62: Urinary System Development Flashcards
Where does the Urinary System develop from?
Intermediate mesoderm & Urogenital sinus
Where is the intermediate mesoderm located?
between paraxial and lateral mesoderm; extends along dorsal body wall of the embryo
How does the development of kidneys begin?
as a longitudinal elevation of intermediate mesoderm on the
dorsal wall of the embryo
Urogenital ridge
Nephrogenic cord: gives rise to urinary components
Gonadal ridge: gives rise to genital system components
What are the 3 systems of the kidney during development?
Pronephros: rudimentary sequential systems
Mesonephros: functions very briefly during the early fetal period
Metanephros: forms the permanent kidney
Pronephros
Beginning of week 4
7-10 cell groups in the
cervical region
Forms vestigial excretory units = nephrotomes
Regress caudally & disappears by end of week
Mesonephros
Beginning of week 5
Excretory tubules appear, lengthen to form an S-shaped loop
Acquires a tuft of blood vessels medially; primitive glomerulus
tubules form the
bowman’s capsule
tubules elongate laterally, join w/ longitudinal collecting duct (mesonephric duct)
Ureteric bud
outgrowth of mesonephric duct covered by metenephric blastoma (cap)
forms primitive renal pelvis and splits into caudal and cranial portion (gives rise to major calyces)
Permanent Kidney
ureteric bud stalk forms ureter
diverticulum undergoes branching (major & minor calyces, & collecting tubules)
The end collecting
tubule divides and become arched
mesenchymal
cells form small metanephric vesicles which elongate to form S shaped
renal tubules
Capillaries grow into renal tubules, proximal ends invaginated by glomeruli
Lobulated Kidney
fetal kidney lobulated
lobulations disappear after birth b/c connective tissue growth, vascularity & increasing size of nephrons
if process fails, results in fetal lobulations after birth
When is nephron formation complete?
at birth
How many nephrons are in each kidney?
1-2 million in each
Excretory part of nephron
Bowman’s capsule, loop of Henle, Distal and Proximal Convoluted tubules
Where does Excretory part of nephron develop from?
From mesenchyme of the metanephric blastema
Conducting part of nephron
Collecting tubules, minor calyces, major calyces, pelvis
and ureter
Where does Conducting part of nephron develop from?
from the ureteric bud
What happens when the kidneys ascent?
initially hila face ventrally & get blood from branches of common iliac
embryo grows, kidneys higher in stomach
as kidneys “ascend”
they rotate medially
almost 90 degrees
What happens when the kidneys FURTHER ascent?
they are supplied by higher branches of aorta
renal arteries persist
week 9: kidneys reach suprarenal (adrenal) glands and reach final position
Accessory Renal Arteries
arise above or below main renal artery
cross over ureter at (lower pole) & can cause obstruction (hydronephrosis)
renal segmental arteries are end arteries
injury or ligation of
accessory artery leads to ischemia of segment supplied
Renal Agenesis
Early degeneration or failure of formation of the ureteric bud
Unilateral Renal Agenesis
common in boys
Left kidney usually absent
usually asymptomatic if Right kidney normal
Bilateral Renal Agenesis
Oligohydramnios (low amniotic fluid)
Pulmonary hypoplasia (underdeveloped lungs)
POTTER sequence (clubbed feet, pulmonary hypoplasia, and cranial anomalies)
Incompatible with post-natal life
Supernumerary Kidney
3 kidneys, very rare
two kidneys, two ureters: from 2 separate ureteric buds
two kidneys, one bifid ureter (double kidney): early and complete division of one ureteric bud
Horseshoe Kidney
1:500 births (common)
Fusion of lower poles while still in pelvis
Ascent interrupted at the inferior mesenteric artery
Ureters
starts at ureteropelvic jxn
travel along posterior abdominal wall
Blood supply of Ureters
Renal arteries
Abdominal aorta
Iliac arteries
3 Constrictions or Ureters
Ureteropelvic
junction (UPJ): At junction of ureters and renal pelvis
At point that ureters cross the brim of pelvic outlet
Ureterovesical junction (UVJ): During passage through wall of the urinary bladder
Female Ureter
“Water under the bridge”
ureter (water) crosses under uterine artery & vein (bridge)
Clinical significance: ureter can be accidentally clipped or cut during hemispherectomies
Male Ureter
“Water under the bridge”
ureter (water) crosses under gonadal artery & vein (bridge)
Crossed fused ectopia
Left kidney fused with right kidney (while in pelvis) then carried along ascent of right kidney
Urinary bladder
Muscular organ for collection of urine
Where is the bladder located?
posterior to the pubic symphyses area
Empty vs. Full bladder
Empty: 4-sided pyramid, resides in true pelvis
Full: ovoid, protrudes into abdominal cavity
Where is the apex of bladder attached?
to umbilicus by the median umbilical fold
What is the blood supply of bladder?
superior and inferior
vesicle artery
What is the lymphatic drainage of bladder?
external iliac nodes
Retropubic space
extra peritoneal space located between the pubic symphysis and the urinary bladder
Urinary bladder ligaments
pelvic fascia/loose connective
tissue
Pubovesical ligament (♀)
Puboprostatic ligament (♂)
Hold neck of
bladder in place & help
support/suspend bladder
Bladder Trigone
smooth area of the bladder in the nondistended state
Detrusor muscle
smooth muscle of bladder wall
relaxes to allow filling
contracts to empty
autonomic innervation (SNS relaxes, PSNS contracts)
Internal Urethral Sphincter
located at neck of the bladder
continuation of detrusor (smooth muscle)
autonomic innervation (SNS contracts, PSNS relaxes)
Sphincter Urethrae (external urethral sphincter)
located in deep perineal space
skeletal muscle
somatic innervation (pudendal nerve) - voluntary
Sensation of filling/fullness (stretch)
Afferents accompanying PSNS (pelvic splanchnics)
Infant bladders
no cortical control of the external sphincters or of the voiding reflex (automatic voiding)
Adult bladders
cortical control of external sphincters and voiding reflex is learned
Innervations of bladder
Parasympathetic from S2-4 (Pelvic splanchnic)
Sympathetic T10-12, L1&2 (Hypogastric plexus)
Visceral afferents for pain & distention travel with the parasympathetic nerves
Pudendal (S2- S4) somatic motor to the external urethral sphincter
Where area is the pain from the bladder referred to?
Perinuem
Where are the sympathetic
innervation to the
kidneys, ureters and
bladder are derived from?
lesser and least
thoracic and lumbar
splanchnic nerves
How do ureters receive their innervation?
Segmentally
What does the cloaca divide into?
urogenital sinus anteriorly and anal canal posteriorly which are divided by urorectal septum
Urogenital sinus
Upper: largest, forms bladder
Middle: give rise to prostatic and membranous portions of male urethra and entire female urethra
Phallic: differs b/n the sexes, forms most of penile urethra in males
How do the ureters enter the bladder during development?
caudal portion of mesonephric ducts are absorbed into wall of urinary bladder
Male urethra
divided into: prostatic, membranous and penile/spongy urethra
Female urethra
4 cm in length
membranous urethra
Ascending UTI
more common in women b/c of short urethra, proximity to vagina and anus, and intercourse (honeymoon cystitis)
Urethral catheterization
Inserting flexible tube through urethra
2 bends in urethra:
1st, spongy urethra (less painful)
2nd, membranous urethra (more painful)
can damage bulb of penis
Suprapubic catheterization
inserted through skin, 1 inch above pubic symphysis
general or local anesthetic
used for closed drainage
may be left in place for a time
sutured to the abdominal skin
Pros of Suprapubic catheterization
Lower incidence of urinary tract infection, ease of voiding naturally when catheter clamped, and ease of ambulation
Cons of Suprapubic catheterization
Initially inserted by physician
insertion site must be cleaned daily using
sterile technique
Suprarenal (Adrenal) glands
superomedial pole of each kidney surrounded by renal fascia
Blood supply of Suprarenal glands
superior, middle and inferior supra-renal arteries
Suprarenal vein (left empties into renal vein, right into IVC)
Innervation of Suprarenal glands
Preganglionic sympathetic innervation to medulla
Ureteric Orifices
openings of the ureter into the bladder
