Development of the Renal System Flashcards
What 3 systems develop craniocaudally?
Pronephros
Mesonephros
Metanephros
Where do the 3 systems develop from?
Intermediate mesoderm - either side of midline during gastrulation
- between paraxial and lateral plate mesoderm
Describe the Pronephros?
5-7 paired cervical segments of intermediate mesoderm produce nephric vesicles called nephrotomes
Describe nephrotomes?
Hollow epithelial balls
non-functional
formed in week 4 disappear by end
Describe mesonephros?
Wk4 thoracolumbar region
Mesonephric tubules from swellings
Mesonephric ridges either side of intermediate mesoderm
40 pairs produced craniocaudally
What forms 30 pairs?
Cranial regression during caudal diffrentiation
What happens in wk 5/6 to mesonephros?
Massive cranial regression leaves 20 pairs of lumbar mesonephric tubules
What are the mesonephric excretory units?
Menonephric tubules diffrentiatite into Bowmans capsule and glomerulas (from dorsal aorta)
What froms the MEU?
renal corpuscle and mesonephric tubule
What are the mesonephric wolffian ducts?
thoracic region wk.4
longitudial intermediate mesoderm rods condense dorsolaterally to mesonephric tubules
Grow caudally
diverge from intermediate mesoderm in lumbar region
Fuse with ventrolateral walls of cloaca by d.26 (future bladder)
Cavitate at distal end to produce lumen
Describe the MEU?
Lateral tips fuse with mesonephric duct
Allows passage from meu to cloaca
function in wk 6/10 for urine
Regress after wk10 - mesonephric regress in Female too
In male, mesonephric duct part of genital system SEED
Describe the Metanephros?
Formed in sacral by pair of urteric buds
describe ureteric buds?
sprout from distal mesonephric duct at wk4 end
Penetrate sacral intermediate mesoderm called metanephric blastema to encourage bifurcation of ureteric bud
What is the Ureteric growing tip called?
Ampulla
Caplike aggregation near ampulla brancing bud causes lobe formation seperate by sulcus
14-16 lobes formed by wk16
sulci eventually filled obscure lobulated appearance
What is the reciprocal interaction?
Diffrentiation of ureters and collecting ducts depend on metanephric blastema
Differentiation of nephrons depend on ureteric bud
What does the collecting system have?
Major calyx Minor Clayx (plurals)
Describe nephron formation?
Wk 6 metanephric tissue caps form around ampulla of bifurcating collecting ducts (embroyological distinct)
When do Distal tubules connect fully to collecting tubules?
Wk 10 - functional MEU
What is fetal urine function for?
Supplementing production of amniotic fluid
When is the normal ascent of kidneys?
Wk 9
Transient inferior arteries sometimes fail to regress causing accessory renal arteries (pelvic kidney, horseshoe kidney)
Describe Urinary tract formation?
Cloaca split by urorectal septum between wk 4 and 6 to form:
PUS (primitive urogenital sinus)
Rectum
What does superior part of PUS and allantois become?
The bladder
What does constricted pelvic urethra and membranous prostatic become?
Constricted - female urethra
Membranous - male urethra
What does the Distal part of PUS expand and become?
Vaginal vestibule in Females
Penile Urethra - males
Describe bladder formation?
Week 6 - root of mesonephric duct exstrophies into wall of bladder
Completed by week 12
What does mesonephric duct do to form the bladder?
Pushes the origin of ureteric buds into bladder walls creating ureteric openings
Opening of mesonephric duct to be pushed inferiorly to level of pelvic urethra
Exstrophied wall of mesonephric duct incorporated to bladder forming trigone
