chapter 7

• Excretion

  The removal of the waste products of metabolism
• Organs involved in excretion

  • Lungs
  • Liver
  • Sweat glands
  • Alimentary canal
  • Kidneys
• Deamination


  1. Removal of the amino group from amino acids

  2. Remaining part forms carbohydrates for energy production

  3. Occurs in the liver
• Conversion of amino group

  1. To ammonia

  2. Then to urea

  3. Excreted by the kidneys
• Skin


  • Covers the body
  • Helps regulate body temperature
  • Involved in excretion of salt, lactic acid, urea and some drugs through sweat
• Components of the urinary system


  • Kidney
  • Bladder
  • Urethra
  • Ureters
• Renal capsule


  • Surrounds the outer renal cortex
  • Renal cortex lies outside the renal medulla
• Renal medulla


  • Divided into renal pyramids by the renal columns
• Renal pelvis


  • Hollow that leads to the hilum on the concave side of the kidney
• Nephron


  Microscopic unit of the kidney, made up of a renal corpuscle and a renal tubule
• Blood filtration in the renal corpuscle


  1. Blood travels through the glomerulus

  2. Filtrate is collected in the glomerular capsule
• Selective reabsorption


  1. In the proximal convoluted tubule, Loop of Henle, distal convoluted tubule and collecting duct

  2. Of useful substances including water, glucose, amino acids and some ions
• Tubular secretion


  Moves substances such as drugs, potassium, creatinine and hydrogen ions from the blood to the urine in the distal convoluted tubule
• Urine travel


  1. From collecting ducts to renal pelvis

  2. Then to ureters

  3. To bladder for storage

  4. Excretion through urethra
• Components of urine


  • Water
  • Ions
  • Urea
  • Uric acid
  • Creatinine
• Kidney stones


  • Solid crystals formed when urine is too concentrated
  • May block ureter, bladder or urethra, causing pain
• Kidney failure


  • Blood is not able to be filtered correctly
  • Lifestyle choices can affect kidney health
• Dialysis


  1. Peritoneal or haemodialysis

  2. Used to remove wastes from the blood of people with kidney failure
• Liver disease


  • Toxins are unable to be processed for elimination
  • Caused by infection, autoimmune disease, genetic disorders, cancer and lifestyle choices
• excretion is the removal of the wastes of metabolism from the body and elimination is getting rid of the undigested food molecules in the digestive system
• 3 processes that occur in nephrons and where they occur

  1. filtration - renal corpuscle
  2. selective reabsoption- renal tubule
  3. tubular secretion - renal tubule
• how do lungs, liver, sweat glands and alimentary canal contribute to excretion


  lung - removes co2 when breathing out

  liver- detoxify substances and processes them for excretion

  sweat glands- removes sweat which contains water, salt and urea

  alimentary canal- releases bile pigments from the breakdown of haemoglobin.
• formula for deamination


  amino acid + oxygen --> carbohydrate + ammonia
• formula for production of urea

  energy + carbon dioxide + ammonia --> urea + water