maintaining water and nitrogen balance
Cards (7)
- what do the kidneys do?
- make urine by taking waste products out of the blood
- substances are filtered out of the blood as it passes through the kidneys
- useful substances and some ions and water are reabsorbed into the blood for selective reabsorption
- which substances are removed from the body in urine?
- urea - proteins cannot be stored by the body so any excess amino acids are converted into fats and carbs for storage
- ammonia is produced as waste
- ammonia is toxic so it ia converted into urea in the liver and transported to the kidneys where it is filtered out of tue blood and excreted in the urine
- how is water conc controlled?
- the body must balance water from skin in sweat and lungs
- we cannot control how much we lose so the extra water is balanced by water consumption and urination
- how is urine concentration controlled?
- controlled by ADH released into the bloodstream by the pituitary
- if water content is too low it is detected by a receptor in the brain. the coordination centre receives this and tells the pituitary gland to release more ADH so more water is reabsorbed by the kidney tubules
- the reverse happens if water content is too high
- if the kidneys don't work properly, waste substances build up in the blood and you lose the ability to regulate ion and water levels
- cures for kidney failure - kidney failure
- kidney transplant - normally taken from people who have died but can be taken from live donors. however the kidney may be rejected by the immune system so the patient must take immunosuppressants
- cheaper than dialysis in the long term
- dialysis
- blood flows between a partially permeable membrane allowing ions, water and urea to pass through. dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood so that useful substances will not be lost
- many patients have to do this 3 times a week in 3-4 hour sessions. can cause blood clots and infections
- takes a long time and is expensive to run