Anatomy of Urinary System Urinary System Organs Kidneys (2) Ureters (2) Urinary bladder Urethra Kidney Functions Control blood volume and composition. Filter blood plasma, eliminate wastes. Regulate blood volume, pressure, and fluid osmolarity. Secrete renin and erythropoietin (EPO). Regulate PCO2, acid-base balance. Synthesize calcitriol (Vitamin D). Detoxify free radicals and drugs. Perform gluconeogenesis. Kidney Anatomy Renal Fascia: Attaches to the abdominal wall. Adipose Capsule: Provides fat cushioning for the kidney. Renal Capsule: Fibrous sac that protects from trauma and infection. Renal Sinus: Contains blood vessels, lymphatics, nerves, and urine-collecting structures. Renal Parenchyma: Outer Cortex Inner Medulla Renal Pyramids: Extensions of cortex dividing medulla. Renal Columns: Connect cortex and medulla. Renal Pelvis: Collects urine from pyramids. Ureter: Carries urine to the bladder. Remember, the kidneys play a crucial role in maintaining homeostasis by regulating fluid balance, electrolytes, and waste elimination. Ureter Anatomy Overview The ureters are bilateral, muscular, tubular structures responsible for transporting urine from the kidneys to the urinary bladder for storage and eventual excretion. After blood filtration in the kidneys, the filtrate undergoes reabsorption and exudation along the convoluted tubules. The urine then passes through the collecting tubules and enters the collecting ducts. From the collecting ducts, it flows through the calyces into the renal pelvis, marking the beginning of the ureters. Histology of Ureter The lumen of each ureter is lined by a mucosal layer of urothelium (transitional epithelium). The ureteral wall contains two muscular layers: Longitudinal layer Circular layer In the lower segment of the ureters, an additional longitudinal layer is found proximal to the bladder. Urine is propelled along the ureters by peristaltic motions initiated by pacemaker cells in the proximal renal pelvis. Relations Both ureters pass inferiorly over the abdominal surface of the psoas major muscle. The right ureter travels posterior to the duodenum and is crossed by branches of the superior mesenteric vessels. The left ureter is also posterior to the psoas major and is crossed by branches of the inferior mesenteric vessels. Posterior Abdominal Wall Construction Bony: Extends from the 12th rib above to the pelvic brim below. Muscular part: Composed of muscles and fasciae. Fasciae: Provides stability and support for retroperitoneal organs, vessels, and nerves. Remember, understanding the anatomy of the ureter and posterior abdominal wall is essential for clinical pracPosterior Abdominal Wall Construction Bony: Extends from the 12th rib above to the pelvic brim below. Muscular part: Composed of muscles and fasciae. Fasciae: Provides stability and support for retroperitoneal organs, vessels, and nerves. Muscles of Posterior Abdominal Wall Psoas Major: Origin: Continuously attached from T12 (lower border) to L5

1. ANATOMY OF THE KIDNEY, URETER & POSTERIOR
ABDOMINAL WALL
MWANGI K.J

2.  By the end of the lecture, the student should be able to describe the:
1. Anatomical features of the kidneys:
 position, extent, relations, hilum, peritoneal coverings.
 Internal structure of the kidneys: Cortex, medulla and renal sinus.
 The vascular segments of the kidneys.
 The blood supply and lymphatics of the kidneys
2. Anatomy of suprarenal gland
3. Anatomy of posterior abdominal wall
Objectives

3. POSITION OF THE KIDNEYS
• Kidneys are retroperitoneal paired organs.
• Each kidney lies on the posterior abdominal
wall, lateral to the vertebral column
• In the supine position, the kidneys extend from
approximately T12 to L3.
• The right kidney is slightly lower than the left
kidney because of the large size of the right
lobe of the liver.
• With contraction of the diaphragm during
respiration, both kidneys move downward in a
vertical direction (high of one vertebra, 1 inch,
2.5 cm).

4. POSITION OF THE KIDNEYS
Location of the kidneys:
• surface projection in relation to the anterior
abdominal wall.
• The figure in the inset on the right shows
the vertebral levels of the kidneys.
• Note the transpyloric plane (TPP) passes
through the upper part of the hilum of the
right kidney and the lower part of the hilum
of the left kidney

5. • The kidney is a reddish brown, bean-shaped organ
with the dimensions 12 x 6 x 3cm.
• Although they are similar in size and shape, the left
kidney is slightly longer and more slender than the
right kidney, and nearer to the midline.
• Each kidneys has:
Convex upper & lower ends.
Convex lateral border.
Convex medial border at both ends, but its middle
shows a vertical slit called the hilum.
Internally the hilum extends into a large cavity called the
renal sinus.
Hilum
Renal
sinus
Color, Shape & Dimensions
Renal sinus

6. HILUM & RENAL SINUS
• The hilum transmits, from anterior to posterior,
the renal vein, renal artery & the ureter (VAU).
• Lymph vessels & sympathetic fibers also
pass through the hilum.
• The renal sinus contains the upper expanded
part of the ureter called the renal pelvis.
• Perinephric fat is continues into the hilum and
the sinus and surrounds all these structures.
V
A
U

7. COVERINGS
1. Fibrous capsule:
Is closely adherent to its surface
2. Perirenal fat:
covers the fibrous capsule.
3. Renal fascia:
Condensation of areolar connective tissue that
lies outside the Perirenal fat and encloses
the kidney and the suprarenal gland.
4. Pararenal fat:
Lies external to the renal fascia, is part of the
retroperitoneal fat.
The last 3 structures support the kidneys and
hold it in position on the posterior abdominal wall.

8. RELATIONS
I- ANTERIOR
The anterior surface of both
kidneys are related to
numerous structures, some
with an intervening layer of
peritoneum
and others lie directly against
the kidney without peritoneum.

9. Left kidney:
• A small part of the superior pole, along the
medial border , is covered by left
suprarenal gland.
• The rest of the superior pole is covered by
the intraperitoneal stomach and spleen.
• The retroperitoneal pancreas covers the
middle part of the kidney.
• Its lower lateral part is directly related to the
left colic flexure and beginning of
descending colon.
• Its lower medial part is covered by the
intraperitoneal jejunum.

10. right kidney
• A small part of the upper pole is covered by
right suprarenal gland.
• The rest of the upper part of anterior surface is
related to the liver and is separated by a layer of
peritoneum.
• The 2nd part of duodenum lies directly in front
of the kidney close to its hilum.
• The lower lateral part is directly related to the
right colic flexure and, on its lower medial side,
is related to the intraperitoneal small intestine.

11. • Right Kidney:
• Diaphragm
• Costodiaphragmatic recess, of
the pleura
• 12th rib, last intercostal space
• Psoas major
• Quadratus lumborum,
transversus abdominis.
• Subcostal (T12),
iliohypogastric & ilioinguinal
nerves.
Left kidney:
Diaphragm
Costodiaphragmatic recess of the
pleura
11th & 12th ribs; last intercostal
space
Psoas major
Quadratus lumborum transversus
abdominis.
Subcostal (T12),
iliohypogastric & ilioinguinal nerves.
Posteriorly, the right and left kidneys are almost related to similar structures.
Posterior Relations

12. VERTEBROCOSTAL & RENAL
ANGLES
• The angle between the last rib and the
lateral border of erector spinae
muscle is occupied by kidney and is
called the ‘Renal angle’
• The Vertebrocostal angle is occupied
by the lower part of the pleural sac.
E
r
e
c
t
o
r
s
p
i
n
a
e
Renal angle
Vertebro-
costal angle

13. INTERNAL STRUCTURE
 Each kidney consists of an outer renal cortex
and an inner renal medulla.
 The renal cortex is a continuous band of pale
tissue that completely surrounds the renal
medulla.
 Extensions of the renal cortex, the renal
columns project into the inner aspect of the
kidney, dividing the renal medulla into
discontinuous aggregations of triangular-
shaped tissue, the renal pyramids.
Renal column Renal
pyramid
Medulla
Cortex

14.  The bases of the renal pyramids are
directed outward, toward the cortex,
while the apex of each renal pyramid
projects inward, toward the renal
sinus.
 The apical projection (renal papilla)
is surrounded by a minor calyx
 In the renal sinus, several minor
calices unite to form a major calyx,
and two or three major calices unite
to form the renal pelvis, which is the
funnel-shaped superior end of the
ureters.
Base Apex, Renal papilla
Minor
calyx
Major
calyx
Renal
pelvis

15. ARTERIAL SUPPLY
 The renal artery arises from the aorta at the
level of the second lumbar vertebra.
 Each renal artery divides into 5 segmental
arteries that enter the hilum of the kidney, 4 in
front of the renal pelvis and one behind it.
 They are distributed to the different
segments of the kidney.
 Each segmental artery gives rise to number of
lobar arteries, each supplies a renal pyramid.
 Before entering the renal substance, each
lobar artery gives off two or three interlobar
arteries.
Segmental
arteries
Interlobar
arteries
Lobar
arteries

16.  The interlobar arteries run toward
the cortex on each side of the renal
pyramid.
 At the junction of the cortex and the
medulla, the Interlobar arteries give
off the arcuate arteries, which arch
over the bases of the pyramids.
 The arcuate arteries give off several
interlobular arteries that ascend in
the cortex and give off the afferent
glomerular arterioles.
Arcuate arteries
Interlobular
arteries
Interlobar
arteries

17. SEGMENTAL BRANCHES & VASCULAR
SEGMENTS OF KIDNEYS
• Each kidney has 5 segmental branches
and is divided into 5 vascular segments:
1. Apical.
2. Caudal.
3. Anterior Superior.
4. Anterior Inferior.
5. Posterior.
1
5
2
3
4
5
4
3
2
1

18. BLOOD SUPPLY
• Abdominal aorta
• Renal artery
• Segmental arteries
• lobar arteries
• Interlobar arteries
• Arcuate arteries
• Interlobular arteries
• afferent glomerular arterioles
 Inferior vena cava
 Renal vein
 Interlobar veins
 Arcuate veins
 Interlobular veins

19. VENOUS DRAINAGE
 Both renal veins drain to the inferior vena cava.
• The right renal vein is behind the 2nd part of the
duodenum and sometimes behind the lateral part of the
head of the pancreas
• The left renal vein is three times longer than the right
(7.5 cm and 2.5 cm).
• So, for this reason the left kidney is the preferred side for
live donor nephrectomy.
• It runs from its origin in the renal hilum, posterior to the
splenic vein and the body of pancreas, and then
across the anterior aspect of the aorta, just below the
origin of the superior mesenteric artery.
• The left gonadal vein enters it from below and the left
suprarenal vein, usually receiving one of the left inferior
phrenic veins, enters it above but nearer the midline.
• The left renal vein enters the inferior vena cava a little
above the right vein.

20. Nerve Supply:
The nerve supply is the renal sympathetic plexus. The afferent fibers that travel through
the renal plexus enter the spinal cord in the 10th, 11th, and 12th thoracic nerves.
Lymphatic Drainage:
• The lymph vessels follow
the arteries.
• Lymph drains to the lateral
aortic lymph nodes around
the origin of the renal artery.

21. MICROSCOPIC STRUCTURE
 Histologically, each kidney consists of 1 to 3 millions
of uriniferous tubules.
 Each uriniferous tubule consists of 2 components::
 nephron
 collecting tubule
 The nephron is the structural and functional unit of
kidney..
 Each nephron consists of a glomerulus and a tubule
system.
 The glomerulus is a tuft of capillaries surrounded by
Bowman’s capsule

22.  The tubular system consists of the proximal convoluted
tubule, loop of Henle, and distal convoluted tubule.
 Each collecting tubule begins as a junctional
(connecting) tubule from the distal convoluted tubule.
 Many collecting tubules unite together to form collecting
duct (duct of Bellini) which opens on the apex of renal
papilla.
 The collecting tubules radiate from the renal pyramid into
the cortical region to form radial striations called
medullary rays
MICROSCOPIC STRUCTURE

23. URETER
 The ureter is a narrow, thick-walled,
expansile muscular tube which conveys
urine from the kidney to the urinary
bladder.
 The urine is propelled from the kidney to
the urinary bladder by the peristaltic
contractions of the smooth muscle of the
wall of the ureter
 Measurements
 Length: 25 cm (10 inches).
 Diameter: 3 mm

24. COURSE AND RELATIONS OF THE URETERS
 The ureter begins as a downward continuation of a funnel-shaped
renal pelvis at the medial margin of the lower end of the kidney.
 It passes downward and slight medially on the psoas major, which
separates it from the transverse processes of the lumbar
vertebrae & enters the pelvic cavity by crossing in front of the
bifurcation of the common iliac artery at the pelvic brim in front of
the SAJ.
 In the pelvis, the ureter first runs downward, backward,& laterally
along the anterior margin of the greater sciatic notch.
 Opposite to the ischial spine, it turns forward and medially to
reach the base of the urinary bladder, where it enters the bladder
wall obliquely

25. COURSE AND RELATIONS OF THE URETERS

26. ANTERIOR RELATIONS OF THE ABDOMINAL PARTS OF THE URETERS

27. SITES OF ANATOMICAL NARROWINGS/
CONSTRICTIONS
1. At the pelviureteric junction where the renal pelvis joins
the upper end of ureter. It is the upper most constriction,
found approximately 5 cm away from the hilum of kidney.
2. At the pelvic brim where it crosses the common iliac
artery.
3. At the uretero-vesical junction (i.e., where ureter enters
into the bladder).

28. ARTERIAL SUPPLY
 The ureter derives its arterial supply from the branches of
all the arteries related to it. The important arteries
supplying ureter from above downward are :
1. Renal.
2. Testicular or ovarian.
3. Direct branches from aorta.
4. Internal iliac.
5. Vesical (superior and inferior).
6. Middle rectal.
7. Uterine

29. NERVE SUPPLY
1. The sympathetic supply
 derived from T12–L1 spinal segments through renal, aortic, and hypogastric plexuses.
2. The parasympathetic supply
 From S2–S4 spinal segments through pelvic splanchnic nerves.

30. SUPRARENAL (ADRENAL GLANDS)

31.  It is a pair of endocrine glands situated on the
upper poles of the kidneys
 It is closed in the same fascial sheath as that of
kidneys (renal fascia).
 Each gland consists of two parts:
a) a relatively thick outer cortex which develops
from the mesoderm (mesodermal lining of the
peritoneal cavity)
b) a central medulla which develops from the
neural crest and is equivalent to a group of
sympathetic ganglion cells
SUPRARENAL (ADRENAL) GLANDS

32. SUPRA RENAL GLANDS
 The cortex secretes a considerable number of
steroid hormones which are responsible for:
1. Controlling electrolyte and water balance.
2. Maintaining blood sugar concentration.
3. Maintaining liver and muscle glycogen
stores.
4. Controlling inflammatory reactions.
The medulla is composed of large granular
chromaffin cells which secrete adrenaline and
noradrenaline (catecholamines)

33. POSTERIOR ABDOMINAL WALL
MWANGI KJ

34. EXTENT OF POSTERIOR
ABDOMINAL WALL
 It extends from the 12th rib above to the pelvic
brim below.
 It is strong and stable because it is constructed by
bones, muscles, and fasciae.
 It supports retroperitoneal organs, vessels, and
nerves

35. PARTS OF POSTERIOR ABDOMINAL WALL
 It is formed by:
1. Bony part:- In the median plane - Composed of bodies, intervertebral disc, and transverse
processes of the 5 lumbar vertebrae.
2. Muscular part:
 Above the iliac crest, from medial to lateral sides, it is made up of psoas major, quadratus
lumborum, and transversus abdominis muscles.
 Below the iliac crest on either side of the lumbar vertebral column from medial to lateral
sides, it is made up of psoas major and iliacus muscles
3. Fasciae: The psoas major and iliacus muscles are covered by fascia iliaca. The quadratus
lumborum is enclosed between the anterior and posterior layers of the thoracolumbar fascia

36. PARTS OF POSTERIOR ABDOMINAL WALL

37. STRUCTURE TO BE STUDIED IN THE POSTERIOR ABDOMINAL
WALL
1. Muscles and fasciae of the posterior abdominal wall.
2. Great vessels of the abdomen (e.g., abdominal aorta and inferior vena
cava
3. Azygos and hemiazygos veins.
4. Lymph nodes and lymphatics of the posterior abdominal wall.
5. Nerves of the posterior abdominal wall

38. 1. MUSCLES OF POSTERIOR ABDOMINAL WALL
 Diaphragm
 Psoas major
 Psoas minor
 Quadratus lumborum
 Transversus abdominus
 Iliacus

39. 1. MUSCLES OF POSTERIOR ABDOMINAL WALL

40. 1. MUSCLES OF POSTERIOR ABDOMINAL WALL

41. PSOAS MAJOR
Origin
 Intervertebral discs, adjoining bodies of T12-
L5 vertebrae
 Medial half, anterior aspect of five lumbar
transverse processes
 Fibrous arches on the sides of the bodies of
the four upper four lumbar vertebrae, over
four lumbar arteries
Inserted into the lesser trochanter of femur
 Nerve L2,3

42. PSOAS MINOR
 Minor
 Origin
 T12 – L1
 Insertion
 Arcuate line
 Iliopubic eminence

43. PSOAS MAJOR MUSCLE AND FASCIA
 The psoas is covered by fascia which is
attached medially to the lumbar vertebrae
 To the fibrous arches
 Medially along the brim of the pelvis to the
arcuate and pectineal lines.
 Laterally, the fascia is attached to the
transverse processes of the lumbar vertebrae.
 Medial arcuate ligament is a thickening of fascia
over the psoas

44. RELATIONS OF PSOAS MAJOR MUSCLE
 It is a key muscle & relations provide the layout of structures in this region:
1. Lumbar plexus forms within the substance of psoas.
2. 5 nerves emerge from underneath the lateral border of the psoas major from above downward as follows:
a) Subcostal nerve.
b) Iliohypogastric nerve.
c) Ilioinguinal nerve.
d) Lateral cutaneous nerve of thigh.
e) Femoral nerve.
3. 1 nerve (genitofemoral nerve) runs downward on the front of the psoas major & sometimes may be mistaken for the
tendon of psoas minor muscle.
4. 3 important structures lying on the medial side of the psoas major. From medial to lateral side are: (a) lumbosacral
trunk, (b) iliolumbar artery, and (c) obturator nerve

45. RELATIONS OF PSOAS MAJOR MUSCLE

46. FASCIAE OF THE POSTERIOR ABDOMINAL WALL
 The fasciae of posterior abdominal wall are:
1. Psoas fascia – form psoas sheath.
2. Fascia iliaca.
3. Thoraco-lumbar fascia.

47. PSOAS SHEATH
 The psoas major muscle is enclosed in a fascial sheath called (psoas sheath) formed by the psoas
fascia.
 The attachments of psoas fascia are as follows:
 Above: It is thickened to form medial arcuate ligament, which extends from the body of L1 vertebra
to the tip of its transverse process.
 Laterally: It blends with the anterior layer of the thoracolumbar fascia.
 Medially: It is attached to the bodies and intervening intervertebral discs of lumbar vertebrae and
presents four tendinous arches.
 Below: It fuses with the arcuate line of the pelvis and the fascia covering the iliacus muscle (iliac
fascia)

48. CLINICAL CORRELATE
PSOAS ABSCESS:
• Tubercular infection of vertebrae of the thoraco-
lumbar region causes destruction of their bodies
leading to the formation of an abscess.
• The pus cannot spread anteriorly due to anterior
longitudinal ligament. Therefore, it spreads laterally
into the psoas sheath forming psoas abscess.
• The pus can also enter the psoas sheath from the
posterior mediastinum through a gap deep to medial
arcuate ligament. Pus may then spread downward
along the psoas muscle, under the inguinal ligament
into the femoral triangle where it produces a soft
swelling

49. QUADRATUS LUMBORUM

50. GREAT VESSELS OF THE ABDOMEN
 Are:
 1. abdominal aorta
 2. inferior vena cava

52. BRANCHES OF THE ABDOMINAL AORTA

53. CLINICAL CORRELATE
1. Pulsations of the abdominal aorta: - felt in the median
plane on the anterior abdominal wall at the level of L4
vertebra.
2. Aortic aneurysm -localized dilatation of the aorta
commonly occurs below the origin of the renal arteries
(95%) usually in elderly men. Most common cause is
atherosclerosis, which weakens the aortic wall.

55. NERVES OF POSTERIOR ABDOMINAL WALL