Kidney function

Kidney function

1. Nephrons are the filtration units in the kidneys

   • 1. Ultrafiltration
     • 1. A high pressure is built up which squeezes water, urea, ions and sugar out of the blood and into the Bowman's Capsule
       • 2. The membranes between the blood vessels & the Bowman's Capsule act like filters, so big molecules e.g. proteins are NOT squeezed out, they stay in the blood
   • 2. Reabsorption
     • As the liquid flows along the nephron, USEFUL substances are REABSORBED back into the blood
       • 1. ALL the SUGAR is reabsorbed. This involves the process of ACTIVE TRANSPORT
         • 2. SUFFICIENT IONS are reabsorbed- ACTIVE TRANSPORT
           • 3. SUFFICIENT WATER is reabsorbed
   • 3. Release of wastes
     • 1. The remaining substances (including urea) continue out of the NEPHRON, into the URETER and down to the BLADDER as URINE

2. Kidney failure

   • The kidneys remove waste substances from the blood- loss of kidney- loss of control- death
     • Dialysis Machines filter the blood
       • 1. Dialysis has to be done regularly to keep the concentrations of DISSOLVED SUBSTANCES in the blood at normal levels, and to remove substances
         • 2. In a dialysis machine, the person's blood flows alongside a selectively permeable barrier, surrounded by dialysis fluid- mirrors membrane of kidney
           • 3. Dialysis fluid has same concentration of dissolved ions & glucose as healthy blood
             • 4. Only substances e.g. urea & excess ions and water diffuse across the barrier
   • Transplanted organs can be rejected by the body
     • Donor kidneys can be rejected by the patient's immune system- the foreign antigens on the donor kidney are attacked by the body's antibodies
       • Patient is treated with drugs that suppress the immune system- immune system won't attack