Urethra anatomy 2

Urethra anatomy 2

1. ANATOMY OF MALE & FEMALE
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. 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

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4. GROSS STRUCTURE

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5. SUBDIVISION

• anterior urethra :

•PROXIMAL COMPONENT the bulbar urethra, which is surrounded
by the bulbospongiosus
A PENDULOUS OR PENILE COMPONENT,
which continues on to the tip of the penis.

• posterior urethra
•PREPROSTATIC,
• PROSTATIC ; AND
•MEMBRANOUS SEGMENTS.

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6. Dept Of Urology, KMC and GRH, Chennai 6

7. •In the flaccid penis, the urethra has a DOUBLE
CURVE.
• The urethral canal is a mere slit, except during
voiding urine
• IN TRANSVERSE SECTION
-- transversely arched >>prostatic part
-- stellate >> preprostatic&membranous
-- transverse>> bulbar and penile portions,
-- sagittal >> external orifice.
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8. PRE-PROSTATIC URETHRA
At its midpoint ,the urethra turns 35 degree anteriorly
*This angle divides this segment into
pre –prostatic --1—1.5 cm
prostatic
•* circular smooth M.is thickened to form
invol.int.sphincter
*small periurethral glands, extend bet.long.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.
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9. 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 most of 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.
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10. PROSTATIC URETHRA …CONTD
•An elevation, THE 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. Male equivalent of
vagina.
•
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.

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11. PROSTATIC URETHRA
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12. MEMBRANOUS URETHRA
•Within the urogenital diaphragm. From apex
of prostate to perineal memb.
•Thickly invested by Smooth &striated M.
•Striated ext.coa t-vol.urinary sphincter.
•M. form an incomplete ring at post.midline-
•Resembling omega letter
•Its action is more of compressive than
spincteric.
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13. Ext.urethral sphincter
•Signet ring shape, broad at its base ,narrowing as
it passes thr’ urogenital hiatus of L.ANI.
•At the apex of prostate,surrounds by circular
circular fib.
*Post. Inserts into perineal body-
on contraction,urethra is pulled towards it.
*Fib. Rich in myosin ATPase –tonic contraction
*Anterior-dorsal vein complex
lateral –levator ani .
*Pudendal N. &sacral plexus
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14. Dept Of Urology, KMC and GRH, Chennai 14

15. 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.


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16. Membranous&prostatic sphincter

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17. Reproductive & urinary tract

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18. BULBAR URETHRA

•Enveloped by penile bulb,bulbospongious M.
•Sup. -suspensory ligament.
•Inf. -penoscortal junction
•Bifurcation of urethral crest extents from
prostatic apex to penile bulb
•Bulbourethral glands drain into prox.bulbar.U.
•Intra bulbar part –dilated.
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19. Bulbar(spongy) urethra

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20. 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
puboprostaticliagamentsposteriorlyand 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 20

21. Dept Of Urology, KMC and GRH, Chennai 21

22. 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.
• calculous can lodge.
Dept Of Urology, KMC and GRH, Chennai 22

23. NARROWINGS
3 narrow areas:

 at the membraneous part

 at the junction of glans with corpous
spongiosum

 at ext.urethral meatus.
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24. Dept Of Urology, KMC and GRH, Chennai 24

25. Urethral curvatures
•1. penoscortal angle
•2.bulb -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 25

26. • intramual 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
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27. 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
•- -Catch tip of catheter, instruments are
introduced their back downwards.
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28. Posterior wall of male urethra
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29. Urethral epithelium

•Prostatic - transitional
•Membraneous –stratified columnar
•Penile -pseudostratified columnar
•Fossa naviculoris-stratified squmous

•UROEPITHELIUM – same pathological process
(ex.) papillomata.
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30. MALE URETHRA
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31. 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
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32. 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
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33. VEINS
•
anterior urethra drains into the dorsal veins
of the penis & internal pudendal veins, which
drain to the prostatic plexus.

•posterior urethradrains into the prostatic
plexuses, which drain into the internal iliac
veins.and vesical venous


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34. Dept Of Urology, KMC and GRH, Chennai 34

35. LYMPHATIC DRAINAGE

•Vessels from the posterior urethra pass mainly to the
internal iliac nodes (a few may end in the external 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.
NOTE : Some may end in superficial nodes, others may traverse
the inguinal canal to end in the external iliac nodes.

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36. 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 preganglionicfibresare axons from
neurones in the second to fourth sacral spinal segments.
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37. Dept Of Urology, KMC and GRH, Chennai 37

38. • 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.

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39. Embryogenesis
•Prostatic U .
prox.-mesonephric duct. Distal –urogenital sinus.
•Membranous U. & prox. Penile U.
-urogenital sinus -
•Distal penile U.-ingrowth of ectodermal cells of glans.
•
•EPISPADIAS.-
urethral opening over dorsum of penis - due to shift of
lat.analge of gen.tubercle
•HYPOSPADIAS
•Failure of function of urethral fold
•Urethral opening over perineum/penoscortam
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40. 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.
• ext. along abd.wall to colles &scarpa F.
•Contusion,complete&incomplete injuries
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41. ANT. URETHRAL INJURY
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42. Posterior urethral injury
•Prostato-membraneous part lies bet.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
*lack of.accessability
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43. URETHRAL INJURY
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44. POST. URETHRAL INJURY
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45. Urethral strictures
•Scarring induced by local tissue injury
1)trauma- pelvic #,iatrogenic
2)inflamatory-gonococal
3) malignancy
*Reconstruction is better with traumatic
stricture.
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46. Urethral strictures

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47. Male urethral carcinoma
•80% -squamous cell ca.
Mc—bulbomembraneous urethra.
Ant.urethral ca: --
amenable to surgery,better prognosis.
Post.urthral ca:.
-extensive local invasion,distant metastsis
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48. Female urethra
length :3 to 5 cm. Diameter: 6mm.
Can be dilated upto 1cm.
From neck of UB to ext. meatus.
Open into vestibule 2.5 cm below clitoris.
At the side of ext.meatus paraurethral glands open
Fibromuscular tube -composed of
-mucosa
-submucosa
-muscle

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49. FEMALE URETHRA
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50. Female urethra
•More distensible –elastic tissue,smooth M.
•Easily dilated- instrumentation without inj.
•Commonly infected-short, open thr’ vestibule.
•In contrast to male prox.U., NO cicular smooth
M. sphincter.
•Sus. lig. Of clitoris (ant. Urethral lig.)
pubourethral lig. (post. Urethral lig.) form a
sling that support urethra beneath pubis.
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51. •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.
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52. 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.
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53. •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
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54. 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.


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55. Female urethra
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56. 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
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57. Muscle layer
•Thick seat of long.fibers &thin outer circular F.
•Distal 2/3-circular layer of striated smooth M
•Rhabdosphincter-
type 1 fiber& 3muscles.
•Proximally,the M. forms ring(sphincter
urethra)
•Distally,the M. fans out laterally along
inf.border of pubic rami(compressor urethra)
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58. 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
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59. SPHINCTERS OF FEMALE URETHRA
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60. 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
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61. MUSCLES OF EXT SPHINCTER
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62. Mucosal coaptation
•AV complex located bet.smooth muscle coat
&epithelial lining.
•Filling of this vasculature with blood,improves
mucosal coaptation by causing urethral walls
to seal
•-> increase the urethral resting pressure >>
•Preventing involuntary urine loss
•They are estrogen sensitive
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63. 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.

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64. 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

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65. Dept Of Urology, KMC and GRH, Chennai 65

66. THANK U

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67. Female continence mechanism

 involuntary int.sphincter-vesical neck
Voluntary ext.sphincter-muscles of urethra
Mucosal coaptation-urethral submucosal vascular
plexus.
support of UB &UV junction:
pubocevical fascia which is attached to
levator ani ,
pelvic floor muscles

Dept Of Urology, KMC and GRH, Chennai 67