Prostate anatomy, embryology

ANATOMY AND EMBRYOLOGY
OF PROSTATE
 Dept of Urology
 Govt Royapettah Hospital and Kilpauk Medical College
 Chennai
1

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, GRH and KMC,
Chennai. 2

PROSTATE
 Inverted pyramidal shape
 18 gms
 3*4*2 cms
 Anterior,posterior and two lateral surfaces
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Chennai.

 Inverted pyramidal shape with base (sup),
apex (inf), four surfaces
1. Surfaces: posterior, anterior, right &
left inferolateral
2. Base (aka: vesicular surface): superior
a. Attached to neck of urinary bladder
b. Prostatic urethra enters middle of
base close to anterior surface
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Chennai.

 Broad base superiorly-outer longitudinal
fibres of detrussor fuse with the fibrous
tissue of the capsule
 Narrow apex inferiorly- continuous with
striated sphincter
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Chennai.

 3. Apex: inferior
 a. Rests on superior fascia of urogenital
diaphragm muscle
 b. Associated with sphincter urethrae
 c. Contacts medial margins of levator ani
muscles
4. Posterior surface: triangular, flat
5. Anterior surface: narrow, convex
 6. Inferiorolateral surfaces
 a. Meet with anterior surface
 b. Rest on levator ani fascia above
urogenital diaphragm 6
Chennai.

7
Chennai.

CAPSULE
TRUE FALSE
- Anatomical capsule - Surgical capsule
- Formed of endopelvic
fascia
- Formed due to
compression of peripheral
zone by enlarging adenoma
False capsule provides plane of clavage for surgical
enucleation of hyper plastic tissue leaving behind
prostatic plexus of veins
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Chennai.

 True capsule absent in apex and base of
bladder
 Posterolaterally fuses with denonvillers fascia
 Anteriorly and anterolaterally fuses with
endopelvic fascia
False capsule-compressed AFMS because of
BPH
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Chennai.

FASCIA
 Levator ani fascia
 Endopelvic fascia/pelvic fascia
 Lateral prostatic fascia
Between pelvic fascia and prostatic
fascia-space filled by areolar fat which
has NV bundle
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Chennai.

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LOBES
 Anatomically 5 in number
 Distinguished in fetal gland < 20 weeks of gestation
 Anterior
– Devoid of glandular tissue
 Posterior
 Middle or median
– Wedge between urethra and ejaculated ducts
– related superiorly to trigone
– Rich in glandular element
– Affected in BPH
 Lateral
– Two in number
– Separated by a shallow vertical groove
– Rich in glandular tissue
– Affected in BPH
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Chennai.

PROSTATE
 70% GLANDS AND 30%
FIBROMUSCULAR STROMA
 Tubuloalveolar glands lined by cuboidal or
columnar epithelium
 Flattened basal cells beneath secretory
epithelial cells
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STRUCTURE OF PROSTRATE
Composition
70% glandular element 30% fibromuscular
stroma made up of
collagen and smooth muscle cells
Traversed by urethra at junction of anterior and middle 1/3rd
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McNEAL ZONES
 Discrete zones- based on location of ducts
in prostatic urethra,embryological origin and
differing pathological lesion
 Transition zone- 5 to 10 %
At an angle btn preprostatic sphincter and
prostatic urethra ,the ducts of TZ arise .
Discrete FMS seperates TZ from other
areas (TRUS) ,commonly gives rise to BHP.
20% Adenocarcinoma
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Chennai.

McNEAL ZONES
 Central zone-25%
Ducts arise circumferentially around
opening of ejaculatory duct .
Cone shape
Wolffian duct origin
1 to 5 % carcinoma
 Peripheral zone-70%
Ducts opening into prostatic sinus along
entite length of prostatic urethra .
70% carcinoma
MC zone of chronic prostatitis 17
Chennai.

McNEAL ‘S ZONES
 Transitional zone surrounds the urethra
proximal to the ejaculatory ducts.
 The central zone surrounds the ejaculatory
ducts and projects under the bladder base.
 The peripheral zone constitutes the bulk of
the apical, posterior, and lateral aspects of
the prostate.
 The anterior fibromuscularstroma extends
from the bladder neck to the striated urethral
sphincter. 18
Chennai.

McNEAL ZONES
 AFMS-upto 1/3rd of prostatic mass
Bladder neck to striated sphincter.
False capsule in BPH.
 Clinically P/R- 2 lateral lobes and central
sulcus
middle lobe projects into bladder
relates to pathological enlargement of TZ
laterally and periurethral glands centrally
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SIGNIFICANCE
 NV bundle
artery and veins
 sphincteric mechanism
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VENOUS ANATOMY
 Veins of the prostate drain into Santorini’s
plexus.(doral vein complex of the
penis/pudental plexus)
 DEEP DORSAL VEIN-leaves penis under
Buck’s fascia between corpora cavernosa and
penetrates urogenital diapragm dividing into
three major branches Superficial branch, right
and left lateral venous plexuses.
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Chennai.

VENOUS ANATOMY
 The superficial branch travels between
puboprostatic ligaments is the centrally
located vein overlying the bladder neck and
prostate.
 The superficial branch lies outside the
anterior prostatic fascia
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VENOUS ANATOMY
 The common trunk and lateral venous
plexuses are covered and concealed by
prostatic and endopelvic fascia
 The lateral venous plexus traverse
posterolaterally and communicate freely with
the pudendal obturator and vesical plexuses
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Chennai.

VENOUS ANATOMY
 The lateral plexus interconnects with the
other venous systems to form inferior
vesical vein,which empties into internal iliac
vein
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ARTERIAL SUPPLY
 Prostate recieves arterial blood supply from
the inferior vesical artery
 Acording to Flocks(1937) after the inferior
vesical artery provides branches to seminal
vesicle and base of the bladder and prostate
the artery terminates in two large groups of
prostatic vessels-the urethral and capsular
groups
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Chennai.

1. Arteries derived
from:
a. Internal pudendal
artery
b. Inferior vesical
artery
c. Middle rectal
artery
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Chennai.

ARTERIAL SUPPLY
• Inferior vesical artery
• Divides into two branch
• Urethral artery Capsular artery
• Approaches at bladder Runs posterolaterally
neck at 1 to 5 O’clock along with
and 7 to 11 O’clock neurovascular
• On resection of gland bundle
• These vessels bleed
significantly specially
those at 4 and 8 O’clock
position
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Chennai.

ARTERIAL SUPPLY
 The urethral vessels enter the prostate at
posterolateral vesicoprostatic junction and supply
the vesical neck and periurethral portion of the
gland.
 The capsular branches run along the pelvic
sidewall in the lateral pelvic fascia posterolateral
to the prostate providing branches that course
ventrally and dorsally to supply the outer portion
of the prostate. 32
Chennai.

ARTERIAL SUPPLY
 On histologic examination the capsular
arteries and veins are surrounded by an
extensive network of nerves (Walsh and
Donker 1982)
 These capsular vessels provide
macroscopic landmark to aid in the
identification of microscopic branches of the
pelvic plexus that innervate the corpora
cavernosa
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Chennai.

ARTERIAL SUPPLY
 The major arterial supply to carpora cavernosa
is derived from the internal pudendal artery
 However pudendal arteries can arise from
obturator inferior vesical and superior vesical
arteries.
 Because these aberrant branches travel along
lower part of bladder and anterolateral part of
prostate, they are divided during radical
prostatectomy(Erectile dysfn)
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PELVIC PLEXUS
 The autonomic innervatin of the pelvic organs and external
genitalia arises from pelvic plexus which is formed by
parasympathetic, visceral, efferent,preganglionic fibres
that arise from sacral center(S2 To S4)and Sympathetic
fibres via hypogastric nerve from thoracolumbar center
 Para sympathetic sacral + superior hypogastric plexus=
inferior hypogastric plexus(PELVIC PLEXUS)
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PELVIC PLEXUS
 The pelvic plexus in men is located retroperitoneally
on either side of rectum 5to11cm from the anal verge
and forms a fenestrated rectangular plate that is in the
sagittal plane within its mid point at the level of tip of
seminal vesicle
 Length 4 to 5 cm
 The pelvic plexus provides visceral branches that
innervate the bladder ureter,seminal vesicles,prostate,
rectum,membranous urethra,and carpora cavernosa.
39
Chennai.

PELVIC PLEXUS
 The branches of inferior vesical artery and vein
that supply the bladder and prostate perforate
the pelvic plexus.
 For this reason ligation of the so called pelvic
pedicle in its mid portion not only interrupts
the vessel but also transects the nerve supply
to the prostate ,urethra and carpora cavernosa.
40
Chennai.

PELVIC PLEXUS
 The branches to the membranous urethra
and carpora cavernosa travel outside the
prostatic capsule in the lateral pelvic fascia
dorsolaterally between the prostate and
rectum.
 Although these nerves are microscopic their
anatomic location can be estimated
intraoperatively by use of capsular vessels
as landmark
This is refered as neuro vascular bundle
of Walsh
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Chennai.

NV BUNDLE OF WALSH
 ACCORDING TO Takenaka and Costello (2004) the
cavernous branches join the capsular arteries and
veins in the spray like distribution to form the
neurovascular bundle 20 to 30mm distal to the junction
of bladder and prostate
 The neurovascular bundle is located in the lateral
pelvic fascia between the prostatic and levator fascia-
a crescentric deposition with respect to posterolateral
capsule of the prostate
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LYMPAHATIC SUPPLY
 Mainly to obturator and internal illiac nodes
 Rarely ext illiac and presacral nodes
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EMBRYOLOGY OF PROSTATE
 Primitive gut tube endoderm gives rise to
foregut,midgut ,hindgut and cloaca.
 Cloaca is divided by urorectal septum during
embryogenesis to create separate urinary and
digestive outlets.
 The ventral urinary compartment is called the
primitive urogenital sinus ,which further
segments into urinary bladder at its cranial
end and the urethra at its caudal terminus.
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 Prostate develops from urogenital sinus through
dihydrotestosterone stimulation.
 Prostate budding :
prostate develops caudal to bladder
neck via proliferation of epithelial buds
extending out from urogenital sinus epithelium
and this process is androgen dependant.
Prostate buds invade at stereotyped locations
that pattern the future development of zones of
prostate. 48
Chennai.

 These regions prepare for epithelial bud
invasion by mesenchymal condensation ,a
process in which urogenital sinus
mesenchymal cells become closely packed
together.This condensation is androgen
independent.
 In humans prostate budding occurs during
10th week of gestation.
49
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A. Pronephros is group of tubules
emptying on either side into the
primary nephric ducts, which
extend caudad to discharge
ultimately into the cloaca. Later in
development a second group of
tubules arises, more caudal in
position than the pronephric
tubules. B. Mesonephric tubules in
their growth extend toward the
primary nephric ducts and open
into them. C. represents
approximately the conditions
attained by the human embryo
toward the end of the 4th week. D.
Depicts the conditions after sexual
differentiation has taken place:
female-left, male-right. Müllerian
ducts arise during the 8th week, in
close association with the
mesonephric ducts. The müllerian
ducts are the primordial tubes from
which the oviducts, uterus, and
vagina of the female are formed.
Note that although both
mesonephric and müllerian ducts
appear in all young embryos, the
müllerian ducts become vestigial in
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Embryologic Development by 5th
Week
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pelvic urethra
Embryologic Development by 5-6th Weeks
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Normal Development of Prostate and
Seminal Vesicle
10th week development of male accessory sexual glands
Mesenchyme induces
endodermal evagination
5
reductase
Testostero
ne
DHT
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Prostate and Seminal Vesicle
Development
 11th week- 5 independent solid cords of
prostatic tissue develop lumens and acini
 13th week- prostatic acini began to develop
secretory activity
 Mesenchyme surrounding prostate develops
into muscle and connective tissue
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MOLECULAR FEATURES OF
PROSTATE DEVELOPMENT
 Induction of prostate budding:
AR signalling throughDHT is the primary
motivating force.Epithelial expression of NK
homeobox transcription family member
Nkx3.1 is earliest marker of induction of
prostate development at molecular level.
Genes required for prostate epithelial budding
TP63
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 Mutations in TP63: abolish epithelial budding.
 Mutations in Noggin: impair ventral lobe
budding.
 AR signalling is required in the mesenchyme
for epithelial budding but dispensable in
epithelium.
 Thus the action of androgens in this process
appears to be indirect.
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Chennai.

 This has led to hypothesis that
messenchymal cells secrete inductive
factors in response to androgens called
Andromedins.
 Mesenchymal condensation: BMP signalling
pathway.
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APPLIED ANATOMY
 Placement of fascial incision above and
parallel to the bundle for nerve sparing
radical prostatectomy
 For wide resection and bundle sacrifice
parallel incision made below and posterior to
bundle(avoiding rectal injury)
Endopelvic fascia incised much laterally
from bladder and prostate to avoid
venous complex injury
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APPLIED ANATOMY
 In perineal operation surgical anatomic entry
line is along the lateral edge of
prostatorectal(denonvilliers fascia) and
medial to bundle if preservation aimed
 High anterior release of NV bundles at the
apex before division of dorsal vein complex-
speed up recovery of sexual function and
continence
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APPLIED ANATOMY
 In retropubic surgery distal transection of the
puboprostatic ligaments far beyond the
prostatourethral junction may lead to
sphincteric(membranous) urethral injury-so
proximal transection advised
 NO MANS LAND-zone distal to prostato
urethral junction( NV bundle+ sphincter)-for
preservation of erectile function and urinary
control
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APPLIED ANATOMY
 ACCESSORY PUDENTAL ARTERY-
Cadaver 70% angio 7% men 4% (rogers et
al 2004)-anterolateral surface of prostate-
Preservation needed for erectile function
 Incising the apex in enlarged prostatic
gland-not to slope but a perpendicular cut
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Prostate anatomy, embryology

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