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Related Experiment Videos

Urinary concentrating processes in vertebrates.

B Schmidt-Nielsen

    The Yale Journal of Biology and Medicine
    |November 1, 1979
    PubMed
    Summary
    This summary is machine-generated.

    Mammalian kidneys use a specialized inner medulla to concentrate urea, unlike avian kidneys. The renal pelvis may help dilute medullary urea during increased urine flow, aiding kidney function.

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    Area of Science:

    • Comparative physiology
    • Renal physiology
    • Urea transport

    Background:

    • Avian and mammalian kidneys achieve urine hyperosmolarity via renal countercurrent systems.
    • Birds are uricotelic, excreting nitrogen as uric acid, while mammals are ureotelic, excreting nitrogen as urea.
    • Mammalian kidneys possess an inner medulla absent in avian kidneys, crucial for urea accumulation.

    Purpose of the Study:

    • To investigate the role of the mammalian inner medulla in urea accumulation.
    • To explore the relationship between urea accumulation, vascular bundle complexity, and cortical urea recycling.
    • To propose a model for urea recycling via vascular bundles and assess the function of the renal pelvis.

    Main Methods:

    • Comparative analysis of avian and mammalian kidney structures.

    Related Experiment Videos

  • Examination of urea accumulation in the inner medulla relative to vascular bundle complexity and cortical urea recycling index.
  • Development of a model for urea recycling through vascular bundles.
  • Correlation analysis of renal pelvis size with kidney structure and urea concentration.

    • Main Results:

    • Urea accumulation in the mammalian inner medulla is inversely related to vascular bundle complexity and cortical urea recycling.
    • A model for urea recycling via vascular bundles was proposed.
    • Renal pelvis size showed no correlation with vascular bundle type, cortical recycling index, or inner medullary urea accumulation.
    • Urine reflux into the renal pelvis occurs only during increased urine flow.

    Conclusions:

    • The mammalian inner medulla is key for concentrating urea.
    • The renal pelvis may facilitate urea reduction in the medulla during high urine flow by interacting with dilute urine.
    • Renal pelvis size might correlate with inner medullary volume, though other factors are implicated.