Excretory System 💦

• The lungs are involved in the excretion of the carbon dioxide that is produced by all body cells during cellular respiration.
• The liver has an important role in processing many substances so that they can be excreted.
• Sweat glands in the skin secrete sweat, which is largely water, for cooling. Sweat contains by-products of metabolism such as salts, urea and lactic acid.
• The alimentary canal passes out bile pigments, which enter the small intestine with the bile. These pigments are the breakdown products of hemoglobin from red blood cells.
• The kidneys are the principal excretory organs. They are responsible for maintaining the constant concentration of materials in the body fluids. The toxic wastes removed by the kidneys are the nitrogenous wastes urea, uric acid and creatinine.
• Urea is produced in the liver from the breakdown of amino acids, which comes from protein metabolism.
• The proteins, which have been built up from amino acids, become the primary constitutes of cell structures, enzymes, antibodies and many glandular secretions.
• Deamination is the removal of the amino group an amino acid molecule.
• Deamination occurs in the liver with the aid of enzymes.
• The urea is eliminated from the body in urine.
• Deamination equation:

  Amino acids + oxygen -enzymes-> Carbohydrates + ammonia
• Ammonia is extremely soluble in water and is highly toxic to cells. The cells of the liver rapidly convert ammonia to the less toxic molecule urea. It is easily excreted by the kidneys and is eliminated from the body in the urine. Small amounts of urea are also lost in sweat from the sweat glands.
• Urea production:

  Energy + Carbon Dioxide + Ammonia --> Urea + Water
• The liver also:

  • Detoxifies alcohol and many other drugs such as antibodies
  • Deactivates many hormones and converts them into a form that can be excretes by the kidneys
  • Breaks down hemoglobin from dead red blood cells to produce bile pigments, which are then passes out of the body with the feces.
• Even when there is no visible perspiration on the skin, the sweat glands secrete about 500 ml of water per day. Dissolved in the water are sodium chloride, lactic acid and urea. These substances are being excretes 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 at a pore. Cells surrounding the glands are able to contract and squeeze the sweat to the skin surface.
• The renal capsules are tough fibrous layers surrounding the kidney.
• The renal cortex is the outer part of the kidney.
• The renal medulla is the inner part of the kidney.
• The renal pelvis is the cavity of the kidney that collects urine before it passes to the ureter.
• The renal hilum is a depression in the kidney where the blood vessels and the ureter enter.
• The renal pyramid is a section of the renal medulla.
• The renal column is an extension of the renal cortex that divides the renal medulla into renal pyramids.
• The nephron is the functional unit if the kidney, as it is where the urine is formed.
• Each nephron consists of a renal corpuscle and renal tubule.
• Renal corpuscle is the filtration structure of the nephron composed of the glomerulus and glomerular capsule.
• The renal tubule leads away from the glomerular capsule and empties into a collecting duct.
• Blood enters the nephron through the afferent arteriole. It is filtered in the glomerulus, a network of capillaries, and then exists via the efferent arteriole.
• Lungs


  Involved in the excretion of the carbon dioxide that is produced by all body cells during cellular respiration
• Liver


  Has an important role in processing many substances so that they can be excreted
• Sweat glands


  • Secrete sweat, which is largely water, for cooling
  • Sweat contains by-products of metabolism such as salts, urea and lactic acid
• Alimentary canal


  • Passes out bile pigments, which enter the small intestine with the bile
  • These pigments are the breakdown products of haemoglobin from red blood cells
• Kidneys


  • The principal excretory organs
  • Responsible for maintaining the constant concentration of materials in the body fluids
  • Remove the most toxic wastes, which are the nitrogenous wastes urea, uric acid and creatinine
• Urea


  Produced in the liver from the breakdown of amino acids, which come from protein metabolism
• Deamination


  1. Amino group (NH2) is removed from amino acids

  2. Occurs in the liver with the aid of enzymes

  3. Ammonia (NH3) is then converted to urea

  4. Remaining part of the amino acid is converted into a carbohydrate
• The cells of the liver rapidly convert ammonia to the less toxic molecule urea
• Liver


  • Detoxifies alcohol and many other drugs such as antibodies
  • Deactivates many hormones and converts them into a form that can be excreted by the kidneys
  • Breaks down haemoglobin from dead red blood cells to produce bile pigments, which are then passed out of the body which the faeces
• Skin


  • Provides a protective covering over the surface of the body
  • Regulates body temperature
  • Has an important role in excretion
• Even when there is no visible perspiration on the skin, the sweat glands secrete about 500 ml of water per day
• Dissolved in the water are sodium chloride, lactic acid and urea. These substances are being excreted from the body