Development of GU System Flashcards
Describe the derivation of the GU system
- from intermediate mesoderm
- grows into intraembryonic coelom to form urogenital ridge
- genital ridge medially and nephrogenic ridge laterally
What does the nephrogenic ridge give rise to?
- pronephros
- mesonephros
- metanephros
What are the components of a definitive kidney?
- collecting portion
- excretory portion
How is the collecting portion of a definitive kidney formed?
- ureteric buds sprout from caudal mesonephric ducts into metanephric mesenchymal cap
- the bud bifurcates to form a primitive renal pelvis
- subsequent generations form major and minor calyces
- continued divisions penetrate into metanephric tissue creating pyramidal arrangement
How is the excretory portion of a definitive kidney formed?
- metanephric caps cover collecting tubules
- induces the tissue cap to form vesicles that lengthen and are penetrated by capillaries at one end and the other end connects with collecting ducts
- further lengthening forms nephron
Describe the development of the kidneys after its components have been formed
- growth in lumbar and sacral regions cause kidney to change relative position superiorly
- rotate 90 degrees moving hilum medially
- aorta provides more branches to developing kidneys
What are some congenital abnormalities of the kidneys?
- horse shoe kidney: inferior poles fuse
- pelvic kidney: fails to rise from pelvis
Describe the development of the trigone
- ureteric and mesonephric ducts become incorporated into posterior walls of developing bladder
- ascent of kidneys and growth of ladder draws ureteric entry to bladder cranially aiding formation of trigone
Describe the development of the indifferent gonad
- primordial germ cells within yolk sac migrate by dorsal mesentery to intermediate mesoderm
- proliferating epithelium forms somatic supportive cells that envelope PGCs forming primitive sex cords
What is the function of sertoli cells in male development
- secrete AMH which causes degradation of paramesonephric duct
- stimulate gonadal ridge cells to form leydig cells that secrete testosterone
- testosterone induces formation of epididymis, vas deferens and seminal vesicles
- dihydrotestosterone induces male specific external genitalia development and prostate
What happens with persistent mullerian duct syndrome?
- mutations of AMH or AMH receptor genes
- no regression of paramesonephric duct
- presents with uterus, vagina and uterine tubes, testes ihn ovarian location and male external genitalia
Describe descent of testes
- pulled caudally by gubernaculum
- failure of one or both is called crytochidism
What are the male accessory glands derived from?
- prostate and bulbourethral glands: endodermal invaginations from urethra
- seminal vesicle: mesonephric duct
What is the role of thecal cells in female development?
- produce oestrogen which with maternal sources stimulates formation of female external genitalia and development of paramesonephric ducts
- give rise to uterine tubes, uterus and superior vagina
What are the 3 parts of the paramesonephric ducts in females?
- cranial portion: opens into coelomic cavity
- horizontal portion: crosses mesonephric duct
- caudal portion: fuses with paramesonephric duct on opposite side
