The kidneys

• The role of the kidneys is to regulate the water content of the blood and to excrete toxic waste products of metabolism
• Blood is brought to the kidneys in renal artery which branches off aorta
• Kidneys regulate water and salt content and removes urea
• Filtered excess water, salts and urea form urine
• Urine moves to bladder to be excreted
• Purified blood returns through the renal vein and into heart through vena cava
• Kidney is packed with a million nephrons
• Nephrons are what regulates water and salt levels and removes urea
• ADH stands for anti diuretic hormone
• Water content of blood is controlled by the hormone ADH
• DIfferent amounts of ADH are released into blood stream by a gland in the brain according to concentration
• The concentration of blood can be altered by

  -excess drinking

  -excess sweating

  consumption of salty foods
• If there is high concentration in plasma, the issue is there's too little water so ADH release increases so more water is reabsorbed by nephrons and the urine becomes more concentrated
• If there is a low concentration in the plasma the issue is that there's too much water so ADH release increases and less water is reabsorbed by nephrons and the urine becomes more dilute
• Pituitary gland releases ADH
• If more ADH released then there is less water lost in urination
• Selective reabsorption is when useful substances like glucose, right amount of water and some ions are reabsorbed
• Dialysis is when machines filter the blood
• Dialysis has to be done regularly to keep concentrations of dissolved substances in blood at normal levels and remove waste products
• If you get kidney failure you either need dialysis or a transplant
• If kidneys don't work properly, waste substances build up in the blood and you loose your ability to control ion and water levels resulting in death
• Concentration of urine is controlled by ADH which is released into the blood by the pituitary gland
• If water content is too high, less ADH released so less water reabsorbed by kidneys
• There has to be a constant balance of water in the body
• We loose water from the skin and lungs and we can't control how much in these ways so it's balanced by what we consume and what's lost in urine