The Kidneys

All about the kidneys

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  • Created by: Amy
  • Created on: 05-05-13 17:17

Roles of the Kidneys

Three main roles:

Removal of urea from the blood. (Urea produced in liver, from breakdown of excess amino acids.

Adjustment of ion levels in the blood.

Adjustment of water content in the blood.

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Nephrons are filtration units in the kidneys. 

1) Ultrafiltration:

High pressure built up, this squeezes water, urea,ions and glucose out of the blood into the BOWMAN'S CAPSULE.

The GLOMERULUS and BOWMAN'S CAPSULE act like filters. (Big molecules like proteins and blood cells not removed.)


Useful substances reabsorbed such as all the glucose. (Moved from nephron back into blood AGAINST CONC GRADIENT)

Sufficient water reabsorbed according to level of ADH.This process is called OSMOREGULATION.

3)Release of wastes:

Urea and excess water not reabsorbed. 

Continue out of nephron, into URETER and down to the BLADDER as URINE.

URINE released through URETHRA.

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Negative Feedback System

1) Amount of water reabsorbed in kidney nephrons controlled by ADH

2) Brain monitors water content and instructs PITUTITARY GLAND to release ADH into brain according to how much needed.

3) Water content regulation controlled by NEGATIVE FEEDBACK. (Changes in environment trigger response that counteracts change.

Water gain - Brain detects- pituitary gland releases less ADH - lack of ADH. kidney reabsorbs less water.

Water loss - Brain detects - Pituitary gland releases more ADH - ADH makes kidney reabsorb more water.

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Kidney Dialysis

Patients with kidney failure cannot filter blood properly.

Dialysis used daily to help them.

Dialysis fluid has same conc. of salts and glucose as blood plasma has. (So they arent removed from blood.)

Barrier is permeable to ions and waste substances (Not big molecules like proteins removed from blood)

Waste substances like urea and excess ions and water in blood move across membrane into dialysis fluid. 

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Kidney Transplants

Only cure for kidney disease is a kidney transplant.

Healthy kidneys removed from people who have died suddenly and are on the donor register with permission of family.

Kidney can be rejected by patients immune system (Attacked by anti-bodies)

Precautions taken:

Donor wth similar tissue type to patient.

Patient treated with drugs to suppress the immune system. (Immune system wont attack donor kidney)

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