Topic 13: Excretion

• What is excretion?

  removal of the waste substances of metabolic reactions, toxic materials and substances in excess of requirements
• What is the role of liver?

  Assimilation

  Produces bile

  Storage of glucose

  Interconversion of glucose and glycogen

  Transamination

  Deamination

  Remove old red blood cells

  Detoxification
• Define the term 'deamination'?

  removal of the nitrogen containing part of amino acid to form urea (nitrogenous waste)
• Outline the role of liver in excretion?

  1. Deamination to produce urea
  2. urea passes into blood
  3. breakdown of hormones/toxins/drugs/excess vitamins
  4. breakdown of worn out red blood cells
  5. excretory products put in bile
• What is the role of kidney?

  regulates water content and filters blood
• What is the role of ureter?

  carries urine from the kidneys to the bladder
• What is the role of bladder?

  stores urine, excess water, salts and urea as it is produced by the kidney
• What is the role of urethra?

  tube connects the bladder to the exterior, where urine is removed.
• What is the process of ultrafiltration?

  • renal artery carries blood under high pressure which will force out the smaller substance such as water, glucose, urea and salt through the tiny gaps in the wall of glomerulus capillaries.
  • The Bowman's capsule collects the filtrates
  • The larger substances such as plasma proteins and red blood cells and white blood cells stays in the blood capillaries as they are too big to pass through the tiny gaps of capillaries.
• What makes the renal artery to carry the blood at high pressure?

  The blood vessel carries blood from the heart through aorta whereby the blood was pumped by heart left ventricle chamber, the muscles of the left ventricles chambers contacts harder, thus blood travels through the aorta at high pressure.
• Why the plasma proteins unable to pass through the wall of glomerulus capillaries?

  Larger molecules unable to pass through the tiny gap in the wall of capillaries, thus it gets within the blood capillaries; glomerulus.
• Selective reabsorption

  • the useful substances such as water, glucose and salt requires to reabsorb back into the blood capillaries.
  • All glucose depending on the concentration gradient, some salt reabsorbed via active transport.
  • Some water reabsorbed via osmosis process.
• Where does selective reabsorption happen?

  Happens in the Nephron tubule (first coiled tubule and loop of Henle) also water at collecting duct.
• How the cells in the kidney tubule adapted to do active transport?

  The cell membrane of the kidney tubule have carrier/transport/channel proteins and also have lots of mitochondria in the cell to provide energy by doing cellular respiration.