the kidneys

• kidneys clean the blood
• the kidney makes urine by taking waste products out of your blood. substances are filtered out of the blood as it passes through the kidneys. useful substances like glucose, some ions and water are absorbed back into the blood, this is called selective reabsorption
• substances that are removed from the body in urine include urea, ions and water
• the concentration of urine is controlled by a hormone called anti-diuretic hormone. this is released into the bloodstream by the pituitary gland
• the brain monitors the water content of the blood and instructs the pituitary gland the release anti-diuretic hormone into the blood according to how much is needed
• the process of water content regulation is controlled by negative feedback. if water content gets too high or too low a mechanism will be triggered that brings it back to normal.
• there is 2 main waste products

  • carbon dioxide from respiration
  • urea produced from breakdown of proteins and building amino acids
• co2 is excreted from inhaling (excretion - removing from blood). it is dissolved to produce acidic solution which can damage cells, must be exhaled.

  faeces removed from egestion (egestion- not in blood).

  urea made from deamination of excess amino acids. ammonia is produced, toxic to cells, removed by urination
• renal vein

  carries blood away from kidney, after urea has been removed from blood