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
