apparatus. Note the endothelial cells of fenestrated capillaries, the
proximal tubule. They have few microvilli, and so the tubular lumen
filtration slits between podocyte pedicels and their thick shared basal
has a more distinct outline. The basolateral folds containing mitochon-
lamina. Abbreviations: BL, basal lamina; C, lumina of capillary loops;
dria are deep, almost reaching the luminal aspect. Enzymes concerned
E, endothelial cell cytoplasm; F, fenestrations; FS, filtration slits; P,
with active transport of sodium, potassium and other ions are abun-
podocyte; P and P, primary and secondary foot processes that rest on
the glomerul1 ar basa2 l laminae. (A, With permission from Igaku-Shoin, dant. At the junction of the straight and convoluted regions, the distal
Tokyo, from Fujita T, Tanaka K, Tokunaga J 1981 SEM Atlas of Cells and tubule comes close to the vascular pole of its parent renal corpuscle.
Tissues. B, With permission from Young B, Heath JW 2000 Wheater’s Here, tubular cells form the macula densa, a sensory structure that is
Functional Histology. Edinburgh: Churchill Livingstone.) concerned with the regulation of blood flow and, thus, filtration rate.
Cells in the terminal part of the distal tubule have fewer basal folds and
mitochondria, and constitute a connecting duct formed from metane-
Collecting ducts originate in the cortical medullary rays and join phric mesenchyme during embryogenesis. Collecting ducts are lined by
others at intervals. They finally open into wider papillary ducts, which simple cuboidal or columnar epithelium. This increases in height from
open on to a papilla, their numerous orifices forming a perforated area the cortex, where the ducts receive the contents of distal tubules, to the
cribrosa on the surface at its tip (see Fig. 74.14). wide papillary ducts that discharge at the area cribrosa. The pale-
Renal tubules are lined throughout by a single-layered epithelium staining principal cells have relatively few organelles or lateral interdigi-


(see Fig. 74.16; Fig. 74.20). The type of epithelial cell varies according tations, and only occasional microvilli. A second cell type, intercalated
to the functional roles of the different regions, e.g. active transport and or dark cells (also present in smaller numbers in the distal convoluted
passive diffusion of various ions and water into and out of the tubules; tubule), has longer microvilli and more mitochondria, and secretes H+
reabsorption of organic components such as glucose and amino acids; into the filtrate; these cells function in the maintenance of acid–base
uptake of any proteins which leak through the glomerular filter. homeostasis.
The proximal convoluted tubule is lined by cuboidal or low colum-
Renal vessels
nar epithelium and has a brush border of tall microvilli on its luminal
surface. The shape of the cells depends on tubular fluid pressure, which,
in life, distends the lumen and flattens the cells (they become taller Renal, interlobar and arcuate arteries are typical large muscular arteries
when glomerular blood pressure falls post mortem or at biopsy). The and the interlobular vessels resemble small muscular arteries. Afferent
cytoplasm of proximal tubular cells is strongly eosinophilic and the glomerular vessels have a typical arteriolar structure with a muscular
nuclei are euchromatic and central. The basal cytoplasm is rich in coat 2–3 cells thick; this coat and the connective tissue components of
mitochondria, orientated perpendicularly, and the basal plasma mem- the wall diminish near a glomerulus until a point 30–50 µm proximal
brane is highly infolded. The lateral surfaces of adjacent epithelial cells to it, where arteriolar cells begin to show modifications typical of the
interdigitate, increasing the complexity of the basolateral plasma mem- juxtaglomerular apparatus. The efferent arterioles from most cortical
brane. The microvilli on the luminal surfaces significantly increase the glomeruli have thicker walls and a narrower calibre than corresponding
area of plasma membrane in contact with tubular fluid and the extra- afferents. Although the afferent arteriole is generally considered to be


tubular space, facilitating the transport of ions and small molecules solely responsible for tubuloglomerular feedback, the peritubular and
against steep concentration gradients. The abundant mitochondria medullary capillaries possess a well-defined basal lamina and their
supply the energy, as adenosine triphosphate (ATP), needed for this endothelial cells have typically fenestrated cytoplasm, as do the ascend-
process. Sodium/potassium adenosine triphosphatase (Na+/K+ ATPase) ing vasa recta, whereas the descending vasa recta have a thicker, continu-
is located in apical and basal membranes, and the cytoplasm contains ous endothelium (Davies 1991).


Kidney and ureter
1250
8
nOitCeS
Other renal cells The rest of the tubule reabsorbs most of the water (to a variable extent,
up to 95%), so that, when it reaches the calyces, urine is generally much
reduced in volume and hypertonic to blood. The process depends on
Other cells essential to renal structure and function lie between the
the establishment of high osmolality in the medullary interstitium, in
renal tubules and blood vessels. Connective tissue is inconspicuous in
order to exert sufficient osmotic pressure on water-permeable regions
the cortex but prominent in the medulla, particularly in the papillae.
of the tubule, and is achieved by a countercurrent multiplier
Medullary interstitial cells, which may be modified fibroblasts, form
mechanism.
vertical stacks of tangentially orientated cells between the more distal
collecting ducts, like the rungs of a ladder. These cells secrete prosta-
Countercurrent multiplier mechanism
glandins and may contribute, with cortical tubular cells, to the renal
The countercurrent multiplier mechanism is responsible for producing
source of erythropoietin.
a high osmolality in the extratubular interstitial tissue of the renal
medulla. Water passes freely from the tubular lumen into the adjacent
Calyces and pelvis
medullary interstitium along the descending limb of the loop of Henle.
This part of the tubule is less permeable to solutes. In the thick segment
The wall of the proximal part of the urinary tract is composed of three of the ascending limb, sodium and chloride ions are actively transported
layers: an outer connective tissue adventitia, an intermediate layer of from the tubule lumen to interstitial spaces, while the tubular epithe-
smooth muscle and an inner mucosa. The mucosal lining of the renal lium remains impermeable to water. The increased interstitial osmolal-
calyces and pelvis is identical in structure to that of the ureter (see ity causes water to be withdrawn from the descending part of the loop,
below). The adventitia consists of loose fibroelastic connective tissue thus concentrating the filtrate. Tubular fluid flows in a countercurrent
that merges with retroperitoneal areolar tissue. Proximally, the coat on its descent into and ascent out of the medulla; it is augmented by


fuses with the fibrous capsule of the kidney lining the renal sinus. new isotonic fluid entering the loop, and depleted by hypotonic fluid
The smooth muscle of the renal calyces and pelvis is composed of leaving the loop as solutes are actively resorbed. The osmotic gradient
two distinct types of smooth muscle cell. One type of muscle cell is within the interstitium is, thus, multiplied from the corticomedullary
identical to that described for the ureter and can be traced proximally boundary to the medullary pyramids, where it reaches an equilibrium
through the pelviureteric region and renal pelvis, as far as the minor of four to five times the osmolality of plasma. Although the tonicity of
calyces. The other type of cell forms the muscle coat of each minor calyx the tubular fluid changes during its passage through the steep osmotic
and continues into the major calyces and pelvis, where it forms a distinct gradient within the medulla, the osmotic gradient between ascending
inner layer. The cells also form a thin sheet of muscle that covers each and descending limbs at each level never exceeds 200 mOsm/kg, a force
minor calyx and extends across the renal parenchyma between the that can be sustained by the cells of the tubular wall.
attachments of neighbouring minor calyces, thereby linking each minor
calyx to its neighbours. This discrete inner layer of atypical smooth Countercurrent exchange mechanism
muscle ceases in the pelviureteric region, so that the proximal ureter Rapid removal of ions from the renal medulla by the circulation of
lacks such an inner layer. Pacemaker cells that initiate renal pelvic and blood is minimized by another looped countercurrent system. This is
ureteric peristalsis are sited within the calyces (Gosling and Dixon 1974). the countercurrent exchange mechanism, in which arterioles entering
These allow coordinated peristalsis of the ureter six times a minute. the medulla pass for long distances parallel to the venules leaving it,
before ending in capillary beds around tubules. This close apposition
of oppositely flowing blood allows the direct diffusion of ions from
PRODUCTION OF URINE outflowing to inflowing blood, so that the vasa recta (see Fig. 74.14)
conserve the high osmotic pressure in the medulla.


Glomerular filtration
Concentration of urine
Glomerular filtration (see Figs 74.14, 74.16) is the passage of water
containing dissolved small molecules from the blood plasma to the Because sodium and chloride ions are selectively resorbed by the cells
urinary space in the glomerular capsule. Larger molecules, e.g. plasma of the ascending limbs and distal tubules under aldosterone control,
proteins above 70 kilodaltons and those with a net negative charge, the filtrate at the distal end of the convoluted tubules is hypotonic. As
polysaccharides, lipids and cells, are largely retained in blood by the it reaches the collecting ducts, fluid descends again through the medulla
selective permeability of the glomerular basal lamina. and, thus, re-enters a region of high osmotic pressure. The cells lining
Filtration occurs along a steep pressure gradient between the large the collecting ducts are variably permeable to water, under the influence
glomerular capillaries and the urinary space, the principal structure of neurohypophysial ADH. Water follows an osmotic gradient into the
separating the two being the glomerular basal lamina (Fig. 74.19B). adjacent extratubular spaces, so that the tonicity of the filtrate gradually
This gradient far exceeds the colloid osmotic pressure of blood, which rises along collecting ducts, until, at the tip of the renal pyramids, it is
opposes the outward flow of filtrate. In the peripheral renal cortex, the above that of blood. This complex system is highly flexible and the
arteriolar pressure gradient is enhanced because afferent glomerular balance between the rate of filtration and absorption can be varied to
arterioles are wider than efferent glomerular arterioles. In all glomeruli, meet current physiological demands.
the rate of filtration can be altered by changes in the tone of the Control of hydrogen and ammonium ion concentrations is essential
glomerular arterioles. When first formed, the glomerular filtrate is iso- to the regulation of acids and bases in the blood. Secretion of various
tonic with glomerular blood and has an identical concentration of ions ions occurs at several sites. Over 91% of ingested potassium is excreted


and small molecules. in urine, largely through secretion by cells of the distal tubule and col-
The assessment of glomerular filtration is fundamental to the diag- lecting duct. (For further details of renal physiology, see Madias and
nosis of renal glomerular pathology and the management of drug Adrogué (2005), Tannen and Hallows (2005), Singh and Thomson
therapy, where clearance depends on the glomerular filtration, and in (2011).)
chronic kidney disease to facilitate timely management decisions. Meas-
urements of glomerular filtration rate (GFR) are based on the renal Juxtaglomerular apparatus
clearance of a marker in plasma, expressed as the volume of plasma
completely cleared of the marker per unit time. Markers used to measure
The juxtaglomerular apparatus provides a tubuloglomerular feedback
GFR may be endogenous (creatinine, urea) or exogenous (inulin, iotha-
system that maintains systemic arterial blood pressure during a reduc-
lamate) substances. The ideal marker is endogenous, freely filtered by
tion in vascular volume and decrease in filtration rate. The elements of
the glomerulus, neither reabsorbed nor secreted by the renal tubule,
a juxtaglomerular apparatus are juxtaglomerular and lacis cells, and the
and eliminated only by the kidney.
macula densa. The afferent and efferent arterioles at the vascular pole
of a glomerulus and the macula densa of the distal tubule of the same
Selective resorption
nephron lie in close proximity, enclosing a small cone of tissue popu-
lated by extraglomerular mesangial (lacis) cells (see Fig. 74.16). The
Selective resorption from the filtrate is an active process and occurs cells of the tunica media of afferent and, to a lesser extent, efferent,
mainly in the proximal convoluted tubules, which resorb glucose, arterioles differ from typical smooth muscle cells. These juxtaglomeru-
amino acids, phosphate, chloride, sodium, calcium and bicarbonate, lar cells are large, rounded, myoepithelioid cells and their cytoplasm


and take up small proteins (e.g. albumin) by endocytosis. Cells of the contains many mitochondria and dense, renin-containing vesicles,
proximal tubules are permeable to water, which passes out of the 10–40 nm in diameter. Each macula densa of the distal tubule is a
tubules passively, so that the filtrate remains locally isotonic with blood. cluster of up to 40 tightly packed cells in the tubule wall; the cells have


ureter
1251
47
retPaHC
A B Fig. 74.21 Relations of the lower
ureter, seen from above. A, The
Ureter male pelvis. B, The female pelvis.
Ureter Common iliac artery (With permission from Drake RL,
Vogl AW, Mitchell A (eds), Gray’s
Anatomy for Students, 2nd ed,
Elsevier, Churchill Livingstone.
Copyright 2010.)
Internal iliac artery
Uterine artery
Uterus
Vas deferens
Pelvic brim
(pelvic inlet)
Bladder
Anterior
abdominal wall
large, oval nuclei and apically concentrated mitochondria. They are the gonadal vessels. It enters the lesser pelvis either anterior to the end
osmoreceptors, sensing the NaCl content of the filtrate after its passage of the common iliac vessels or at the origin of the external iliac vessels
through the loop of Henle. (Fig. 74.22).
When NaCl concentrations in the filtrate change, tubuloglomerular The inferior vena cava is medial to the right ureter, while the left
feedback mechanisms operate to maintain the inverse relationship ureter is lateral to the aorta. The inferior mesenteric vein has a long
between salt concentration and glomerular filtration rate. Juxtaglomeru- retroperitoneal course lying close to the medial aspect of the left ureter.
lar cells release renin, an enzyme that acts on circulating angiotensino- At its origin, the right ureter is usually overlapped by the descending
gen to activate the cascade whereby angiotensin II increases blood part of the duodenum. It descends lateral to the inferior vena cava, and
pressure (and therefore filtration rate), stimulates aldosterone and ADH is crossed anteriorly by the right colic and ileocolic vessels. Near the
release and increases sodium ion and water resorption, primarily from superior aperture of the lesser pelvis, it passes behind the lower part of
the distal tubule, to increase plasma volume. Macula densa cells are the mesentery and terminal ileum. The left ureter is crossed by the
thought to respond to high salt concentration in the distal tubule by gonadal and left colic vessels. It passes posterior to loops of jejunum


releasing nitric oxide, which inhibits the tubuloglomerular feedback and sigmoid colon and its mesentery in the posterior wall of the inter-
response and reduces filtration rate. The role of macula densa cells in sigmoid recess.
the stimulation of renin release to increase filtration rate is less well In the pelvis, the ureter lies in extraperitoneal areolar tissue. At first,
understood. it descends posterolaterally on the lateral wall of the lesser pelvis along
The third element of the juxtaglomerular apparatus is a population the anterior border of the greater sciatic notch. Opposite the ischial
of extraglomerular mesangial cells that form a network (or lace; hence, spine, it turns anteromedially into fibrous adipose tissue above levator
their alternative name of lacis cells) of stellate cells connecting the ani to reach the base of the bladder. On the pelvic side wall, it is anterior
macula densa sensory cells with the juxtaglomerular effector cells. It is to the internal iliac artery and the beginning of its anterior trunk, pos-
likely that extraglomerular mesangial cells transmit the sensory signal, terior to which are the internal iliac vein, lumbosacral nerve and sacro-
possibly through gap junctions. They may also signal to contractile iliac joint. Laterally, it lies on the fascia of obturator internus. It
glomerular mesangial cells and effect vasoconstriction directly within progressively crosses to become medial to the umbilical, inferior vesical
the glomerulus. Adrenergic nerve fibres occur in small numbers among and middle rectal arteries.
these cells. In males, the pelvic ureter hooks under the vas deferens (Fig. 74.23);
it then passes anterior and slightly superior to the upper pole of the
seminal vesicle to traverse the bladder wall obliquely before opening at
URETER
the ipsilateral trigonal angle. Its terminal part is surrounded by tributar-
ies of the vesical veins. In females, the pelvic part initially has the same
The ureters are two muscular tubes whose peristaltic contractions convey relations as in males but, anterior to the internal iliac artery, it is imme-


urine from the kidneys to the urinary bladder (see Figs 74.1, 74.10, Fig. diately behind the ovary, forming the posterior boundary of the ovarian
74.21). Each measures 25–30 cm in length, is thick-walled and narrow, fossa (see Fig. 77.8). In the anteromedial part of its course to the
and is continuous superiorly with the funnel-shaped renal pelvis. Each bladder, it is related to the uterine artery, uterine cervix and vaginal
descends slightly medially, anterior to psoas major, and enters the pelvic fornices. It is in extraperitoneal connective tissue in the inferomedial
cavity, where it curves initially laterally, then medially, to open into the part of the broad ligament of the uterus, where it may be damaged
base of the urinary bladder. The diameter of the ureter is normally 3 mm, during hysterectomy (see Fig. 77.7). In the broad ligament, the uterine
but is slightly less at its junction with the renal pelvis, at the brim of the artery is anterosuperior to the ureter for approximately 2.5 cm and then
lesser pelvis near the medial border of psoas major, and where it runs crosses to its medial side to ascend alongside the uterus. The ureter turns
within the wall of the urinary bladder, which is its narrowest part. These forwards slightly above the lateral vaginal fornix and is, generally, 2 cm
are the most common sites for renal stone impaction. lateral to the supravaginal part of the uterine cervix in this location. It
then inclines medially to reach the bladder, with a variable relation to
the anterior aspect of the vagina. As the uterus is commonly deviated
RELATIONS to one side, one ureter, usually the left, may be more extensively
apposed to the vagina, and may cross the midline.
In the abdomen, the ureter descends posterior to the peritoneum on The distal 1–2 cm of each ureter is surrounded by an incomplete
the medial part of psoas major, which separates it from the tips of the collar of non-striated muscle (sheath of Waldeyer). The ureters pierce


lumbar transverse processes. During surgery on intraperitoneal struc- the posterior aspect of the bladder and run obliquely through its wall
tures, the ureter can be tented up as the peritoneum is drawn anteriorly, for a distance of 1.5–2.0 cm before terminating at the ureteric orifices
resulting in inadvertent ureteric injury. Anterior to psoas major, it (see Fig. 75.10B). This arrangement is believed to assist in the preven-
crosses anterior to the genitofemoral nerve and is obliquely crossed by tion of reflux of urine into the ureter, since the intramural ureters are


Kidney and ureter
1252
8
nOitCeS
Fig. 74.22 Relations of male
lower right ureter. (With
Middle permission from Walsh PC,
sacral Retik AB, Vaughan ED et al
Common
artery (eds) 2002 Campbell’s Urology,
iliac artery
8th edn. Philadelphia:
Iliolumbar Saunders.)
Deep artery
circumflex iliac
artery Superior
gluteal
Inferior artery
epigastric
artery Lateral
sacral
Right ureter artery
Internal iliac Inferior
artery gluteal
artery
External
iliac artery
Internal
Median umbilical pudendal
ligament artery
Obturator artery
Sciatic nerve
Vas deferens
Middle rectal
Superior vesical
artery
artery
Left ureter Inferior
vesical
artery
Bladder
Prostate gland Rectum
thought to be occluded during increases in bladder pressure at the time or pass directly to the lateral aortic nodes near the origin of the gonadal
of micturition. There is no evidence of a classic ureteral sphincter mech- artery; those from the lower abdominal ureter drain to the common
anism in humans. The longitudinally orientated muscle bundles of the iliac nodes; and those from the pelvic ureter drain to common, external
terminal ureter continue into the bladder wall and, at the ureteric ori- or internal iliac nodes.
fices, become continuous with the superficial trigonal muscle. In the
distended bladder, in both sexes, the ureteric openings are usually 5 cm
INNERVATION
apart, and 2.5 cm apart when the bladder is empty.
The ureter is supplied from the lower three thoracic, first lumbar, and
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE the second to fourth sacral segments of the spinal cord by branches
from the renal and aortic plexuses, and the superior and inferior
Arteries hypogastric plexuses (see Figs 59.3, 75.11). The ureteric nerves consist
of relatively large bundles of axons that form an irregular plexus in the
adventitia of the ureter. The plexus receives branches from the renal and


The ureter is supplied by branches from the renal, gonadal, common
aortic plexuses (in its upper part); from the superior hypogastric plexus
iliac, internal iliac, vesical and uterine arteries, and the abdominal aorta.
and hypogastric nerve (in its intermediate part); and from the hypogas-
The pattern of distribution is subject to much variation. The abdominal
tric nerve and inferior hypogastric plexus (in its lower part). Numerous
ureter is supplied from vessels originating medial to the ureter; the pelvic
small branches penetrate the ureteric muscle coat; some of the adven-
ureter is supplied by vessels lateral to the ureter (Fig. 74.24). There is a
titial nerves accompany the blood vessels and branch with them as they good longitudinal anastomosis between these branches on the wall of
extend into the muscle layer; others are unrelated to the vascular supply
the ureter, which means that the ureter can be safely transected at any
and lie free in the adventitial connective tissue around the circumfer-
level intraoperatively, and a uretero-ureterostomy performed, without
ence of the ureter.
compromising its viability. The branches from the inferior vesical artery
The density of innervation increases gradually from the renal pelvis
are constant in their occurrence and supply the lower part of the ureter,
and upper ureter (where autonomic nerves are sparse) to a maximum
as well as a large part of the trigone of the bladder. The branch from the
density in the juxtavesical segment. At least three different neurotrans-
renal artery is also constant and is preserved whenever possible in renal
mitter phenotypes – cholinergic, noradrenergic and peptidergic (sub-
transplantation to ensure good vascularity of the ureter.
stance P) – are well known and others have been reported. The
functional significance of these different types of autonomic nerve fibres
Veins
in relation to ureteric smooth muscle activity is not fully understood;
although they are thought to influence the inherent motility of the
The venous drainage of the ureters generally follows the arterial supply. ureter, they are not essential for the initiation and propagation of ure-
teric contraction waves. A branching plexus of fine cholinergic,
Lymphatic drainage


noradrenergic and peptidergic axons occurs throughout the lamina
propria and extends from the inner aspect of the muscle coat towards
Lymph vessels draining the ureter begin in submucosal, intramuscular the base of the urothelium. Some of these axons form perivascular
and adventitial plexuses, which all communicate. Collecting vessels plexuses, while others lie in isolation from the vascular supply and may
from the upper abdominal ureter may join the renal collecting vessels be sensory in function.


ureter
1253
47
retPaHC
Median
Apex of bladder umbilical ligament
Body of bladder,
muscular layer
Ureter
Vas
deferens
Ampulla of
vas deferens
Ampulla of
vas deferens,
diverticula
Seminal vesicle
of ampulla
Seminal vesicle
Prostate,
posterior surface
Fig. 74.25 A coronal CT urogram volume-rendered image demonstrates a
Fig. 74.23 The posterior aspect of the male urogenital organs, showing duplicated right collecting system and ureter, along with dilation of the
the relationship of the lower ureter to the vas deferens and seminal collecting system of the lower pole moiety. No urothelial lesion is seen.
vesicles. (With permission from Waschke J, Paulsen F (eds), Sobotta Atlas
of Human Anatomy, 15th ed, Elsevier, Urban and Fischer. Copyright 2013)
initiated, the contraction is propagated through the wall of the adjacent
major calyx and activates the smooth muscle of the renal pelvis. Con-
Fig. 74.24 The arterial
supply of the left traction waves are propagated away from the kidney, and so undesirable
ureter. The proximal pressure rises are not directed against the renal parenchyma. Since
part takes its blood several potential pacemaker sites exist, the initiation of contraction
supply medially, and waves is unimpaired by partial nephrectomy; the minor calyces
the distal part is spared by the resection remain in situ to continue their pacemaking
supplied laterally. (With function. Pressures within the ureter at the time of peristalsis reach
permission from Walsh 20–80 cm HO.
2
PC, Retik AB, Vaughan Experimental evidence indicates that autonomic nerves do not play
ED et al (eds) 2002 a major part in the propagation of peristalsis. It seems more likely
Campbell’s Urology, that they play a modulatory role on the contractile events occurring in
8th edn. Philadelphia: the musculature of the upper urinary tract. The most likely mecha-
Saunders.) nism to account for impulse propagation is myogenic conduction
Renal artery mediated by the electrotonic coupling of one muscle cell to its imme-
diate neighbours by means of intercellular ‘gap’ junctions; there are


Gonadal artery numerous regions of close approach between ureteric smooth muscle
cells and also between both types of muscle cell in the renal pelvis
Aorta
and calyces.
Referred pain Excessive distension of the ureter or spasm of its
muscle may be caused by a stone (calculus) and provokes severe pain
Common iliac artery (ureteric colic, which is commonly, but mistakenly, called renal colic).
The pain is spasmodic and agonizing, particularly if the obstruction is
gradually forced down the ureter by the muscle spasm. It is referred to
cutaneous areas innervated from spinal segments that supply the ureter,
mainly T11–L2, and shoots down and forwards from the loin to the
Internal iliac artery
groin and scrotum or labium majus; it may extend into the proximal
anterior aspect of the thigh by projection to the genitofemoral nerve
Superior vesical artery (L1, 2). The cremaster, which has the same innervation, may reflexly
retract the testis.
Uterine artery
Middle rectal artery
RENAL AND URETERIC CALCULI
Vaginal artery
Inferior vesical artery An understanding of intrarenal and ureteric anatomy is essential
when managing patients with calculi, particularly now that mini-
mally invasive techniques are widely used to treat this common
pathology.
Ureteric peristalsis
MICROSTRUCTURE
Under normal conditions, contraction waves originate in the proximal
part of the upper urinary tract and are propagated in an anterograde Like the calyces and the renal pelvis, the wall of the ureter is composed
direction towards the bladder. Atypical smooth muscle cells in the wall of an external adventitia, a smooth muscle layer and an inner mucosal
of the minor calyces act individually or collectively as pacemaker sites. layer. The mucosal layer consists of a urothelium (see Fig. 2.5D) and
A peristaltic wave begins at one (or possibly more) of these sites. Once an underlying connective tissue lamina propria.


Kidney and ureter
1253.e1
47
retPaHC
Smaller renal calculi are treated with extracorporeal shock wave
lithotripsy. Stones in the lower pole of the kidney clear less well if the
angle between the infundibulum of the calyx containing the stone and
the ureter is acute, or if there is a particularly long and narrow infundibu-
lum. Percutaneous stone extraction is most frequently achieved by
puncturing a posterior calyx with a needle.
Ureteric calculi tend to be arrested in their descent in either the
pelviureteric region, or the point where the ureter passes over the pelvic
brim as it crosses the common iliac artery, or the vesico-ureteric junc-
tion, because these are the three areas where the ureter is narrowest.
The vesico-ureteric junction is the narrowest of these areas and can be
responsible for arresting the passage of stones of as little as 2–3 mm.
The kidney and upper ureter move with respiration within the peri-
renal fascia, and this can affect the visualization and tracking of a stone,
both at the time of extracorporeal shock wave lithotripsy and at retro-
grade endoscopy.


Kidney and ureter
1254
8
nOitCeS
The ureteric adventitial blood vessels and connective tissue fibres are normal in some individuals. In the male, the ureter can insert at the
orientated parallel to the long axis of the ureter. Throughout its length, bladder neck or posterior urethra, or, rarely, into the seminal vesicle,
the muscle coat of the ureter is fairly uniform in thickness and, in cross- but it always inserts cranial to the external urethral sphincter. In the
section, measures 750–800 µm in width. The muscle bundles that con- female, ectopic insertion can be distal to the external urethral sphincter
stitute this coat are frequently separated from one another by relatively in the urethra, or into the vagina, resulting in persistent childhood
large amounts of connective tissue. However, branches that intercon- incontinence.
nect muscle bundles are common and there is frequent interchange of
muscle fibres between adjacent bundles. As a consequence of this exten- Ureteroceles A ureterocele is a cystic dilation of the lower end of the
sive branching, individual muscle bundles do not spiral around the ureter; the ureteric orifice is covered by a membrane that expands as it
ureter, but form a complex meshwork of interweaving bundles. More- is filled with urine and then deflates as it empties. Ureteroceles can vary
over, unlike the gut (Ch. 65), the muscle bundles are so arranged that in size and usually have no influence on ureteric drainage; however,
morphologically distinct longitudinal and circular layers cannot be they can be a cause of obstruction in the ureter and pelvicalyceal system
clearly distinguished. In the upper part of the ureter, the inner muscle more proximally. Prolapsing ureteroceles, though small, prolapse from
bundles tend to lie longitudinally while those on the outer aspect have their position around the ureterovesical junction region into the urethra,
a circular or oblique orientation. In the middle and lower parts, there causing intermittent bladder outflow obstruction.
are additional outer longitudinally orientated fibres, and as the uretero- They are identified antenatally with ultrasound (Fig. 74.26). In


vesical junction is approached, the muscle coat consists predominantly adults, ureteroceles tend to be bilateral and small, and are often found
of longitudinally orientated muscle bundles. incidentally when the urinary tract is being imaged in the investigation
The mucosa of the ureter consists of an epithelium, the urothelium, of a coincidental pathology. Radiologically, they classically result in a
lying on a layer of subepithelial fibroelastic connective tissue lamina ‘cobra-head’ halo around the ureteric orifice following administration
propria. The latter varies in thickness from 350 to 700 µm and is a of contrast on intravenous urography.
conduit for small blood vessels and bundles of unmyelinated nerve
fibres. Occasional lymphocytes may be present in the lamina propria Retrocaval ureter A persistence of the posterior cardinal vein, asso-
but their aggregation into definitive lymph nodules is rare. The urothe- ciated with high confluence of the right and left common iliac veins or
lium is usually extensively folded, giving the ureteric lumen a stellate a double inferior vena cava, may result in a retrocaval (or circumcaval)
outline. ureter that passes behind the inferior vena cava, usually at the level of
the inferior edge of the third part of the duodenum, before it emerges
Developmental anomalies of the ureter anterior to it to pass from medial to lateral. Retrocaval ureter occurs in
1 in 1500 individuals. Most commonly, it has no clinical sequelae,
Duplex ureters In 1 in 125 individuals, two ureters drain the renal although it can result in upper ureteric obstruction (Fig. 74.27).
pelvis on one side; this is termed a duplex system (Fig. 74.25). Bilateral
duplex ureters occur in approximately 1 in 800 cases. Duplex ureters
are the product of two ureteric buds arising from the mesonephric duct;
they share a single fascial sheath and may either fuse at any point along Bonus e-book images
their course, or remain separate until they insert through separate ure-
teric orifices into the bladder.
Care must be taken not to compromise the blood supply of the
Fig. 74.13 Marked dilation of the right renal pelvis and calyces, and


second ureter when excising or reimplanting a single ureter of a duplex.
non-dilation of the right ureter without an associated lesion due to
The ureter from the upper pole of the kidney (the longer ureter) inserts
ureteropelvic junction obstruction.
more medially and caudally in the bladder than the ureter from the
lower pole (Weigert–Meyer rule). This reflects the embryological devel-
Fig. 74.26 A–B, Sagittal grey-scale ultrasound images through the
opment of the ureter: the ureteric bud that is initially more proximal pelvis of a 2-day-old girl demonstrate a dilated left ureter, which
on the mesonephric duct has a shorter time to be pulled cranially in contains layering echogenic debris, and an anechoic round filling
the bladder and so it inserts more distally in the mature bladder. The defect in the inferior bladder with increased through-transmission
ureter from the lower pole has a shorter intramural course than the and an echogenic rim, in keeping with a ureterocele.
longer ureter and is prone to reflux.
Fig. 74.27 An intravenous urogram showing a classic retrocaval (or
Ectopic ureters Single ureters, and, more commonly, the longer circumcaval) ureter.
ureter of a duplex system, can insert more caudally and medially than
KEY REFERENCES
Brödel M 1911 The intrinsic blood-vessels of the kidney and their signifi- An early paper describing the identification of pacemaker cells in various
cance in nephrotomy. Bull Johns Hopkins Hosp 12:10–13. species.
The original description of a relatively avascular longitudinal zone within
Merklin RJ, Michels NA 1958 The variant renal and suprarenal blood supply
the kidney, proposed as a site for surgical incision.
with data on the inferior phrenic, ureteral, and gonadal arteries: a sta-
Burkhill GJ, Healy JC 2000 Anatomy of the retroperitoneum. Imaging 12: tistical analysis based on 185 dissections and a review of the literature.
10–20. J Int Coll Surg 29:41–76.
A review of the imaging literature describing the contentious anatomy of the A review of renal vascular anatomy in almost 11,000 kidneys.


perirenal fascia.
Mitchell GA 1950 The renal fascia. Br J Surg 37:257–66.
Gosling JA, Dixon JS 1974 Species variation in the location of upper urinary An account that demonstrates that the perirenal fascia is a multilaminar
tract pacemaker cells. Invest Urol 11:418. structure rather than a single fused fascia.


Kidney and ureter
1254.e1
47
retPaHC
B 4
U
1
2
A
3
B
U
Fig. 74.27 An intravenous urogram showing a classic retrocaval (or
circumcaval) ureter. A degree of obstruction has resulted in a markedly
dilated upper ureter. The ureter passes cranially, medially and then
caudally, and can be followed into the pelvis. Key: 1, contrast within
B dilated collecting system of right kidney and upper ureter; 2, contrast
within ureter turning behind inferior vena cava; 3, contrast within normal
Fig. 74.26 A–B, Sagittal grey-scale ultrasound images through the pelvis calibre ureter seen below the obstruction; 4, contrast within normal
of a 2-day-old girl demonstrate a dilated left ureter (U), which contains collecting system of left kidney and upper ureter.
layering echogenic debris, and an anechoic round filling defect (*) in the
inferior bladder (B) with increased through-transmission and an echogenic
rim, in keeping with a ureterocele.


Kidney and ureter
1254.e2
8
nOitCeS
REFERENCES
Brödel M 1911 The intrinsic blood-vessels of the kidney and their signifi- tistical analysis based on 185 dissections and a review of the literature.
cance in nephrotomy. Bull Johns Hopkins Hosp 12:10–13. J Int Coll Surg 29:41–76.
The original description of a relatively avascular longitudinal zone within A review of renal vascular anatomy in almost 11,000 kidneys.
the kidney, proposed as a site for surgical incision.
Mitchell GA 1950 The renal fascia. Br J Surg 37:257–66.
Burkhill GJ, Healy JC 2000 Anatomy of the retroperitoneum. Imaging 12: An account that demonstrates that the perirenal fascia is a multilaminar
10–20. structure rather than a single fused fascia.
A review of the imaging literature describing the contentious anatomy of the
Novick AC 1998 Anatomic approaches in nephron-sparing surgery for renal
perirenal fascia.
cell carcinoma. Atlas Urol Clin North Am 6:39.
Davies A, Blakeley AG, Kidd C 2001 The renal system. In: Human Physiol- Ramage IJ, Howatson AG, McColl JH et al 2002 Glomerular basement
ogy. Edinburgh: Elsevier, Churchill Livingstone; Ch. 8, pp. 713–97. membrane thickness in children: a stereologic assessment. Kidney Int
Davies JM 1991 The role of the efferent arteriole in tubuloglomerular feed- 62:895–900.
back. Kidney Int Suppl 32:S71–3. Schneider A, Ferreira CG, Delay C et al 2013 Lower pole vessels in children
Gosling JA, Dixon JS 1974 Species variation in the location of upper urinary with pelviureteric junction obstruction: laparoscopic vascular hitch or
tract pacemaker cells. Invest Urol 11:418. dismembered pyeloplasty? J Pediatr Urol 9:419–23.
An early paper describing the identification of pacemaker cells in various Scott JE 2002 Fetal, perinatal, and infant death with congenital renal
species. anomaly. Arch Dis Child 87:114–17.


Madias NE, Adrogué HJ 2005 Hypo-hypernatraemia: disorders of water Singh P, Thomson SC 2011 Renal homeostasis and tubuloglomerular feed-
balance. In: Davison AM, Cameron JS, Grunfeld J-P et al (eds) Oxford back. Curr Opin Nephrol Hypertens 19:59–64.
Textbook of Clinical Nephrology. Oxford: Oxford University Press; Tannen RL, Hallows KR 2005 Hypo-hyperkalaemia. In: Davison AM,
Ch. 2.1, vol. 1. Cameron JS, Grunfeld J-P et al (eds) Oxford Textbook of Clinical Neph-
Manalich R, Reyes L, Herrera M et al 2000 Relationship between weight at rology. Oxford: Oxford University Press; Ch. 2.2, vol. 1.
birth and the number and size of renal glomeruli in humans: a histo- Veyrac C, Baud C, Lopez C et al 2003 The value of colour Doppler ultra-
morphometric study. Kidney Int 58:770–3. sonography for identification of crossing vessels in children with pelvi-
Merklin RJ, Michels NA 1958 The variant renal and suprarenal blood supply ureteric junction obstruction. Pediatr Radiol 33:745–51.
with data on the inferior phrenic, ureteral, and gonadal arteries: a sta-


CHAPTER
75
Bladder, prostate and urethra
umbilical ligament (urachus) ascends behind the anterior abdominal
URINARY BLADDER
wall from the apex to the umbilicus, covered by peritoneum to
form the median umbilical fold (Fig. 75.3, see Fig. 72.19) (see below
The urinary bladder is a reservoir. Its size, shape, position and relations and p. 1077).
all vary, according to its content and the state of the neighbouring The anterior surface of the bladder is separated from the transversalis
viscera. When the bladder is empty, it lies entirely in the lesser pelvis, fascia by adipose tissue in the potential retropubic space (of Retzius)
but as it distends, it expands anterosuperiorly into the abdominal cavity (Fig. 75.4). This is more adherent to the bladder than to the anterior
(Video 75.1). An empty bladder is somewhat tetrahedral and has a base surface of the prostate, which aids reliable identification of the region
(fundus), neck, apex, and a superior (dome) and two inferolateral of the bladder neck surgically. In males, each inferolateral surface is
surfaces. related anteriorly to the pubis and puboprostatic ligaments. In females,
the relations are similar, except that the pubovesical ligaments replace
the puboprostatic ligaments. The inferolateral surfaces are not covered
RELATIONS by peritoneum. The triangular superior surface is bounded by lateral
borders from the apex to the ureteric entrances, and by a posterior
The base of the bladder is triangular and located posteroinferiorly. In border that joins them. In males, the superior surface is completely
females, it is closely related to the anterior vaginal wall (Fig. 75.1); in covered by peritoneum, which extends slightly on to the base and con-
males, it is related to the rectum, although it is separated from it supe- tinues posteriorly into the rectovesical pouch and anteriorly into the
riorly by the rectovesical pouch, and inferiorly by the seminal vesicle median umbilical fold; it is in contact with the sigmoid colon and


and vas (ductus) deferens on each side, and by Denonvilliers’ fascia the terminal coils of the ileum (see Fig. 75.2). In females, the superior
(Fig. 75.2). The neck, which is most fixed, lies most inferiorly, 3–4 cm surface is largely covered by peritoneum, which is reflected posteriorly
behind the lower part of the pubic symphysis and just above the plane on to the uterus at the level of the internal os (the junction of the
of the inferior aperture of the lesser pelvis. The bladder neck is, essen- uterine body and cervix), to form the vesicouterine pouch. The posterior
tially, the internal urethral orifice, which lies in a constant position part of the superior surface, devoid of peritoneum, is separated from
that is independent of the varying positions of the bladder and rectum. the supravaginal cervix by fibroareolar tissue.
In males, the neck rests on, and is in direct continuity with, the base These relationships are important in managing bladder trauma.
of the prostate; in females, it is related to the pelvic fascia that Extraperitoneal injuries can often be managed conservatively because
surrounds the upper urethra. In both sexes, the apex of the bladder urine is contained, whereas intraperitoneal injuries usually require sur-
faces towards the upper part of the pubic symphysis. The median gical repair.
Fig. 75.1 The relations of the
female bladder, sagittal section of
the pelvis. (With permission from
Ureter
Waschke J, Paulsen F (eds),
Sigmoid colon Sobotta Atlas of Human
Anatomy, 15th ed, Elsevier,
External iliac artery and vein Urban & Fischer. Copyright 2013.)
Ovarian follicles
Uterine fundus
Rectal ampulla
Inferior epigastric artery and vein
Parietal peritoneum
Linea alba
Recto-uterine pouch
Median umbilical
ligament
Cervix
Internal urethral
orifice
Rectovaginal fascia
Corpus cavernosum
clitoris
Frenulum of clitoris Ureteric orifice
Labium minor
External urethral orifice
Labium majus
1255


Bladder, prostate and urethra
1256
8
noItCes
A
Sigmoid colon
Internal urethral meatus
Ureteric orifice
Small intestine
Median umbilical ligament
Retropubic space
(of Retzius)
Rectovesical pouch
Linea alba
Pubic symphysis Rectal ampulla
Suspensory ligament of penis Denonvilliers’s fascia
Deep dorsal vein of penis Prostate
Visceral pelvic fascia
Dorsal vein of penis Anococcygeal ligament
External anal sphincter
Internal anal sphincter
Deep transverse perineal muscle
Perineal membrane
Membranous urethra
Bulb of penis
Parietal
peritoneum
Full bladder
Parietal
peritoneum
Rectum
Empty
bladder
Rectum Prostate
Prostate
Fig. 75.2 A, The relationship of the bladder and prostate: sagittal section, male pelvis. The relationship of the bladder to the peritoneum and anterior
abdominal wall on filling allows suprapubic cystostomy without intraperitoneal urinary leak. ( With permission from Waschke J, Paulsen F (eds), Sobotta
Atlas of Human Anatomy, 15th ed, Elsevier, Urban & Fischer. Copyright 2013.)
Continued
As the bladder fills, it becomes ovoid (Fig. 75.5; see Fig. 75.2 and between the summit and the anterior abdominal wall; this recess often
Video 75.1). Anteriorly, it displaces the parietal peritoneum from the contains coils of small intestine. At birth, the bladder is higher than in
suprapubic region of the abdominal wall. Its inferolateral surfaces the adult because the true pelvis is shallow, and the internal urethral
become anterior and rest against the abdominal wall without interven- orifice is level with the upper symphysial border. The bladder is then
ing peritoneum for a distance above the pubic symphysis that varies abdominal rather than pelvic, and extends about two-thirds of the
with the degree of distension, but is commonly 5–7 cm. The distended distance towards the umbilicus.
bladder may be punctured just above the pubic symphysis without


traversing the peritoneum (suprapubic cystostomy) (see Fig. 75.2); sur-
gical access to the bladder through the anterior abdominal wall is LIGAMENTS OF THE BLADDER
usually by this route. The summit of the full bladder points up and
forwards above the attachment of the median umbilical ligament, so The bladder is anchored inferiorly to the pubis, lateral pelvic side
that the peritoneum forms a supravesical recess of varying depth walls and rectum by condensations of pelvic fascia; although these


Bladder, prostate and urethra
1256.e1
57
retpahC
Urine samples may, therefore, be obtained in children by performing 1300.00
97
suprapubic needle puncture. A normogram of bladder volume index 95
90
(BVI = length × width × depth of bladder), based on sonographic meas- 1200.00 75
50
urements in children, is shown in Figure 75.6. The bladder progres-
1100.00 25
sively descends with growth, and reaches the adult position shortly after 10
5
puberty. 1000.00 3
900.00
800.00
700.00
600.00
500.00
400.00
300.00
200.00
100.00
0.00
0 1 2 3 4 5 6 7 8 9 10
Age (years)
Fig. 75.6 Centiles of bladder volume index in children. (Redrawn with
permission from Leung VY, Chu WC, Yeung CK et al Nomograms of total
renal volume, urinary bladder volume and bladder wall thickness index in
3,376 children with a normal urinary tract, Pediatric Radiology (2007);
37:181–188.)
)3mc(
)IVB(
xedni
emulov
reddalB
11 12 13 14 15 16 17 18 19


urinary bladder
1257
57
retpahC
Rectus abdominis Bladder Seminal vesicle Left lateral border of perivesical fat Left medial umbilical ligament
(entrance to space of Retzius) (obliterated umbilical artery)
Median umbilical
ligament (urachus)
Right medial
umbilical ligament
(obliterated
umbilical artery)
Urinary bladder
A
Left lateral border of perivesical fat Left medial umbilical ligament Median umbilical
(entrance to space of Retzius) (left obliterated umbilical artery) ligament (urachus)
B
Body of pubis Corpus Bulb of penis Prostate Rectum
cavernosum Origin of left
Fig. 75.2, cont’d B, A sagittal T2-weighted magnetic resonance image of inferior epigastric
the male pelvis, showing the bladder, prostate and relations. vessels
Left gonadal
vessels
condensations are not true anatomical ligaments, the term is applied
in routine clinical use (see p. 1224 for a further description of the vis-
ceral pelvic fascia).
In both sexes, stout bands of fibromuscular tissue, the pubovesical
ligaments, extend from the bladder neck to the inferior aspect of the B
pubic bones; they lie on each side of the median plane, leaving a
midline hiatus through which numerous small veins pass. The pubo-
Left vas deferens Peritoneum covering bladder dome
vesical ligaments are derived from the detrusor muscle, part of the
detrusor apron (Fig. 75.7). In the female, they constitute the superior Fig. 75.3 A, A view of the midline anterior abdominal wall and ligaments
extensions of the pubourethral ligaments. In the male, the detrusor during laparoscopy. B, A view of the left side of the anterior abdominal
wall and ligaments during laparoscopy.
apron is described as an extension of detrusor that extends over the
anterior surface of the prostate, and condenses distally and anteriorly
to form the puboprostatic ligaments.
Other ligaments that have been described in relation to the base of BLADDER INTERIOR
the urinary bladder are the lateral, sacrogenital/uterosacral and cardinal


ligaments. The literature is sometimes confusing and even contradic- Vesical mucosa
tory. The lateral ligament was described by Miles in 1908; although Almost all of the vesical mucosa (Fig. 75.10) is attached only loosely
never described in anatomical cadaveric dissection studies, it is recog- to subjacent muscle; it folds when the bladder empties, and the folds
nized clinically as an important structure in the pararectal space at are stretched flat as it fills. Over the trigone, immediately above and
operation. It is a broad band of dense connective tissue, varying in behind the internal urethral orifice, it is adherent to the subjacent
depth from 5 to 7 cm, and passing between the lateral wall of the pelvis muscle layer and is always smooth. The anteroinferior angle of the
and the base of the bladder at the point where the ureter terminates. It trigone is formed by the internal urethral orifice, its posterolateral
contains the middle rectal artery and lymphatic vessels that pass from angles by the ureteric orifices. The superior trigonal boundary is a
the lower rectum to the iliac lymph nodes (Takahashi et al 2000). The slightly curved inter-ureteric bar, which connects the two ureteric ori-
apex of the bladder is connected to the umbilicus by the remains of the fices and is produced by the continuation into the vesical wall of the
urachus, which forms the median umbilical ligament (see Fig. 75.3; ureteric internal longitudinal muscle. Laterally, this ridge extends
Video 75.2). Composed of longitudinal muscle fibres derived from the beyond the ureteric openings as ureteric folds, produced by the terminal
detrusor, it becomes more fibrous towards the umbilicus. It usually parts of the ureters, which run obliquely through the bladder wall. At
maintains a lumen lined with epithelium that persists into adult life cystoscopy, the inter-ureteric crest appears as a pale band and is a guide
but is only rarely complicated by a urachal cyst, sinus, fistula or to the ureteric orifices (Fig. 75.10B).
adenocarcinoma.
Trigone


From the superior surface of the bladder, the peritoneum is carried
off in a series of folds: the ‘false’ ligaments of the bladder. Anteriorly, The smooth muscle of the trigone consists of two distinct layers, some-
there are three folds (Fig. 75.8): the median umbilical fold over the times termed the superficial trigonal muscle and deep trigonal detrusor
median umbilical ligament (urachus), and two medial umbilical folds muscle. The latter is composed of muscle cells, indistinguishable from
over the obliterated umbilical arteries. The inferior epigastric vessels those of the detrusor, and is simply the posteroinferior portion of the
(Fig. 75.9) are lateral to these folds on the anterior abdominal wall and detrusor muscle proper. The superficial trigonal muscle represents a
are termed lateral umbilical ligaments in descriptions of anterior morphologically distinct component of the trigone, which, unlike the
abdominal wall anatomy. detrusor, is composed of relatively small-diameter muscle bundles that


Bladder, prostate and urethra
1257.e1
57
retpahC
The urachus may play a critical role in maintaining fetal life when Left inferior epigastric vessels Left medial umbilical ligament Urinary bladder
atresia of the urethra results in complete obstruction to the flow of
amniotic fluid. Anhydramnios noted at 17 weeks’ gestation has been
reported to resolve by 21 weeks when the patent urachus acts as a fistula
between the bladder and the amniotic space, preserving pulmonary and
renal function (Stalberg and Gonzalez 2012).
Left medial umbilical ligament Median umbilical ligament
Left testicular vessels
Fig. 75.9 A laparoscopic view of the left inferior epigastric vein (lateral
umbilical ligament) in a 12-month-old boy. (Courtesy of Mr Girish
Jawaheer.)
Urinary bladder Right medial umbilical ligament
Fig. 75.8 A laparoscopic view of the empty bladder and median and
medial umbilical folds in a 12-month-old boy. (Courtesy of Mr Girish
Jawaheer.)


Bladder, prostate and urethra
1258
8
noItCes
Left superior Endopelvic Left puboprostatic Dorsal venous
A
pubic ramus fascia ligament complex
Bladder
Pubis
Fibres of detrusor
muscle
Urethra
Striated urethral sphincter
Striated urethral meatus
Pubovesical ligament
B
Bladder
Detrusor apron
Bladder (released from Prostate
Seminal
the anterior abdominal wall)
vesicle
Fig. 75.4 A transperitoneal view of the male pelvis, as seen during
robotic-assisted laparoscopic radical prostatectomy. The bladder is
released from the anterior abdominal wall, the space of Retzius is Pubis
developed and the endopelvic fascia opened.
Prostate
Medial umbilical ligament (obliterated umbilical artery)
Striated urethral sphincter
Bulb of penis
Puboprostatic (pubovesical) ligament
Location of
seminal Fig. 75.7 Ligaments that anchor the neck of the bladder and pelvic part
vesicles and of the urethra to the pelvic bone. A, In the female. B, In the male. In
vas deferens males, the detrusor extends over the anterosuperior aspect of the
prostate and inserts into the pubic bone. It condenses to form
pubovesical/puboprostatic ligaments. (A–B, With permission from Drake
Tip of
Foley RL, Vogl AW, Mitchell A, Tibbitts R, Richardson P (eds), Gray’s Atlas of
catheter Anatomy, Elsevier, Churchill Livingstone. Copyright 2008.)
Rectovesical unit. The arrangement of smooth muscle in this region is quite different
pouch in males and females, and therefore will be described separately.
Female
Left Right In the female, the bladder neck consists of morphologically distinct
smooth muscle (Fig. 75.10C). The large-diameter fasciculi characteristic
Fig. 75.5 Laparoscopic view of the full bladder.
of the detrusor are replaced in the region of the bladder neck by small-
diameter fasciculi that extend obliquely or longitudinally into the ure-


are continuous proximally with those of the intramural ureters. The thral wall. In the normal female, the bladder neck sits above the pelvic
superficial trigonal muscle is relatively thin but is generally described floor, supported predominantly by the pubovesical ligaments (see Fig.
as becoming thickened along its superior border to form the interuret- 75.7A), the endopelvic fascia of the pelvic floor and levator ani. These
eric ridge (bar). Similar thickenings occur along the lateral edges of support the urethra at rest; with elevated intra-abdominal pressure, the
the superficial trigone. In both sexes, the superficial trigone muscle levators contract, increasing urethral closure pressure to maintain con-
becomes continuous with the smooth muscle of the proximal urethra, tinence. This anatomical arrangement commonly alters after parturition
and extends in the male along the urethral crest as far as the openings and with increasing age, such that the bladder neck lies beneath the
of the ejaculatory ducts. pelvic floor, particularly when intra-abdominal pressure rises, which
means that the mechanism described above fails to maintain conti-
Ureteric orifices nence and women may experience stress incontinence (Klutke and
The slit-like ureteric orifices are placed at the posterolateral trigonal Siegel 1995).
angles (Fig. 75.10A,B). In empty bladders, they are approximately
Male
2.5 cm apart, and 2.5 cm from the internal urethral orifice; in disten-
sion, these measurements may be doubled. In the male, the bladder neck is completely surrounded by a circular
collar of smooth muscle, with its own distinct adrenergic innervation,
Internal urethral orifice which extends distally to surround the preprostatic portion of the
The internal urethral orifice is sited at the trigonal apex, the lowest part urethra. These smooth muscle bundles are distinct from the smooth
of the bladder, and is usually somewhat crescentic in section. There is muscle bundles that run in continuity from the bladder neck down to
often an elevation immediately behind it in adult males (particularly the prostatic urethra, and from the smooth muscle within the prostate.


past middle age), which is caused by the median prostatic lobe. The bundles that form this ‘preprostatic sphincter’ are small in size
compared with the muscle bundles of the detrusor, and are separated
by a relatively larger connective tissue component rich in elastic fibres.
BLADDER NECK The bladder neck is sometimes called the proximal or internal
sphincter mechanism, to distinguish it from the distal urinary sphincter
The smooth muscle of the bladder neck is histologically, histochemi- mechanism. The internal sphincter contributes to urinary continence
cally and pharmacologically distinct from the detrusor muscle proper and, in the face of distal sphincteric incompetence, can, at times, main-
and so the bladder neck should be considered as a separate functional tain continence independently. Unlike the detrusor and the rest of the


urinary bladder
1259
57
retpahC
Median umbilical ligament
A B
Bladder mucosa
Muscular layer (muscular coat)
Mucosa (mucous membrane)
Interureteric bar Ureteric orifice
C
Internal
Bladder urethral sphincter
(lissosphincter)
Urethra
Ureteric orifice
Interureteric ridge Mucosal folds
External
Uvula of bladder Trigone urethral sphincter
(rhabdosphincter)
Urethral crest Internal urethral meatus
(bladder neck)
Prostatic sinus
Prostatic Prostatic Prostate
urethra utricle
Verumontanum Prostatic ducts
(seminal
colliculus) Ejaculatory
ducts
Fig. 75.10 A, A coronal section of the urinary bladder in the male. The mucosal folds are dependent on the state of filling. B, The ureteric orifice seen at
endoscopy. C, A posterior view of the bladder neck in the female. (A, With permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human
Anatomy, 15th ed, Elsevier, Urban & Fischer. Copyright 2013.)
urethral smooth muscle (common to both sexes), the preprostatic Inferior vesical artery
sphincter is richly supplied with sympathetic noradrenergic nerves and
The inferior vesical artery often arises with the middle rectal artery from
is almost totally devoid of parasympathetic cholinergic nerves (see
the internal iliac artery. It supplies the base of the bladder, prostate,
below).
seminal vesicles and lower ureter, and may sometimes provide the
artery to the vas deferens. Prostatic branches communicate across the
Bladder outflow obstruction
midline.
In progressive chronic obstruction to micturition, e.g. as a result of
prostatic enlargement or urethral stricture, or in children with congeni-
Veins
tal bladder outflow obstruction, e.g. posterior urethral valves, the
muscle of the bladder hypertrophies. The muscle fasciculi increase in
size and, because they interlace in all directions, a thick-walled ‘trabecu- The veins that drain the bladder form a complicated plexus on its infe-


lated bladder’ is produced. Mucosa between the fascicles forms ‘diver- rolateral surfaces and pass backwards in the lateral ligaments of the
ticula’. When outflow is obstructed, emptying is not complete; some bladder to end in the internal iliac veins (see Fig. 77.3).
urine remains and may become infected. Back-pressure from a chroni-
cally distended bladder may gradually dilate the ureters, renal pelves Lymphatic drainage
and even the renal collecting tubules, which can result in progressive
renal impairment. Lymphatics that drain the bladder begin in mucosal, intermuscular and
serosal plexuses (see Fig. 77.3). There are three sets of collecting vessels;
most end in the external iliac nodes. Vessels from the trigone emerge
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE on the exterior of the bladder to run superolaterally. Vessels from the
superior surface of the bladder converge to the posterolateral angle and
Arteries pass superolaterally to the external iliac nodes (some may go to the
internal or common iliac group). Vessels from the inferolateral surface
The bladder is supplied principally by the superior and inferior vesical of the bladder ascend to join those from the superior surface or run to
arteries (see Figs 77.3, 74.22), derived from the anterior trunk of the the lymph nodes in the obturator fossa. Minute nodules of lymphoid
internal iliac artery, and supplemented by the obturator and inferior tissue may occur along the vesical lymph vessels.
gluteal arteries. In the female, additional branches are derived from the
uterine and vaginal arteries.
INNERVATION
Superior vesical artery
The superior vesical artery supplies many branches to the fundus of the The nerves supplying the bladder arise from the pelvic plexuses, a mesh
bladder. The artery to the vas deferens often originates from one of these of autonomic nerves and ganglia lying on the lateral aspects of the
and accompanies the vas deferens to the testis, where it anastomoses rectum, internal genitalia and bladder base (Fig. 75.11). They consist
with the testicular artery. Other branches supply the ureter. The initial of both sympathetic and parasympathetic components, each of which


portion of the superior vesical artery is the proximal, patent, section of contains both efferent and afferent fibres. For further reading, see
the fetal umbilical artery. Mundy et al (1999a).


Bladder, prostate and urethra
1260
8
noItCes
Paravertebral sympathetic chain
Coeliac plexus T12
Inferior mesenteric plexus
Superior hypogastric plexus
L5
Ureter Hypogastric nerve S1
Vas deferens
Urinary bladder
Pelvic splanchnic
Seminal vesicle nerves
Sciatic nerve
Puboprostatic ligament
Prostate
Pelvic (inferior hypogastric) plexus
Striated urethral
Pudendal nerve
sphincter
Inferior rectal nerve
Perineal nerve
Dorsal nerve of penis
Fig. 75.11 Innervation of the lower urinary tract and male genitalia. (Redrawn with permission from Dyck P, Thomas PK, 2005, Peripheral Neuropathy,
Saunders, Elsevier.)
Efferent fibres considered to typify cholinergic nerve terminals, and contain clusters
Parasympathetic fibres arise from the second to the fourth sacral seg- of small (50 nm diameter) agranular vesicles, occasional large
ments of the spinal cord and enter the pelvic plexuses on the postero- (80–160 nm diameter) granulated vesicles and small mitochondria.
lateral aspects of the rectum as the pelvic splanchnic nerves. The Terminal regions approach to within 20 nm of the surface of the muscle
sympathetic fibres are derived from neuronal cell bodies in the lower cells and may be partially surrounded by Schwann cell cytoplasm; more
three thoracic and upper two lumbar segments of the spinal cord and often, they are naked nerve endings. The human detrusor muscle pos-
form the coeliac and mesenteric plexuses around the great vessels in the sesses a sparse but definite supply of sympathetic noradrenergic nerves
abdomen; from here, the hypogastric plexuses descend into the pelvis that generally accompany the vascular supply and only rarely extend
as fairly discrete nerve bundles within the extraperitoneal connective among the myocytes. Non-adrenergic, non-cholinergic nerves have
tissue posterior to the ureter on each side. The anterior part of the pelvic been identified, and a number of other neurotransmitters or neuro-
plexus is known as the vesical plexus. Small groups of autonomic neu- modulators have been detected in intramural ganglia, including the


rones occur within the plexus and throughout all regions of the bladder peptide somatostatin. The superficial trigonal muscle is associated with
wall. These multipolar intramural neurones are rich in acetylcholinester- more noradrenergic (sympathetic) fibres than cholinergic (parasympa-
ase (AChE) and occur in ganglia consisting of up to 20 neuronal cell thetic) nerves, a difference that supports the view that the superficial
bodies. The majority of the preganglionic nerve terminals correspond trigonal muscle should be regarded as ‘ureteric’ rather than ‘vesical’ in
morphologically to presumptive cholinergic fibres. Noradrenergic ter- origin. It is, however, important to emphasize that the superficial trigo-
minals also relay on cell bodies in the pelvic plexus; it is not known nal muscle forms a very minor part of the total muscle mass of the
whether similar nerves synapse on intramural bladder ganglia. bladder neck and proximal urethra in either sex and is probably of little
The urinary bladder (including the trigonal detrusor muscle) is pro- significance in the physiological mechanisms that control these regions.
fusely supplied with nerves, which form a dense plexus among the The smooth muscle of the bladder neck in males is predominantly
detrusor muscle cells. The majority of these nerves contain AChE and orientated obliquely or circularly. It is sparsely supplied with cholin-
occur in abundance throughout the muscle coat of the bladder. Axonal ergic (parasympathetic) nerves but possesses a rich noradrenergic (sym-
varicosities adjacent to detrusor muscle cells possess features that are pathetic) innervation. A similar distribution of autonomic nerves also


Male urethra
1261
57
retpahC
occurs in the smooth muscle of the prostate gland, seminal vesicles and bladder. This layer is often very superficial, lying close beneath the
vasa deferentia. Stimulation of sympathetic nerves causes contraction urothelium, but is sometimes deeper in the lamina propria, where it
of smooth muscle in the wall of the genital tract, resulting in seminal may be well developed; it must be distinguished from the muscularis
emission. Concomitant sympathetic stimulation of the proximal ure- propria. Several functions have been proposed for the lamina propria,
thral smooth muscle causes sphincteric closure of the preprostatic including acting as the capacitance layer of the bladder (determining
sphincter, thereby preventing reflux of ejaculate into the bladder. bladder compliance and enabling adaptive changes to increasing
It is extensively disrupted in the vast majority of men undergoing volumes); providing factors that influence the growth of the urothelium
bladder neck surgery, e.g. transurethral resection of the prostate, which and/or detrusor; and playing a role in signal transduction (Andersson
may result in retrograde ejaculation. Similarly, anejaculation can result and McCloskey 2014).
when the sympathetic fibres are disrupted during retroperitoneal lymph
node dissection surgery. Interstitial cells of Cajal-like cells
Although this genital function of the bladder neck of the male is Interstitial cells of Cajal (ICC) are a specialized population of cells
well established, it is not known whether the smooth muscle of this involved in smooth muscle excitability that were initially described in
region plays an active role in maintaining urinary continence. In con- the gastrointestinal tract (p. 1043). Cells with a similar morphology but
trast, the smooth muscle of the bladder neck of the female receives rela- expressing platelet-derived growth receptor alpha (PDGFRα), rather
tively few noradrenergic nerves but is richly supplied with presumptive than the tyrosine kinase receptor Kit that typifies ICC, and therefore
cholinergic fibres. The sparse supply of sympathetic nerves presumably designated interstitial cells of Cajal-like cells (ICC-LC), have been
relates to the absence of a functioning ‘genital’ portion of the wall of reported in the urethra, vas deferens, prostate, bladder, corpus caverno-


the female urethra. sum, ureter, Fallopian tube, oviduct and uterus, where they form a
The lamina propria of the fundus and inferolateral walls of the functional syncytium with nerves and smooth muscle cells. They may
bladder is virtually devoid of autonomic nerve fibres, apart from some function as electrical pacemakers in the urethra and prostate. In the
noradrenergic and occasional presumptive cholinergic perivascular bladder, they are found closely apposed to detrusor smooth muscle
nerves. However, the density of nerves unrelated to blood vessels cells, in the lamina propria and within the suburothelium; it has been
increases closer to the urethral orifice. At the bladder neck and trigone, tentatively suggested that one of their functions in the bladder is to act
a nerve plexus of cholinesterase-positive axons extends throughout the as intermediary cells transducing nerve signals to detrusor smooth
lamina propria, independent of blood vessels. Some of the larger- muscle cells (Drumm et al 2014).
diameter axons are myelinated and others lie adjacent to the basal
Muscularis propria
urothelial cells. In the absence of any obvious effector target sites, the
subepithelial nerve plexuses of the bladder and the ureter are assumed The muscularis propria is the detrusor muscle of the bladder wall. It
to subserve a sensory function. consists of three indistinct layers: an inner and outer longitudinal, and
an intermediate circular layer. In contrast to the muscularis mucosae,
Afferent fibres which consists of small wispy fibres, the muscularis propria is made up
Vesical nerves are also concerned with pain and awareness of distension, of larger, poorly defined, bundles of smooth muscle that form well-
and are stimulated by distension or spasm due to a stone, inflammation defined inner circular and outer longitudinal layers at the neck of the
or malignant disease; they travel in sympathetic and parasympathetic bladder.
nerves, but predominantly in the latter. Division of the sympathetic
Serosa
paths (e.g. ‘presacral neurectomy’) or of the superior hypogastric plexus,
therefore, does not materially relieve vesical pain, whereas considerable The serosa partially covers the bladder. It is lined externally by mesothe-


relief follows bilateral anterolateral cordotomy. Since nerve fibres medi- lium, beneath which there is a variable amount of vascularized adipose
ating awareness of distension travel in the posterior columns (fasciculus tissue that frequently extends into the muscularis propria and, occasion-
gracilis), the patient still retains awareness of the need to micturate after ally, into the lamina propria.
anterolateral cordotomy. The nerve endings detecting noxious stimuli
are probably of more than one type; a subepithelial plexus of fibres
MALE URETHRA
containing dense vesicles, which are probably afferent endings, has
been described.
The male urethra (Fig. 75.12, see Fig. 75.2) is 18–20 cm long, and extends
from the internal orifice in the urinary bladder to the external opening,
MICROSTRUCTURE
or meatus, at the end of the penis. It may be considered in two parts. The
anterior urethra is approximately 16 cm long and lies within the peri-
The bladder consists of four layers: a lining epithelium (urothelium), neum (proximally) and the penis (distally), surrounded by the corpus
lamina propria, muscularis propria and serosa. spongiosum. The posterior urethra is 4 cm long and lies in the pelvis
proximal to the corpus spongiosum, where it is acted on by the urogenital
Lining epithelium or urothelium sphincter mechanisms. Functionally, both parts act as a conduit.
Urothelium (transitional epithelium; see Fig. 2.5D) is 4–7 cells thick; The anterior urethra is subdivided into a proximal component, the
it may appear to be attenuated to 2–3 cells thick when the bladder is bulbar urethra, which is surrounded by bulbospongiosus and entirely
fully distended. It contains three distinctive cell layers: a basal layer, an within the perineum, and a pendulous or penile component, which
intermediate layer and a superficial (‘umbrella’ cell) layer (see Fig. continues to the tip of the penis. The posterior urethra is divided into


75.15). The basal layer consists of small cuboidal cells from which the preprostatic, prostatic and membranous segments. In the flaccid penis,
upper layers arise. The intermediate layers are polygonal and possess the urethra has a double curve. The urethral canal is a mere slit, except
the capacity to stretch and flatten. The superficial layer forms a protec- during the passage of fluid; in transverse section, it is transversely arched
tive, almost impermeable, surface for the bladder mucosa and consists in the prostatic part, stellate in the preprostatic and membranous por-
of large, sometimes multinucleated, cells displaying degenerative tions, transverse in the bulbar and penile portions, and sagittal at the
changes in their cytoplasm; these cells are ultimately exfoliated into the external orifice.
urine. The apical surface of the umbrella cell layer is covered by 16 nm
Posterior part
protein particles packed hexagonally to form two-dimensional crystals
of asymmetric unit membranes (AUMs), which contribute to the per- preprostatic urethra
meability barrier function of the urinary bladder, preventing reabsorp- The preprostatic urethra is approximately 1 cm in length, and extends
tion of urine across the urothelium into the blood stream. Islands or from the base of the bladder to the prostate (Fig. 75.12). Small peri-
nests of urothelium (von Brunn’s nests) may become separated from urethral glands at this site may contribute to benign prostatic hyperpla-
the surface during development and are found embedded in the under- sia (BPH) and symptoms of outflow obstruction in older men.
lying lamina propria; they may undergo central degeneration to form
cysts (cystitis cystica). prostatic urethra
The prostatic urethra is 3–4 cm in length and tunnels through the
Lamina propria
substance of the prostate, closer to the anterior than the posterior
The lamina propria forms a connective tissue bed supporting the overly- surface of the gland (Fig. 75.13; see Fig. 75.10). It is continuous above
ing urothelium, from which it is separated by a basement membrane. with the preprostatic part and emerges from the prostate slightly ante-


It is rich in capillaries, lymphatics and nerve endings, and contains rior to its apex (the most inferior point of the prostate). Throughout
elastic fibres and a thin, poorly defined, layer of smooth muscle fibres, most of its length, the posterior wall possesses a midline ridge, the
the muscularis mucosae, which is variably distributed within the urethral crest, that projects into the lumen, causing it to appear


Bladder, prostate and urethra
1262
8
noItCes
A B
Bladder mucosa –
base of bladder
Fundus
Left ureteral
Interureteric ridge orifice
Mucosal folds
Trigone
Trigone
Left lateral
bladder neck
Ureteral orifice
Uvula of bladder Posterior
Internal urethral bladder
meatus (bladder neck) neck
Preprostatic urethra
Seminal colliculus Left lateral
(verumontanum) lobe of
prostate
Prostatic urethra Ejaculatory ducts Prostatic utricle
Prostatic ducts
Urethral crest
Urethral crest
Prostatic
Membranous urethra Bulbourethral gland Bulb of penis sinus
and duct
Crus of penis Verumontanum
Prostatic utricle
Bulbourethral glands
Urethral crest and
verumontanum
Mucosal folds of
external urethral
sphincter mechanism
Male urethra Bulbar urethra
Corpus spongiosum
Membranous
urethra
Bulbar urethra
Penile urethra
Corpus cavernosum
Penile urethra
Urethral lacunae
Urethral lacuna
Penile urethra
Glans penis
Navicular fossa
Prepuce
External urethral
meatus (orifice) Navicular fossa
Fig. 75.12 A, The male urethra. B, Endoscopic views (top to bottom): posterior bladder wall and trigone, bladder neck, urethral crest, membranous
urethra, bulbar urethra, penile urethra, navicular fossa. (A, with permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human Anatomy, 15th ed,
Elsevier, Urban & Fischer. Copyright 2013.)
crescentic in transverse section. On each side of the crest, the floor of a Membranous urethra
shallow depression, the prostatic sinus, is perforated by the orifices of The membranous part of the urethra is the shortest (2–2.5 cm), least


15–20 prostatic ducts. An elevation, the verumontanum (seminal col- dilatable and, with the exception of the external orifice, the narrowest
liculus), occurs at about the middle of the length of the urethral crest; section of the urethra. It descends with a slight ventral concavity from
at this point, the urethra turns anteriorly and contains the slit-like the prostate to the bulb of the penis, passing through the perineal
orifice of the prostatic utricle. The extent of angulation most often membrane, 2.5 cm posteroinferior to the pubic symphysis. The wall of
approximates 30–35° but can change with age and differs between the membranous urethra consists of a muscle coat that is separated from
individuals. The verumontanum is used as a surgical landmark for the the epithelial lining by a narrow layer of fibroelastic connective tissue.
urethral sphincter during transurethral resection for benign enlarge- The muscle coat contains a relatively thin layer of bundles of smooth
ment of the prostate. muscle, which are continuous proximally with those of the prostatic
The two small openings of the ejaculatory ducts open on both sides urethra, and a prominent outer layer of circularly orientated striated
of, or just within, the prostatic utricle, a cul-de-sac approximately 6 mm muscle fibres, which together form the external urethral sphincter.
long, that runs upwards and backwards in the substance of the prostate Urinary continence at the level of the membranous urethra is medi-
behind its median lobe. Its walls are composed of fibrous tissue, muscular ated by the radial folds of urethral mucosa, the submucosal connective
fibres and mucous membrane, the latter pitted by the openings of numer- tissue, the intrinsic urethral smooth muscle, the striated muscle fibres
ous small glands. It develops from the paramesonephric ducts or urogeni- and the pubourethral component of levator ani. The muscle coat of the
tal sinus, and has been thought to be homologous with the vagina of the urethra and puborectalis surround the membranous urethra and are


female so that it is sometimes called the ‘vagina masculina’; the more attached to the inner surface of the ischiopubic ramus; fibres also reach
usual view is that it is a uterine homologue – hence the name ‘utricle’. up to the lowest part of the neck of the bladder and lie on the surface
The lowermost part of the prostatic urethra is fixed by the pubopros- of the prostate. The striated external urethral sphincter has a posterior
tatic ligaments and is therefore immobile. fibrous defect and is inserted throughout its length into the perineal


Bladder, prostate and urethra
1262.e1
57
retpahC
Cystic dilation of the prostatic utricle (Fig. 75.14) may present in
childhood with urinary tract infections, recurrent epididymitis or
haematuria.
Fig. 75.14 Cystic dilation of the prostatic utricle (arrow) demonstrated in
an 8-month-old child during a micturating cystourethrogram. (Courtesy of
Mr Alok Godse.)


Male urethra
1263
57
retpahC
Urethral sinuses Fig. 75.13 The prostatic part of the male urethra.
Internal urethral sphincter The raised part of the urethral crest is
(smooth muscle) the seminal colliculus, known clinically as the
Urethral crest verumontanum. (With permission from Drake RL,
Vogl AW, Mitchell A (eds), Gray’s Anatomy for
Prostate Students, 2nd ed, Elsevier, Churchill Livingstone.
Seminal colliculus Copyright 2010.)
(verumontanum)
Prostatic utricle
Glandular elements
of prostate
Openings of ducts of
glandular elements
of prostate Fibromuscular stroma
(smooth muscle and
Openings of fibrous connective tissue)
ejaculatory ducts
External urethral sphincter
(skeletal muscle)
Deep perineal pouch
Perineal membrane
body. It is related to the dorsal vein complex anteriorly, levator ani later- through the corpus spongiosum is so plentiful that the urethra can be
ally, and the perineal body and rectourethralis posteriorly; it is sus- divided without compromising its vascular supply.
pended from the pubis by fibrous tissue that extends from its anterior
and lateral parts to the puboprostatic ligaments posteriorly and to the Veins
suspensory ligament of the penis anteriorly. The bulbourethral glands The venous drainage of the anterior urethra is to the dorsal veins of the
are invested in sphincteric muscle and drain into the membranous penis and internal pudendal veins, which drain to the prostatic plexus.
urethra during sexual excitement. The posterior urethra drains into the prostatic and vesical venous plex-
uses, which drain into the internal iliac veins.
Anterior part
The anterior, or spongiose, part of the urethra lies within the corpus Lymphatic drainage
spongiosum penis (see Fig. 76.3). In the flaccid penis, it is about 15 cm Vessels from the posterior urethra pass mainly to the internal iliac nodes;
long and extends from the end of the membranous urethra to the a few may end in the external iliac nodes. Vessels from the membranous


external urethral orifice on the glans penis. It starts below the perineal urethra accompany the internal pudendal artery. Vessels from the ante-
membrane at a point anterior to the lowest level of the pubic symphysis rior urethra accompany those of the glans penis, most ending in the
as the bulbar urethra, the widest part of the urethra, surrounded by deep inguinal nodes; some may end in superficial nodes, while others
bulbospongiosus. The bulbourethral glands open into the bulbar may traverse the inguinal canal to end in the external iliac nodes.
urethra approximately 2.5 cm below the perineal membrane. The
urethra next curves downwards as the penile urethra. It is a narrow,
transverse slit when empty, and has a diameter of approximately 6 mm INNERVATION
when passing urine. It is dilated at its termination within the glans
penis, where it is known as the navicular fossa. The external urethral
The prostatic plexus supplies the smooth muscle of the prostate and
orifice is the narrowest part of the urethra and, in the adult, is a sagittal
prostatic urethra (see Fig. 75.11). On each side, it is derived from the
slit, about 6 mm long, bounded on each side by a small labium.
pelvic plexus and lies on the posterolateral aspect of the seminal vesicle
The urethral epithelium, particularly in the bulbar and distal penile
and prostate. The cavernous (deep, cavernosal) nerves, both major and
segments, presents the orifices of numerous small mucous urethral
minor, pierce the bulb of the corpus spongiosum to innervate the cav-
glands that lie in the submucosa. It also contains a number of small
ernous bodies of the penis. The sympathetic autonomic nerves that
pit-like recesses, or lacunae, of varying sizes with orifices directed for-
supply the internal urethral sphincter are derived from the pelvic plexus
wards. One, the lacuna magna, is larger than the rest and is situated in
as it descends in the pelvis adjacent to the inferior prostatovesical


the roof of the navicular fossa.
pedicle and prostate, and function to prevent retrograde ejaculation.
Traumatic injury to the male urethra Parasympathetic preganglionic axons arise from neuronal cell bodies in
the second to fourth sacral spinal segments. The nerve supply of the
external urethral sphincter is controversial. It is generally believed to be
Available with the Gray’s Anatomy e-book
supplied by neurones in Onuf’s nucleus and by perineal branches of
Congenital anomalies of the male urethra the pudendal nerve lying on the perineal aspect of the pelvic floor; in
both instances, the axons arise from neurones in the second to fourth
sacral spinal segments. Fibres from Onuf’s nucleus (somatic) travel with
Available with the Gray’s Anatomy e-book
the pelvic plexus on each side until they branch off to run on the pelvic
aspect of the pelvic floor to enter the membranous urethra.
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
MICROSTRUCTURE
Urethral artery
The urethral artery arises from the internal pudendal artery or common The epithelium lining the preprostatic urethra and the proximal part
penile artery just below the perineal membrane, and travels through the of the prostatic urethra is a typical urothelium (Fig. 75.15). It is con-
corpus spongiosum to reach the glans penis. It supplies the urethra and tinuous with that lining the bladder, and with the epithelium lining the
the erectile tissue around it. The urethra is also supplied by the dorsal ducts of the prostate and bulbourethral glands, the seminal vesicles,
penile artery, via its circumflex branches on each side and in a retrograde and the vasa deferentia and ejaculatory ducts. These relationships are
fashion from the glans, by its terminal branches. The blood supply important in the spread of urinary tract infections.


Bladder, prostate and urethra
1263.e1
57
retpahC
The mean length of the slit is 5.4 mm in boys between the ages of
0.3 and 15 years (Hutton and Babu 2007). The width of the external
urethral orifice in uncircumcised boys between the ages of 5 months
and 16 years varies from 3.5 to 7.5 mm (Orkiszewski and Madej 2010).
The urethra may be ruptured by a fall-astride (straddle) injury to the
bulbar urethra in the perineum, or by an injury related to a pelvic
fracture. These injuries usually affect the junction of the membranous
with the bulbar segments across the perineal membrane. One of the
complications associated with such injuries is extravasation of urine.
After an injury to the bulbar urethra, urine usually extravasates between
the perineal membrane and the membranous layer of the superficial
fascia (clinically, known as Colles’ fascia). As both of these are attached
firmly to the ischiopubic rami, extravasated fluid cannot pass posteri-
orly because the two layers are continuous around the superficial trans-
verse perineal muscles. Laterally, the spread of urine is blocked by the
pubic and ischial rami. Urine cannot enter the lesser pelvis through the
perineal membrane if this remains intact, and so it tracks anteriorly into
the loose connective tissue of the scrotum and penis, and, from there,
to the anterior abdominal wall. If the posterior urethra is injured, urine
is extravasated into the pelvic extraperitoneal tissue; if the perineal
membrane is also torn, then urine may be extravasated into the
perineum.
Hypospadias, found in 1 in 300 boys, most often results in the urethra
opening in the distal penis, either on the ventral aspect of the penis or,
more proximally, on to the perineum. There is also an associated abnor-
mality of the prepuce, which is longer dorsally and lacking ventrally,
and often an associated chordee, which causes a ventral curvature of


the penis. The microvessel density of the prepuce is reduced in children
with hypospadias and this has surgical implications when preputial
flaps are used for the repair of hypospadias (Yucel et al 2004, Cagri
Savas et al 2011). Anomalies of arterial vascular anatomy of the prepuce
have been described in boys with hypospadias; it is, therefore, impor-
tant for hypospadias to be identified prior to circumcision because the
abnormal foreskin is sometimes used for surgical correction of the
deformity. The anogenital distance (distance from the anus to the base
of penis) is reduced in Caucasian boys with hypospadias (Hsieh et al
2012).
Epispadias occurs in approximately 1 in 100,000 boys; it is typically
part of the exstrophy–epispadias complex but may occur in isolation.
The urethra is either completely open dorsally or uncovered to the level
of the pubic symphysis. The neurovascular bundles are anterolateral
along the proximal portions, and lateral along the middle and distal
portions, of the corporeal bodies (Hurwitz et al 1986). Other features
of epispadias are shortened penis and dorsal chordee; the incidence of
cryptorchidism is increased ten-fold.
Posterior urethral valves occur in 1 in 5000–8000 males and are the
most common cause of urinary outflow obstruction in male infants.
The most common type (type I) is believed to occur if the Wolffian
ducts open too anteriorly on to the primitive prostatic urethra; this
abnormal migration of the ducts leaves behind thick vestigial tissue that
forms rigid valve cusps extending caudally from the verumontanum.
Megalourethra may be associated with posterior urethral valves. Con-
genital anterior urethral valves are a rare cause of urethral obstruction
in boys and may be associated with posterior urethral valves and
hypospadias.
Very rarely, urethral duplication occurs; the two urethrae almost
invariably lie on top of each other rather than side by side. One of the
urethrae, usually the more dorsal, may be blind-ending. Congenital


prepubic sinus consists of a midline tract in the skin passing from the
suprapubic region towards the anterior bladder without communica-
tion, and is believed to be a variant of dorsal urethral duplication.
Congenital urethrocutaneous fistulae are very rare anomalies in which
the urethra opens on the ventral surface of the penis in the absence of
chordee or hypospadias.
Congenital rectourethral fistulae may be present in children born
with anorectal malformation. The prostatic or bulbar urethra is usually
affected, and the rectum and urethra share a common wall immediately
above the fistula site.


Bladder, prostate and urethra
1264
8
noItCes
Veins
U
The venous plexus around the urethra drains into the vesical venous
plexus around the bladder neck and into the internal pudendal veins
(see Fig. 77.3). An erectile plexus of veins along the length of the urethra
is continuous with the erectile tissue of the vestibular bulb.
LP Lymphatic drainage
The urethral lymphatics drain into the internal and external iliac
nodes.
INNERVATION
Parasympathetic preganglionic axons arise from neuronal cell bodies in
the intermediolateral column of the second to fourth segments of the
sacral spinal cord, run in the pelvic splanchnic nerves, and synapse in
the vesical plexus in or near the bladder wall (see Fig. 77.5B). Postgan-
glionic fibres are distributed to the smooth muscle of the urethral wall.
Somatic fibres to the striated muscle are also derived from the second
Fig. 75.15 The bladder is lined by urothelium with a surface ‘umbrella
to fourth segments of the sacral spinal cord, and run in the pelvic
cell’ layer (U) and a layer of intermediate cells (3–5 cells thick). The
splanchnic nerves but do not synapse in the vesical plexus. Sensory
lamina propria (LP) consists of stroma with blood vessels and von
fibres run in the pelvic splanchnic nerves to the second to fourth seg-
Brunn’s nests.
ments of the sacral spinal cord. Postganglionic sympathetic fibres arise
from the plexus around the vaginal arteries.
The epithelium changes below the openings of the ejaculatory ducts
to a pseudostratified or stratified columnar type, which lines the mem-
MICROSTRUCTURE
branous urethra and the major part of the penile urethra. Mucus-
secreting cells are common throughout this epithelium and frequently
The mucosa lining the female urethra consists of a stratified epithelium
occur in small clusters in the penile urethra. Branching tubular para-
and a supporting lamina propria of loose fibroelastic connective tissue.
urethral glands secrete protective mucus on to the urethral epithelial


The latter is bulky and well vascularized, and contains numerous thin-
lining and are especially numerous on its dorsal aspect. In older men,
walled veins. Its abundant elastic fibres are orientated both longitudi-
many of the deep recesses of the urethral mucosa contain concretions
nally and circularly around the urethra. The lamina propria contains a
similar to those found within prostatic glands (see Fig. 75.23A). Towards
fine nerve plexus, believed to be derived from sensory branches of the
the distal end of the penile urethra, the epithelium changes once again,
pudendal nerves. The proximal part of the urethra is lined by urothe-
becoming stratified squamous in type with well-defined connective
lium, identical in appearance to that of the bladder neck. Distally, the
tissue papillae. This epithelium also lines the navicular fossa and
epithelium changes into a non-keratinizing stratified squamous type
becomes keratinized at the external meatus. The epithelial cells lining
that lines the major portion of the female urethra. This epithelium is
the navicular fossa are glycogen-rich. This may provide a substrate for
keratinized at the external urethral meatus, where it becomes continu-
commensal lactobacilli, which, as in the female vagina, provide a
ous with the skin of the vestibule.
defence against pathogenic organisms.
The wall of the female urethra consists of an outer muscle coat and
an inner mucosa, which lines the lumen and is continuous with that
of the bladder. The muscle coat consists of an outer sheath of striated
FEMALE URETHRA
muscle, together with an inner coat of smooth muscle fibres. The female
external urethral sphincter is anatomically separate from the adjacent
The adult female urethra is approximately 4 cm long and 6 mm in periurethral striated muscle of the anterior pelvic floor. The muscle cells
diameter. The average length of the urethra is 26 mm in girls, increas- forming the external urethral sphincter are all small-diameter, slow-


ing from 23 mm at birth to 32 mm at 15 years (Hirdes et al 2010). It twitch fibres.
begins at the internal urethral orifice of the bladder, approximately The smooth muscle coat extends throughout the length of the
opposite the middle of the pubic symphysis, and runs anteroinferiorly urethra and consists of slender muscle bundles, the majority of which
behind the pubic symphysis, embedded in the anterior wall of the are orientated obliquely or longitudinally. A few circularly arranged
vagina (see Fig. 75.1). It is suspended beneath the pubis by the pos- muscle fibres occur in the outer aspect of the non-striated muscle layer
terior pubourethral ligaments, and anteriorly, by the suspensory liga- and intermingle with the skeletal muscle fibres forming the inner part
ment of the clitoris. It crosses the perineal membrane and normally of the external urethral sphincter. Proximally, the urethral smooth
ends at the external urethral orifice in the vestibule as an anteropos- muscle extends as far as the bladder neck, where it is replaced by fasci-
terior slit with rather prominent margins, directly anterior to the cles of detrusor smooth muscle. This region in the female lacks a well-
opening of the vagina and 2.5 cm behind the glans clitoris. It some- defined circular smooth muscle component comparable with the
times opens into the anterior vaginal wall. Except during the passage preprostatic sphincter of the male. Distally, urethral smooth muscle
of urine, the anterior and posterior walls of the urethra are in apposi- bundles terminate in the subcutaneous adipose tissue surrounding the
tion and the epithelium is thrown into longitudinal folds, one of external urethral meatus.
which, on the posterior wall of the canal, is termed the urethral crest. The smooth muscle of the female urethra receives an extensive pre-
Many small, mucous urethral glands and minute, pit-like recesses or sumptive cholinergic parasympathetic nerve supply but contains rela-
lacunae open into the urethra and may give rise to urethral diverticula. tively few noradrenergic nerves. In the absence of an anatomical bladder


On each side, near the lower end of the urethra, a number of these neck sphincter, competence of the female bladder neck and proximal
glands, Skene’s glands, are grouped together and open into the para- urethra is unlikely to be totally dependent on smooth muscle activity,
urethral duct; each duct runs down in the submucous tissue and ends and is more probably related to the support provided by the ligamen-
in a small aperture on the lateral margin of the external urethral tous structures that surround them. The innervation and longitudinal
orifice. orientation of most of the muscle fibres suggest that urethral smooth
Epispadias is a rare congenital anomaly that may affect the female muscle in the female is active during micturition, serving to shorten
urethra. It may occur in isolation or as part of the exstrophy–epispadias and widen the urethral lumen.
complex. Isolated epispadias in girls is characterized by the urethra
opening at the clitoris, which is typically bifid.
MICTURITION AND URINARY CONTINENCE
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
The central integration of nervous control of the bladder and urethra is
essential for normal micturition (Fig. 75.16). (For further reading, see
Urethral artery
Yoshimura and Chancellor (2012).)
The urethra is supplied principally by the vaginal artery, but also receives Micturition consists of storage and voiding phases. During the
a supply from the inferior vesical artery. storage phase, the bladder accommodates an increasing volume of urine