Lecture 1: Urinary System Embryology Flashcards
which structures compose the adult urinary system?
- kidneys: nephron, collecting duct, calyces and pelvis.
- ureter
- bladder
- urethra
- blood supply
which embryological tissue gives rise to the urogenital system (kidneys, reproductive)?
intermediate plate mesoderm
what is Allantois? what is its functions?
- Allantois is an outpouching of endoderm at the hindgut that extends into the body stalk.
- collects waste products of the embryo, in time the allantois grows into the umbilical cord/body stalk and therefore excretory products go out through the blood vessels and trhough the placenta of the maternal system.
what does the cloaca get divided into?
what is the cloaca?
- distal part of hindgut that serves as a common opening for the urinary system and the digestive system and when the reproductive system develops that also will be opening into this future cloaca.
what is the layer of mesoderm called that divides the cloaca into the rectum posteriorly and the urogenital sinus anteriorly?
urorectal septum
what does the urogenital sinus form?
- urinary bladder
- terminal bit forms the urethra
At birth, the allantois gets obliterated to form what?
the urachus
are the bladder and urethra formed from endoderm, mesoderm or ectoderm?
endoderm
discuss the development of pronephros
- early in the 4th week the intermediate mesoderm in the neck region of the embryo becomes the pronephros > 1st set of kidneys > pronephric kidneys.
- pronephros = pronephric duct + rudimentary pronephric tubules.
- pronephric duct dains into cloaca.
- in humans, the pronephros mainly degenerates by 5th week (except the pronephric duct).
discuss the development of the mesonephros
- by late 4th week, intermediate plate mesoderm in the trunk region of the embryo starts developing into the urinary system > mesonephros.
- pronephric duct now becomes the mesonephric duct.
- mesonephric tubules develop and drain into the mesonephric duct.
- mesonephric duct initially opens into the cloaca, but as division occurs it opens into the anterior urogenital sinus.
- mesonephros functions as the kidney for approx. 4 weeks to end of week 9.
discuss the devlopment of the metanephros/definitive kidneys
- the metanephros starts to develop from about week 5, but only starts to function around week 9.
- consists of: ureteric bud that comes off the mesonephric duct, metanephric mesoderm (the most caudal part of the intermediate mesoderm).
what happens to the mesonephros when the metanephros develops?
- Much of the mesonephros will be incorporates into the developing gonad (testes or ovary).
- In males, mesonephric tubules are going to form the tubules (rete testis) that carry the newly formed sperm to the spermatic cord.
- In males, the mesonephric duct becomes the spermatic cord = vas deferens.
- In females, the mesonephros becomes the ovary but the tubules and mesonephric duct degenerate. Paramesonephric ducts form fallopian tubes.
discuss the further development of the uteric bud
- the uteritic bud undergoes repeated branching at its distal end.
- the stalk becomes the ureter, the expanded cranial end becomes the renal pelvis.
- the metanephric mesoderm surrounds the uteric bud and forms the parenchyma of the kidney.
- the first 4 generations of branches become confluent to become the major calyces, the next four generations form the minor calyces.
- the remaining generations of branches form the collecting tubules.
what does the nephron develop from?
metanephric mesoderm
which congential abnormalities of the urinary system are illustrated?
A = congenital polycystic kidney
B = aberrant renal arteries (failure to degrade when kidney ascends)
C = lobulated kidney
D, E & F = transposition of kidney
G & H = horseshoe kidney
I = pancake kidney
