Kidney Overview

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  • Kidney Overview
    • The kidneys filter blood to excrete waste as urine and maintain appropriate solute and water concentrations throughout the body. 
    • Mechanism (broadly)
      • Filtration
      • Reabsorption
      • The kidneys throw out almost everything indiscriminately (filtration), then selectively taking back what it wants (reabsorption)
    • Roles
      • Waste removal
        • Elimination of nitrogenous waste, including urea, uric acid, ammonia, and phosphate in urine
      • Blood volume (pressure) control
        • via solute reabsorption
          • Na+ reabsorption is coupled to water (and Cl-), thereby affecting blood volume
        • Regulated by RAAS system
          • Renin released in response to low blood pressure
      • Blood osmolality control
        • via water reabsorption
          • ADH regulates water reabsorption in collecting ducts
      • Acid/base balance
        • via bicarbonate reabsorption and H+ (acid) secretion
    • Composed of:
      • outer cortex
      • inner medulla 
        • More “salty”, or higher in osmolarity
    • Functional unit is the nephron