Introduction

• Retroperitonium is a region behind the

peritoneal cavity on posterior abdominal
wall
• Viscera
– Urinary organs: kidneys and ureters
– Endocrine organ: suprarenal glands
• Blood vessels: aorta and inferior vena cava
• Nerves: lumbar plexus and ANS
• Lymphatics
The Urinary System
 Introduction
• The urinary system consists of
– Paired kidneys: filter blood and form urine
– Paired ureters: carry urine from the kidneys
– Urinary bladder: temporarily stores urine
– Urethra: conducts urine from the urinary
bladder to the exterior
 Functions of the Urinary System
• This system helps maintain
homeostasis by a complex combination
of processes that involves:
– Filtration of cellular wastes from blood
– Selective reabsorption of water and solutes
– Excretion of the wastes and excess water
as urine
• Filtration of the blood
– Occurs in the glomerulus of the kidney
nephron
– Contributes to homeostasis by removing
toxins or waste
• Reabsorption of vital nutrients, ions and
water
– Occurs in most parts of the kidney
nephron
– Contributes to homeostasis by
conserving important materials
• Secretion of excess materials
– Assists filtration in removing material
from the blood
– Contributes to homeostasis by
preventing a build-up of certain
materials in the body such as drugs,
waste, etc.
• Urine produced in the kidneys passes
through the ureters to the bladder for
temporary storage and is then released to
the exterior through the urethra
• The two kidneys produce about 125 mL of
filtrate per minute, of which 124 mL is
reabsorbed and 1 mL is released into the
ureters as urine
• About 1500 mL of urine is formed every 24
hours
• Activation of Vitamin D
– Vitamin D, initially produced in skin
keratinocytes, is hydroxylated in kidneys to an
active form
– Active Vitamin D (D3) assists homeostasis by
increasing calcium absorption from the
digestive tract
• Kidneys are the site of production of
– Renin
• Renin stimulates the formation of a powerful
vasoconstrictor called Angiotensin II
• participates in the regulation of blood pressure
– Erythropoietin: stimulates the production of
erythrocytes
– Prostaglandins
• Prostaglandins dilate kidney blood vessels
• Dilated blood vessels contribute to homeostasis
by maintaining blood flow in the kidneys
• Kidneys regulate the fluid and electrolyte
balance of the body
– Secretion of H+ and reabsorption of HCO3-
• Eliminates excess hydrogen ions and
conserves buffer material such as
bicarbonate
• Contributes to homeostasis by
controlling acid/base conditions in body
fluids
Kidneys
Location
• Each kidney lies in paravertebral grooves
on posterior abdominal wall
retroperitoneally
• kidneys extend from the level of the T12 to
L3
• They receive some protection from ribs
 Position

• The kidneys are retroperitoneal, or behind the

peritoneum
 Location

• The right lies

somewhat
lower than left
as it is
positioned
under liver
Relations
• Posterior:
– Muscles: diaphragm, psoas major, quadratus
lumborum and the origin of the transversus
abdominis from medial to lateral
– Nerves: subcostal, iliohypogastric and ilioinguinal
nerves
• Anterior:
– Right kidney
• Superior pole: liver, suprarenal gland
• Hilum: duodenum
• Inferior pole: part of small intestine, right colic
flexure
– Left kidney
• Suprarenal gland, stomach, spleen, pancreas,
jejunum, descending colon
External Anatomy
• The adult kidney weighs about 150 g
• Size: 12 cm long, 6 cm wide, 3 cm thick
• Color: reddish-brown
• Shape: bean-shaped
• Each kidney has
– concave medial border, convex lateral
surface
• Medial surface has a vertical cleft called the
renal hilum that leads into the space within the
kidney called the renal sinus
• Nerves enter, the ureter exits, and blood and
lymph vessels enter and exit the hilum
• These structures occupy the renal sinus
Supportive tissue
• Kidneys are supported by three layers of supportive
tissue
• Renal capsule
– outer membrane that encloses, supports and
protects the kidney
– adheres directly to the kidney surface and
isolates it from surrounding region
• Adipose capsule
– Immediately outside the renal capsule, there is
an accumulation of extraperitoneal fat-the
perinephric fat (perirenal fat), which completely
surrounds the kidney
– attaches the kidney to the posterior body wall
and cushions it against trauma
• Renal fascia
– Enclosing the perinephric fat is a membranous
condensation of the extraperitoneal fascia
(the renal fascia)
– The suprarenal glands are also enclosed in
this fascial compartment, usually separated
from the kidneys by a thin septum
– dense fibrous connective tissue which
surrounds the kidney and anchors these
organs to the surrounding structures
• In addition to perinephric fat and the renal
fascia, a final layer of paranephric fat (pararenal
fat) completes the fat and fascias associated
with the kidney. This fat accumulates posterior
and posterolateral to each kidney.
 Internal Anatomy

• The kidney
has three
distinct
regions
– Cortex
– Medulla
– Pelvis
Cortex

• The outer layer of the kidney

• Light in color and has a granular
appearance
• Contains most of the nephron; main site
for filtration, reabsorption and secretion
 Medulla
• Deep to the cortex; inner core of the kidney
• Contains the pyramids, columns, papillae,
and parts of the nephron
• Darker tissue which exhibits 8–15 cone
shaped tissue masses called medullary or
renal pyramids
• Renal pyramids are separated by cortical
extensions called renal columns
• Each medullary pyramid plus the cortical
tissue at its base and along its sides
constitutes a renal lobe
• Renal pyramid
– Each renal pyramid has a base which is
convex, and an apex which tapers
toward its papilla
– House the loops of Henle and collecting
ducts of the nephron
– Appear striped because they are formed
almost entirely of roughly parallel
bundles of urine collecting tubules
• Renal Papilla
– The tip of the renal pyramid that
releases urine into a calyx
Renal pelvis
• Within the renal sinus is the renal pelvis
• The expanded upper end of the ureter, called the renal
pelvis
• This flat, funnel shaped tube is continuous with the ureter
leaving the hilus
• Branching extensions of the renal pelvis form 2-3 major
calyces, each of which sub-divides to form several minor
calyces
• Calyx
– A collecting sac surrounding the renal papilla
– transports urine from the papilla to the renal pelvis
• The area surrounding the calyces, called the renal sinus,
usually contains considerable adipose tissue
• Renal pelvis collects urine from all of the calyces
• Urine flows through the renal pelvis into the ureter, which
transports it to the bladder
• The walls of the calyces, pelvis, and ureter contain smooth
muscle which contract to move urine
Blood Supply
• Kidneys possess an extensive blood supply
– Under normal resting conditions, the renal arteries
deliver approximately one-fourth of the total systemic
cardiac output (1200 ml) to the kidneys each minute
Renal artery
• A single large renal artery, a lateral branch of the
abdominal aorta, supplies each kidney
– arise just inferior to the origin of the superior
mesenteric artery between vertebrae L1 and L2
– The left renal artery usually arises a little higher than
the right, and the right renal artery is longer and
passes posterior to the inferior vena cava
• Accessory renal arteries are common
– They originate from the lateral aspect of the
abdominal aorta, either above or below the primary
renal arteries, enter the hilum with the primary
arteries or pass directly into the kidney at some other
level, and are commonly called extrahilar arteries.
Segmental arteries
• Each renal artery divides close to the hilum into five
segmental arteries that are end arteries (i.e., they do
not anastomose significantly with other segmental
arteries
– superior (apical) segmental artery
– anterosuperior segmental artery
– anteroinferior segmental artery
– inferior segmental artery
• These arteries originate from the anterior
branch of the renal artery
– posterior segmental artery
• originates from a continuation of the
posterior branch of the renal artery
• The area supplied by each segmental artery is an
independent, surgically resectable unit or renal
segment
• Segmental arteries are distributed to the renal segments
• In the renal sinus segmental arteries
branch further to form the interlobar
arteries extending between the renal
pyramids toward the corticomedullary junction
• Here the interlobar arteries branch further to
form the arcuate arteries which travel in an
arc along this junction at the base of each
renal pyramid
• Smaller interlobular arteries branch off at
right angles from the arcuate arteries and
enter the cortex
• From the interlobular arteries arise the
microvascular afferent arterioles, which
supply blood to a tuft of capillaries called the
glomerulus, each of which is associated with
a renal corpuscle
• Blood leaves the glomerular capillaries, not
via venules, but via the efferent
arterioles, which at once branch again to
form another capillary network, the
peritubular capillaries that nourish cells
of the proximal and distal tubules and carry
away reabsorbed substances
• The efferent arterioles associated with
glomeruli near the medulla continue as long,
straight vessels directly into the medulla
providing nutrients and oxygen there, and
then loop back into the cortex as venules
– These small medullary vessels and their
intervening capillary plexuses comprise the vasa
recta
• Blood leaves the kidney in veins that follow
the same courses as arteries and have the
same names
Renal veins
• Several renal veins drain each kidney and
unite in a variable fashion to form the
right and left renal veins
• The right and left renal veins lie anterior
to the right and left renal arteries
• The longer left renal vein receives the left
suprarenal vein, the left gonadal
(testicular or ovarian) vein, and a
communication with the ascending
lumbar vein
• The longer left renal vein crosses the
midline anterior to the abdominal aorta
and posterior to the superior mesenteric
artery
• Each renal vein drains into the IVC
Lymphatic drainage and Innervation of kidneys

• Lymph vessels follow renal veins and drain

into lumbar lymph nodes

• Nerve supply is from renal plexus (vagus

and lesser and least splanchnic nerves)
Ureters
• Thick walled muscular duct with narrow
lumen
• Carry urine from kidneys to urinary bladder
• It measures 25cm
• Each leaves the renal pelvis, descends
behind the peritoneum to the base of the
bladder, turns and then runs obliquely
through the medial bladder wall
• Urine is transported down the ureters by
peristaltic contractions
• It can be divided into abdominal and pelvic
parts
• Abdominal part
– Runs down anterior to the psoas major,
retroperitoneally
– Right ureter lies closely related to inferior
vena cava, lumbar lymph nodes and
sympathetic trunk
– Inferiorly, testicular or ovarian vessels
cross over the ureter
– Crosses pelvic brim and external iliac
artery just beyond bifurcation of common
iliac arteries
• Pelvic part
– Course posteroinferiorly on lateral wall of
pelvis anterior to internal iliac arteries
– Opposite the ischial spine, they curve
anteromedially, superior to the levator ani,
to enter the base of urinary bladder
– In males
• the only structure that passes between the
ureter and the peritoneum is the ductus
deferens
• The ureter lies posterolateral to the ductus
deferens
– In females
• the ureter passes medial to the origin of the
uterine artery and continues to the level of the
ischial spine, where it is crossed superiorly by
the uterine artery
• The ureter then passes close to the lateral part
of the fornix of the vagina
– Enters posterosuperior angle of bladder
– It passes inferomedially through the
muscular wall of the urinary bladder
– This oblique passage through the bladder
wall forms a one-way flap valve that
prevents the backflow of urine; the
internal pressure of the filling bladder
compresses and closes the intramural
passage and ends of the ureters
(physiological valve)
– Opening has no anatomical valve
• The ureters play an active role in
transporting urine
– Distension of the ureters by incoming urine
stimulates the muscularis layer to contract,
which propels the urine into the bladder
• The strength and frequency of peristaltic
waves are adjusted to the rate of urine
formation
Vasculature
• Arterial supply:
• Branches arise from
– Abdominal part
» Renal artery
» Aorta
» Gonadal artery
– Pelvic part
» Common and internal iliac arteries
» in females: branches of the uterine arteries
» in males: branches of the inferior vesical
arteries
• Venous drainage:
• Accompany the arteries and have corresponding
names
• Lymphatic drainage:
•
Innervation
• Derive from adjacent autonomic plexuses
– renal, aortic, testicular/ovarian, superior
and inferior hypogastric
• The ureters are superior to the pelvic pain
line; therefore, afferent (pain) fibers from
the ureters follow sympathetic fibers
retrogradely to reach the spinal ganglia and
spinal cord segments T11 - L1 or L2
Obstruction of ureter (Ureteric calculi)
• Obstruction results from ureteric calculus (kidney
stones)
• Ureteric calculi may cause complete or intermittent
obstruction of urinary flow
• Ureters dilate if obstructed
– Excessive distension causes severe pain – ureteric
colic, results from hyperperistalsis in ureter
• The obstruction may occur anywhere along the
ureter; however, it occurs most often where the
ureters are relatively constricted:
– at the junction of the ureters and renal pelvis
– where they cross the external iliac artery and the
pelvic brim
– where they passes through the wall of the bladder
Adrenal (Suprarenal) Glands
• Pair, on the upper poles of each kidneys
• Right suprarenal gland
– Triangular, partly covered with peritoneum
– Relations
• Posteriorly – diaphragm
• Postero-inferiorly – right kidney
• Anteriorly – liver and inferior vena cava
• Medial border - celiac ganglion
• Left suprarenal gland
– Semilunar, partly covered with peritoneum
of the lesser sac
– Relations
• Posteriorly – diaphragm
• Anteriorly – stomach (forms stomach
bed) separated by lesser sac
• Postero-inferiorly - left kidney
• Medial border - celiac ganglion
General structures
• Invested by dense capsule
– bringing arteries to serve radial capillaries
draining down towards the venules and central
vein of the medulla
– Arterioles also penetrate the cortex to serve a
medullary capillary bed
• Two parts
– Cortex
• Polyhedral glandular cells, in cords usually two
cells wide, run roughly radially
– Medulla
• thin strip of basophilic cells
• Structurally, embryologically and functionally, they
are two glands in one
– Adrenal medulla – nervous tissue that acts as part of the SNS,
derived from neural crest
– Adrenal cortex – glandular tissue derived from embryonic
mesoderm
Neurovasculature
• Arterial supply
– Superior suprarenal arteries - from phrenic
artery
– Middle suprarenal arteries - from abdominal
aorta
– Inferior suprarenal arteries - from renal
artery
• Veins – single vein from each
– Left – drains into left renal vein
– Right- directly into IVC
• Nerve supply
– Sympathetic preganglionic from splanchnic
nerves, reach through celiac & renal
Neurovasculature
Abdominal aorta
Location
• Continuation of thoracic aorta
• Lies in the midline against vertebral bodies
• It enters the abdomen through aortic hiatus at T12
and L1 level
• Ends at L4, left of the midline by dividing into the 2
common iliac arteries
• The main continuation of the aorta is the median or
middle sacral artery
Relations
• Superior: diaphragm
• Anterior: celiac trunk and plexus, pancreas, left renal
vein, duodenum, mesentry
• Posterior: bodies of L1-L4 vertebrae, cisterna chylli
• Lateral: inferior vena cava (right), sympathetic trunk
Branches
• Subdivided into groups of 4:
– 3 unpaired visceral
– 3 paired visceral
– 5 paired parietal
– 1 unpaired parietal
• Inferior phrenic: T12
• Celiac trunk: T12
• SMA: L1
• Renal: L1
• Gonadals: L2
• IMA: L3
• Bifurcation: L4
Unpaired visceral branches
• Ventral branches; arise from anterior surface
– arteries to the fore-, mid- and hindgut
respectively
• celiac trunk
• superior mesenteric
• inferior mesenteric
• Celiac trunk
– Foregut - esophagus to second part of
duodenum
• Superior mesenteric
– Midgut - second part of duodenum to proximal
2/3 transverse colon
• Inferior mesenteric
– Hindgut - distal 1/3 transverse colon to upper
2/3 of rectum
Paired visceral branches
• Arise from sides; lateral branches
• Supply suprarenal glands, kidneys and gonads
• Renal arteries
– Arise just below the superior mesenteric artery
– The right renal artery passes posterior to the inferior
vena cava
– They also send branches to the suprarenal glands
and the renal pelvis
– Pass to hilum of kidney between ureter and renal
vein
• Gonadal (ovarian or testicular) arteries
– Arise from the aorta just below the renal arteries
– Descend lying anterior to the surface of the psoas to
reach the ovary or pass into the inguinal canal to go
to the scrotum
• Middle suprarenal arteries
– Arise near the origin of SMA
Paired parietal branches
• Arise from posterolateral surface
• Are branches to the body wall
• The inferior phrenic arteries
– Gives branch to the suprarenal gland and
ramify on the inferior surface of the
diaphragm
• The 4 lumbar arteries
– gives
• posterior branch: going through the back and
giving a spinal branch
• anterior branch: runs in the anterior
abdominal wall between the transversus
abdominis and the internal oblique muscles
Unpaired parietal branch
• The median (middle) sacral artery
• Arise from posterior surface at bifurcation
of aorta
• Descend in the midline anterior to the
sacrum
Inferior Vena Cava
• Returns blood from lower limbs, abdominal wall
and abdominopelvic viscera
• Begins infront of the body of L5 by union of
common iliac veins
• Ascends on right psoas muscle right to aorta to
the diaphragm
• Pierce the central tendon at T8 forming vena
caval foramen
• Relations
– posterior: bodies of L3-L5, right psoas major muscle,
right sympathetic trunk, right renal artery, right
suprarenal gland
– anterior: superior mesenteric vessels, head of
pancreas, duodenum
– lateral: aorta (left), right ureter and kidney (right)
Tributaries
• Ventral tributary: right testicular or ovarian
veins
• Lateral tributaries: renal and right
suprarenal and hepatic veins
• Tributaries from the body wall: the inferior
phrenic and lumbar veins
• Correspond to the named arteries except
on the left where the suprarenal and
gonadal veins open into the left renal vein
• Median sacral vein opens into the left
common iliac vein
Lymphatics
• Lymphatic drainage from all structures and
regions of the body below the diaphragm
converges on collections of lymph nodes and
vessels associated with the major vessels of
the posterior abdominal region
• Lymph from the lower limb and perineum
passes upward to the collection of nodes and
vessels associated with the external iliac
artery and vein
• It continues its upward journey to lymph nodes
and vessels around the common iliac artery
and vein
• At this point, it is joined by lymph from the
pelvic cavity that has passed through nodes and
• Approaching the aortic bifurcation, the
collections of lymphatics associated with the
two common iliac arteries and veins merge, and
multiple groups of lymphatic vessels and nodes
associated with the abdominal aorta and
inferior vena cava pass superiorly
– These collections may be subdivided into
• pre-aortic nodes, which are anterior to the
abdominal aorta
• right and left lateral aortic or lumbar nodes,
which are positioned on either side of the
abdominal aorta
• As these collections of lymphatics pass
through the posterior abdominal region,
they continue to collect lymph from a
variety of structures
– The lateral aortic or lumbar lymph nodes
receive lymphatics from the body wall, the
kidneys, the suprarenal glands, and the
testes or ovaries
• The pre-aortic nodes are organized
around the three anterior branches of the
abdominal aorta
– They are divided into celiac, superior
mesenteric, and inferior mesenteric nodes,
and receive lymph from the organs supplied
by the similarly named arteries
• Finally, the lateral aortic or lumbar
nodes form the right and left lumbar
trunks, while the pre-aortic nodes form
the intestinal trunk
• These trunks come together and form a
confluence that, at times, appears as a
saccular dilation (the cisterna chyli)
– This confluence of lymph trunks is posterior
to the right side of the abdominal aorta and
anterior to the bodies of vertebrae L1 and
L2
– It marks the beginning of the thoracic duct
Lumbar plexus
• Lies in the psoas major
• Formed by the anterior primary rami of L1, 2,
3, and 4
• The sacral plexus is from L4, 5, S1, 2, 3 and 4
• L4 is also called the nervus furcalis or
lumbosacral trunk because it splits itself
between the lumbar and sacral plexuses
• The sacral and lumbar plexuses overlap
substantially
• Since the fibers of the lumbar plexus
contribute to the sacral plexus via the
lumbosacral trunk, the two plexuses are
often referred to as the lumbosacral plexus
Branches
• Its proximal branches innervate parts of the
abdominal wall and iliopsoas
• Major branches of the plexus descend to
innervate the medial and anterior thigh
• Branches
– Iliohypogastric nerve
– Ilioinguinal nerve
– Genitofemoral nerve
– Lateral cutaneous nerve of the thigh
– Femoral nerve
– Obturator nerve
• Ilioinguinal and Iliohypogastric nerves (L1)
– arise from the anterior ramus of L1,
entering the abdomen posterior to the
medial arcuate ligament and passing
inferolaterally, anterior to the quadratus
lumborum
– run superior and parallel to the iliac crest,
piercing the transversus abdominis near
the ASIS
– then pass through the internal and
external obliques to supply the abdominal
muscles and skin of the inguinal and pubic
regions
– the division of the L1 anterior ramus may
occur as far distally as the ASIS, so that
often only one nerve (L1) crosses the
posterior abdominal wall instead of two
• Genitofemoral nerve (L1, L2)
– pierces the psoas major and emerges from the
anterior surface of the psoas major
– runs inferiorly on its anterior surface, deep to
the psoas fascia
– divides lateral to the common and external iliac
arteries into femoral and genital branches
– supplies cremaster muscle via its genital
branch and a small area under the inguinal
ligament by its femoral branch
• Lateral cutaneous nerve of the thigh (L2, L3)
– emerges from the lateral border of the psoas
– runs inferolaterally on the iliacus and enters the
thigh deep to the inguinal ligament/iliopubic
tract, just medial to the ASIS
– supplies skin on the anterolateral surface of the
thigh
• Femoral nerve (L2-L4)
– emerges from the lateral border of the psoas
major
– innervates the iliacus and passes deep to the
inguinal ligament/iliopubic tract to the anterior
thigh, supplying the flexors of the hip and
extensors of the knee
• Obturator nerve (L2-L4)
– emerges from the medial border of the psoas
major near the brim of the pelvis
– lying posterior to the common iliac vessels
– it then travels anteriorly and inferiorly, anterior
to obturator internus and leaves the pelvis by
passing through the superior part of the
obturator foramen to the medial thigh, supplying
the adductor muscles
• The lumbosacral trunk (L4, L5)
– passes over the ala (wing) of the
sacrum and descends into the pelvis
to participate in the formation of the
sacral plexus with the anterior rami of
S1-S4 nerves
Posterior abdominal wall
Introduction
• The posterior abdominal wall consists
– Bones
• lumbar vertebrae
• sacrum
• ilium
– Muscles
• psoas
• quadratus lumborum
• transversus abdominis muscle
• posterior part of the diaphragm and its crura
• The parietal peritoneum covers the posterior
abdominal wall along with the retroperitoneal
organs
– duodenum and the kidneys lying on the
vertebrae and muscles
Bones
Muscles
Psoas major
• Origin
– Transverse processes and sides of the bodies and intervertebral discs
of the 5 lumbar vertebrae
– Because the muscle fills in the angle between the transverse
processes and the sides of the bodies of the vertebrae, it covers the
intervertebral foramina
– The lumbar plexus thus enters the psoas major and its branches
emerge from the surface of the muscle
– Passes with iliacus (iliacus arises from the inner surface of ilium) under
the inguinal ligament
• Insertion
– Lesser trochanter of femur fusing with iliacus (iliopsoas)
• Innervation
– L1, 2 and 3 inside the abdomen
• Action
– Acting inferiorly with iliacus, it flexes thigh
– Acting superiorly it flexes vertebral column laterally
– It is used to balance the trunk
– When sitting it acts inferiorly with iliacus to flex trunk
Iliacus
• Origin - Superior two thirds of iliac fossa,
ala of sacrum, and anterior sacroiliac
ligaments
• Insertion - lesser trochanter of femur
• Innervation - femoral nerve (L2-L4)
• Action - flexes thigh and stabilizes hip joint;
acts with psoas major
Iliopsoas
• Iliacus and psoas muscle
• Covered by dense layer of fascia so
that muscles and lumbar plexus are
behind fascia and iliac vessels are in
front of it
 Psoas
minor
• An occasional small
muscle belly with its
long tendon lying
over the psoas major
• Origin - transverse
processes and bodies
of T12 and L1
• Insertion - rim of
acetabulum
• Action - flexes lumbar
vertebrae
Quadratus lumborum
• Lies lateral to psoas, running between the
iliac crest and R12
• Origin - medial half of inferior border of 12th
ribs and tips of lumbar transverse processes
• Insertion - iliolumbar ligament and internal
lip of iliac crest
• Innervation - anterior branches of T12 and
L1-L4 nerves
• Action - extends and laterally flexes
vertebral column; fixes 12th rib during
inspiration