Excretory System

• Main organs of excretion

  • Lungs
  • Skin
  • Kidneys
  • Liver
• Lungs excrete


  Water, Volatiles like ethanol, CO2
• Skin excrete


  Sweat (water, salts and urea)
• Kidneys excrete


  Urine (water, drugs, salts, urea, uric acids)
• Liver excrete


  Bile pigments, fat soluble drugs and substrates
• Elimination


  Removal of undigested materials unused by body
• Excretion


  Removal of metabolic waste
• Elimination includes: Water, undigested food, bacteria and remains of cells
• Excretion includes: Bile Pigments
• Liver's role


  • Detoxifies alcohol and other drugs like antibodies
  • Deactivated hormones into different form that can be excreted
  • Breakdown haemoglobin into bile pigment which is then excreted in faeces
  • Deamination
• Deamination


  Body can't store proteins- proteins are chains of amino acids. Liver is used to break down amino acids into ammonia- this process is deamination. Once it's changed into ammonia, it can be changed into urea so it can be excreted from the body.
• Deamination


  Amino Acid + Oxygen Carbohydrate + Ammonia
• Urea comes from the liver
• Amino acids contain a nitrogen (amino) group
• Excess amino acids cannot be stored
• Deamination in the liver removes the amino groups from the acid
• Amino group is converted to ammonia and then to urea (less toxic), to be excreted by the kidneys
• The liver synthesises proteins
• The skin (Integumentary System)

  • Provide protective covering
  • Regulate body temperature
• Sweat


  Contains sodium chloride, lactic acid, and urea. These substances are being excreted from the body.
• Sweat glands are located in the lower layers of the skin
• A duct carries the sweat to a hair follicle or to the skin surface where it opens a pore. Cells around the glands are able to contract and squeeze the sweat to the skin
• Patients with liver disease have a higher than normal levels of ammonia in their blood because damage to the liver limits its ability to process ammonia. The scarred liver cells can't properly produce enzymes that normally react with ammonia to create urea and remove toxins from the body.
• Kidneys filter blood to remove waste products from the body.
• Glomerulus is a cluster of capillaries within Bowman’s capsule
• Nephron is the functional unit of kidney
• The nephrons consist of glomeruli, proximal convoluted tubules (PCT), loop of Henle, distal convoluted tubules (DCT) and collecting ducts
• The Stratum Cornum is the first layer of the Epidermus
• Osmotic balance


  Maintaining the balance of water and solutes in the body
• Metabolic wastes


  Substances like carbon dioxide and nitrogenous wastes that need to be excreted
• Organs and structures involved in the excretory system

  • Skin
  • Liver
  • Lungs
  • Kidneys
• Urinary system


  The system that includes the kidneys, bladder, ureters, and urethra
• Nephron


  The functional unit of the kidney that processes waste products from the blood to create urine
• Reabsorption


  The process where some of the filtrate is reabsorbed back into the fluid surrounding the nephron (interstitial fluid)
• Secretion


  The process where some substances move from the fluid surrounding the nephron into the nephron
• Urine produced by the nephrons travels down the ureters to the bladder, and is then expelled from the body through the urethra