Kidney

Kidney Takehome Messages: - Kidney is derived from intermediate mesoderm - Uretic bud tip as a classical inducer - Reciprocal induction between bud tip and blastema - many growth factors are involved NEPHRON ANATOMY Urinephrous tubule: Urinephrous Tubule - Nephron – from blastema nephron, blastema - Collecting Ducts – from uretic bud of mesonephric duct mesonephric duct Nephron = renal corpuscle + proximal, distal tubules corpuscle corpuscle = Bowman’s capsule + glomerulus (capillaries) Bowman’s capsule, glomerulus Bowman’s capsule: visceral portion is lined w/ podocytes podocytes (parietal is ss epithelium) Glomerulus: thick basement membrane – filtration barrier basement membrane site of genetic disease vascular pore – where glomerular vessels enter corpuscle vascular pore urinary pore – where distal convoluted tubule leaves urinary pore Kidney DEVELOPMENT: PRONEPHROS – proneprhos mesenchymal  epithelial transition of intermediate mesoderm tube formation progresses anterior  caudal - duct induces adjacent mesenchyme to form pronephric pronephric tubules kidney tubules (no function in mammals) MESONEPHROS – mesonephros nephrogenic cord forms in the nephrogenic cord (separate from wolffian duct) mesonephric tubules = nephrotomes nephrotomes connected via mesonephric (WOLFFIAN) duct Wolffian Duct duct empties into urogenital sinus (bladder + urethra) Wolffian duct persists in male reproductive system METANEPHROS – metanephros ureteric bud emerges from Wolffian duct and grows dorsally ureteric bud eventually forms URETER and COLLECTING DUCTS induces mesenchyme to form nephrons nephrons then induce branching of bud (reciprocal ind.) reciprocal induction CLASSICAL INDUCTION – distal tip of ureteric bud induce BLASTEMA formation blastema blastema (aka nephron vesicle)  nephron tips of distal tubules eventually connect to collecting tubule RECIPROCAL INDUCTION – nephron-forming tissue induces branching of the bud leads to formation of 1-million nephrons blood vessels follow ureteric bud  glomeruli TERMINAL DIFFERENTIATION – tubules elongate epithelial cell polarity pump/channel expression Kidney BIOLOGY OF INDUCTION – requires CONTACT between metanephric mesenchyme and ureteric bud several growth factors, TF’s, and receptors are required 1) Intermediate mesoderm mesenchyme  epithelial tube: - they express several TF’s: Lim1, Pax2 LIM1 – necessary for mesenchyme  epithelial tube P