Excretion

• Excretion is the removal of toxic materials and waste products of metabolism and things you have too much of
• organs in the excretion system are: the lungs, kidneys, and skin
• The kidneys are made up of tubules called nephrons
• The functions of the kidneys:

  1. Filtration & removal of urea, excess water
  2. Reabsorption of glucose & excess salts
• function of nephrons:

  1. blood brought to renal capsule in cortex
  2. renal capsule has glomerulus in middle
  3. vessel to glomerulus is much wider, allowing for a lot of pressure that squeezes blood against capillary walls
  4. water, salt, gluclose, & urea can pass through where as red blood cells and protein can't: this is called ultrafiltration
• selective reabsorbtion: of glucose using active transport carriers at proximal convoluted tubule + some salts and lots of water
• loop of henle: reabsorption of salt and water, salts diffuse and water osmosis occurs here as well
• ADH: pituitary gland hormone

  releases when water levels are below normal, pores in collecting duct become more permeable, water reabsorbed till normal water level achieved
• urine: water with some urea and salts, what is there by the time fluid reaches collecting duct
• Ureter: Long narrow tubes with expanded upper end (renal pelvis). Its function is to carry the urine produced from the kidneys, to the urinary bladder.