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Review Of Literature
Chapter 1
Anatomy And Emberyology of the Penis And
Male Urethra
Fig (1): Ventral aspect of the constituent erectile masses of the penis in erect
position. (Healy j et al, 2008).
The penis, the male copulatory organ, comprises an attached
radix or root in the perineum and a free, normally pendulous corpus or
body completely enveloped in skin.
Root of the Penis
As shown in figure before the root of the penis comprises the
three masses of erectile tissue in the urogenital triangle: the two crura
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and the bulb of the penis, firmly attached to the pubic arch and perineal
membrane respectively. The crura are the posterior regions of the
corpora cavernosa and the bulb, the posterior end of the corpus
spongiosum (Healy j et al, 2008).
Each crus penis commences behind as a blunt, elongated but
rounded process, attached firmly to the everted edge of the ischiopubic
ramus and covered by the ischiocavernosus. Anteriorly it converges
towards its fellow and is slightly enlarged posterior to this. Near the
inferior symphyseal border the two crura bend sharply down and
forwards to become the corpora cavernosa (Healy j et al, 2008).
The bulb of the penis lies between the crura and is firmly
connected to the inferior aspect of the perineal membrane, from which
it receives a fibrous covering. Oval in section, the bulb narrows
anteriorly into the corpus spongiosum, bending sharply down and
forwards at this point. Its convex superficial surface is covered by
bulbospongiosus; its flattened deep surface is pierced above its centre
by the urethra, which traverses it to reach the corpus spongiosum. This
part of the urethra has an intrabulbar fossa (Healy j et al, 2008).
Corpus of the Penis
The corpus of the penis contains three elongated erectile masses,
capable of much enlargement when engorged with blood during
erection. When flaccid it is cylindrical, but when erect it is triangular
with rounded angles, The surface which is poster superior during
erection is termed the dorsum of the penis and the opposite aspect the
urethral surface. The erectile masses are termed the right and left
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corpora cavernosa, and the median corpus spongiosum penis,
continuations of the crura and bulbous penis (Healy j et al, 2008).
The corpora cavernosa form most of the corpus, (fig 2) In close
apposition throughout, they have a common fibrous envelope and are
separated only by a median fibrous septum. On the urethral surface
their combined mass has a wide median groove, adjoining the corpus
spongiosum, dorsally a similar but narrower groove contains the deep
dorsal vein (Healy j et al, 2008).
Fig (2 ): Cross section of the penis at the junction of its middle and distal thirds.
The corpora end distally in the hollow, proximal aspect of the
glans penis in a rounded cone, on which each has a small terminal
projection. They are enclosed in a strong fibrous tunica albuginea,
consisting of superficial and deep straia. The superficial fibers are
longitudinal, forming a single tube round both corpora; the deep fibers
are circularly orientated and surround each corpus separately, joining
together as a median septum of the penis, which is thick and complete
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proximally but imperfect distally where it consists of a pectiniform
(comb-like) series of bands; hence the term pectiniform septum
(Healy j et al, 2008).
The corpus spongiosum penis, traversed by the urethra, adjoins
the median groove on the urethral surface of the conjoined corpora
cavernosa. It is cylindrical, tapering slightly distally, and surrounded by
a tunica albuginea. Near the end of the penis it expands into a
somewhat conical enlargement like an acorn, whence its name, glans
penis (Healy j et al, 2008).
The glans penis projects dorsally over the end of the corpora
cavernosa, with a shallow concave surface to which they are attached.
Its base has a projecting corona glandis, overhanging an obliquely
grooved neck of the penis. The navicular fossa of the urethra is in the
glans and opens by a sagittal slit on or near its apex.
Fig (3 ): Arrangement of the Buck's and dartos fasciae ( Gregory et al ; 2012)
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The superficial penile fascia, (fig 3) which is devoid of fat,
consists of loose connective tissue, invaded by a few fibers of dartos
muscle from the scrotum, and hence called the Dartos fascia. As in the
suprapubic abdominal wall, the deepest layer is condensed here as the
fascia penis or Buck's fascia surrounding both the corpora cavernosa
and corpus spongiosum and separating the superficial and deep dorsal
veins. At the penile neck it blends with the fibrous covering of all three
corpora. Proximally, it is continuous with the dartos muscle and with
the fascia covering the urogenital region of the perineum (Healy j et al,
2008), as shown in figure 3 showing arrangement of the Buck's and
dartos fasciae ( Gregory et al ; 2012)
The corpus penis is supported by two ligaments continuous with
its fascia and consisting largely of elastin fibers. The fundiform
ligament, stemming from the lowest part of the linea alba, splits into
two lamellae which skirt the penis and unite below with the scrotal
septum. The triangular suspensory ligament, deep to the fundiform
ligament, is attached above to the front of the pubic symphysis,
blending below, on each side, with the fascia penis (Gregory et al,
2012)
The male urethra is divided into six parts: bladder neck, prostatic
urethra, membranous urethra, bulbous urethra, penile (pendulous
urethra), and the fossa navicularis within the distal glans. The corpus
spongiosum is the erectile tissue inferior to the corpora cavernosa, the
penile and bulbar urethra lie within the spongiosum, the penile urethra
lies in a central location within the spongiosum, whereas the bulbar
urethra lies eccentrically closer to the dorsal spongiosum prior to
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exiting dorsally to become the membranous urethra to join the prostate
(Brooks ; 2007).
This is described in the following (fig 4&5) showing post wall of
urethra and parts of urethra.
Fig (4): Posterior wall of the male urethra. (Gregory et al; 2012)
Fig (5): Parts of the urethra (Gregory et al; 2012)
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The superficial fascia of the penis, or dartos fascia, is a part of
the membranous layer of the superficial fascia of the groin and
perineum or Colles’ fascia. (Fig6) Imbedded in it are the superficial
penile arteries and the superficial dorsal vein, vessels that supply the
skin. This layer is only loosely applied to the one beneath it and, hence,
is mobile. It separates the superficial veins from the deep dorsal veins.
Buck’s fascia has a dense structure, in contrast to the loose superficial
fascia of the penis. It is composed of longitudinally running fibers and
is firmly attached to the underlying tunica albuginea. (Gregory et al;
2012)
Fig (6): Arrangement of the tunica albuginea (Gregory et al; 2012)
The deepest layer is the tunica albuginea, forming a thick white
coat set in a fibroareolar matrix (fig 6). This layer encloses the corpora
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cavernosa and the corpus spongiosum. It is covered closely by Buck’s
fascia. Two layers may be identified: (1) an outer longitudinal coat and
(2) an inner circular coat. The tunica albuginea becomes thicker
ventrally as it forms a groove for the corpus spongiosum.
Ventromedially, it is thinned as the outer coat becomes attenuated,
leaving only the inner coat. This difference in the thickness of the tunic
explains the greater susceptibility of the urethra to inadvertent entry
during insertion of a penile prosthesis. Similarly, at the crura, it is only
the inner coat that provides the cover. The two corpora cavernosa are
separated in the sagittal plane by a dense tunica albugineal layer that
passes between them as the intercavernous septum. The septum is
incomplete distally, being perforated on its dorsal margin by vertically
oriented openings in the pectiniform septum that provide free vascular
communication between the corpora. Continuous with the inner surface
of the tunica albuginea within the corporal bodies are numerous
flattened columns or sinusoidal. (Gregory et al; 2012)
Most cases of hypospadias, regardless of severity, are associated
with a prepuce that could be sufficient to create a neourethra to bridge
the existing gap and cover the repair with skin. Success is in a major
part dependent on three preconditions:
 The inner layer of the prepuce has to be long enough.
 The epithelial surface of the prepuce has to be adequate.
 The subcutaneous tissue between the outer and inner layer of the
prepuce has to be sufficient and carry enough blood vessels for
vascularisation of the two layers.
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However, any technique using the prepuce for the repair affect
the blood supply and the result. Knowledge of the blood supply of the
prepuce is essential so that preservation of the preputial vascularisation
is not ignored (Zachariou, 2004).
Mucous Membrane of the Male Urethra
The penile urethra is lined with pseudostratified columnar
epithelium. However, islands of stratified squamous epithelium are
found near the meatus, reflecting the ectodermal source of this portion
of the urethra. The urethra in the distal portion of the glans is lined with
more differentiated squamous cells lying over connective tissue
papillae. These cells even become keratinized at the meatus, which is
further evidence of their separate origin. (Gregory et al ; 2012)
The surface epithelium has no muscularis mucosae because it is
separated from the smooth muscle of the spongy tissue by loose
connective tissue. The lateral and especially the dorsal surfaces of the
fossa navicularis contain numerous pockets. (Gregory et al ; 2012)
One large pocket, the lacuna magna (Morgagni), opens on the
roof of the fossa navicularis. On the anterior wall of the distal urethral
segment are small recesses, the urethral lacunae. In addition, on the
posterior wall of the penile and bulbar urethra are orifices of the ducts
draining minute clusters of mucus-secreting cells, the glands of Littré,
that lubricate the urethra prior to ejaculation. (Gregory et al ; 2012)
These ducts run obliquely beneath the submucosal connective
tissue to open toward the meatus and so may be entered inadvertently
during urethral instrumentation. These glands, rich in goblet cells,
penetrate the spongy tissue among the trabeculae and vascular spaces.
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This tissue reacts by dense fibrous proliferation to infection arising in
these glands or from urinary extravasation. Subsequent contraction of
the inflamed spongy tissue creates the spongiofibrosis of urethral
strictures. (Gregory et al ; 2012)
The preputial skin with its accompanying superficial fascia and
vessels is ideal for the constructions of flaps for hypospadias repair. It
is relatively thin and pliable, and especially the thin epithelialised layer
on the inside of the prepuce tolerates prolonged contact with urine
better than any other tissue except the bladder urothelium (Zachariou,
2004).
Urethral Sphincters
Of the two urethral sphincters, the internal sphincter vesical
controls the vesical neck and the prostatic urethra above the ejaculatory
ducts. It is composed of no striated muscle and supplied by sympathetic
fibers from the vesical plexus. The external sphincter urethrae
surrounds the membranous urethra; it consists of striated muscle and is
supplied by the perineal branches of the pudendal nerve (S2, 3 and 4);
it is voluntary after early infancy. (Gregory et al ; 2012)
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Blood Supply of the Urethra and penis
Fig (7): normal position of the neuro-vascular bundle (Gregory et al; 2012)
Regarding the arterial supply of the urethra, (fig7&8&9) there
are anastomotic communications between the dorsal arteries and the
bulbourethral arteries, the urethra receives arterial supply from both
distal and proximal directions, this enables complete transaction of the
urethra without necrosis of the distal segment (Yiee et al,2010).
Fig (8): arterial supply of the urethra (Kavoussi et al, 2012)
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(1) Superficial Arterial System
The superficial arterial supply to the penile skin and prepuce lies in
the superficial layer of the superficial fascia of the penis overlying
Buck’s fascia. The penile skin is well-vascularized with a very flexible
cutaneous blood supply of coiled vessels running along the shaft. Two
more or less symmetrically arranged, longitudinally oriented vessels,
the superficial penile arteries, arise from each inferior external
pudendal artery, a branch of the femoral artery. (Gregory et al; 2012)
Regarding the prepuce, its arterial supply is via four branches
from the inferior external pudendal arteries (2 dorso-laterally and 2
ventro-laterally). (fig9) These arteries divide into anterolateral and
posterolateral branches, so in hypospadias repair it is necessary to keep
intact at least one and preferably two of the four branches of these
arteries supplying the penile skin . (Uskiewenski et al;1982)
The superficial penile arteries divide on each side, usually into a
dorsolateral and a ventrolateral branch. However, there are equally
common arrangements that make the skin partially dependent on one or
the other principal superficial artery. When the blood supply is
symmetric, each artery enters the lateral aspect of the penis near the
base, then branches as it runs out the shaft to form a dorsolateral and a
ventrolateral vessel. When the total supply comes from one artery, that
vessel divides soon after entering the penis, so that one branch crosses
over the dorsum to the opposite side. In either case, subsequent
branches course dorsolaterally and ventrolaterally on each side. At
intervals, these vessels give off fine branches to the skin. The only
point of connection between the deep and superficial systems is an
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anastomosis at the coronal sulcus, where the superficial vessels circle
back dorsally to join the dorsal artery of the penis(. (Gregory et al ;
2012)
Also there is a fact that a flap from the shaft will have a better
blood supply than one from the prepuce, which in turn, will be more
vascular than one taken from the inner preputial surface, because the
vessels are arranged axially, only longitudinal pedicles can be raised,
because the prepuce is not supplied by vessels distally from the corona,
all flaps must be based on the superficial fascial system of blood
vessels that enter the prepuce proximally (Hinman et al; 1991)
Fig (9):the prepuce and its blood supply the prepuce and its blood supply (Gregory
et al ; 2012 )
The blood supply of the penile skin (fig10) is symmetrical
(Juskiewenski et al. 1982). The superior and inferior external pudendal
arteries arise from the femoral artery. They are attached to the Scarpa
fascia, which extends to the base of the penis. At this point they divide
into four branches as superficial penile arteries. Two enter the
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superficial penile fascia dorsolaterally and two enter it ventrolaterally.
Numerous collaterals between these four arteries create a fine
subcutaneous arterial plexus up to the preputial ring (Quartey 1997).
Behind the sulcus in the distal part of the penile shaft, small
vessels penetrate the Buck's fascia, making an anastomosis with the
dorsal penile artery. Beyond the preputial ring on the inner surface the
terminal branches become minute. Variations of the superficial penile
arteries are possible with dominance of one side pair. (Zachariou,
2004).
Fig (10): Peripheral arterial blood supply of the penis
The blood supply to the frenulum (fig11) is also symmetrical and
arises from the dorsal penile artery, which branches at the level of the
sulcus with small arteries that curve around each side of the distal shaft
to enter the glans and the frenulum ventrally. (Zachariou, 2004).
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Fig (11): Arterial blood supply of the frenulum
(2) Deep Arterial Supply to the Penis
The anterior branch of the internal iliac artery divides to form the
inferior gluteal artery and the internal pudendal artery. Viewed from
within the pelvis, the internal pudendal artery passes beneath the
sacrospinous ligament and over the sacrotuberous ligament and
bifurcates into the perineal artery and continues as the penile artery,
which runs under the superficial transverse perineal muscle and the
symphysis. (Gregory et al; 2012)
The penile artery pierces the urogenital diaphragm along the
medial margin of the inferior ramus of the ischium behind the
superficial transverse perineal muscle near the bulb of the urethra, and
divides into three branches: (1) the bulbourethral artery (artery to the
bulb of the penis), (2) the urethral artery, and (3) the cavernous artery
or the deep artery of the penis. It then terminates as the dorsal artery of
the penis. Considerable variation can be found: an accessory internal
pudendal artery is common, arising from the obturator artery, the
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inferior vesical artery, or the contralateral superior vesical artery. It is
this alternate but essential blood supply to the corpora that may be
inadvertently divided in total prostatectomy and cystectomy, resulting
in vasculogenic impotency. (Gregory et al; 2012)
The bulb urethral artery (subject to several variations in origin,
occasionally arising from the cavernous, dorsal, or accessory pudendal
arteries) supplies the bulb of the urethra, the corpus spongiosum, and
the glans. These structures are anatomically independent from the body
of the penis. This, the first branch of the penile artery, is a short,
relatively large-caliber artery that passes medially to traverse the
inferior layer of the urogenital diaphragm before entering the bulb. It
supplies the bulb through a posterior group of branches and also
supplies the proximal quarter of the cavernous tissue of the corpus
spongiosum through an anterior group. The urethral artery, the second
branch, is not always present. It may arise from the artery to the bulb,
but if present, it more commonly takes origin directly from the penile
artery or from the cavernous artery or dorsal artery. It runs on the
ventral surface of the corpus spongiosum beneath the tunica albuginea.
(Gregory et al; 2012)
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Fig (12): arterial supply of the urethra (Gregory et al; 2012)
(3) Venous drainage of the penis and urethra is through:
The venous drainage of the penile skin and prepuce is less well
organized. Multiple minute veins in the prepuce form a plexus without
particular orientation joining the superficial dorsal penile vein, which
drains into the external pudendal vein, which in turn empties into the
saphenous or femoral vein (Zachariou, 2004).
Fig (13): Peripheral venous drainage of the penis
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(1) the deep dorsal vein lying in the dorsal groove between the corporal
bodies beneath Buck's fascia. There is free anastomosis with veins from
the corpus spongiosum (Fig 10) At the base of the penis this large vein
passes between the two divisions of the suspensory ligament and enters
the plexus of veins around the prostate.
(2) superficial veins from the penile skin drain through a superficial
dorsal vein, which empties into the saphenous system.
(3) The crural vessels, departing the corpora cavernosa at the crus of
the corpora and draining into the periprostatic plexus.
(4) the cavernosal venous system departing the corpora proximal to the
crus in part to join the dorsal vein of the penis and the periprostatic
plexus. (Gregory et al; 2012)
Fig (14): Deep venous drainage of the urethra and penis. From
(Horton et al, 1990)
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The multiple small veins in the prepuce are distributed without
particular orientation. In the skin of the shaft, they join one or two
superficial penile veins that drain through the inferior external pudendal
vein into the saphenous vein.(Gregory et al; 2012)
(4) Lymphatic Drainage of the Penis and Urethra
The lymphatic drainage from the glans penis passes to the deep
inguinal and external iliac lymph nodes, while lymphatics from the
deep urethra drain into the hypogastric and common iliac lymph nodes
(Tanagho, 1992).
The surface of the glans penis has three superposed networks,
one in the papillae, another in the superficial mucosal layer, and a third
beneath the other two. The collecting trunks converge on the frenulum,
where they pick up collectors from the urethral mucosa. One to three
trunks then pass around to the dorsum in the coronal sulcus to join
those from the opposite side. One or more major collecting trunks
running with the deep dorsal vein carry the lymph to the region of the
suspensory ligament where they join the presymphyseal plexus. Two or
three trunks run from this plexus to the superficial inguinal nodes along
either a femoral or an inguinal path. Delicate preputial lymphatics arise
both from the inner and, more abundantly, from the outer surfaces of
the prepuce. As they run proximally, they anastomose and curve to
become confluent on the dorsum .(Gregory et al 2012)
From 5 to 10 channels course to the base of the penis, uniting as
they go. The penile skin proper is drained by lymphatics that run from
the median raphe obliquely around the penis to join the dorsal
lymphatic channels already draining the prepuce. At the base of the
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penis, branches from the skin and prepuce connect with a
presymphyseal plexus before passing right and left to join trunks
draining the perineal and scrotal skin. The joint trunks run with the
superficial external pudendal vessels to drain into the superficial
inguinal lymph nodes, especially the super medial ones. Anastomoses
loosely connect the right and left sides (Gregory et al; 2012)
Some drainage occurs through the femoral route, passing into the
femoral canal to enter a deep node there, to enter the node of Cloquet,
and also to enter a medial retro femoral node. For the inguinal route, a
single trunk approaches the inguinal canal below the spermatic cord to
reach the lateral retro femoral node. Thus, the lymphatics of the penile
skin empty through the superficial lymphatic drainage system into the
superficial inguinal nodes, particularly the super medial group, whereas
the glans and penile urethra drain into the deep inguinal nodes and the
presymphyseal nodes and, occasionally, into the external iliac
nodes.(Gregory et al 2012)
Regarding the nerve supply and the blood supply of the penis,
it is important to note that the dorsal nerves do not lie directly in the
dorsal midline, but rather extend from the 11 and 1 O’clock
positions, the structure of hypospadiac penis has showed that the nerves
and the corporal bodies have the same anatomical relationship as the
normal penis, the most important difference between the normal and
hypospadiac penis was in the vascularity and the deficient corpus
spogiosum surrounding the abnormal part of the urethra (Baskin et
al;2000)
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