Excretory System

• Purpose of the excretory system is to remove unwanted and undesirable products from the body to maintain a stable and balanced internal environment
• Waste products include nitrogenous waste in the form of urea
• Why urinate?


  1. Excess amino acids transported to liver, liver converts amino acids into ammonia (toxic), ammonia is then converted into urea (harmless in larger concentrations)

  2. Kidneys filter blood for ions and water via nephrons, nephrons reabsorb desired substances and secrete unwanted ones
• Nephron structure


  Glomerulus + bowman's capsule: Filtration, high blood pressure in glomerulus forces small molecules and fluids out, this is the primary filtrate

  Proximal convoluted tubule: Reabsorption of ions, water, amino acids, and glucose, secretion of toxins and ammonia

  Loop of Henle: Reabsorption of water, secretion of urea, ions are taken out of the ascending loop to increase concentration, creates counter-current osmotic mechanism

  Distal convoluted tubule: Optional reabsorption of water and ions, secretion of ions and toxins, fine tunes the filtrate

  Collecting duct: Optional reabsorption of water, secretion of urea, ions, ammonia, toxins, further fine tuning
• All the multi folded tubules of the nephron around capillaries allow for increased SA:V for increased filtration of fluids and bloods, making the system more efficient