HS

Chapter 11: Excretion

  • %%Catabolic activities%% are chemical processes which cause the breakdown of complex substances into simpler ones. For example, tissue respiration and deamination of proteins and amino acids to form urea.

  • %%Anabolic activities%% are chemical processes in which the simpler substances are built up into more complex substances. For example, the formation of new protoplasm from amino acids (proteins) and process of photosynthesis.

  • The sum of all chemical activities within the body is %%metabolism.%%

  • %%Excretion%% is the process by which metabolic waste products and toxic materials are removed from the body of an organism.

    Excretory Products:

  • Carbon dioxide - lungs - gas is expired

  • Nitrogenous waste products - kidneys - urine

  • Excess Water

    • kidneys - urine
    • skin - sweat
    • lungs - expired air

  • Bile pigments - liver - intestines

Mammalian Urinary System:

  • Consists of a pair of kidneys, pair of ureter, a urinary bladder and urethra.
  • ^^kidneys^^:
    • Bean shaped.
    • Attached to dorsal body wall.
    • Lie above waistline.
    • Renal artery & renal vein connected.
  • Urine from each kidney passes through the ureter to the Urinary Bladder.
  • Urinary bladder:
    • elastic muscular bag.
    • ventral to the rectum.
    • stores urine.
    • when the bladder is full the sphincter muscle relaxes to allow the urine flow into urethra and pass out of the body.

Longitudinal section of kidney:

  • Two regions:

    • ^^Cortex^^
    • outer region.
    • ^^Medulla^^
    • inner region.
    • projects into a funnel shape space renal pelvis.
    • nephrons.
      • contains glomeruli; where blood is filtered and glucose, urea and salts are removed.
      • contains tubule; where water and some mineral salts are reabsorbed (after filtration in glomerulus). This prevents loss of too much water. (urea is not reabsorbed leading to a high concentration in urine).

Formation of Urine:

  • the glomerulus filters water and other substances from the bloodstream.
  • the filtration membrane keeps blood cells and large proteins in the bloodstream.
  • reabsorption moves nutrients and water back into the bloodstream.
  • waste ions and hydrogen ions secreted from the blood complete the formation of urine.

Kidney as Osmoregulators:

  • %%Osmoregulation%% is the control of water and solute levels in the blood to maintain a constant water potential in the body.

Function of Kidneys:

  • excretory organs.
  • help regulate salt and water balance of the body fluid.

KIdney Failure:

  • two solutions:

    • dialysis

    %%Dialysis fluid%% contains essential salts for the body - if the blood lacks essential salts dialysis fluid will diffuse its salts to it through membrane.