Urinary System- Kidney

Urinary System- Kidney  Overall function – Osmoregulation (water, salt) – Nitrogenous waste in tetrapods – Ammonia in amphibians – Urea in mammals – Uric acid in birds and reptiles – Note: uric acid in birds is 3000x more concentrated than blood! Kidney - Nephron  The functional unit of the kidney  Filters blood to make urine  Glomerulus is a network of permeable blood capillaries – Afferent glomerular arteriole – Efferent glomerular arteriole Kidney - Nephron Bowman’s capsule is a cup-shaped capsule around the glomerulus to catch filtrate  Renal corpuscle – Glomerulus plus the Bowman’s capsule since they function as a unit  Kidney - Nephron  Renal Tubules  Increase in complexity with higher vertebrates  Function to secrete substances directly from blood to tubule  Function for reabsorption from tubules back to bloodstream based on need Kidney - Nephron  ADH = Antidiuretic hormone promotes water reabsorption from renal tubules  Aldosterone – hormone that promotes sodium reabsorption from renal tubules and water passively follows  Renal tubules are countercurrent for maximum efficiency Key Points  Define countercurrent.  Look at the following picture and explain how countercurrent is advantageous. Kidney - Nephron  Peritubular capillaries pick up substances being reabsorbed from renal tubules  Common collecting tubule collects urine from all renal tubules Kidney  Longitudinal kidney duct – Carries urine to cloaca in all but placental mammals – Various names for this duct depending on group Kidney Types based on Embryology  Pronephros  Forms from intermediate mesoderm (mesomere) very far cranially  Renal tubules are temporary pronephric tubules  Pronephric duct carries urine to cloaca  Pronephric duct persists in anamniotes but changes its name to Mesonephric duct  Pronephros is the functional embyronic kidney in anamniotes Kidney Types  Mesonephros  Middle region of intermediate mesoderm  Longitudinal duct is Mesonephric duct (we called it archinephric duct in lab)  Functional embryonic kidney in amniotes  Adult kidney of anamniotes Kidney Types  Mesonephros – Mesonephric tubules invade testes and form the Vasa efferentia which carry sperm from testicle to mesonephric duct – Mesonephric duct carries sperm & urine in anamniotes – Mesonephric duct in amniotes will only carry sperm & is called the Spermatic Duct or Vas Deferens Mammalian Vasa Efferentia & Persistent Mesonephric Duct Kidney Types  Metanephros  Caudal-most intermediate mesoderm  Becomes the adult amniote kidney Kidney Types Metanephros – adult amniote kidney  Cortex –outer region  Medulla – inner region  – Pyramids – Papillae  Pelvis – slit-like funnel collecting urine from medulla Kidney Types Metanephros – adult amniote kidney  Ureter = Metanephric duct  Carries urine caudally  Urinary bladder  Cyclostomes & Elasmobranchs have none  Most fish have a widening of the mesonephric ducts that form the urinary bladder  Dipnoans have a bladder that is an outpocketing of the cloaca Urinary Bladder  Tetrapods have a urinary bladder that is an outpocketing of the cloaca  The urinary bladder then empties into the cloaca in all except placental mammals Urinary Bladder  The urinary bladder is formed from the embryonic membrane called the allantois  The remnant of the allantois is called the urachus which becomes an umbilical ligament Urinary Bladder  In mammals, the urinary bladder is drained by the URETHRA Urinary Bladder  Functions: – Water reservoir except placental mammals – Under ADH control – Holding tank in placental mammales – Pheromones – Marking territory Key Points  What are two roots that both mean kidney?  Can you live without one kidney? Can you live without two? Why or why not?