
Dept Of Urology, KMC and GRH, Chennai 12

13. Prostatic urethra …CONTD
• Verumontanum(seminal colliculus), is seen at about the middle of the
length of the urethral crest: surgical landmark for the
urethral sphincter during TURP

• At this point the urethra turns anteriorly by 35° and contains the slit-like
orifice of the PROSTATIC UTRICLE.
•
•Utricle ,a 6mm mullerian remnant, a sac project into prostate. Forms
diverticulam in ambiguous genitalia pt

•Both sides of, or just within, this orifice are the two small openings of
the ejaculatory ducts.
.
•The lowermost part of the prostatic urethra is fixed by the puboprostatic
ligaments and is therefore immobile.

Dept Of Urology, KMC and GRH, Chennai 13

14. PROSTATIC URETHRA
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15. Membranous urethra
•Within the urogenital diaphragm

• From apex of prostate to perineal membrane

•Thickly invested by Smooth & striated Muscle

•M. form an incomplete ring at post.midline resembling omega letter

•Its action is more of compressive than spincteric.
Dept Of Urology, KMC and GRH, Chennai 15

16. Dept Of Urology, KMC and GRH, Chennai 16

17. • Urinary continence

•located along the urethra from
the bladder neck to the distal
membranous urethra
•Continence after anastomotic
urethroplasty for post-traumatic
posterior urethral stenosis is
maintained solely by the
proximal urethral continence
mechanism
Dept Of Urology, KMC and GRH, Chennai 17

18. • Urinary continence

•Five “sphincters” are recognized
Dept Of Urology, KMC and GRH, Chennai 18

19. Dept Of Urology, KMC and GRH, Chennai 19

20. Urinary continence at the level of the
membranous urethra is mediated by

•radial folds of urethral mucosa-lumen occlude

•submucosal connective tissue-urethral sealing intrinsic urethral smooth
muscle,

•striated muscle fibres pubourethral component of levatorani.


Dept Of Urology, KMC and GRH, Chennai 20

21. Membranous & prostatic sphincter

Dept Of Urology, KMC and GRH, Chennai 21

22. Bulbar urethra

•Enveloped by penile bulb,bulbospongious Muscle
•Sup. -suspensory ligament
•Inf. -penoscortal junction

•Bifurcation of urethral crest extents from prostatic apex to penile bulb

•Bulbourethral glands drain into proximal bulbar.U

•Intra bulbar part –dilated
Dept Of Urology, KMC and GRH, Chennai 22

23. Bulbar urethra
•RELATIONS :

- dorsal vein complex………>anteriorly,
- levatorani…………………………….>laterally
- perineal body & rectourethralis ………>posteriorly,

• suspended from the pubis by fibrous tissue that extends from its
anterior and lateral parts to the puboprostatic liagaments
posteriorly and to the suspensory ligament of the penis anteriorly.

•The bulbourethral glands are invested in sphincteric muscle and drain
into the membranous urethra during sexual excitement.

Dept Of Urology, KMC and GRH, Chennai 23

24. Bulbar(spongy) urethra

Dept Of Urology, KMC and GRH, Chennai 24

25. Dept Of Urology, KMC and GRH, Chennai 25

26. Penile urethra
•Within the corpus spongiosum

•Extents from Inf. fascia of Urogenital diaphragm to ext.urethral meatus

•Transversely slit like lumen,during micturation it expands to 6 mm

•Navicullar fossa-dilated part

•External urethral meatus-narrowest part

Dept Of Urology, KMC and GRH, Chennai 26

27. Narrowings
3 narrow areas:

 at the membraneous part

 at the junction of glans with corpous spongiosum

 at external urethral meatus
Dept Of Urology, KMC and GRH, Chennai 27

28. Dept Of Urology, KMC and GRH, Chennai 28

29. Urethral curvatures
•Reverse S shaped
•1. Penoscortal angle

•2.Bulbar urethra raises up behind symphysis. Overcome by lowering
the instrument.

•3.large endovesical median lobe: compensated by lowering eye
piece of instrument, pain in unanethetized pt.
Forceful advancement may perforate median lobe.
Dept Of Urology, KMC and GRH, Chennai 29

30. • intramural part- varies in length & caliber –depends on bladder
capacity

•Prostatic U.-widest & most dilatable

•Memb. U. least dilatable = tone of urethral sphincter & rigid
perineal membrane

•Penile U. Most dependent part. Common site for ch. Inflammation &
strictures
Dept Of Urology, KMC and GRH, Chennai 30

31. Glands & recesses
•Bulbourethral glands(cowper’s )
-on the floor of memb.urethra

•Submucosal urethral glands(littre’s)
-on the roof of penile urethra

•Lacuna magna
-large recesses in the roof of F. navicularis
Dept Of Urology, KMC and GRH, Chennai 31

32. Posterior wall of male urethra
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33. Urethral epithelium

•Prostatic - transitional

•Membraneous –stratified columnar

•Penile -pseudostratified columnar

•Fossa naviculoris-stratified squmous

Dept Of Urology, KMC and GRH, Chennai 33

34. Devlopmental anamoly of urethra
•Posterior urethral valve

•Congenital Urethral Fistula

•Congenital Urethral stricture

•Congenital Urethral polyp

•Urethral Duplication

•megalourethra

Dept Of Urology, KMC and GRH, Chennai 34

35. Arterial Supply of the Urethra


•Dual artrial supply
•Proximal urethra in an antegrade fashion, and the distal urethra in a
retrograde fashion.
•The internal pudendal artery branches into the perineal artery and
posterior scrotal artery

Dept Of Urology, KMC and GRH, Chennai 35

36. Arterial supply

•Prostatic - inf. Vesical, mid.rectal A.
•Membranous - artery of bulb (int.pudendal A.)
•Penile -urethral,bulbar, penile A.

•Blood supply through C. Spongiosum is plenty

•Urethra can be divided without compromising its vascularity
Dept Of Urology, KMC and GRH, Chennai 36

37. Arterial supply

•Prostatic - inf. Vesical,mid.rectal A.
•Memb. - art. Of bulb (int.pudendal A.)
•Penile -urethral,bulbar, penile A.
•
•Blood supply through C. Spongiosum is plenty
•Urethra can be divided without compromising
• - its vascularity
Dept Of Urology, KMC and GRH, Chennai 37

38. • After division of the bulbar
arteries, blood supply of the
proximal bulbar urethra
depends on the retrograde
blood supply along its spongy
tissue.
Dept Of Urology, KMC and GRH, Chennai 38

39. VENOUS SUPPLY

Anterior urethra drains into the dorsal veins of the penis & internal
pudendal veins, which drain to the prostatic plexus.

•Posterior urethra drains into the prostatic plexuses, which drain into
the internal iliac veins and vesical venous plexus



Dept Of Urology, KMC and GRH, Chennai 39

40. Dept Of Urology, KMC and GRH, Chennai 40

41. LYMPHATIC DRAINAGE

•Vessels from the posterior urethra pass mainly to the internal iliac
nodes
• Vessels from the membranous urethra accompany the internal
pudendal artery.

•Vessels from the anterior urethra accompany those of the glans penis,
ending in the deep inguinal nodes.

Dept Of Urology, KMC and GRH, Chennai 41

42. NERVE INNERVATION
• prostatic plexus supplies the smooth muscle of the prostate & prostatic
urethra.

•On each side it is derived from the pelvic plexus and lies on the
posterolateral aspect of the seminal vesicle and prostate

•Lesser cavernous nerves pierce the bulb of the corpus spongiosum
proximally to supply the penile urethra.

•Greater cavernous nerves carry the sympathetic supply which causes
contraction of the preprostatic sphincter during ejaculation and prevents
reflux of ejaculate into the bladder.

• parasympathetic preganglionic fibres are axons from neurones in the
second to fourth sacral spinal segments.
Dept Of Urology, KMC and GRH, Chennai 42

43. • The nerve supply of the external urethral sphincter is controversial.

It is believed to be supplied by neurones in Onuf's nucleus& by perineal
branches of the pudendal nerve lying on the perineal aspect of the
pelvic floor


•Fibres from Onuf's nucleus (somatic) travel with the pelvic plexus on
each side until they branch off and run on the pelvic aspect of the pelvic
floor to enter the membranous urethra.

Dept Of Urology, KMC and GRH, Chennai 43

44. Dept Of Urology, KMC and GRH, Chennai 44

45. Ant. Urethral injuries
•Extravasation depends upon which fascial covering is involved.
•When buck’s fascia remains intact, hematoma extends into base of
penis
•When it is violated,butterfly like hematoma is seen over perineum,
contained by dortus F. which extend along abd.wall to colles & scarpa
F.
•Contusion,complete & incomplete injuries
Dept Of Urology, KMC and GRH, Chennai 45

46. ANT. URETHRAL INJURY
Dept Of Urology, KMC and GRH, Chennai 46

47. Posterior urethral injury
•Prostato-membraneous part lies between 2 fixed points
• 1)memb. U-to ischiopubic rami by UGD


2)Prostatic U-to pubis by puboprostatic lig.
Almost all are ass. With pelvic #
sphincter mechanism defect
difficulty in accessability
Dept Of Urology, KMC and GRH, Chennai 47

48. URETHRAL INJURY
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49. POST. URETHRAL INJURY
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50. Urethral strictures
•Scarring induced by local tissue injury

•Trauma- pelvic #,iatrogenic

•Inflamatory-gonococal

•Malignancy

• *Reconstruction is better with traumatic stricture.
Dept Of Urology, KMC and GRH, Chennai 50

51. Female urethra
•From the bladder neck to the meatus
length :3 to 5 cm. Diameter: 6mm.
Can be dilated upto 1cm.
Open into vestibule 2.5 cm below clitoris
At the side of ext.meatus paraurethral glands open
Fibromuscular tube -composed of
-mucosa
-submucosa
-muscle

Dept Of Urology, KMC and GRH, Chennai 51

52. FEMALE URETHRA
Dept Of Urology, KMC and GRH, Chennai 52

53. Female urethra
•More distensible –elastic tissue,smooth M.

•Commonly infected-short, open through vestibule.

•In contrast to male prox.U., No circular smooth M. sphincter.

•Sus. lig. Of clitoris (ant. Urethral lig.) pubourethral lig. (post.
Urethral lig.) form a sling that support urethra beneath pubis.
Dept Of Urology, KMC and GRH, Chennai 53

54. •Except during the passage of urine, the anterior and posterior walls of
the urethra are in apposition
•The epithelium is thrown into longitudinal folds, one of which, on the
posterior wall of the canal, is termed the urethral crest.

• Many small mucous urethral glands and minute pit-like recesses or
lacunae open into the urethra and may give rise to urethral diverticula.

•On each side, near the lower end of the urethra, a number of these
glands, Skene's glands (female prostate), are grouped together and
open into the para-urethral duct.
Dept Of Urology, KMC and GRH, Chennai 54

55. VASCULAR SUPPLY AND LYMPHATIC DRAINAGE

•URETHRAL ARTERY
supplied principally by the vaginal artery, but also receives a supply
from the inferior vesical artery.

•VEINS
The venous plexus around the urethra drains into the vesical venous
plexus around the bladder neck then into the internal pudendal veins.

An erectile plexus of veins along the length of the urethra is continuous
with the erectile tissue of the vestibular bulb.

•LYMPHATIC DRAINAGE
internal and external iliac nodes.
Dept Of Urology, KMC and GRH, Chennai 55

56. •Like male, striated urethral sphincter receives dual somatic
innervation,from pudendal &pelvic.


•Somatic &autonomic N. travel along lat. Wall of vagina,near urethra.


•During transvaginal incontinence surgery,ant.vag. Wall should be
incised laterally –to prevent incontinence
Dept Of Urology, KMC and GRH, Chennai 56

57. MICROSTRUCTURE
•The mucosa consists of a stratified epithelium and a supporting lamina
propriaof loose fibroelastic connective tissue.

•The lamina propria contains a fine nerve plexus, believed to be derived
from sensory branches of the pudendal nerves.

•The proximal part of the urethra is lined by urothelium, identical in
appearance to that of the bladder neck.

•Distally the epithelium changes into a non-keratinizing stratified
squamoustype which lines the major portion of the female urethra.

•keratinized at the external urethral meatuscontinuous with the skin of
the vestibule.


Dept Of Urology, KMC and GRH, Chennai 57

58. Female urethra
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59. Mucosa &submucosa
•Mucosa:
prox- transitional cell
distal –nonkeratinised stratified squmous
•Submucosa:
 long&circular elastic fibers with prominent venous system
 Act as washer producing a seal that contribute to urethral closer
pressuree
In hypoestrogenic state>thinning of tissue>incontinence
Dept Of Urology, KMC and GRH, Chennai 59

60. Muscle layer
•Thick seat of long.fibers &thin outer circular F.
•Distal 2/3-circular layer of striated smooth M
•Rhabdosphincter-
type 1 & 3 muscles fiber
•Proximally,the M. forms ring(sphincter urethra)
•Distally,the M. fans out laterally along inf.border of pubic
rami(compressor urethra)
Dept Of Urology, KMC and GRH, Chennai 60

61. Internal sphincter
•Located at UV JUNCTION.
•Formed by trigonal ring, 2 U –shaped loops from detrusor muscle
•Innervated by autonomic fibers
•Pudendal N.dysfunction-
- birth injury
-prior anti incontinence procedure
- myelodysplasia
•Lead to incontinence even the anatomic support is normal
Dept Of Urology, KMC and GRH, Chennai 61

62. SPHINCTERS OF FEMALE URETHRA
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63. EXTERNAL SPHINCTER
•Proximal portion:
sphincter urethrae muscle
•Distal portion
1.compressor urethrae M.
2. urethrovaginal M.
 located above perineal membrane in the deep compartment of
urogenital triangle
As a unit they contract voluntarily&prevent incontinence if urine gets
passed in a marginally functioning int.sphincter
Dept Of Urology, KMC and GRH, Chennai 63

64. MUSCLES OF EXT SPHINCTER
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65. Mucosal coaptation
•-> increase the urethral resting pressure

•AV complex located between smooth muscle coat &epithelial lining

•Filling of this vasculature with blood,improves mucosal coaptation by
causing urethral walls to seal

•Preventing involuntary urine loss

•They are estrogen sensitive
Dept Of Urology, KMC and GRH, Chennai 65

66. Pubocervical fascia
•Located on the vagina, underneath bladder.
•Ant. Vaginal fascia providing sling for urethra & bladder.
•Prox. -attaches to cervix
•Distal –travels beneath urethra,fuses with perineal membrane.
•Laterally-connected to pelvic wall at fascial white line (F. of levator
ani)
increased abd. Pressure ,lower urinary tract is forced
inferiorly,&compressed against pubocervical F. >>
this UV junction trapping promotes continence.

Dept Of Urology, KMC and GRH, Chennai 66

67. Muscles of pelvic floor
•Levator ani M. –pubococcygeus
• iliococcygeus
•Perineal surface- br.of pudendal N.
•Pelvic surface- motor eff. From S2—S4
•Unlike other striated M., pelvic floor muscles,are in constant state of
contraction>> efficient positioning of UV junction

Dept Of Urology, KMC and GRH, Chennai 67

68. Dept Of Urology, KMC and GRH, Chennai 68

69. Female continence mechanism

 involuntary int.sphincter-vesical neck
Voluntary ext.sphincter-guarding reflex

Mucosal coaptation-urethral submucosal vascular plexus.
•Hammock hypothesis”—abdominal pressure transmitted through
the proximal urethra presses the anterior wall against the posterior
wall
Support of UB &UV junction: pubocevical fascia which is attached to
levator ani ,pelvic floor muscles

Dept Of Urology, KMC and GRH, Chennai 69