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Renal Physiology

Renal Physiology. Biol 66. Function of the Kidney. Regulates the osmolarity of the blood fluids Keeps the osmolarity of the body fluids around 300 mOsm/L Reabsorption of water, salts, and essential nutrients (i.e. glucose, amino acids) Filters out waste (urea) from the blood.

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Renal Physiology

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  1. RenalPhysiology Biol66

  2. Functionof the Kidney Regulates the osmolarity of the blood fluids Keeps the osmolarity of the body fluids around 300 mOsm/L Reabsorption of water, salts, and essential nutrients (i.e. glucose, amino acids) Filters out waste (urea) from the blood

  3. The Kidney and Nephron

  4. The Nephron

  5. What Happens Where • Glomerulus • filters what goes into the urine, filters neutral substances up to 8nm in diameter, however this can vary for charged particles • Proximal convoluted tubule • Sodium, glucose, phosphate, amino acids, chloride, Bicarbonate, and water are reabsorbed • Descending Loop of Henle • Water is reabsorbed

  6. What Happens Where • Ascending Loop of Henle • Sodium is reabsorbed • Distal Convuluted Tubule • Sodium and water are reabsorbed • Water is reabsorbed in the collecting ducts

  7. Hormone Activation Sites

  8. Aldosterone (the RAA pathway) The Macula Densa (MD) cells of the juxtaglomerular (JG) apparatus sense a decrease in blood pressure by a decrease in sodium ion concentration The MD cells stimulate the JG cells to produce the enzyme renin, which converts angiotensinogen to angiotensin I Angiotensin I is converted to angiotensin II by the angiotensin-converting enzyme (ACE from lung tissue) Angiotensin II stimulates the release of Aldosterone Aldosterone stimulates Sodium reabsorption in the distal convoluted tubule by causing the fusion of sodium transporters to the membrane

  9. Vasopressin (ADH) In response to low blood pressure the hypothalamic neurons produces ADH which is carried down the axon to be secreted from the posterior pituitary into the bloodstream. ADH causes the insertion of aquaporins into the membrane of the collecting ducts This allows for the further reabsorption of water and an increase in blood pressure

  10. Atrial Natriuretic Hormone Released by cells in the right atrium in response to high blood pressure Causes the excretion of sodium and water into the urine which leads to a larger urine volume (proximal convoluted tubule) Antagonizes the effects of Aldosterone Leads to a decrease in blood pressure

  11. What We Will Examine Today Urine volume pH (~6-7) Sodium concentration (by looking at Chloride) (~7mg/ml) Specific gravity is the density of water, concentration of particles grams/ml (~1.02) Multistix Urine sediment

  12. The Chloride Test • Will give us a measure of the Sodium concentration in the urine • Chloride follows Sodium by electrostatic attraction • Want to convert from mg/100ml to mEq/L • First convert mg/100ml to molarity • Convert molarity to millimolarity • Since Chloride has -1 charge, multiply millimolarity by one to get mEq/L

  13. Multistix Analysis Nitrate-not normally found, associated with bacteria infection Urobilinogen- normal 0.2-1 mg/dl Protein-not normally found pH-about 6-7 Blood-not normally found Specific gravity-about 1.02 Ketone-from fat metabolism, negative is normal Bilirubin-not normally present Glucose-not normally present

  14. Urine sediment A few WBC’s are fine per field of view, any more may indicate an infection RBC’s should not be seen in urine, their presence may indicate renal disease A small number of casts are fine, but a lot may indicate disease A small number of crystals is normal, but a lot may indicate pathology

  15. Today’s Lab Collect urine at the start of the lab, note the time and volume Drink assigned water or saline load within 10 minutes On the first urine collection use the multistix, perform the chloride assay, determine specific gravity, pH, and spin down urine for sediment analysis Collect urine every 30 minutes

  16. Today’s Lab For each subsequent urine collection just determine the volume, the pH, the specific gravity, and the chloride ion concentration Get the specific gravity by the refractometer method and the urinometer

  17. Helpful hints for studying for the exam! Write down all results (for those presenting AND for yourself!) Identify the mechanisms that are occurring based on the test results. You should be able to identify what hormones are activated for each state and how those results (from tests) correlate! Who is the control?

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