Chapter 28 Cont.
Evolution of the Kidney in Vertebrates
* Vertebrates have 2 kidneys
* On the back of the abdominal cavity
* Kidney has a
* Renal capsule
* Cortex (towards the outside)
* Medulla (towards the central region)
* Structure and function of kidneys can differ depending animal type and developmental stage * 3 kinds of vertebrate kidneys
* Adult hagfish & (embryos fish and amphibians) * Mesonephros
* Adult fish and amphibians & embryos of reptiles, birds, and mammals * Metanephros
* Adult mammals , adult reptiles & birds
* Mesonephric kidney
* Body fluid has lower ion concentrations
* Water tends to leave the fish causing dehydration.
* Drinks lots of saltwater, secrete ions through gills and excrete urine concentrated with ions. Freshwater Fish
* Most have a mesonephric kidney
* Body fluid h higher ion concentrations
* Water tends to enter the fish causing excess hydration. * Ions move out of fish
* Do not drink much water, absorb ions through gills and excrete large amounts of dilute urine. Amphibians
* Similar kidney to freshwater fish
* Take up ions and water in what they eat and drink, through skin and through the urinary bladder that balances what is lost by evaporation. * The urinary bladder is a water and ion storage site
Birds, Reptiles, and Mammals
* Have a metanephros kidney
* Can remove more water than other kidneys
* Primary organs for osmoregulation
* The functional unit is the nephron
* Begins with the glomerular capsule.
* An arteriole enters the glomerular capsule and branches into a network of capillaries called the glomerulus. * Efferent arteriole divides to form pertibular capillaries -> merge into a vein leading out of the kidney. * Proximal convoluted...
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