Topographical anatomy of the urinary system Flashcards
Overview of the urinary system
Composed of kidneys, ureters, bladder and urethra
Posterior abdominal region: kidneys
and ureters
* Distal end of the ureters, bladder and
urethra are pelvic urinary organs
* Kidneys and abdominal part of the
ureters are retroperitoneal
Retroperitoneal structures
Structures that lies posterior to the parietal peritoneum
Peritoneum: it is a serous membrane supported by
connective tissue. It lines the innermost surface of
the abdominal walls.
Primary retroperitoneal
Structures that develop and are located
posterior to peritoneum (i.e. kidneys,
suprarenal glands, vessels)
- Presence of perinephric fat, which
protects the kidneys, along with the
peritoneum
The kidneys - surface anatomy
Function: to filtrate blood, the
result is the produced urine
▪ 2 kidneys
▪ Located at each side of the
vertebral column
▪ Levels T12-L3 vertebrae
▪ Right kidney located slightly lower
than the left
▪ Approximately 10 cm long, 5 cm
width, 2,5 cm thickness (left
kidney slightly longer than the R
and closer to the midline)
The kidneys - anatomical relationships
The right kidney
Anterior: suprarenal gland, liver, 2nd part of
duodenum, R colic flexure
Posterior: diaphragm, rib 12, psoas muscle,
quadratus lumborum, transversus abdominis,
subcostal nerve
The left kidney
Anterior: suprarenal gland, spleen, stomach,
pancreas, left colic flexure, descending colon,
jejunum
Posterior: diaphragm, ribs 11 and 12, psoas
muscle, quadratus lumborum, transversus
abdominis, subcostal nerve
The kidneys - anatomy
Red/brown fibrous capsule
▪ Hilum: renal vein, branches from the
renal artery, renal pelvis
▪ Lymphatic system around the
vessels
▪ The kidney consists of an outer renal cortex that
completely surrounds the inner renal medulla
▪ The renal cortex projects into the inner part of the kidney
forming renal columns.
▪ The renal columns divide the renal medulla into renal
pyramids
▪ The minor calyces receive urine from the papillary ducts
(openings at the renal papilla).
▪ 2 or more minor calices form a major calyx. 2-3 major
calices form the renal pelvis.
▪ Nephrons are the functional unit of the
kidney.
▪ Each human kidney contains 800,000 –
1,000,000nephrons
▪ The kidney cannot regenerate nephrons
following injuries/diseases etc.
▪ Nephrons that have glomeruli located in
the outer cortex are called cortical
nephrons
▪ About 20% to 30% of the nephrons have
glomeruli that lie deep in the renal cortex
near the medulla and are
called juxtamedullary nephrons.
▪ The vascular structures supplying the juxtamedullary nephrons differ from those supplying the
cortical nephrons.
▪ In the cortical nephrons the tubular system is surrounded by peritubular capillaries
▪ In the juxtamedullary nephrons, there are arterioles from the glomeruli into the outer
medulla and then divide in vasa recta. The vasa recta empties in the cortical veins. The
capillaries are what play a role in the concentration of urine.
The kidneys - renal arteries
Right and left renal arteries from aorta between L1-L2
level
▪ It usually divides into anterior and posterior branches
and then into segmental arteries that enter the hilum
▪ Right renal artery is longer than the left renal artery
▪ Arteries inside the kidneys: lobar arteries interlobar
arteries, arcuate arteries, afferent glomerular arterioles
The kidneys - veins and lymph
Renal veins empty into the IVC
▪ Left vein: longer than the right vein; passes
behind the splenic vein and body of the
pancreas
▪ L gonadal vein and L suprarenal vein joins the
L renal vein
▪ R renal vein passes behind the descending
duodenum
▪ Clinical correlation: the left vein is longer and
crosses the abdominal aorta anteriorly and is
posterior to the superior mesenteric artery. The
L renal vein can be compressed if there is an
aneurysm in any of those two vessels. This is
referred to as the Nutcracker syndrome.
▪ Lymph drains to the aortic nodes around the
origin of the renal artery
The kidneys - nerve supply
Innervation from renal
sympathetic plexus
* parasympathetic nerve
innervation via the vagus nerve
* sensory output from the
kidneys gets transmitted to the
spinal cord at the T10-T11 level
* Sympathetic cause
vasoconstriction – release
noradrenaline
The ureters
Ureters convey urine from the kidneys to the bladder
▪ They are muscular ducts long approximately 25-30 cm
long
▪ Urine is propelled by contractions of the ureter wall and
by filtration pressure from the glomeruli
▪ Abdominal part of the ureters is retroperitoneal
▪ They go from the hilus, over the psoas surface, crosses
the bifurcation at the common iliac artery at the sacroiliac joint, enter the bladder at the trigone
Three areas of constriction:
* At junction between the ureters and the renal pelvis
* Where the ureters cross the pelvic brim
* At the trigone where they enter the wall of the
bladder
→ Constrictions are important because they can be
sites of obstruction
Ureters - arteries and veins , lymph and nerves
▪ Blood supply changes along the length
of the ureters
▪ Proximal part: from renal artery
▪ Middle part: testicular or ovarian artery
▪ Lower portion: superior vesical artery
▪ Correspondence between arteries and
veins
▪ Proximal part of ureters, lymph to lateral
aortic nodes at L1
▪ Nerves are from renal, testicular/ovarian
and hypogastric plexuses
▪ Afferent fibres enters the spinal cord at
L1 and L2
The bladder - anatomical relations
▪ Located in the pelvis
▪ In children is in the abdomen
▪ Covered by peritoneum
▪ Located posterior to the pubic bones
▪ Has transitional epithelium and rugae
▪ Can hold up to 500 ml
▪ When full can raise above the pelvic
brim
▪ Base of bladder held by ligaments.
Neck held in place by puboprostatic
(male) and pubovesical (female)
ligaments
The bladder- anatomy
▪ The bladder has an apex, a base, a superior surface,
two inferolateral surfaces.
▪ Base of the bladder is triangular.
▪ Trigone: internal area of smooth mucous membrane.
▪ Trigone: area where ureter enter the bladder and the
urethra exits.
▪ Detrusor muscle: smooth muscle. Its contraction is
essential for emptying the bladder.
▪ Circular sphincter vesicae present at neck that is
continuous with detrusor muscle, referred to as
internal urethral sphincter. It is present in male
individuals, while its presence is debatable in female
individuals.
▪ External sphincter of the bladder is formed by skeletal
muscle and is present in the urogenital diaphragm.
This is voluntary skeletal muscle and consciously
prevents urination.
Bladder - arteries , veins , lymphatic drainage
▪ Arteries: 2 superior and 2 inferior vesical arteries for each R and L sides
▪ Inferior vesical arteries in males supply fundus and neck of the bladder
▪ In females the inferior vesical arteries corresponds to vaginal arteries and supply the fundus of the
bladder and the posterior region
▪ Veins: vesical plexus, drains into internal iliac vein
▪ Lymphatic drainage to internal iliac nodes
Bladder - nerve supply bladder
▪ Sympathetic innervation: hypogastric plexus and
nerve (T12-L2). Relaxation detrusor muscle and
promotes urine retention
▪ Parasympathetic innervation: nerve fibres from
sacral and spinal cord levels via splanchnic nerves
and inferior hypogastric plexus and pelvic nerve
(S2-S4). Motor to detrusor muscle, increased
signals cause contraction of the muscle and
stimulate micturition.
▪ Somatic innervation: pudendal nerve (S2-S4). It
innervates the external urethral sphincter and
provides voluntary control over micturition.
▪ Sensory afferent nerves are distributed in the
bladder wall and give signals when there is the
need to urinate.
The urethra
The urethra begins at the base of the bladder and ends
with an external opening in the perineum. The paths taken
by the urethra differ significantly in male and female
individuals.
Blood supply and veins
▪ In females:
- blood by the internal pudendal and vaginal arteries
- veins follow the arteries
- Innervation from the pudendal nerve and vesical nerve plexus
▪ In males:
- the intramural and prostatic parts of the urethra are supplied by the
prostatic branches of the inferior vesical and middle rectal arteries.
- The veins from the proximal two parts of the urethra drain into the
prostatic venous plexus.
- Innervation from the prostatic nerve plexus.
Lymphatic drainage: main drainage is to internal iliac node
▪ In males:
spongy urethra to deep inguinal nodes
▪ In females:
a small number of nodes drains to sacral nodes
