Micturition and urinary continence
1265
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Lateral aspect Medial aspect Fig. 75.16 The micturition control centre is in
the paramedian pontine reticular formation on
Anterior cingulate cortex (ACCx)
each side and consists of a medially placed
micturition centre, ‘M’, and a laterally placed
5 Paracentral lobule
storage centre, ‘L’. Neurones project from the
‘M’ centre and the storage centre ‘L’ to
parasympathetic neurones in segments 2–4 of
the sacral spinal cord, and to Onuf’s nucleus,
which is in the same segments, and which
innervates the external urethral sphincter. At
higher levels, neurones in the right prefrontal
and anterior cingulate cortex, right preoptic
Ventral posterior
4 nucleus of thalamus nucleus and periaqueductal grey matter are
involved in the control of micturition. Vesical
afferents from stretch receptors in the detrusor
Periaqueductal grey
and trigonal mucosa relay the extent of
matter (PAG)
bladder filling to the brainstem and thalamus
via spinoreticulothalamic fibres (1). Activity in
Inferior frontal gyrus
the sympathetic system that maintains
Preoptic area
increases in bladder compliance (via β2
receptors on detrusor fibres) and
parasympathetic activity is inhibited (2).
Pons Spinoreticular fibres synapsing in the ‘L’
nucleus in the pons activate Onuf’s nucleus to
'L' centre 'M' centre increase the tone of the external sphincter (3).
If micturition is deferred, fibres projecting from
the inferior frontal gyrus inhibit the right
anterior cingulate gyrus, preoptic area and
periaqueductal grey matter (4). Voluntary
contraction of the pelvic floor musculature,
controlled by the prefrontal cortex driving the
perineal ‘area’ of the motor cortex (5), cannot
be long sustained once filling is complete.
(With permission from FitzGerald MJT,
3
Preganglionic sympathetic supply Folan-Curren J 2001 Clinical Neuroanatomy,


Spinoreticulothalamic fibre to pelvic ganglia 4th edn. London: Saunders.)
Internuncial neurone
S2/S3 posterior nerve
Sacral parasympathetic neurone
root in cauda equina
Motor neurone to levator ani
Onuf 's nucleus
1 1
Mucosal afferent fibre 2
To levator ani
To external urethral sphincter To pelvic ganglia
without any change in intravesical pressure, partly because of the vis- urinary continence in the male
coelastic properties of its walls, and partly because a gating mechanism Urinary continence at the level of the membranous urethra is mediated
operates in the spinal cord that reflexively inhibits preganglionic para- by the radial folds of urethral mucosa, the submucosal connective
sympathetic activity. A gating mechanism in the pelvic ganglia prevents tissue, the intrinsic urethral smooth muscle, the striated external ure-
the activation of postganglionic parasympathetic neurones until pre- thral sphincter and the pubourethral component of levator ani, pubo-
ganglionic activity has reached a threshold level (Chancellor and perinealis (Fig. 75.17). The external urethral sphincter represents the
Yoshimura 2002). point of highest intraurethral pressure in the normal, contracted, state.
Mean bladder capacity in adult males varies around 400 ml but The striated muscle component of the external urethral sphincter is
micturition commonly occurs at smaller volumes. Voluntary control is devoid of muscle spindles. The striated muscle fibres themselves are
imposed from the inferior frontal gyrus of the cerebral cortex. Filling unusually small in cross-section (15–20 µm in diameter), and are phys-
to 500 ml may be tolerated; beyond this level, pain caused by tension iologically of the slow-twitch type, unlike the pelvic floor musculature,
in the bladder wall leads to the urgent desire to micturate. The pain is which is a heterogeneous mixture of slow- and fast-twitch fibres of
referred to the cutaneous areas supplied by T10–L2 and S2–4, includ- larger diameter. The slow-twitch fibres of the external sphincter are


ing the lower anterior abdominal wall, perineum and penis. Threshold capable of sustained contraction over relatively long periods of time
afferent stimulation activates the micturition centre in the rostral pons and actively contribute to the tone that closes the urethra and maintains
(the ‘M’ centre) (see Fig. 75.16), which drives preganglionic parasym- urinary continence. They are innervated by neurones that lie in Onuf’s
pathetic neurones in the intermediolateral grey column of the second, nucleus in the anterolateral grey matter of the second to fourth sacral
third and fourth sacral spinal segments via descending spinal path- spinal segments. Their firing is controlled centrally by a storage centre
ways. The axons of these neurones run to the inferior hypogastric within the rostral pons (the ‘L’ centre) (see Fig. 75.16). Just before the
plexus in the pelvic splanchnic nerves; they synapse on postganglionic onset of voiding, the external urethral sphincter is relaxed by central
neurones in ganglia lying within the plexus and in the wall of the inhibition of Onuf’s nucleus.
bladder. Postganglionic axons ramify throughout the thickness of the
detrusor smooth muscle coat. When stimulated, they release acetylcho- urinary continence in the female
line, which activates muscarinic receptors in the detrusor layer of the The urethral sphincter mechanism consists of the intrinsic striated and
bladder wall and produces the sustained bladder contraction required smooth muscle of the urethra, the mucosa and submucosal connective
for micturition. The distal urethral sphincter maintains urethral tissue, and the puborectalis component of levator ani (which surrounds
closure. the urethra at the point of maximum concentration of those muscles).


Bladder, prostate and urethra
1266
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noItCes
Bladder
Prostate
Striated sphincter &
membranous urethra
Levator ani (puboperinealis)
Bulbourethral glands
Anterior recess of ischioanal fossa
Perineal membrane
Ischiopubic ramus
Corpus spongiosum (bulb)
Corpus cavernosum
Ischiocavernosus
A B
Fig. 75.17 A, Coronal illustration of male anterior levator ani (urogenital) hiatus: prostate above, intervening striated urethral sphincter and perineal
membrane with corporal bodies below. B, This coronal T2-weighted MRI includes the cephalad extension of the smooth muscle urethral sphincter, which
cannot be discriminated from striated urethral sphincter; bulbourethral glands are offset from expected symmetry. (A, B Courtesy of Robert P Myers MD,
Akira Kawashima MD and Bernard F King MD, used with permission of Mayo Foundation for Medical Education and Research.)
The striated muscle component of the urethral sphincter mechanism about 8 g in youth but, almost invariably, enlarges with the develop-
surrounds the middle and lower thirds of the urethra in the female. ment of BPH; it usually weighs 40 g, but sometimes as much as 150 g
Proximally, it forms a complete ring around the urethra, while, more or even more, after the first five decades of life. The small prostate
distally, it covers the anterior and lateral aspects of the urethra; it blends without BPH is described as a croissant shape (short anterior commis-
above with the smooth muscle of the bladder neck and below with the sure, prominent apical notch and posterior lip of prostatic tissue), and
smooth muscle of the lower urethra and vagina. Contraction of this part the enlarged gland is more doughnut-shaped. The shape of the prostate
of the sphincter compresses the urethra against the relatively fixed affects the relationship of the prostatic apex to the external urethral
anterior vaginal wall. At its most distal point; the striated sphincter sphincter. This relationship is important when removing the prostate


encompasses the urethra and vagina as the urethrovaginal sphincter. at radical prostatectomy for cancer, and anastomosing the bladder to
The mucosa and submucosa are oestrogen-dependent and atrophy the urethra to maintain sphincter integrity. The external urethral sphinc-
postmenopausally, possibly resulting in stress incontinence. ter is flush to a large doughnut-type gland, and so a perpendicular
incision will separate the prostate and external urethral sphincter accu-
rately. In a small prostate, the external urethral sphincter fills the defect
PROSTATE
in the anterior aspect of the prostate, and so a perpendicular incision
at the level of the posterior lip of the croissant-shaped gland will excise
The prostate is a globular fibromuscular gland that surrounds the pro- much external urethral sphincter and leave the patient incontinent.
static urethra from the bladder base to the membranous urethra (Myers Superiorly, the base is largely contiguous with the neck of the
2001). It is enclosed by firmly adherent tissue that has been variously bladder. The apex is inferior, surrounding the junction of the prostatic
termed the prostatic capsule or the prostatic fascia (parietal fascia cover- and membranous parts of the posterior urethra. The apical posterior
ing the adjacent part of levator ani, lateral pelvic fascia, periprostatic relation of the prostate and external urethral sphincter is rectourethralis,
fascia, parapelvic fascia), reflecting, in part at least, inter-individual a Y-shaped muscle that originates from the outer longitudinal coat of
variability and sampling site (Myers et al 2010) (Fig. 75.18). Histologi- the rectum. The upper limbs of the Y extend from the lateral rectal wall
cally, it is a multilayered connective tissue (Hinata et al 2013). There is to the midline, where rectourethralis inserts into the perineal body at
no true fibrous capsule at the base or apex of the prostate, and the pres- the anorectal junction (Brooks et al 2002).
ence of a capsule between the apex and base is variable. The anterior surface lies in the arch of the pubis, separated from it


The muscular tissue within the prostate is mainly smooth muscle. by the dorsal vascular complex (Santorini’s plexus) and loosely attached
Anterior to the urethra, a layer of smooth muscle merges with the main adipose tissue. It is transversely narrow and convex, extending from the
mass of muscle in the fibromuscular septa; it blends superiorly with apex to the base. Near its superior limit, it is connected to the pubic
vesical smooth muscle. Anterior to the layer of smooth muscle, a trans- bones by the puboprostatic ligaments. The urethra emerges from this
versely crescent-shaped mass of skeletal muscle is continuous inferiorly surface anterosuperior to the apex of the gland. The anterior part of the
with the external urethral sphincter in the deep perineal pouch. Its fibres prostate is relatively deficient in glandular tissue and is largely com-
pass transversely internal to the capsule and are attached to it laterally posed of fibromuscular tissue. The anterior and lateral aspects of the
by diffuse collagen bundles; other collagen bundles pass posteromedi- prostate are covered by a layer of fascia derived from the endopelvic
ally, merging with the prostatic fibromuscular septa and the septum of fascia on each side, called the lateral prostatic fascia. This is adherent
the urethral crest. This muscle, supplied by the pudendal nerve, probably medially to the prostate, continues posteriorly over the lateral aspect of
compresses the urethra but it may pull the urethral crest back and the the prostate, neurovascular bundles and rectum (lateral rectal fascia),
prostatic sinuses forwards, dilating the urethra. Glandular contents may and passes distally over the urethra (see Fig. 75.18A). The prostatic
be expelled simultaneously into the urethra when it has expanded in venous plexus (see Fig. 75.19) lies between this extension of the
this way, so that it contains 3–5 ml seminal fluid prior to ejaculation. endopelvic fascia and the prostate. Anteroinferiorly, the parietal and
The prostate lies at a low level in the lesser pelvis, behind the inferior visceral fasciae of the prostate merge and blend with the puboprostatic


border of the pubic symphysis and pubic arch (see Fig. 75.2A; Fig. ligaments. The anterior surface of the prostate and associated vascular
75.19), and anterior to rectourethralis and the rectal ampulla, through plexus is covered by the detrusor apron (Myers 2002).
which it may be palpated. It presents a base or vesical aspect superiorly, The inferolateral surfaces are related to the muscles of the pelvic side
an apex inferiorly, and posterior, anterior and two inferolateral surfaces. wall; the anterior fibres of levator ani embrace the prostate in the pubo-
The prostatic base measures about 4 cm transversely. The gland is 2 cm urethral sling or pubourethralis. These muscles are separated from the
in its anteroposterior, and 3 cm in its vertical, diameters. It weighs prostate by a thin layer of connective tissue.


prostate
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A Parietal endopelvic Superficial The posterior surface of the prostate is transversely flat and vertically
fascia dorsal vein convex. Near its superior (juxtavesical) border is a depression where it
Detrusor apron Dorsal vascular is penetrated by the two ejaculatory ducts. Below this is a shallow,
complex median sulcus, usually considered to mark a partial separation into
right and left lateral lobes. It is separated from prerectal fat in the pre-
rectal space (see Figs 75.2A, 75.18A) and rectum by Denonvilliers’
Prostate
Lateral prostatic fascia, a condensation of pelvic fascia that develops by obliteration of
fascia Levator ani the rectovesical peritoneal pouch, and by loose yellow, fatty areolar
tissue. The rectovesical pouch is obliterated from below upwards as fetal
life progresses, forming Denonvilliers’ fascia; at birth, this fascia sepa-
rates the prostate, the seminal vesicles and the ampullae of the vasa
deferentia from the rectum. The superior limit of Denonvilliers’ fascia
is the peritoneum of the rectovesical pouch. Laterally, Denonvilliers’
fascia fuses with the lateral pelvic fascia; anterior to Denonvilliers’
fascia, the lateral pelvic fascia is called the lateral prostatic fascia and,
posterior to Denonvilliers’ fascia, it is called the lateral rectal fascia.
The prostate is traversed by the urethra and ejaculatory ducts, and
contains the prostatic utricle. The urethra enters the prostate near its
anterior border and usually passes between its anterior and middle
thirds. The ejaculatory ducts pass anteroinferiorly through its posterior
region to open into the prostatic urethra.
ZONAL ANATOMY OF THE PROSTATE
The prostate gland was once thought to be divided into five anatomical
lobes, but it is now recognized that five lobes can only be distinguished
in the fetal gland prior to 20 weeks’ gestation. Between then and the
onset of BPH, only three lobes are recognizable: two lateral and a
median lobe. Clinicians refer to left and right ‘lobes’ when describing


either what can be felt on rectal palpation, or the endoscopically visible
abnormalities that are seen in the diseased state when prostatic anatomy
is distorted by BPH.
From an anatomical, and particularly from a morbid anatomical,
perspective, the glandular tissue may be subdivided into three distinct
zones (Figs 75.20–75.22): peripheral (70% by volume), central (25%
by volume) and transitional (5% by volume) (Mundy et al 1999b).
Non-glandular tissue (fibromuscular stroma) fills the space between the
peripheral zones anterior to the preprostatic urethra. The central zone
surrounds the ejaculatory ducts, posterior to the preprostatic urethra,
and is more or less conical in shape, with its apex at the verumontanum.
The fibromuscular stroma includes the smooth muscle detrusor apron
Lateral rectal Denonvilliers’ Rectal wall Prerectal fat Neurovascular
superoanteriorly and striated urethral sphincter fibres that extend ante-
fascia fascia bundle
riorly over the anterior prostate on to the bladder neck. The transitional
zone lies around the distal part of the preprostatic urethra just proximal
to the apex of the central zone and the ejaculatory ducts; it includes the
smooth muscle of the preprostatic urethral wall. Its ducts enter the
PC prostatic urethra just below the preprostatic sphincter and just above
the ducts of the peripheral zone. The peripheral zone is cup-shaped and
NVB encloses the central transitional zone and the preprostatic urethra,
except anteriorly, where the space is filled by the anterior fibromuscular
stroma. Simple mucus-secreting glands lie in the tissue around the
preprostatic urethra, above the transitional zone and surrounded by the
preprostatic sphincter. These simple glands are similar to those in the
female urethra and unlike the glands of the prostate.
On magnetic resonance imaging (MRI), the prostate gland has a
zonal anatomy on T2-weighted images (see Fig. 75.21). The normal
peripheral zone has high-signal intensity, as does fluid within the
seminal vesicles. The central and transitional zones have relatively low


signal and are often referred to as the ‘central gland’. The verumonta-
num may be seen as high-signal within the central gland. The relation-
ship of the zones of the gland normally changes with age. The central
B
zone atrophies, and the transitional zone enlarges secondary to BPH.
This often produces a low-signal band at the margin of the hypertro-
Fig. 75.18 A, The endopelvic fascia. The fascia covers the pelvic viscera
phied transitional and compressed peripheral zones: the surgical pseu-
and continues posteriorly over the lateral aspect of the prostate, as the
docapsule, which is well seen on T2-weighted MR images.
lateral prostatic fascia and, on the lateral aspect of the rectum, as the
lateral rectal fascia. Its relationship with Denonvilliers’ fascia may be The zonal anatomy of the prostate is clinically important because
visualized as an ‘H’. The deep dorsal vein and lateral branches run deep most carcinomas arise in the peripheral zone, whereas BPH affects the
to the endopelvic fascia and the lateral prostatic fascia, although transitional zone, which may grow to form the bulk of the prostate.
communicating with perforators to the pelvic side wall. Denonvilliers’
fascia is adherent to the prostate in the posterior midline but, like the
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
lateral prostatic fascia, is separated from the prostatic tissue by the
neurovascular structures and fatty tissues elsewhere. Between
Denonvilliers’ fascia and the rectum is a fatty potential plane, the prerectal Arteries
space. B, The prostatic capsule (PC) is a condensation of connective
tissue (green) on the surface of the gland and encloses the neurovascular The prostate is supplied by branches from the inferior vesical, internal
bundle (NVB). The prostatic fibromuscular stroma and glands lie beneath
pudendal and middle rectal arteries (see Fig. 75.19). They perforate the
the capsule.
gland along a posterolateral line from the junction of the prostate with
the bladder down to the apex of the gland.


Bladder, prostate and urethra
1267.e1
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As the transitional zone grows, it produces the appearance of ‘lobes’
on either side of the urethra. In due course, these lobes may compress
or distort the preprostatic and prostatic parts of the urethra and produce
symptoms. The central zone surrounding the ejaculatory ducts is rarely
involved in any disease. It shows certain histochemical characteristics
that differentiate it from the rest of the prostate; it is thought to be
derived from the Wolffian duct system (much like the epididymi, vasa
deferentia and seminal vesicles), whereas the rest of the prostate is
derived from the urogenital sinus (p. 1218).


Bladder, prostate and urethra
1268
8
noItCes
Hypogastric nerve (Sympathetic) S2–S4 (Parasympathetic)
Colon
Ureter
Vas deferens
Peritoneum
Inferior vesical artery and
vein
Pelvic plexus
Seminal vesicle
Bladder/detrusor Levator ani
Pubic bone Arterial blood
Superficial branch supply to bladder neck
of dorsal vein
Rectum
Puboprostatic ligaments
Capsular artery and vein
Vas deferens of the prostate
Cremaster
Dartos External anal sphincter
Crus penis Deep transverse perineal muscle
Cavernous artery
Bulbospongiosus
Ischiocavernosus
Prostate Bulbourethral gland
Urethral sphincter Cavernous nerve
Fig. 75.19 A sagittal section of the male pelvis. The pelvic plexus lies with its midpoint level with the tip of the seminal vesicles. It gives branches to the
prostate, bladder urethra, seminal vesicles, rectum and corpora cavernosa via the cavernous nerves. The cavernous nerves are the continuation of the
neurovascular bundles, lying posterolateral to the prostate. These bundles may be damaged at radical prostatectomy, resulting in impotence.
The inferior vesical artery often arises from the internal iliac artery Commentary 8.1). The prostatic capsule is covered by numerous nerve
with the middle rectal artery. It gives rise to two groups of branches: the fibres and ganglia posterolaterally, forming a crescentic periprostatic
urethral and capsular. The urethral vessels enter at the prostatovesical nerve plexus. The greatest density of nerves is found in the preprostatic
junction, principally posteriorly at the 5 and 7 o’clock positions, but sphincter; fewer fibres are found in the anterior fibromuscular stroma,
also anteriorly at 1 and 11 o’clock. This bladder neck arterial anatomy and the peripheral zone is the least densely innervated. Nerves contain-
is always apparent at transurethral resection of the prostate and open ing neuropeptide Y and vasointestinal polypeptide (VIP) are localized


removal of BPH adenomas. The capsular arteries run posterolaterally in the subepithelial connective tissue, in the smooth muscle layers of
and inferiorly in the neurovascular bundles, providing perpendicular the gland, and in the walls of its blood vessels. Neurovascular bundles
perforating vessels to the prostate. The most constant in position and (Walsh and Donker 1982) containing autonomic nerves that supply the
prominence is the apical perforator at the prostatourethral junction, an prostate, seminal vesicles, prostatic urethra, ejaculatory ducts, corpora
important landmark for this point and for the neurovascular bundle at cavernosa, corpus spongiosum, membranous and penile urethra, and
radical prostatectomy. bulbourethral glands are closely applied to, but separable from, the
posterolateral margins of the prostate (see Commentary 8.1). They are
Veins intimately related to the prostatic fascia. These nerves may be damaged
during radical prostate surgery for organ-confined prostate cancer, pro-
ducing impotence, or sacrificed as part of wide local excision of the
The veins run into a plexus around the anterolateral aspects of the
prostate (Tewari et al 2006, Pisipati et al 2014).
prostate, posterior to the arcuate pubic ligament and the lower part of
The somatic pudendal nerve supplies the external urethral sphincter.
pubic symphysis, anterior to the bladder and prostate. The chief tribu-
The branches enter at the 5 and 7 o’clock positions. Sensory branches
tary is the deep dorsal vein of the penis. The plexus also receives anterior
pass through the penile hilus in association with the dorsal venous
vesical and prostatic rami (which connect with the vesical plexus and
complex and dorsal vein of the penis.
internal pudendal vein), and drains into vesical and internal iliac veins.
Lymphatic drainage
MICROSTRUCTURE
Collecting vessels from the vas deferens drain into the external iliac
nodes, while those from the seminal vesicle drain to the internal and The glandular tissue consists of numerous follicles with frequent inter-
external iliac nodes. Prostatic vessels end mainly in internal iliac, sacral nal papillae. Follicles open into elongated canals, which join to form


and obturator nodes. A vessel from the posterior surface accompanies 12–20 main ducts. The follicles are separated by loose connective tissue,
the vesical vessels to the external iliac nodes, and another from the supported by extensions of the fibrous capsule and muscular stroma,
anterior surface reaches the internal iliac group by joining vessels that and enclosed in a delicate capillary plexus. Follicular epithelium is
drain the membranous urethra. variable but predominantly columnar, and either single-layered or
pseudostratified.
Prostatic ducts open mainly into the prostatic sinuses in the
INNERVATION floor of the prostatic urethra. They have a bilayered epithelium, the
luminal layer is columnar, and the basal layer is populated by small
The prostate receives an abundant nerve supply from the inferior cuboidal cells. Small colloid amyloid bodies (corpora amylacea) are
hypogastric (pelvic) plexus (see Figs 59.4, 75.11 and Fig. 8.1.1 in frequent in the follicles (Fig. 75.23). Prostatic and seminal vesicular


prostate
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Central and transitional Verumontanum Bladder Peripheral zone of
zones of prostate prostate
TZ TZ
PZ PZ
A
A
TZ
PZ
B
Fig. 75.20 Ultrasound of the prostate. A, An axial view showing the
hypoechoic transition zone (TZ) and the more echogenic peripheral zone
(PZ). Their interface is the surgical capsule (*). B, A sagittal view showing
the hypoechoic transition zone (TZ) and the more echogenic peripheral
zone (PZ).
secretions form the bulk of seminal fluid. Prostatic secretions are
slightly acid, and contain acid phosphatase, amylase, prostate-specific
antigen, fibrinolysin and zinc. Numerous neuroendocrine cells, con- B
taining neurone-specific enolase, chromogranin and serotonin
(5-hydroxtryptamine, 5-HT), are present in the glandular epithelium; Peripheral zone of Prostatic Central and transitional Bladder
their numbers decline after middle age and their function is unknown. prostate urethra zones of prostate
Histological sections just above the level of the verumontanum
Fig. 75.21 Magnetic resonance imaging (MRI) of the prostate. A, A
reveal two concentric, partially circumurethral, zones of glandular
T2-weighted MRI scan showing the normal high signal of the peripheral
tissue. The larger outer zone is the peripheral zone and has long, zone and the intermediate signal of the central and transitional zones and
branched glands, whose ducts open mainly into the prostatic sinuses. the verumontanum in the central gland. B, A T2-weighted coronal MRI
The inner zone is the transitional zone and consists of glands whose scan of the prostate showing the zonal anatomy.
ducts open on the floor of the prostatic sinuses and colliculus seminalis,
and a group of simple mucosal glands that surround the preprostatic
urethra. Anteriorly, in the prostatic isthmus, the peripheral zone and
submucosal glands are absent. the ductal branches. Morphogenesis and differentiation of the epithelial
cords starts in an intermediate part of the epithelial anlage and proceeds


to the urethral and subcapsular parts of the gland; the latter is reached
AGE CHANGES IN THE PROSTATE by the age of 17–18 years. The glandular epithelium is initially multi-
layered squamous or cuboidal, and is transformed into a pseudostrati-
At birth, the prostate has a system of ducts embedded in a stroma that fied epithelium consisting of basal, exocrine secretory (including
forms a large part of the gland. Follicles are represented by small end- mucous) and neuroendocrine cells. The mucous cells are temporary,
buds on the ducts. Before birth, the epithelium of the ducts, seminal and are lost as the gland matures. The remaining exocrine secretory cells
colliculus and prostatic utricle display hyperplasia and squamous meta- produce a number of products, including acid phosphatase, prostate-
plasia, possibly due to maternal oestrogens in the fetal blood. This specific antigen and β-microseminoprotein. Growth of the secretory
subsides after birth and is followed by a period of quiescence lasting component is associated with condensation of the stroma, which
for 12–14 years. diminishes relative to the glandular tissue. These changes are probably
At puberty, between the ages of approximately 14 and 18 years, the a response to the secretion of testosterone by the testis.
prostate gland enters a maturation phase and more than doubles in size During the third decade, the glandular epithelium grows by irregular
during this time. Growth is almost entirely due to follicular develop- multiplication of the epithelial infoldings into the lumen of the folli-
ment, partly from end-buds on ducts, and partly from modification of cles. After the third decade, the size of the prostate remains virtually


Bladder, prostate and urethra
1270
8
noItCes
Transition zone
CCAA
CCAA
A
Central zone BB
EE
B
Fig. 75.23 A, Prostatic acini show papillary infoldings at the base of the
gland (central zone). They are irregularly divided by fibromuscular stroma.
Peripheral zone Some acini contain eosinophilic (pink) secretions called corpora amylacea
(CA) (×10, haematoxylin and eosin stain). B, Prostatic acini consist of a
double layer of epithelial cells (E), which line the lumen, and basal cells
(B), which give rise to epithelial cells.
Anterior fibromuscular stroma
Bonus e-book images and videos
Fig. 75.6 Centiles of bladder volume index in children.
Fig. 75.8 A laparoscopic view of the empty bladder and median
and medial umbilical folds in a 12-month-old boy.
Fig. 75.9 A laparoscopic view of the left inferior epigastric vein
(lateral umbilical ligament) in a 12-month-old boy.
Fig. 75.14 Cystic dilation of the prostatic utricle demonstrated in an
Fig. 75.22 The zonal anatomy of the prostate. (With permission from 8-month-old child during a micturating cystourethrogram.
Walsh PC, Retik AB, Vaughan ED et al (eds) 2002 Campbell’s Urology,
8th edition. Philadelphia: Saunders.) Video 75.1 Laparoscopic view of bladder filling and emptying in
relation to the rectovesical pouch.
Video 75.2 Laparoscopic view of anterior abdominal wall and
unaltered until 45–50 years, when the epithelial foldings tend to disap-
ligaments.
pear, follicular outlines become more regular, and amyloid bodies
increase in number: all signs of prostatic involution. After 45–50 years,
the prostate tends to develop BPH: an age-related condition. If a man
lives long enough, then BPH is inevitable, although not always
symptomatic.
Acknowledgements
Robert P Myers, Emeritus Professor of Urology, and Akira Kawashima
and Bernard F King, Professors of Radiology, Mayo Clinic College of
Medicine.


Bladder, prostate and urethra
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BPH begins as micronodules in the transitional zone, which grow
and coalesce to form macronodules around the inferior margin of the
preprostatic urethra, just above the verumontanum. Macronodules, in
turn, compress the surrounding normal tissue of the peripheral zone
posteroinferiorly, creating a ‘false capsule’ around the hyperplastic
tissue, which, coincidentally, provides a plane of cleavage for its surgical
enucleation (for further reading see Kutikov et al (2006)).


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Key references
KEY REFERENCES
Kutikov A, Guzzo TJ, Malkowicz SB 2006 Clinical approach to the prostate: Walsh PC, Donker PJ 1982 Impotence following radical prostatectomy:
an update. Radiol Clin North Am 44:649–63. insight into etiology and prevention. J Urol 128:492–7.
Details the practical approach to diseases of the prostate. A landmark assessment of the importance of neurovascular anatomy in
prostate surgery.
Myers RP 2001 Practical surgical anatomy for radical prostatectomy. Urol
Clin North Am 28:473–90. Yoshimura N, Chancellor MB 2012 Physiology and pharmacology of the
Details clinically relevant anatomy of the prostate and surrounding bladder and urethra. In: Wein AJ, Kavoussi LR, Novick AC et al (eds)
structures. Campbell-Walsh Urology, 10th ed. Philadelphia: Elsevier, Saunders;
Ch. 60.
Mundy AR, Fitzpatrick J, Neal D et al 1999a Structure and function of the
An overview of physiology and pharmocology of the lower urinary tract.
lower urinary tract. In: The Scientific Basis of Urology. Oxford: Isis
Medical Media; Ch. 11, pp. 217–42.
A detailed assessment of the structure and function of the lower urinary
tract.
Mundy AR, Fitzpatrick J, Neal D et al (eds) 1999b The prostate and benign
prostatic hyperplasia. In: The Scientific Basis of Urology. Oxford: Isis
Medical Media; Ch. 13, pp. 257–76.
An account that includes a review of prostatic zonal anatomy.


Bladder, prostate and urethra
1271.e1
57
retpahC
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Brooks JD, Eggener SE, Chao W-E 2002 Anatomy of the rectourethralis Details clinically relevant anatomy of the prostate and surrounding
muscle. Eur Urol 41:94–100. structures.
Cagri Savas M, Kapucuoglu N, Gursoy K et al 2011 The microvessel density Myers RP 2002 Detrusor apron, associated vascular plexus, and avascular
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Guide, 10th ed. Philadelphia: Elsevier, Saunders; Ch. 23. higher cortical centres to molecular events within the cells of the detrusor
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Drumm BT, Koh SD, Andersson KE et al 2014 Calcium signalling in Cajal-
like interstitial cells of the lower urinary tract. Nat Rev Urol 11: Myers RP, Cheville JC, Pawlina W 2010 Making anatomic terminology of the
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Hinata N, Sejima T, Takenaka A 2013 Progress in pelvic anatomy from the and suggestions for revision in the 21st century. Clin Anat 23:18–29.
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Hirdes MM, de Jong TP, Dik P et al 2010 Urethral length in girls with lower cumcised boys. J Pediatr Urol 6:130–3.
urinary tract symptoms and forme fruste of female epispadias. J Pediatr Pisipati S, Ali A, Mandalapu RS et al 2014 Newer concepts in neural anatomy
Urol 6:372–5. and neurovascular preservation in robotic radical prostatectomy. Indian
Hsieh MH, Eisenberg ML, Hittelman AB et al 2012 Caucasian male infants J Urol 30:399–409.
and boys with hypospadias exhibit reduced anogenital distance. Hum Stalberg K, Gonzalez R 2012 Urethral atresia and anhydramnios at 18 weeks
Reprod 27:1577–80. of gestation can result in normal development. J Pediatr Urol 8:
Hurwitz RS, Woodhouse CR, Ransley P 1986 The anatomical course of the e33–5.
neurovascular bundles in epispadias. J Urol 136:68–70. Takahashi T, Ueno M, Azekura K et al 2000 Lateral ligament: its anatomy
Hutton KA, Babu R 2007 Normal anatomy of the external urethral meatus and clinical importance. Semin Surg Oncol 19:386–95.
in boys: implications for hypospadias repair. BJU Int 100:161–3. Tewari A, Takenaka A, Mtui E et al 2006 The proximal neurovascular plate
Klutke CG, Siegel CL 1995 Functional female pelvic anatomy. Urol Clin and the trizonal neural architecture around the prostate gland: impor-
North Am 22:487–98. tance in the athermal robotic technique of nerve sparing prostatectomy.
BJU Int 98:314–23.
Kutikov A, Guzzo TJ, Malkowicz SB 2006 Clinical approach to the prostate:
an update. Radiol Clin North Am 44:649–63. Walsh PC, Donker PJ 1982 Impotence following radical prostatectomy:
Details the practical approach to diseases of the prostate. insight into etiology and prevention. J Urol 128:492–7.


A landmark assessment of the importance of neurovascular anatomy in
Miles WE 1908 A method of performing abdominoperineal excision for prostate surgery.
carcinoma of the rectum and of the terminal portion of the pelvic colon.
Lancet 2:1812–14. Yoshimura N, Chancellor MB 2012 Physiology and pharmacology of the
bladder and urethra. In: Wein AJ, Kavoussi LR, Novick AC et al (eds)
Mundy AR, Fitzpatrick J, Neal D et al 1999a Structure and function of the
Campbell-Walsh Urology, 10th ed. Philadelphia: Elsevier, Saunders;
lower urinary tract. In: The Scientific Basis of Urology. Oxford: Isis
Ch. 60.
Medical Media; Ch. 11, pp. 217–42.
An overview of physiology and pharmocology of the lower urinary tract.
A detailed assessment of the structure and function of the lower urinary
tract. Yucel S, Guntekin E, Kukul E et al 2004 Comparison of hypospadiac and
normal preputial vascular anatomy. J Urol 172: 1973–6.
Mundy AR, Fitzpatrick J, Neal D et al (eds) 1999b The prostate and benign
prostatic hyperplasia. In: The Scientific Basis of Urology. Oxford: Isis
Medical Media; Ch. 13, pp. 257–76.
An account that includes a review of prostatic zonal anatomy.


CHAPTER
76
Male reproductive system
mesothelium.Thepotentialspacebetweenthevisceralandparietal
INTRODUCTION
layers–thecavityofthetunicavaginalis–isnormallyoccupiedbya
thinfilmofclear,straw-colouredfluid.Thevolumeofthisfluidcan
Themalereproductivesystemconsistsofthegonads(testes),sperm- increasewithobstructionoflymphaticdrainage,duetoinflammatory,
aticcord,sexaccessoryglandsandexternalgenitalia.Thetestesperform traumaticorneoplasticconditionsofthetestis,resultinginahydrocele.
bothspermatogenicandsteroidogenicfunctions.Theuniqueanatomy
ofthereproductivetract,bothgrossandmicroscopic,isoptimally Vascular supply and lymphatic drainage
suitedforthesefunctionstobecarriedoutefficientlyandeffectively.
Arteries
TESTIS AND EPIDIDYMIS Thearterialsupplytothetestisandepididymisisderivedfromthree
sources.Indescendingorderofcontribution,thesearethetesticular
TESTIS artery(supplyingapproximatelytwo-thirdsofthetesticularblood
supply),thevasalartery(arterytovasdeferens,arterytoductusdefer-
Thetestesareovoidorgansresponsibleforspermandtestosterone ens,vasalartery,ductalartery)andthecremastericarteries(together


production.Inadults,theytypicallymeasure4–5cminlength,2–3cm supplyingapproximatelyone-thirdofthetesticularbloodsupply)(Fig.
inbreadthand3–4cminanteroposteriordiameter(Tishler1971);their 76.7)(HarrisonandBarclay1948,RamanandGoldstein2004).
weightvariesbetween12and20g.Averagetesticularvolumeranges
Testicular artery
from15to25ml(Prader1966,Goede2011).
Thetestesaresuspendedinthescrotumbythespermaticcord(Figs Thetesticularartery(internalspermaticartery)arisesfromtheabdomi-
76.2,76.3).Thelefttestisusuallylieslowerthantherighttestis;both nalaorta,inferiortotheoriginoftherenalartery,andcoursesinfero-
arepositionedobliquely,suchthattheupperpoleistiltedanterolater- laterallyundertheparietalperitoneum,alongpsoasmajor,towardsthe
allywhilethelowerpoleistiltedanteromedially.Thelocationofthe pelvis.Ontheright,itcoursesanteriortotheinferiorvenacavaand
testesinthescrotum,combinedwiththecharacteristicsofthescrotal posteriortothemiddlecolicandileocolicarteriesandtheterminal


skin,aswellasthecounter-currentheatexchangemechanismofthe ileum.Ontheleft,itcoursesposteriortotheinferiormesentericvein,
testicularpampiniformplexus,maintainsthetestesatatemperature leftcolicarteryandthedescendingcolon.Astherightandlefttesticular
3–4°Cbelowbodytemperature. arteriesenterthepelvis,theylieanteriortothegenitofemoralnerves,
Thetestesareenclosedinatoughcapsulemadeupofthreelayers: uretersandexternaliliacarteries.Botharteriesthenenterthedeep
aninnermosttunicavasculosa,anintermediatetunicaalbugineaand internalinguinalringandtravelwiththeipsilateralspermaticcordin
anoutertunicavaginalis(Fig. 76.4).Theposterioraspectofthetestis theinguinalcanaltothescrotum(seeFigs76.2,76.5).
isthesiteofattachmentoftheepididymisandis,therefore,onlypartly Initscoursetothetestis,thetesticulararterygivesoffoneormore
coveredbyserosa.Here,thetunicaalbugineaprojectsinwardstoform internalspermaticarteries,aninferiortesticularartery,andbranches
themediastinumtestis,andthetunicavaginalisprojectsoutwardsto supplyingthecaput,corpusandcaudaepididymis(Macmillan1954).


covertheepididymis.Withinthescrotum,thetestesareseparatedbya Thelevelatwhichthisbranchingoccursisvariable;in31–88%ofcases,
fibrousmedianseptum. itoccurswithintheinguinalcanal(Becketal1992,Jarowetal1992).
Atthelevelofthetestis,branchesofthetesticulararteryenterthe
Tunica vasculosa Thetunicavasculosacontainsaplexusofblood tunicaalbugineainthemediastinumtestisandramifyinthetunica
vesselsandlooseconnectivetissue.Itlinestheinnersurfaceofthe vasculosabeforereachingtheirdistribution.Ramificationofthetesticu-
tunicaalbuginea,aswellasallofthesurfacesandseptationswithinthe lararteriesoccursprimarilyintheanterior,medialandlateralportions
testis. ofthelowerpoleofthetestis,andintheanteriorsegmentoftheupper
pole(Jarow1991),whichhasimportantimplicationsforplanning
Tunica albuginea Thetunicaalbugineaisadense,blue–whitelayer testicularbiopsies.(Forfurtherreadingaboutvariationsintheorigin,
composedprimarilyofcollagenfibres.Itcoversthetunicavasculosa courseandnumberofthetesticulararteries,seeAsalaetal(2001),Pai


andissurroundedbytheviscerallayerofthetunicavaginalis.Atthe etal(2008)).
posterioraspectofthetestis,itprojectsinwardsasathickbutincom-
Vasal artery (artery to vas deferens, artery to
pletefibrousseptum–themediastinumtestis–whichextendsfrom
theuppertothelowerpoleofthetestis.Itisherethatvessels,nerves ductus deferens, deferential artery, ductal artery)
andtesticularductstraversethetesticularcapsule(Fig. 76.5). Thevasalarteryisabranchofthesuperior(and,occasionally,inferior)
vesicalartery,whicharisesfromtheinternaliliacartery.
Tunica vaginalis Thetunicavaginalisisacontinuationoftheperi-
tonealprocessusvaginalis,whoseformationprecedesthedescentofthe Cremasteric artery
fetaltestisfromtheabdomentothescrotum.Followingtesticular Thecremastericartery(externalspermaticartery)isabranchofthe
migrationintothescrotum,theportionoftheprocessusvaginalisthat inferiorepigastricartery.Itaccompaniesthespermaticcordandsup-
fallsbetweentheinternalinguinalringandthetestiscontractsandis pliesthecremasterandothercoveringsofthecord.Boththevasaland


1272 layer.Theinnersurfaceoftheparietallayerhasasmooth,moist, vasalarteries.


Male reproductive system
1272.e1
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RETPAHC
Thevolumeoftheleftandrighttestis,asmeasuredbyultrasono-
graphyinboysbetweeninfancyandadolescence,isshowninTable
76.1;referencecurvesformeantesticularvolumeareshowninFigure
76.1.
20
2.0
15
1.5
10
1.0
5
0.5
0 0
1 6 12
Age (years) Age (years)
Fig. 76.1 A, Reference curves for mean testicular volume measured by
ultrasound. P , P and P indicate tenth, fiftieth and ninetieth centiles,
10 50 90
respectively. B, Enlargement of the reference curves for mean testicular
volume measured by ultrasound. (With permission from Goede J, Hack
WW, Sijstermans K et al; Normative values for testicular volume measured
by ultrasonography in a normal population from infancy to adolescence.
Horm Res Paediatr. 2011;76(1):56–64.)
)lm(
emulov
sitseT
Table 76.1 Volume of the left and right testis, as measured by ultrasound in boys
between infancy and adolescence
Ultrasound (ml)
Age Boys Left SD Right SD Mean SD
(years) (n) volume volume volume
A B
1 40 0.48 0.14 0.48 0.13 0.48 0.13
P90
P90 2 38 0.47 0.09 0.45 0.1 0.46 0.09
3 36 0.52 0.18 0.5 0.13 0.51 0.15
4 38 0.52 0.18 0.5 0.15 0.51 0.16
P50
5 48 0.59 0.15 0.58 0.15 0.58 0.15


6 42 0.63 0.25 0.64 0.28 0.63 0.26
P10 P50 7 62 0.64 0.18 0.66 0.18 0.65 0.17
8 59 0.64 0.2 0.67 0.24 0.66 0.22
P10 9 53 0.78 0.46 0.8 0.48 0.79 0.46
10 49 0.95 0.51 0.99 0.52 0.97 0.51
11 60 1.31 0.95 1.35 1.14 1.33 1.03
12 55 2.31 1.8 2.35 1.79 2.33 1.77
18 1 2 3 4 5 6 7 8 9 1011 13 47 4.21 2.44 4.62 2.95 4.42 2.66
14 35 7.2 4.13 7.42 4.16 7.31 4.11
15 26 8.69 3.06 8.69 2.86 8.69 2.91
16 31 11.48 2.99 11.55 3.24 11.51 3.03
17 27 12.14 2.87 12.09 2.95 12.12 2.8
18 23 13.67 3.49 13.8 3.77 13.73 3.51
(SD = standard deviation)
(With permission from Goede J, Hack WW, Sijstermans K et al; Normative values for testicular volume
measured by ultrasonography in a normal population from infancy to adolescence. Horm Res Paediatr.
2011;76(1):56–64.)


Testis and epididymis
1273
67
RETPAHC
Fig. 76.2 The external male genitalia, ventral aspect.
Fundiform ligament of penis
Nerves and vessels exposed by extensive removal of
Suspensory
Dorsal artery of penis ligament of penis the skin and the superficial fascia of the penis. The
layers of the spermatic cord have been incised on the
Superficial
right; note the pampiniform venous plexus surrounding
inguinal ring
Spermatic cord the testicular artery. (With permission from Waschke J,
Ilioinguinal nerve
Paulsen F (eds), Sobotta Atlas of Human Anatomy, 15th
Testicular vein ed, Elsevier, Urban and Fischer. Copyright 2013.)
Spermatic cord
Genitofemoral nerve,
Cremasteric artery,
genital branch
cremasteric vein
Deep dorsal vein of penis
Dorsal nerve of penis
External pudendal
artery and vein
Pampiniform plexus
Vas deferens
Anterior scrotal branches
Testicular artery
Deep dorsal vein of penis
Deep fascia of penis
Superficial dorsal vein of penis
Subcutaneous tissue, Fig. 76.3 The external male genitalia,
Superficial inguinal ring, medial crus
fatty layer ventral aspect. The skin of the abdomen
and parts of the skin of the scrotum have
Internal oblique
been removed, and the body of the penis
Inguinal canal has been severed, revealing the internal
Ilioinguinal nerve structure of the penis. The layers of the
spermatic cord and the coverings of the
Superficial inguinal External oblique, testis have been dissected on the right.
ring, lateral crus aponeurosis (With permission from Waschke J, Paulsen
F (eds), Sobotta Atlas of Human Anatomy,
External spermatic 15th ed, Elsevier, Urban and Fischer.
fascia Copyright 2013.)
Cremasteric fascia, Deep dorsal vein of penis;
cremaster dorsal artery and
nerve of penis
Cavernous artery of penis
Corpus cavernosum
Urethra
Corpus spongiosum
Head
Epididymis
Appendix Cremasteric fascia, cremaster
Appendix of testis
Tunica vaginalis, visceral layer


External spermatic fascia
Tunica vaginalis, parietal layer
Dartos fascia
Internal spermatic fascia
(superficial fascia of scrotum),
Cremaster dartos muscle
External spermatic fascia Skin
Septum of scrotum Raphe of scrotum
theirvascularwalls,permittingtheexchangeofheatandsmallmole-
Veins
cules(Harrison1949),andfacilitatingthemaintenanceoflowertes-
Pampiniform plexus ticulartemperatures.Thepampiniformplexusascendsanteriortothe
Testicularveinsemergeposteriorlyfromthetestis,draintheepididymis, vasdeferens,andisdrainedby3–4veinsintheinguinalcanal.The
andunitetoformseveralhighlyanastomoticchannelssurroundingthe veinsentertheabdomenthroughthedeepinguinalringandcoalesce
testis,knownasthepampiniformplexus,amajorcomponentofthe intoasingletesticularveinthatdrainsintotheinferiorvenacavaon
spermaticcord(seeFig.76.2).Thisvasculararrangementmeansthat theright,andintotherenalveinontheleft.Therighttesticularvein
counterflowingarteriesandveinsareseparatedonlybythethicknessof joinstheinferiorvenacavaatanacuteangle,justinferiortothelevel


MAlE REPRoduCTiVE sysTEM
1274
8
NoiTCEs
A
Head of
epididymis
Spermatic cord
Cremasteric fascia; cremaster
Mediastinum of Lobules of
Internal spermatic fascia Head of epididymis testis testis
Tunica vaginalis, parietal layer
Septa of
Appendix testis
testis
Appendix epididymis
Superior ligament of epididymis
Tunica
Upper pole Tail of epididymis albuginea
Sinus of epididymis
B
Posterior border Lateral surface
Pampiniform
Inferior ligament of plexus
epididymis Testicular
Anterior border artery
Tail of epididymis Efferent
ductules
Lower pole Head of
Tunica
epididymis
albuginea
Lobules of
Fig. 76.4 The left testis, exposed by incising and laying open the testis
cremasteric fascia and parietal layer of the tunica vaginalis on the lateral
aspect of the testis. (With permission from Waschke J, Paulsen F (eds),
Sobotta Atlas of Human Anatomy, 15th ed, Elsevier, Urban and Fischer.
Copyright 2013.)
Vas deferens
oftherenalveins,whilethelefttesticularveinjoinstheleftrenalvein
atarightangle(Fig. 76.8).Thetesticularveinscontainvalves. Body of epididymis
Lymphatic drainage
Testicularlymphaticflowisabundantandconsistent,andfollowsthe
generalretroperitonealschemeofverticaldrainage,withlateralflow Inferior aberrant
fromrighttoleft.Lymphaticvesselsfromtherighttestisdrainprimarily ductule
intotheinter-aortocavalnodesandparacavalnodes,withsomedrain- Septa of
testis


ageintotheleftpara-aorticnodes.Lymphaticvesselsfromthelefttestis
drainintotheleftpara-aorticandinter-aortocavalnodes.
Tail of epididymis
Innervation
Fig. 76.5 A, A vertical section through the testis and epididymis. B, The
Thetestisisinnervatedeitherbynervefibresthatarisefromthetenthand arrangement of the ducts of the testis and the mode of formation of the
vas deferens. (With permission from Waschke J, Paulsen F (eds), Sobotta
elevenththoracicspinalsegments,viatherenalandaorticplexuses,and
Atlas of Human Anatomy, 15th ed, Elsevier, Urban and Fischer. Copyright
accompanythetesticularvessels,orbyfibresthatarisefromthepelvic
2013.)
plexusandaccompanythevasdeferens(Rauchenwaldetal1995).Inter-
estingly,someafferentandefferentnerveshavebeenshowntocrossover
tothecontralateralpelvicplexus(Taguchietal1999),whichmaybeone epitheliumthatalsocontainsnon-ciliated,activelyendocyticcells.
reasonwhypathologicalprocessesinonetestiscanaffecttheother. Outsidetheepitheliallining,theductulesaresurroundedbyathin
circularcoatofsmoothmuscle.
Microstructure
Thereisareductioninthediameteroftheseminiferoustubules
duringthethirdtrimesterofpregnancyandimmediatelybeforebirth,


Thetestisisenclosedwithinatough,collagenoustunicaalbuginea, whichisfollowedbyagradualincreaseinthediameterthroughout
whichthickensposteriorlyasthemediastinumtestis.Bloodvessels, childhood(MendezandEmery1979).Seminiferoustubulesarerespon-
lymphaticsandgenitalductsallenterandleavethetestisatthemedia- sibleforupto80%ofthetotaltesticularvolume.Itisestimatedthat
stinum(Fig. 76.9).Septationsoriginatingatthemediastinumtestis thecombinedlengthofthe600–1200tubulesinthehumantestisis
extendinternallytopartitionthetestisintoapproximately250lobules approximately250metres.Eachtubuleissurroundedbyabasallamina,
thatdifferinsize,thelargestandlongestlobulesbeingnearthecentre restingonacomplex,stratifiedepithelium.Incross-section,thelumen
(seeFig.76.5).Eachlobulecontains1–4convolutedseminiferous oftheseminiferoustubuleislinedbySertolicells,andcontainssperm-
tubulesandinterstitialtissuecomposedofLeydigcells,mastcells, atozoainvariousstagesofdevelopment,fromspermatogonialstem
macrophages,nervesandbloodvessels. cellsnearthebase,toprogressivelymatureforms(spermatogonia,


Seminiferoustubulesaretypicallylong,highlycoiledandlooped; spermatocytes,spermatidsandspermatozoa)arrangedinasystematic
bothendsterminateinthemediastinumtestis.Spermatogenesisoccurs fashiontowardsthecentreofthetubule.Residualbodies,spherical
inthehighlycoiledportions(Fig. 76.10).Asthetubulesreachthe structures derived from surplus spermatid cytoplasm shed during
apicalportionofthelobulenearthemediastinum,theybecomemuch spermatozoalmaturation,maybefoundamongthespermatids.
lessconvolutedandformshorttubulirecti,whichlackspermatogenic SpecializedtightjunctionalcomplexesbetweenadjacentSertolicells
cellsandare,instead,linedbycuboidalepithelium.Withinthemedia- formafunctional‘blood–testisbarrier’thatsubdividestheseminiferous
stinumtestis,tubulirectianastomosetoformtheretetestis,whichis epitheliumintobasalandadluminalcompartments.Spermatogonia
linedbyaflatepithelium.Here,tubularfluidisreabsorbedandsperm- anddevelopingspermatocyteslieoutsidetheblood–testisbarrier,in
atozoabecomeconcentrated.Theretetestiscoalescestoform7–15 thebasalcompartment,whereasmaturespermatocytesandspermatids


efferentductules,whichactasconduitstocarryspermatozoaintothe are sequestered above the blood-testis barrier, in the adluminal
caputepididymis.Theefferentductulesarelinedbyaciliatedcolumnar compartment.


Male reproductive system
1274.e1
67
RETPAHC
Thelongerlengthofthelefttesticularveinanditsangleofinsertion
intotheleftrenalveinhavebeensuggestedaspossibleaetiologiesfor
theoccurrenceofvaricoceles.Additionally,thetesticularveinsmay
anastomosewiththeexternalpudendal,cremastericandvasalveins,
allowingvaricocelestopersistorrecurafterablativeproceduresthatdo
notaddressthesepotentialcollaterals.


Testis and epididymis
1275
67
RETPAHC
Fig. 76.6 A
laparoscopic view of a
persistent
communication
between the scrotum
and peritoneal cavity in
a 4-month-old boy
(patent processus
vaginalis).
2
3
Patent Right vas Right testicular
processus deferens vessels
vaginalis 4
1
Cremasteric artery Testicular artery and vein
Pampiniform plexus
Vasal artery
Head of epididymis
Fig. 76.8 A multislice computed tomogram of the inferior vena cava,
showing the left testicular vein draining to the left renal vein, and the right
Tail of epididymis
testicular vein draining directly to the inferior vena cava. Key: 1, right
testicular vein; 2, inferior vena cava; 3, left renal vein; 4, left testicular
vein.
Fig. 76.7 The arterial blood supply and venous drainage of the testis.
(With permission from Waschke J, Paulsen F (eds), Sobotta Atlas of
Human Anatomy, 15th ed, Elsevier, Urban and Fischer. Copyright 2013.)
Spermatogonia Spermatogonia,thegermcellsforallspermatozoa,
aredescendedfromprimordialgermcellsthatmigrateintothegenital
cordsofthedevelopingtestis.Inthefullydifferentiatedtestis,theyare
locatedalongthebasallaminaeoftheseminiferoustubules(Fig.
76.10B).Basedontheircellularandnucleardimensions,distribution
ofnuclearchromatin,andhistochemicalandultrastructuralproperties,
spermatogoniaarecharacterizedaseitherdark-typeA(Ad),pale-typeA
(Ap)ortypeB.Adspermatogoniadividemitoticallytomaintaintheir


ownpopulation,andcandifferentiatetogiverisetoApcells,theprecur-
sorsoftypeBcells,whicharecommittedtothespermatogenesiscycle.
TypeBcellsgiverisetotypeIspermatocytes;theyleavethebasalcom-
partmentoftheseminiferoustubuleandcrosstheblood–testisbarrier
toentertheadluminalcompartmentinastepcoordinatedbySertoli
cells.
Thegenerationofmaturespermatozoafromspermatogoniatakes Fig. 76.9 A colour Doppler scan of the scrotal contents showing normal
approximately64days.Incross-section,aseminiferoustubuleshows flow. The linear echogenic band (arrow) seen centrally represents the
morethanonephaseofthecyclearounditscircumferencebecause mediastinum testis, which is composed of fibrofatty material.
wavesofprogressionthroughaspermatogeniccycleoccurinspirals
alongthelengthofatubule(seeFig.76.10B).
proportionofspermatidsdegenerateduringmaturation,reducingthe
Primary and secondary spermatocytes Primaryspermatocytes expectedyield.
haveadiploidchromosomenumber,withduplicatedsisterchromatids
(4NDNAcontent).Theyarelargecellswithroundnuclei,inwhichthe Spermatids Spermatidsundergoaseriesofnuclearandcytoplasmic
chromatiniscondensedintodark,thread-like,coiledchromatids.They changes,termedspermiogenesis,inordertodevelopintomaturesper-


MAlE REPRoduCTiVE sysTEM
1276
8
NoiTCEs
Acrosomal cap
Head 4 µm
ST Nucleus
Centriole Neck 0.3 µm
Spiral mitochondria
Middle piece 7 µm
L
Axoneme
Principal piece 40 µm
A
L
M
End piece 5–7 µm
S
SC
SZ Fig. 76.11 The main ultrastructural features of a mature spermatozoon.
ST
tened nucleus with condensed, dark-staining chromatin, covered
SG anteriorlybyanacrosomalcap.Thelattercontainsacidphosphatase,
hyaluronidaseandproteasesnecessaryforoocytefertilization.Thehead
isconnectedbyashortneck,approximately0.3µminlength,toalong
tail,whichisdividedintomiddle,principalandendpieces.Themid-
B
pieceofthetailisalongcylinder,approximately7µminlength.It
consistsofanaxialbundleofmicrotubules,theaxoneme,surrounded
Fig. 76.10 A, Seminiferous tubules (ST; cut in various planes of section)
byacylinderofninedenseoutermicrotubules,surroundedbyahelical
and the interstitial tissue (Leydig cells, L) of the testis. The seminiferous
mitochondrialsheath.Themid-pieceisthepowerhouseofthesperma-
tubules are highly convoluted and lined by a stratified epithelium,
tozoon.Theprincipalpieceofthetailisresponsibleformotility.With
which consists of cells in various stages of spermatogenesis and


spermiogenesis (collectively referred to as the spermatogenic series). alengthof40µmandadiameterof0.5µm,thetailformsthemajority
Non-spermatogenic cells are the Sertoli cells. B, A human seminiferous ofthevolumeofaspermatozoon.Theaxonemalcomplexiscontinuous
tubule showing the differentiation sequence of spermatozoa from basally fromtheneckregiontotheterminusofthetail,withonlytheaxoneme
situated spermatogonia (SG). Large primary spermatocytes (SC) have persistinginthefinal5–7µm.
characteristic thread-like chromatin in various stages of prophase of the
first meiotic division. Smaller haploid spermatids (ST) have round nuclei Sertoli cells Sertolicellshaveeuchromaticandirregularnucleithat
initially, but mature to possess the dense, elongated nuclei and flagella arealignedperpendiculartothebasallaminaandcontainoneortwo
of spermatozoa (SZ). Sertoli cells (S) are identified from their oval or prominentnucleoli.Theyarevariableinshape.Theirbasalendrestson
pear-shaped nuclei, orientated perpendicular to the basal lamina, and thebasallamina,whiletheirapicalendextendsintothetubulelumen.
from their prominent nucleoli. The tubule is surrounded by peritubular Consistentwiththeirphagocyticfunction,theircytoplasmisrichin
myoid cells (M). Clusters of large endocrine Leydig cells (L) are seen in lysosomes.Sertolicellsprovidekeysupportforspermatogenesiswithin
the interstitial connective tissue. theseminiferoustubules.Complexrecessesintheirplasmamembranes


servetoenvelopspermatogonia,spermatidsandspermatozoa,untilthe
latterarematureenoughforrelease.Longcytoplasmicprocessesextend
fromGolgivesicles,generationoftheaxonemefromthecentrioles,and betweenspermatogoniainthebasalcompartmentandspermatocytes
formationoftheacrosomalcapattheanteriorpoleofthespermato- intheadluminalcompartmentoftheseminiferoustubule.Adjacent
zoon.Concurrently,thenuclearchromatincondensesandthenucleus Sertolicellsarejoinedatthislevelbytightjunctionsthatcreateadif-
assumesaspearheadshape.Thecytoplasmicvolumeshrinks,bringing fusionbarrierbetweentheextratubularandintratubularcompartments.
thewalloftheacrosomalvesicleintocontactwiththeplasmamem- Thisso-calledblood–testisbarriercanbedisruptedbytraumaticor
brane.Aperinuclearsheathofmicrotubulesdevelopsfromtheposte- inflammatory events, allowing self-directed immune responses to
rioredgeoftheacrosomeandextendstowardstheposteriorpoleofthe developagainstspermantigens,potentiallyleadingtosubfertility.
spermatozoon.Here,themicrotubulesarearrangedinthetypicalflagel- Inadditiontotheirroleinspermatogenesis,Sertolicellssecrete


larpatternofnineoutermicrotubulessurroundingtwocentralmicro- proteinaceousfluidtofacilitatespermatozoaltransportthroughthe
tubules,theaxonemalcomplexthatextendslongitudinallytoformthe seminiferoustubulesandintotheexcurrentducts.Theyalsoregulate
tailofthespermatozoon.Mitochondriamigratealongtheaxonemal theintratesticularhormonalmilieubysecretinginhibinBandandro-
complexandconcentrateinthemid-pieceofthetail.Inthefinalphase gen binding protein in response to stimulation by pituitary
ofspermiogenesis,excesscytoplasmisdetachedfromthespermato- gonadotropins.
zoonasaresidualbodythatisphagocytosedanddegradedbySertoli
cells.Duringtheformationofresidualbodies,spermatidslosetheir Leydig cells and interstitial tissue Theinterstitialtissuebetween
cytoplasmicbridges,andseparatefromoneanother,beforebeing seminiferoustubulesincludesperitubularmyoidcells,vessels,nerves
releasedintothelumenoftheseminiferoustubule. andclustersofLeydigcells.Myoidcellsarecontractile;theirrhythmic
activityhelpspropelnon-motilespermatozoathroughtheseminiferous
Spermatozoa Spermatozoareleasedintotheseminiferoustubuleare tubulestowardstheretetestisandexcurrentductalsystem.Leydigcells


Testis and epididymis
1277
67
RETPAHC
Age-related changes Functionally,thefetaltestisisprimarily inguinalring,intheinguinalcanal,orbetweenthesuperficialinguinal
anendocrineorganthatproducestestosteroneandanti-Müllerian ringandthescrotum.Retentionintheinguinalcanalisassociatedwith
hormone.Seminiferoustubulesdonotbecomecanalizeduntilapproxi- apatentprocessusvaginalis,andmaybefurthercomplicatedbyacon-
matelytheseventhmonthofgestation.FetalLeydigcells,responsible genitalhernia.Occasionally,thetestismaymigrateoutsideitsnormal
forandrogen-induceddifferentiationofmalegenitalia,degenerateafter pathofdescent,andlieinanectopiclocation.
birth.AsecondwaveofLeydigcelldifferentiationoccurs2–3months Atbirth,3%offull-termmaleinfantshaveaunilateralundescended
afterbirth,brieflyelevatingtestosteronelevelsinmaleinfants.The testis.By6monthsofage,thisnumberdecreasestolessthan1%.Unde-
Leydigcellsofearlyinfancysubsequentlyregressandthetestisremains scendedtestesareassociatedwithahigherriskofinfertilityandtesticu-
inastateofdormancyduringchildhood.InastudyofJapaneseboys, larcancerlaterinlife.


gonocyteswerereportedtoappearatabouttheageof2years,sperma- Incontrast,maldescentinchildrenbetweentheagesof1and
tocytesby4yearsandspermatidsby11years(Yuasaetal2001). 15yearsisassociatedwithSertolicelldegeneration(Runeetal1992).
Pubertyisassociatedwiththedevelopmentofanadultpopulation
ofandrogen-producingLeydigcells,whichpersistthroughoutadultlife. Retractile testis
Thetestesgrowslowlyinsizeuntiltheageof10or11years,atwhich
timethereisamarkedaccelerationofgrowthrate.Thisincreasein Available with the Gray’s Anatomy e-book
testicularsizeislargelyduetotheonsetofspermatogenesis,character-
izedbyproliferationanddifferentiationofpreviouslydormantsperma- Torsion
togonialstemcells.Testicularsize,spermqualityandquantity,andthe
numbersofSertoliandLeydigcellshaveallbeenreportedtodecline Available with the Gray’s Anatomy e-book
withage,althoughnoconsistentordefinitiveagefortheonsetofthis
declinehasbeenidentified.Testicularvolumeoccupiedbyseminiferous
Hydrocele
tubulesdecreases,whereasthatoccupiedbyinterstitialtissueremains
approximatelyconstant.
Available with the Gray’s Anatomy e-book
Themostfrequentlyobservedhistologicalchangeintheageingtestis
istheapparentvariabilityinspermatogenesis;spermatogenesisiscom-


pleteinsomeareas,andreducedinothers,orabsentaltogetherasa Splenogonadal fusion
resultoftubularsclerosis.Intubuleswherespermatogenesisiscom-
plete,morphologicalabnormalities,suchasmultinucleation,maybe Available with the Gray’s Anatomy e-book
observedinthegermcells.Germcellloss,beginningwithspermatids,
andprogressivelyaffectingtheearlierstagesofspermatogenesis,can Transverse/crossed testicular ectopia
alsobeseen.Asaresult,bothspermqualityandquantitymaybe
affected.Insomemen,thischangeisnotableasearlyasthethirdor Available with the Gray’s Anatomy e-book
fourthdecadeoflife.
Sertolicellsarealsoaffectedbyageing,andshowarangeofmor-
Polyorchidism
phologicalchangesincludingde-differentiation,mitochondrialmeta-
plasia,andmultinucleation.InLeydigcells,thereisadeclineinthe
Available with the Gray’s Anatomy e-book
numberofmitochondriaandthequantityofsmoothendoplasmic
reticulum,paralleledbyanincreaseinlipiddroplets,crystallineinclu-
sionsandresidualbodies.Somecellsmayalsobecomemultinucleated.
Functionally,thesechangesaremanifestedasanage-relatedgradual EPIDIDYMIS
declineincirculatingtestosteronelevels.
Theepididymisliesposterior,andslightlylateral,tothetestis.Anatomi-


Sperm motility and maturation Humanspermatozoaacquirean cally,itisdividedintothreesections:caput(head),corpus(body)and
increasedcapacityformotilityastheymigratethroughtheepididymis, cauda(tail).Between8and12efferentductulesfromthesuperiorpole
whichismanifestednotonlyasaquantitativeincreaseinthepercentage ofthetestisdrainintoandformthecaputepididymis.Distally,the
ofspermatozoawithmotiletails,butalsoasaqualitativechangefrom caudaepididymisbecomescontinuouswiththeconvolutedportionof
animmaturetoamorematurepatternofmotility.Spermatozoainthe thevasdeferens(seeFig.76.5B).Theepididymisisinvestedbytunica
proximalepididymisdemonstratehigh-amplitude,low-frequencytail vaginalis,continuouswiththatcoveringthetestis.Laterally,adeep
movements,producinglittlemotion.Thisisincontrasttospermatozoa groove,thesinusepididymis,markstheboundarybetweenthetestis
inthecaudaepididymis,whichdemonstratelow-amplitudeandhigh- andepididymis.Testis–epididymisnon-fusionhasbeendescribedin
frequencytailmovements,resultinginconsiderablygreaterforward childrenwithcryptorchidism;non-fusionmayinvolvetheepididymal


progression(Bedfordetal1973). headortail,orthewholeepididymis(Kraftetal2011).
Whether,andtowhatextent,spermmotilityisdependentonthe
interactionofhumanspermatozoawithaparticularsectionofthe Epididymal cyst and spermatoceles
epididymisisunknown.Inpatientswithcongenitalabsenceorobstruc-
tionofthevasdeferens,spermatozoainthedistalepididymisdemon- Available with the Gray’s Anatomy e-book
strate worse motility compared to spermatozoa in the proximal
epididymis(Silber1989,SchoysmanandBedford1986).Therefore,
Microstructure
intrinsicspermprocesses,aswellasintrinsicepididymalfunction,
appeartoplayanimportantroleinspermmaturation.
Followingejaculation,spermatozoadisplaytheirfullpatternofmo- Theepididymaltubuleis3–4metresinlength(Turneretal1978),and
tility.Althoughspermmotilityishighestinthehoursfollowingejacula- isentirelyencapsulatedbythetunicavaginalis.Extensionsfromthis
tion,motilehumanspermatozoahavebeenrecoveredfromcervical connectivetissuesheathentertheinterductalspaces,formingseptathat
mucusseveraldaysafterinsemination.However,thissurvivalperiod dividethetubuleintohistologicallysimilarregions(Kormanoand


maybeoflittlerelevance,giventhathumanspermatozoaarecapableof Reijonen1976).Thecaputepididymisconsistsof8–12efferentducts
migratingtotheirtubaldestinationwithinanhourofinsemination. andtheproximalsegmentoftheductusepididymis.Theefferentducts
Afterenteringthefemalereproductivetract,spermatozoaundergoa becomelargerandmoreconvolutedthantheyareinthetestis.Each
processknownascapacitation,torenderthemcapableoffertilizingthe ductis15–20cminlength,andopensintoanindividualepididymal
oocyte.Capacitationinvolvesanumberofstructuralandbiochemical tubule.Thetubulesanastomosewithoneanotheralongthelengthof
changes,includingthedevelopmentofhyperactivatedmotilityand theepididymis,eventuallybecomingasingle,coiledtubuleinthe
completionoftheacrosomereaction.Independentofothersperm corpusepididymis.Theyaresurroundedbycontractilesmoothmuscle
characteristicssuchasmotilityandmorphology,capacitationisaneces- cells(Fig. 76.13),whichincreaseinsizeandnumberinthedistal
sarystepforthedevelopmentoffunctionalspermatozoa. epididymis.Peristalticcontractionsgeneratedbythesmoothmuscle
propelthespermatozoainanantegradedirectiontowardsthecauda.


Developmental anomalies of the testis Epithelium Theepithelialliningoftheepididymaltubulecontains
principal,basal,apicalandclearcells.Principalcellsaretallcolumnar
Cryptorchidism Testiculardescentfromtheabdominalcavitytothe cells with basally located, oval nuclei. They bear long stereocilia
scrotummaybearrestedatanypointalongitscourseatthedeep (15µm),andfunctiontoresorbtesticularfluid;approximately90%of


Male reproductive system
1277.e1
67
RETPAHC
Orchidopexyis,therefore,recommendedforpatientswithpersistent Gangrene of appendix testis
cryptorchidismafter6monthsofageandwithin18monthsofage. secondary to torsion
Availableevidencesuggeststhatorchidopexyatanyagemayimprove
spermatogenesis(Shinetal1997),butdoesnotdecreasetheriskof
testicularcancerinacryptorchidtestis.Aninverserelationshiphasbeen
reportedbetweenageatorchidopexyandtotalspermcountandsperm
motility.Thedataareinsupportoforchidopexyinthefirstyearoflife
(Canaveseetal2009).Nevertheless,surgicalcorrectiondoesmaximize
thechanceofearlydetectionofatesticularmass,andistheonlymeans
ofrestoringanormalmilieuforspermatogenesistooccur.Interestingly,
Leydigcellfunctionisusuallyunchangedbymaldescent,soserum
testosteronelevelsremainwithinthenormalrangeinaffectedpatients.
Retractiletestesareseenmorecommonlythanundescendedtestesin
boys.Aretractiletestisisonethatmovestoandfrobetweenthegroin
andthescrotum.Unlikeundescendedtestes,retractiletestescanbe
manipulatedtothelowerpartofthescrotumonclinicalexamination.
Retractiletestesaresmallerthannormaltestes,havingameanvolume
of0.50mlinchildren.


Testiculartorsionreferstorotationofthetestisarounditsbloodsupply,
leadingtotesticularischaemia.Torsionmaybeextravaginalorintra-
vaginal,dependingonwhetheritinvolvesarotationofboththetestis
andthetunicavaginalis,orofthetestisalone,withinanintacttunica
vaginalis.Ineithercase,torsionresultsinseverescrotalpainsecondary Fig. 76.12 Gangrene of the appendix testis secondary to torsion in an
totissueischaemia.Fertilitycanbeaffectedbyasingleepisodeof 8-year-old child.
torsion.Ifunrelievedwithin4–6hours,permanenttissuelosscanoccur.
Testiculartorsionisthereforeconsideredasurgicalemergency.
Otherstructuresinthescrotum,suchastheappendixtestis(hydatid
ofMorgagni)(Fig. 76.12)andappendixepididymis(seeFig.76.4),can
alsoundergotorsion,resultinginscrotalpainthatmaybedifficultto Transverse/crossedtesticularectopiaisanextremelyrareconditionin
differentiatefromtesticulartorsion.Insomeinstances,a‘bluedot’sign whichbothtestesdescendintoasingleinguinalcanalorhemiscrotum.
isnotedattheupperpoleofthetestis,whichisdiagnostic.Thesestruc- Theoriginofthespermaticcordisnormallylocatedoneachside.It


turesaredevelopmentalremnantsoftheparamesonephric(Müllerian) mayoccurinassociationwithpersistentMüllerianductsyndrome
ductandthemesonephros,respectively.Therearenoassociatedlong- (Tiryakietal2005).
termsequelae.
Polyorchidismisararecongenitalanomalyinwhichtherearetwoor
Apatentprocessusvaginalisallowscommunicationbetweentheperi- moretestes.Themostcommontypeconsistsofthreetestes;caseswith
tonealcavityandthespermaticcordorscrotum.Passageofperitoneal fourtesteshavealsobeenreported.Thesupernumerarytestesmayor
fluidintothescrotumpresentsasacommunicatinghydrocele,and maynotbeconnectedtoavasdeferens.
usuallyresolvesspontaneouslyoncetheprocessusisobliterated,by
18–24monthsofage.Alternatively,iftheprocessusispatentproximally Epididymalcystsarisefromtheepididymaltubulesandmayoccur
butobliterateddistally,ahydroceleorcystofthecordmaybenoted. anywhereinthecaput,corpusorcaudaepididymis.Ifasymptomatic,
Surgicaltreatmentmaybeindicatedforpersistent,non-communicating removalisunnecessary,particularlygiventheriskofiatrogenicepidi-


hydroceles.Hydrocelecanalsooccurasaresultoflymphaticobstruc- dymalobstruction.Spermatocelesarecyststhatare,basically,aneu-
tionfromtesticulartumour,epididymitis,orchitisortrauma.A20% rysmsoftheefferentductsthatformthecaputepididymisandcontain
incidenceofhydrocelehasbeenreportedinchildrenhavinglaparo- sperm.Removalisunnecessaryunlesstheygrowtoalargesizeand
scopicen blocligationofthespermaticvesselsontheposteriorab- causepain(Kaufmanetal2011).However,spermatocelesmaybeaspi-
dominalwall(Palomoprocedure).Thiscomplicationisavoidedby ratedasasourceofspermatozoa.
lymphatic-sparingsurgery(Schwentneretal2006).
Splenogonadalfusionisararecongenitalanomalycharacterizedby
splenictissuebeingconnectedtothegonad,resultingfromanabnor-
malconnectionbetweenthespleenandthegonadduringgestation.It
hasahigherpredominanceinmalesandisalmostinvariablyonthe
leftside.Itmaybeofthecontinuoustype,wherethetestisisconnected
tothemainspleen,orofthediscontinuoustype,wherethetestisis
connectedtoectopicsplenictissue.


MAlE REPRoduCTiVE sysTEM
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NoiTCEs
thetotalsecretoryfluidvolumeisabsorbedintheepididymis.Theyalso deriveddirectlyfromtheinternaliliacartery.Veinsfromthevasand
endocytoseothercomponentsofseminalfluidandproduceglycopro- seminalvesiclesdraintothepelvicvenousplexus,whereastheassoci-
teinsthatareessentialforspermmaturation.Basalcellsliebetweenthe atedlymphaticvesselsdrainintotheexternalandinternaliliacnodes.
basesoftheprincipalcellsandarethoughttobeprecursorsofprincipal
cells.Apicalandclearcellsarefarlesscommonthanprincipalandbasal Innervation
cells.Apicalcellsarerichinmitochondriaandaremostabundantin
thecaputepididymis.Incontrast,clearcellsarecolumnarandmost
Thevasadeferentiaareinnervatedbyarichautonomicplexusofpri-
abundantinthecaudaepididymis.Theyhavefewmicrovillibutnumer-
marilypostganglionicsympatheticfibresderivedfromthepelvicplexus.
ousendocyticvesiclesandlipiddroplets.Theirfunctionsareunknown.
Microstructure
VAS DEFERENS, SPERMATIC CORD,
PARADIDYMIS AND EJACULATORY DUCT Inhumans,thevasdeferensis30–35cminlengthand2–3mmin


diameter,withaluminaldiameterof300–500µm.Incross-section,it
consistsofanouteradventitialsheathcontainingbloodvesselsand
VAS DEFERENS
nerves;athick,three-layeredmuscularwallofinnerandouterlongitu-
dinalandmiddlecircularsmoothmuscle;andaninnermucosallining
Thevasdeferens(ductusdeferens)isatubularstructurederivedfrom
ofpseudostratifiedcolumnarepitheliumwithnon-motilecilia(Fig.
themesonephricduct.Itsprimaryfunctionisthetransportofsperm
76.14).Ithasthegreatestmuscletolumenratio(approximately10:1)
fromtheepididymistotheurethra,althoughabsorptiveandsecretory
ofanyhollowviscusinthebody.Duringejaculation,thesmooth
functionshavealsobeendescribed(Hoffer1976).Asitarisesfromthe
musclelayerscontractreflexively,propellingthesperminanantegrade
caudaepididymis,thevasistortuousfor2–3cm(seeFig.76.5B).
direction(seeabove).
Beyondthisconvolutedsegment,itliesposteriorandparalleltothe
vesselsofthespermaticcord,passesthroughtheinguinalcanal(seeFig.
Developmental anomalies
76.16),andemergesinthepelvislateraltotheinferiorepigastricvessels
of the vas deferens


(seeFig.61.3).Attheinternalring,thevasdivergesfromthetesticular
vessels,coursingmedialtothestructuresofthepelvicsidewall,inorder
toreachthebaseoftheprostateposteriorly.Here,thevasonceagain
Available with the Gray’s Anatomy e-book
becomestortuousanddilated(theampullaofthevasdeferens),before
culminatingattheejaculatoryduct(seeFig.74.23).
SPERMATIC CORD
Vascular supply and lymphatic drainage
Thespermaticcordbeginsatthedeeporinternalinguinalring,extends
Thevasdeferensissuppliedbythevasalartery,whichisusuallyderived
thelengthoftheinguinalcanal,exitsthecanalatthesuperficialor
fromthesuperiorvesicalartery,andoccasionallyfromtheinferior
externalinguinalring,andsuspendsthetestisinthescrotum(Fig.
vesicalartery,bothbranchesoftheinternaliliacartery.Rarely,itis
76.15;seeFig.76.3).Betweenthesuperficialinguinalringandthetestis,
thecordliesanteriortothetendonofadductorlongus.Itisflanked
anteriorlybythesuperficialexternalpudendalartery,andposteriorly
bythedeepexternalpudendalartery.Theilioinguinalnerveliesinferior
tothecordasittraversestheinguinalcanal.


Inadditiontotheartery,veins,lymphaticsandnervessupplyingthe
testis,whicharecontainedwithintheinternalspermaticfascia,the
ET spermaticcordincludestheilioinguinalnerve,thegenitalbranchof
thegenitofemoralnerve,thecremastericartery,veinsandlymphatics,
andthevasalartery,veinsandlymphatics,allofwhicharecontained
withintheexternalspermaticfascia(Fig. 76.16;seeFig.76.2).These
fasciallayersarecontinuouswiththelayersoftheabdominalwall.The
internalspermaticfasciaisderivedfromthetransversalisfascia,and
formsathin,looselayeraroundthespermaticcord.Thecremasteric
FCT fascia,whichcontainstheskeletalmusclefibresthatmakeupthecre-
mastermuscle,isderivedfrominternaloblique.Theexternalspermatic
fasciaiscontinuouswiththeaponeurosisofexternaloblique.
Ectopicsuprarenaltissue(adrenalrest)isencounteredwithinthe
distalendofthespermaticcordin2%ofchildrenundergoinginguinal
procedures.Adrenalrestsaretypicallybrightyellowtoorangeincolour,
roundorovalinshape,andupto5mmindiameter;theycontainthe
Fig. 76.13 The microstructure of the epididymis. Abbreviations: ET, threelayersofthesuprarenal(adrenalcortex)butnomedulla(Savaset


epididymal tubule; FCT, fibromuscular connective tissue. al2001).
Fig. 76.14 The vas deferens. A, A low-power view,
transverse section. B, A higher-power view. The
convoluted lumen is lined by pseudostratified
columnar epithelial cells.
A B


Male reproductive system
1278.e1
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RETPAHC
Thevasdeferensmaybecongenitallyabsent,eitherunilaterallyor
bilaterally.Whenbilateral,theconditionisassociatedwithamutation
ofthecysticfibrosistransmembraneconductancegenein80%of
affectedmen.Thisconditionischaracterizedbylowsemenvolumedue
toabsentorhypoplasticseminalvesiclesandazoospermia,although
spermatogenesisisusuallynormal.Absentvasaisusuallytheonly
genitalmanifestationofcysticfibrosis.
Theanatomyofthevasdeferensisworthyofnoteinchildrenwith
cryptorchidism(seeabove).Atlaparoscopicorchidopexyforintra-
abdominaltestis,itisimportanttoexcludea‘loopingvasdeferens’that
enterstheinguinalcanalandloopsbacktotheabdominalcavity
(Shalabyetal2011);failuretorecognizethisanatomicalanomalymay
resultiniatrogenicinjurytothevasdeferens.


Accessory glandular structures
1279
67
RETPAHC
Fig. 76.15 The relationship of
the spermatic cord to the
External oblique
External oblique anterior abdominal wall. (With
permission from Waschke J,
Paulsen F (eds), Sobotta Atlas
of Human Anatomy, 15th ed,
Linea alba Elsevier, Urban and Fischer.
Copyright 2013.)
External oblique,
Internal oblique
aponeurosis
Inguinal ligament
Cremaster
Intercrural fibres
Reflected ligament
Lateral crus
Superficial
Fundiform ligament Medial crus inguinal ring
of penis
Spermatic cord
Fig. 76.16 Structures contained within the
spermatic cord. (With permission from Waschke
J, Paulsen F (eds), Sobotta Atlas of Human
Anatomy, 15th ed, Elsevier, Urban and Fischer.
External oblique, Copyright 2013.)
aponeurosis
Internal oblique
Deep inguinal ring
Transversus
Inferior epigastric
abdominis
arteries and veins
Ilioinguinal nerve
Transversalis fascia
Transversalis fascia
Ilioinguinal nerve Artery of vas deferens
Vas deferens
Superficial inguinal ring
Pampiniform plexus
Genitofemoral nerve, genital branch
Genitofemoral nerve,
genital branch Cremaster
Inguinal ligament
External spermatic fascia
PARADIDYMIS diameterofgreaterthan2.3mmdefinesadilatedorobstructedefferent
duct(Nguyenetal1996).
Theparadidymis(organofGiraldes)isasmallcollectionofconvo-
lutedtubuleslocatedanteriorlyinthespermaticcord,justabove
ACCESSORY GLANDULAR STRUCTURES
thecaputepididymis.Thetubulesarelinedwithcolumnarciliated
epitheliumandarelikelytorepresentavestigialremnantofthe
mesonephros. SEMINAL VESICLES


Theseminalvesiclesarepairedoutpouchingsoftheterminalvasdefer-
EJACULATORY DUCTS ens,locatedatthebaseoftheprostate,betweenthebladderandthe
rectum(Fig. 76.17,seeFig.74.23).Inadults,theseminalvesiclemeas-
Thepairedejaculatoryductsareformedfromtheunionoftheductof uresbetween5and10cminlength,and3and5cmindiameter,with
theseminalvesiclewiththeampullaofthevasdeferens.Eachisapprox- anaveragevolumecapacityof13ml(Goldstein2012).Inthemajority
imately2cminlength,andextendsfromthebaseoftheprostate, ofmen,therightseminalvesicleisslightlylargerthantheleft;thesize
betweenthemedianandlaterallobes,towardsitsopeningontheveru- ofbothglandsdecreaseswithage.
montanum(seeFig.75.13).Theductsdiminishinsizeandconverge Inessence,eachseminalvesicleisacoiledtubewithirregulardiver-
towardstheirends.Ejaculatoryductobstruction,thoughrare,canlead ticula,containedwithinadense,fibromuscularsheathandpartly
tooligospermiaorazoospermia.Causesincludecongenitalcysts,such coveredbyperitoneum.Theupperpoleisacul-de-sac,whilethelower


MAlE REPRoduCTiVE sysTEM
1280
8
NoiTCEs
Rectum Bladder Left seminal vesicle
Fig. 76.18 The microstructure of the seminal vesicles, showing the
tubulo-acinar structure.
locatedlateraltothemembranousurethraandsuperiortotheperineal
membrane.Theyaredrainedbylongexcretoryducts,eachductbeing
almost3cminlength,whichpassobliquelyandanteriorlyfromthe
regionofthemembranousurethra,topenetratetheperinealmem-
brane,andopenonthefloorofthebulbarurethra,approximately
2.5cmbelowtheperinealmembrane.Theglandsaresurroundedby
fibresoftheurinarysphincter.Duringsexualexcitement,contractionof
Obturator internus
themusclefibresleadstoexpulsionofclearmucusfromtheglandsinto
Fig. 76.17 An axial magnetic resonance imaging (MRI) scan
thebulbarurethra.Secretionsofthebulbourethralglandscomprise
demonstrating the normal high signal in the seminal vesicles on a
5–10%ofthetotalejaculatevolume.
T2-weighted scan.
Microstructure
Agenesisoftheseminalvesiclesisacongenitalanomaly,whichis
Eachbulbourethralglandconsistsofseverallobulesenclosedbya
associatedwithabsenceofthevasdeferensorvasoureteralcommunica-
fibrouscapsule.Thesecretoryunitsaretubulo-alveolarinform.The
tion(Wuetal2005).


glandularepitheliumiscolumnar,andsecretesacidicandneutral
mucinsintotheurethrapriortoejaculation;thesecretionsprimarily
Vascular supply and lymphatic drainage havealubricatingfunction.Diffusemucosa-associatedlymphoidtissue
(MALT)isassociatedwiththeglands.
Theprimarybloodsupplytotheseminalvesiclesisfromthevesiculo-
deferentialartery,abranchoftheumbilicalartery(Braithwaite1952). PERIURETHRAL GLANDS
Anadditionalsourceofbloodsupplyistheinferiorvesicalartery,which
arisesfromtheinternaliliacarteryortheinferiorglutealartery.Venous
Theperiurethralglands(glandsofLittre)aremostnumerousinthe
drainageisprovidedbythevesiculodeferentialveinsandtheinferior
penileurethra.Likethebulbourethralglands,theysecretemucusinto
vesicalplexus.Lymphaticdrainage,accordingly,occursviatheinternal
thelumenoftheurethrapriortoejaculation;thesecretionshavea
iliacnodes.
lubricatingfunction.
Innervation
EXTERNAL GENITALIA
Theseminalvesiclesreceivepreganglionicparasympatheticinputfrom
thepelvicnerve,andsympathetic(postganglionic)andparasympa- PENIS
thetic(preganglionic)inputfromthehypogastricnerve.
Thepenisconsistsofanattachedrootintheperineum(radix),anda


Microstructure
free,pendulousbody(shaft),whichiscompletelyenvelopedinskin
(Fig. 76.19).Atitsbase,thepenisissupportedbytwosuspensoryliga-
Afterpuberty,thevesiclesmatureintoelongated,sac-likestructures, ments,whichanchorittothepubicsymphysis(Fig. 76.20B).These
produceaviscouswhite–yellowfluidthatcontributestoatleasttwo- ligamentsarecomposedprimarilyofelasticfibresandarecontinuous
thirdsofthetotalejaculatevolume,andplayanimportantroleinsperm withBuck’sfasciaofthepenis.Thepenileshaftcontainsthreeerectile
motilityandmetabolism.Thesecretedfluidisrichinfructose,coagula- columns–thepairedcorporacavernosaandthecorpusspongiosum;
tionproteinsandprostaglandins,withapHintheneutraltoalkaline theurethra;andtheinvestingfasciae,bloodvesselsandnervesassoci-
range.Thewalloftheseminalvesicleiscomposedofanexternalcon- atedwiththesestructures(Fig. 76.20A).
nectivetissuelayer,amiddlesmoothmusclelayer(significantlythinner Thecorporacavernosalieinintimateappositionwithoneanother


thanthecorrespondinglayerinthevasdeferens),andaninnermucosal alongthelengthofthepenileshaft(Fig. 76.21);thecorpusspongiosum
layerwithahighlyfolded,labyrinthinestructure(Fig. 76.18).The liesintheventralgroovebetweenthecavernousbodies.Proximally,
mucosallayerislinedbycuboidaltopseudostratifiedcolumnarepithe- posteriortothesuspensoryligaments,therightandleftcorporacaver-
lium,featuringtypicalprotein-secretingcells.Contrarytotheimplica- nosadivergetoformtwotaperingprocesses,thecrurapenis,whichare
tionoftheirname,seminalvesiclesarenotreservoirsforspermatozoa, firmlyanchoredtotheischiopubicrami(seeFig.76.20B).Thecorpus
exceptincasesofejaculatoryductobstruction;theycontractduring spongiosumbroadensbetweenthetwocruratoformthebulbospongi-
ejaculationtoreleasesecretionsintotheejaculatoryduct. osusmuscle(seeFig.76.20C).Atthedistalendofthepenis,thecorpus
spongiosumagainenlargesandassumesabulbousshapetoformthe
glanspenis.Theroundedbaseoftheglans,thecorona,separatesthe


BULBOURETHRAL GLANDS glansfromthepenileshaft.Theglansiscoveredbytheforeskin
(prepuce),whichisaloosefoldofretractableskinattachedtothe
Thebulbourethralglands(Cowper’sglands)aresmall,round,yellow, ventralsurfaceoftheglanspenis,underthecorona,atthefrenulum.
lobulatedstructures,measuringapproximately1cmindiameter,and Cutaneoussensitivityisgreatestovertheglanspenis.


External genitalia
1281
67
RETPAHC
A C
Body of penis
Glans penis
Neck of glans
Testis Corona of glans
Prepuce
Epididymis, Glans penis
vas deferens,
vessels,
nerves and
lymphatics
Position of
perineal body
Ischial tuberosity
Body of penis (unattached parts
of corpus spongiosum and
B
D Crus of penis (attached part corpora cavernosa)
of corpus cavernosum) Glans penis
Glans penis
Frenulum
Ventral surface
of body of penis
Raphe
Testis
Bulb of penis (attached part
of corpus spongiosum) Position of perineal body
Fig. 76.19 Structures in the male urogenital triangle. A, An inferior view. B, The ventral surface of the body of the penis. C, A lateral view of the body of
the penis and glans. D, An inferior view of the urogenital triangle of a male, with the erectile tissues of the penis indicated with overlays. (With permission
from Drake RL, Vogl AW, Mitchell A (eds), Gray’s Anatomy for Students, 2nd ed, Elsevier, Churchill Livingstone. Copyright 2010.)
Skin Theskinofthepenileshaftisthin,highlyelasticanddevoidof Shaft Themajorportionofthepenileshaftconsistsofthepaired
appendages(hairorglandularelements),withtheexceptionofsmegma- corporacavernosa.Thesecontainerectiletissue,enclosedwithina
producingglandslocatedatthebaseofthecorona.Itisalsodevoidof densefibroelasticsheathofconnectivetissue,thetunicaalbuginea
fatandquitemobilebecauseoflooseattachmentsbetweenthedartos (seeFigs76.21E,76.22).Theouterlongitudinalandinnercircular


fasciaandtheunderlyingBuck’sfascia.Incontrast,theskinoftheglans fibresofthetunicaformanundulatingmeshworkwhenthepenisis
isimmobile,asaresultofitsdirectattachmenttotheunderlyingtunica flaccidbutbecometightlystretchedonerection.Thecircularfibres
albuginea.Bloodsupplytothepenileskinisindependentoftheerectile surroundeachcorpusseparatelyandthecorporaarethensurrounded
bodies,andisderivedfromtheexternalpudendalbranchesofthe asaunitbytheouterlongitudinalfibres.Smoothmusclebundles
femoralvesselsthatenterthebaseofthepenisandrunlongitudinally traverse the erectile bodies to form endothelium-lined cavernous
withinthedartosfascia,formingarichanastomoticnetwork.Thus,it sinuses,whichgivetheerectiletissueaspongyappearanceongross
ispossibletomobilizepenileshaftskinonavascularpedicleforsurgi- examination.Bloodflowintothesinusesleadstopenileengorgement
calproceduressuchasurethralreconstruction. andcompressionofvenousoutflowchannels,resultinginpenile
Thesuperficialpenilefasciaisdevoidoffat,andconsistsofloose erection.


connectivetissueinterspersedbyfibresofthedartosmusclefromthe Thecorporacavernosaarenotdistinct,separatestructuresbutare
scrotum;itiscommonlyreferredtoasthedartoslayer.Incontrast,the dividedinthemidlinebyafibrousseptumthatiscontinuouswith
deeppenilefasciaisadenserfascialsheath,knownasBuck’sfascia, thedeepcircularfibresofthetunicaalbuginea.Theseptumiscom-
whichenvelopsbothcorporacavernosaandsplitstoenvelopthecorpus pleteandthickproximally,butincompletedistally,permittingcom-
spongiosum(Fig. 76.22B).Distally,itblendswiththetunicaalbuginea municationandexchangeofbloodflowbetweenthecorporalbodies.
coveringallthreecorporalbodies.Proximally,itiscontinuouswiththe Thewidemediangroovealongtheventralaspectofthecorporacaver-
dartosmuscleandthedeepperinealfascia.Bleedingfromatearinthe nosaisoccupiedbythecorpusspongiosum,containingtheurethra.
corporalbodiesisusuallycontainedwithinBuck’sfascia,andecchymo- Dorsally,asimilar,butnarrower,groovecontainsthedorsalneurovas-
sisislimitedtothepenileshaft. cularbundle.Thecorporacavernosaenddistallywithintheglans


penisasindividual,roundedcones(seeFig.76.19D).Thecorpus
Root Theroot(radix)ofthepenisconsistsofthreemassesoferectile spongiosumcontainslesserectiletissuethanthecorporacavernosa,
tissueintheurogenitaltriangle:namely,thetwocruraandthebulb, andisenclosedbyathinnerlayeroftunicaalbuginea.Theurethra
firmlyattachedtothepubicarchandtheperinealmembrane,respec- traversesthelengthofthecorpusspongiosum,terminatingataslit-
tively.Thecruraaretheposteriorextensionsofthecorporacavernosa, likemeatusonthetipoftheglanspenis,whichis,itself,anexpan-
whilethebulbisthedilatedposteriorendofthecorpusspongiosum. sionofthecorpusspongiosum.Numeroussmallpreputialglands
Theurethraentersthebulbviaitsposteriorsurfaceandtravelsthe secretingsebaceoussmegmalinethecoronaalongthebaseofthe
lengthofthepenileshaftwithinthecorpusspongiosum. glanspenis.


MAlE REPRoduCTiVE sysTEM
1282
8
NoiTCEs
A Corpora cavernosa
Body of penis
Corpus spongiosum (cross-section)
containing urethra
Glans penis
Corpus cavernosum
External urethral
meatus (orifice)
Navicular fossa of urethra
Perineal membrane
Corpus spongiosum Crus of penis (attached part of
corpus cavernosum)
Bulbourethral gland
within deep pouch
B Fundiform ligament of penis
Suspensory ligament of penis
Ischiocavernosus
Midline raphe
Bulbospongiosus
Puborectalis
Superficial anal sphincter
Superficial transverse perineal muscle
C Penile skin
Superficial penile (Colles’) muscle
Ischiocavernosus Tunica albuginea
Deep penile (Buck’s) fascia
Glans penis
Corpus spongiosum
Corpus cavernosum
Bulbospongiosus Urethra
Fig. 76.20 A, The erectile tissues of the penis. B, The muscles in the superficial perineal pouch. C, The muscles and erectile tissues of the penis in
section. (A–B, With permission from Drake RL, Vogl AW, Mitchell A (eds), Gray’s Anatomy for Students, 2nd ed, Elsevier, Churchill Livingstone. Copyright
2010. C, Adapted from Drake RL, Vogl AW, Mitchell A, Tibbitts R, Richardson P (eds), Gray’s Atlas of Anatomy, Elsevier, Churchill Livingstone. Copyright
2008.)


External genitalia
1283
67
RETPAHC
Corpus Corpus Prostate Seminal
cavernosum spongiosum vesicle Bladder
A B
Penile Bulbospongiosus Prostatic urethra Corpus cavernosum Corpus spongiosum
urethra
Crus of the corpus cavernosum Corpus cavernosum Tunica albuginea Corpus cavernosum Corpus spongiosum Glans penis
C D E
Bulb of penis Prostate Anal canal Tunica Corpus
albuginea cavernosum
Fig. 76.21 A–B, An MRI scan of the penis showing the corpora cavernosum and spongiosum. Note the corpus spongiosum flaring posteriorly into
the bulbospongiosus. C, An MRI scan showing the bulb of the penis and the attachment of the posterior portion of the corpora cavernosa, the crura.
D–E, An MRI scan of the penis showing the tunica albuginea.
Vascular supply and lymphatic drainage entialbranchestothecorpusspongiosumandurethra.Therichblood
supplytothespongiosumallowssafedivisionoftheurethraduring
stricturerepair.
Arteries
Bloodsupplytothecorporalbodiesisderivedfromtheinternalpuden-
Cavernous (deep, cavernosal) artery of the penis Thecavern-
dalartery,abranchoftheinternaliliacartery,whichtravelswithin
ous(deep,cavernosal)arteryofthepenisisusuallyapairedvesselthat
Alcock’scanalbeforereachingthepenisandperineum(Fig. 76.23).As
piercesthetunicaalbugineaofthecorporacavernosaatthehilumof
itemergesfromAlcock’scanal,theinternalpudendalarterygivesoff


thepenisandthentravelsnearthecentreofthecorporalbodiesinthe
theperinealartery,tosupplyischiocavernosusandbulbospongiosus,
directionoftheglanspenis.Alongitscourse,itgivesoffseveralstraight
andtheposteriorsurfaceofthescrotum,aswellasthecommonpenile
andhelicinebranchesatregularintervals;theyopendirectlyintothe
arterythatsuppliesthedeepstructuresofthepenis(Fig. 76.24).
sinusoidalspacesofthecorporalbodies.
Thecommonpenilearteryhasthreemainbranches:thebulboure-
Variationsinpenilevascularanatomyarecommon,andmayinclude
thralartery,thedorsalpenilearteryandthecavernous(deep,cavern-
asingleorabsentcavernousarteryorthepresenceofaccessorypuden-
osal)artery(Fig. 76.25).
dalarteries(Bareetal1994,Matin2006).Whilepenilearterialsupply
iscommonlyderivedfrombothaccessoryandinternalpudendalarter-
Bulbourethral artery Thebulbourethralarterypenetratestheperi-
ies,itmaybederivedexclusivelyfromeithertheinternalpudendal
nealmembranetoenterthespongiosumfromaboveitsposterolateral
arteriesortheaccessorypudendalarteries(Droupyetal1997).Recog-


borderandsuppliesthepenilebulbandtheurethra,inadditiontothe
nizingsuchvariationisextremelyimportantforanysurgeoncontem-
corpusspongiosumandglanspenis.
platingpenilerevascularizationsurgery.
Dorsal artery of the penis Thedorsalarteryofthepenispasses
Veins
betweenthecruspenisandthepubistoreachthedorsalsurfaceofthe
corporalbodies.Itrunsalongsidethedorsalveinandthedorsalpenile Bloodleavingthepenisisdrainedbyoneofthreevenoussystems:
nerve,andisattached,togetherwiththesestructures,totheunderside superficial,intermediateordeep(seeFigs76.22B,76.23).Thesuperfi-
ofBuck’sfascia.Asitcoursestotheglanspenis,itgivesoffcircumfer- cialveinsarecontainedwithinthedartosfasciaonthedorsolateral


MAlE REPRoduCTiVE sysTEM
1284
8
NoiTCEs
A Dorsal vein Fig. 76.22 A, Layers of the penis and main structures.
B, C, Cross-sectional anatomy of the penile shaft.
Glans
Corpus spongiosum
surrounding urethra External urethral
meatus (orifice)
B
Superficial dorsal vein
Deep dorsal vein
Dorsal artery
Dorsal nerve
Cavernous vein
Tunica albuginea
Cavernous artery Superficial penile
(Colles’) fascia
Septum of penis
Deep penile
(Buck's) fascia
Circumflex vein
Corpus spongiosum
with urethra Sinusoidal spaces
C
Deep dorsal vein Superficial dorsal vein
Dorsal artery
Superficial dorsal artery
Dorsal nerve
Efferent vein
Corpus cavernosum
Cavernous vein
Skin
Emissary vein
Superficial penile
(Colles') fascia
Outer circular layer
Tunica albuginea Areolar tissue
Inner longitudinal layer
Deep penile
Cavernous artery (Buck's) fascia
Helicine artery
Septum of penis
Sinusoid
Bulbourethral vein
Urethral artery
Corpus spongiosum
Urethra
surfaceofthepenis.Theyreceivebloodfromthepenileshaftskinand groovebetweenthetwocorporacavernosa.Itpassesinferiortothe
prepuce,andcoalesceatthebaseofthepenistoformasinglesuperficial pubicsymphysisatthelevelofthesuspensoryligament,leavingthe
dorsalveinthatdrainsintothegreatsaphenousveinviathesuperficial shaftofthepenisatthecrus,anddrainsintotheprostaticplexus.


externalpudendalveins. Deepvenousdrainageoccursviathecruralandcavernous(deep,
Theintermediatedrainagesystemcontainsthecircumflexanddeep cavernosal)veins,whichreceivebloodfromtheproximalthirdofthe
dorsalveins,whichliewithinandbeneathBuck’sfascia.Thissystem penis.Theemissaryveinsconsolidateinto2–5veinsonthedorsome-
receivesbloodfromtheglans,corpusspongiosumandthedistaltwo- dialsurfaceofthecorporacavernosa.Cruralveinsariseinthemidline,
thirdsofthepenis.Circumflexveinsoriginateinthecorpusspongio- inthespacebetweenthecrura,andjointhecavernousveinsatthe
sum,andcoursearoundthecorporacavernosatomeetthedeepdorsal hilumofthepenis,ultimatelydrainingintotheinternalpudendalvein.
veinperpendicularly.Theyareonlypresentinthedistaltwo-thirdsof
Lymphatic drainage
thepenileshaft,andrangebetween3and10innumber.Intermediate
venulesintheerectiletissueofthecorporacavernosaarisefromthe Thepenileandperinealskinisdrainedbylymphaticvesselsthataccom-


External genitalia
1285
67
RETPAHC
External iliac artery and vein nervesandhelicinearteriesareintimatelyassociatedwithsmooth
muscle.Thehelicinearteriesarecontractedandtortuousintheflaccid
Internal iliac artery and vein state,andstraightanddilatedintheerectstate.
Thetunicaalbugineasurroundingthecorporaconsistsofaninner
Internal pudendal circularandouterlongitudinallayerofelasticfibresarrangedinalat-
artery and vein ticednetwork.Venousdrainagefromthecorporacavernosaoriginates
inthetrabeculaebetweentheperipheralsinusoidsandthetunicaalbug-
inea(thesubtunicalvenousplexus)beforeexitingthecorporaviathe
emissaryveins.
Emissaryveinstravelbetweenthetwolayersofthetunicaalbug-
inea,andexittheouterlayerinanobliquefashion.Theouterlayer
compressestheemissaryveinswhenthepenisbecomesengorged
withblood,preventingvenousoutflow,andtherebymaintainsthe
erection.
Thestructureofthecorpusspongiosumissimilartothatofthe
corporacavernosa,withtheexceptionoflargersinusoidsandathinner
tunicaalbuginea.Theglanshasnotunicalcovering.
ERECTION AND EJACULATION
Penileerectionisaneurovascularprocess,initiatedbysexualstimula-
tionandrelaxationofthesmoothmuscleofthecorporacavernosaand


mediatedbyvariousneurotransmittersproducedbytheparasympa-
theticnervesandtheendothelium.Themostimportantneurotransmit-
terisnitricoxide,whichactsviathecyclicguanosinemonophosphate
Vesical venous (cGMP)secondmessengersystem.Followingsmoothmusclerelaxa-
plexus
tion,thereisrapidinfluxofbloodflowfromthehelicinearteries,filling
thecavernousspacesandleadingtopeniletumescence.Theresulting
distensioncompressestheemissaryveins,preventingvenousoutflow.
Thisso-called‘veno-occlusivemechanism’convertstumescenceintoan
Cavernous artery
erection.Continuingcutaneousstimulationoftheglansandfrenulum
Dorsal artery and Cf penis
contributessignificantlytowardsmaintaininganerectionandinitiating
vein of penis
orgasmandejaculation.Erection,therefore,dependsonavarietyof
factors,includinganormalpsychogenicresponsetostimulation,intact
Artery of the bulb parasympatheticnerves,healthycorporalsmoothmusclecapableof
of the penis relaxation,patentarteriescapableofdeliveringbloodattherequired
rate,andanormalvenoussystem.Followingejaculation,thesequence
justdescribedisreversed;smoothmusclecontractioninresponseto
Periprostatic
venous plexus sympatheticstimulationleadstopeniledetumescence.
Emissionandejaculationareseparate,butrelated,processes.Emis-


sionisthetransmissionofseminalfluidfromthevasdeferens,prostate
Fig. 76.23 The perineal vessels. (Adapted from Drake RL, Vogl AW,
andseminalvesiclesintotheprostaticurethraandisundersympathetic
Mitchell A (eds), Gray’s Anatomy for Students, 2nd ed, Elsevier, Churchill
control.Ejaculationistheexpulsionofseminalfluidfromtheprostatic
Livingstone. Copyright 2010.)
urethratotheexteriorandhasbothautonomicandsomaticcompo-
nents.Thefirstdiscernibleeventduringejaculationiscontractionof
bulbospongiosus,whichoccursapproximatelysixtimesandisunder
somaticcontrol.Antegradeejaculationrequiresconcomitantbladder
Innervation
neckclosureandperiurethralmusclecontraction(Ch.75).Relaxation
oftheexternalurethralsphincter,underautonomiccontrol,permits
Arichsensoryinnervationtotheglanspenisisprovidedbythedorsal expulsionofseminalfluidfromtheprostatictothebulbarurethra,and
nerve,adivisionofthepudendalnerve;itfollowsthecourseofthe fromtheretotheexterior.Thetimingofthisprocessissuchthatthe
dorsalpenilearteries(Fig. 76.26,seealsoFig.76.2).Smallbranches ejaculateisexpelledfromtheexternalurethralmeatusbetweenthe


fromtheperinealnerveprovideadditionalinnervationtotheskinon secondandfinalcontractionofbulbospongiosus;insomemen,ejacu-
theventrumofthepenis,asfardistallyastheglans(Uchioetal1999). lationmaybepulsatile.
Sympatheticandparasympatheticinputtothecorporacavernosais
providedbythecavernous(deep,cavernosal)nerve,whichoriginates Erectile dysfunction and priapism
inthepelvicplexus.Itcoursesalongtheposterolateralaspectofthe
prostatebeforeexitingthepelvis,togetherwiththeurethra,andenter-
ingthecorporacavernosaatthecrus.Beforeenteringthecavernous Available with the Gray’s Anatomy e-book
bodies,thecavernousnervesendsbranchestothecorpusspongiosum.
Parasympatheticinputtothepenis(excitatory)originatesintheneu-
ronesofthefirstfoursacralsegmentsofthespinalcordandtravelsvia SCROTUM
thepelvicsplanchnicnerves(nervierigentes)tothepelvicplexus(see
Fig.76.26),wherepreganglionicfibressynapseonpostganglionic
Thescrotumiscomposedofmultiplelayersoftissues,includingskin,
neuronsthatgiverisetothecavernousnerve.Sympatheticinputtothe
dartosmuscleandexternalspermatic,cremastericandinternalsperm-