Functions of the urinary system

Question 1

Function: 1) Homeostatic regulation

Answer 1

Blood plasma volume (water balance) + blood pressure + solute concentration (salt balance):

• regulates blood vol + BP by adjusting volume of water lost in urine (long term control, short term control = autonomic)
• regulates plasma ion concentrations: sodium, pota, chl ions = by controlling quantities lost in urine, calcium + phosphate ion levels

pH (acid-base balance):

• helps stabilise blood pH by controlling amount of H+ and bicarbonate ions (HCO3) excreted in urine
• can lose a lot of bicarbonate due to filtering of blood by kidneys = want to try and conserve as much as possible and recycle back to the blood = done by kidneys

Question 2

Hormones produced by kidney

Answer 2

• Calcitriol = active form of vitamin D

- Erythropoietin = stimulates production of red blood cells

Question 3

Function: 2) Excretion

Answer 3

• removal of organic wastes from body fluids
• filtration of blood + processing of filtrate in nephron
• most toxic endogenous wastes = NITROGENOUS wastes:
  
  • urea: by-product of protein breakdown
  • uric acid: by-product of nucleic acid breakdown
  • creatinine: from creatine phosphate in muscle

Exogenous wastes (foreign wastes excreted through kidneys):
  - drugs (e.g. penicillin)

Question 4

Function: 3) Elimination

Answer 4

• discharge of waste products from the body (urination)
• urinary tract (organs that eliminate urine) = ureters, urinary bladder, urethra
• micturition reflex (process of eliminating urine): contraction of bladder forces urine through urethra + out of body