Development Flashcards
common embryological origin of urinary and reproductive systems
intermediate mesoderm (lies lateral to paraxial mesoderm, which generates bone, muscle, and dermis)
kidney development order
pronephros -> mesanephros -> metanephros; present from cranial (pronephros) to caudal (metanephros)
pronephros: what is it, timeline
first kidney, in cervical region; develops during third week and regresses by fifth week; forms as single rod of IM, separates from IM and grows to and fuses w/ cloaca (day 26); cavitates to form pronephric duct; 4th week: pronephric duct induces IM to develop pronephric vesicles (5-7 paired segments of IM give rise to small epithelial hollow balls); these vesicles become excretory units in lower vertebrates but disappear by day 25 in mammals, while the duct never fully degenerates
mesonephros: what is it, timeline
second kidney, in upper thoracic to 3rd lumbar region (caudal to pronephros); present from third-fourth week to 5th-12th week and can form urine by the 5th week (passage of urine occurs to cloaca during weeks 10-14); regress in females, become vas deferens and efferent ducts of testes in males
metanephros: what is it, timeline
third (and final) kidney; nephrogenesis begins at week 5 and ends by week 36 (poss after birth in premie), although growth/differentiation/remodeling continues after nephrogenesis ends at week 36; functional by week 10 (produces amniotic fluid)
signaling of metanephric development
Pax2 (TF) in metanephric mesenchyme causes metanephric mesenchyme to secrete GDNF; GDNF acts on ureteric bud c-RET-GFR receptor to initiate invasion of the metanephric mesenchyme by the ureteric bud (c-RET-GFR incr Wnt 11, which has positive feedback on GDNF in metanephros); after invasion, ureteric bud undergoes branching (T stage); branching is inhibited by BMP4 (expressed in sleeve of mesenchymal cells adjacent to ureteric epithelium), which is inhibited by GREM1 at the site of uretericbudding
ureteric bud branching
first 4 bifurcations of ureteric bud generate 16 branches, which coalesce to form 3-5 major calyces; the next 4 rounds of bifurcations generate 16 branches, which again coalesce to form minor calyces; the remaining bifurcations generate the collecting ducts
CAKUT
congenital abnormalities of the kidney and urinary tract
kidney ascension timing
kidneys ascend between 6th and 10th week, and their vasculature ascends with them
hypoplastic kidneys
small kidneys w/ fewer calyces and fewer nephrons but retain a moderate degree of excretory fn (discrete renal pelvis is present)
cystic dysplastic kidneys
contain malformed tubules and small cysts but retain some excretory fn (discrete renal pelvis is present)
multicystic dysplastic kidney (MCDK)
no useful excretory fn, pelvis is absent or severely disorganized; often undergo apoptosis and reabsorption
Potter syndrome: etiology (3), sx (3)
due to oligohydraminios, which can be due to bilateral renal agenesis (20% Potter syndrome), obstruction of UT, or prolonged rupture of membranes; sx: pulm hypoplasia (this not compatible w/ postnatal life), limb deformations, Potter facies
ADPKD gene
polycystin 1 and 2; part of cilia -> mutation leads to loss of cell cycle regulation and apical-basal polarity
ADPKD vs ARPKD: frequency, age, cyst areas, other probs (3 in AD, 3 in AR)
ADPKD much more common, onset at adulthood, causes cysts in all nephron segments, and also has cysts in liver and pancreas, systemic HTN, and cerebral/aortic aneurysms; ARKPD is less common, onset in infancy/childhood, causes cysts only in CD, and also leads to biliary dysgenesis and hepatic fibrosis as well as portal and systemic HTN
