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Excretion in Humans (part 3): The two functions of the kidneys & kidney failure

Students should be able to: <br>- outline the role of anti-diuretic hormone (ADH) in osmoregulation<br>- outline the mechanism of dialysis in the case of kidney failure

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Excretion in Humans (part 3): The two functions of the kidneys & kidney failure

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  1. 2 Functions of kidneys 1. Formation of urine (excretory function) 2. Osmoregulator

  2. Kidneys as Osmoregulators • Water potential of the blood must be kept relatively constant High Water Potential Red Blood Cells will burst Water enters cells Cells and tissues becomes dehydrated and shrink (flaccid) Low Water Potential Water leaves cells

  3. Kidneys as Osmoregulators…. Water potential in blood is influenced by: - 1. Concentration of salts in plasma 2. Amount of water in plasma Therefore, the water potential is controlled by controlling the amount of water in the plasma via the kidney •

  4. Kidneys as Osmoregulators…. • The amount of water/water potential is controlled by a hormone named: - • Vasopressin or Anti- diuretic hormone (ADH) • ADH is produced by the posterior pituitary gland

  5. Kidneys as Osmoregulators…. • ADH regulates the water reabsorption in the kidney tubules Secrete More ADH Water potential decreases Pituitary Gland Kidney tubules reabsorb more water Loss of water from body Less Urine is Produced Water Potential Returns to Normal

  6. Kidneys as Osmoregulators…. Secrete Less ADH Water potential increases Pituitary Gland Kidney tubules reabsorb less water Large Intake of Water More Urine is Produced Water Potential Returns to Normal

  7. Kidney Failure Several causes: • Diabetes • High blood pressure (hypertension) • Inherited kidney disease (linked to genetics) • Kidney stones • Infections • Abuse of painkilling drugs top 2 causes

  8. Kidney Failure • Diabetes - A medical condition that keeps the body from utilising sugar in a normal manner. If sugar is not broken down, it acts as poison and damages the blood vessels in the kidney. • High Blood Pressure - Can damage the small blood vessels in the kidneys. When this happens, the blood vessels cannot filter toxins from the blood.

  9. The Dialysis Machine • It is also known as “artificial kidney”. • It is used to cleanse the blood of a person whose kidneys do not work (one can survive with a kidney). • It eliminates the excess salts and nitrogenous waste from the patient’s blood. http://students.sahs.uth.tmc.edu/Ssadeghi /images/Hemodialysis.jpg

  10. How a Dialysis Machine Works (1) It consists of a long cellulose tube coiled up in a water bath. • Blood from an artery in the arm of the patient flows through the tubing in the dialysis machine. (Note: Tubing is partially permeable to allow diffusion of small molecules (e.g. urea) into the dialysis fluid. • Tubing is narrow, long & coiled to increase surface area: volume ratio → speeds up rate of exchange of substances)

  11. How a Dialysis Machine Works (2) • The dialysis tubing is bathed in dialysis fluid contains essential salts for the body. • A diffusion gradient is set up so that the waste products diffuse from the patient’s blood into the dialysis fluid.

  12. Scheme of partially permeable membrane during hemodialysis, where red is blood, blue is the dialysing fluid, and yellow is the membrane.

  13. How a Dialysis Machine Works (3) • The temperature of the dialysis fluid is maintained at body temperature. • The filtered blood is returned to a vein in the patient’s arm. • Patient needs to be treated 2-3 times a week & each treatment takes several hours.

  14. Removal of CO2from the Lungs Aerobic respiration C6H12O6 + 6O2 6CO2+ 6H2O + Energy diffuses into the blood plasma Carried in the form of “hydrogen carbonate ions (HCO3-)” blood passes through the lungs In the Lungs, CO2 concentration is low, convert hydrogen carbonate CO2+ H2O

  15. Removal of CO2from the Lungs hydrogen carbonate convert CO2+ H2O diffuses out of the blood capillaries into the alveolar cavities for exhalation O2 CO2 CO2

  16. Quiz

  17. cortex renal artery renal vein pelvis ureter medulla

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