62: Urinary System Development Flashcards
(63 cards)
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
