Development of urinary tract Flashcards
What are the 3 stages in kidney development?
- Pronephros
- Mesonephros
- Metanephros
What is formed from the paraxial mesoderm?
- Dermis
- Axial and limb muscles
- Axial skeleton
What is formed from the intermediate mesoderm?
- The urinary system
- Nephros
- Urinary ducts
- Adrenal cortex
- Sex cords of gonads
What is formed from the lateral splanchnic mesoderm?
- Extra-embryonic mesoderm
- Mesothelium
- Cardiac tissues
- Connective tissues
- Blood vessels
- Stroma of gonads
What is formed from the lateral somatic mesoderm?
- Extra-embryonic mesoderm
- Mesothelium
- Appendicular skeleton
Describe the development of the nephros
- Intermediate mesoderm develops 2 bilaterally symmetrical sections from cranial to caudal, connected to coelomic cavity
- Activity shifts caudally as embryo develops, cranial sections atrophy, become less important
- Pronephros -> mesonephros -> metanephros
- Trail of destruction either atrophies completely or converted to other glands
Describe the structure, blood supply and fate of the pronephros in mammals
- Segmental
- Segmental drainage and blood supply
- Disappears completely in mammals
Describe the mesonephros
- Degenerates to form gonads
- Some cells rescued and form adrenal cortex
Describe the metanephros
- Has own duct, retained as true kidney
- Metanephric ducts become ureters, pelvis and collecting ducts
Describe the kidney development in fish and amphibians
- Pronephros replaced by mesonephros
- Mesonephros has reproductive and excretory elements in these animals
- Caudal region is true kidney
- Still segmental
- Cranial more reproductive function
- No metanephros
Describe the blood supply to the developing kidney
- Branches from dorsal aorta
- Segmentally paired for pro- and mesonephros
- Paired for metanephros
- Stimulates formation of nephric tubules
Outline the development of the nephric tubules
Intermediate mesoderm projects into coelomic cavity at Th/L region to form bilateral urogenital ridges
Outline the development of urinary ducts
- Holes in mesoderm, fuse to make tube
- Form within mesoderm, drains into cloaca
- Drain nephric tubules as the paired pronephric/mesonephric ducts
Describe the development of the mammalian kidneys
- Ducts grow towards metanephros (not towards cloaca from metanephros)
- Invasion of ducts into metanephros stimulates formation of nephrons
- Blood supply forms glomerular tufts
- Mesoderm forms Bowman’s capsule, proximal convoluted tubules, loops of Henle and distal convoluted tubules
- Ureteric duct forms collecting ducts, renal pelvis, ureter
Describe the formation of the final positions of the ureters and ductus deferentes
- Mesonephric duct becomes d. deferentes
- Wrapping of vas deferens leads to formation of trigone (inside of bladder)
- Meso and metanephric ducts separate
- mesonephric becomes fused with bladder, trail with mesonephric mesoderm embedded in bladder
- Opening does not move - the tube fuses to the bladder wall like plasticine
What forms the trigone of the bladder?
- Absorption of terminal ends of mesonephric ducts into bladder wall
- Trail of mesoderm left from the mesonephric ducts
- Rest of bladder derived from endoderm
Describe the development of the bladder and urethra from the urogenictal system
- Allantoic sac connects to bladder
- Root with gut divided by ureorectal septum to create hindgut and bladder
- Initially have combined excretory region as cloaca
- Split of rectum and bladder comes from behind
- Septum grows and divides (mesoderm grows, approaching cloacal membrane - not apoptosis)
Outline why the development of hte urinary system is closely associated with the development of the gonads
- Splanchnic mesoderm from lateral plate mesoderm forms stroma of gonads
- Germ cells of yolk sac migrate and embed on gonads
- Intermediate mesoderm forms nephros, urinary ducts, adrenal crotex and sex cords of gonads
- Mesonephric tubules and mesonephric ducts eventually become the gonads
Describe the development of the male testes
- Mesonephric tubules form the seminiferous tubules
- Mesonephric ducts form the ductus deferentes
- The paramesonephric duct regresses
- Supporting mesodermal cells
Describe the development of ovaries in the female
- Tubules and ducts regress
- Paramesonephric duct becomes ovarian duct and uterus
- supporting mesodermal cells
Compare development of the gonads in females and males
- Males have simpler routes of development
- Females develop new ducts rather than using old ones
- Connective tissue derived from regressing mesoderm
- In males develop tracts from parts not used anymore
Outline why the development of the urinary system is closely associated with the development of the adrenal gland
- Adrenal gland is merger of 2 endocrine organs
- Adrenal cortex derived from some of regressing mesonephric tubules
- Adrenal medulla derived from neural crest cells which migrate into centre of adrenal cortex
List some developmental defects of the urinary system
- Ectopic ureters Renal agenesis, dysplasia, hypoplasia - Polycystic kidney disease - Double ureters - Horseshoe kidneys - Renal ectopia - Failure of bladder closure - Cysts of mesonephric and paramesonephric ducts (no clinical significance, just embryological remnants)
What do the mesonephric tubules form in males?
The seminiferous tubules
What do the mesonephric ducts form in males?
The ductus deferentes
What happens to the paramesonephric ducts in males?
They regress
What happens to the mesonephric tubules and ducts in females?
They regress
What is formed from the paramesonephric ducts in females?
The ovarian duct and uterus
