Excretion

• Osmoregulation


  Maintaining a stable concentration of water in the body
• Osmoregulation in case of dehydration

  1. Hypothalamus detects low water in blood

  2. Pituitary gland releases more anti-diuretic hormone (ADH)

  3. More water reabsorbed in collecting duct

  4. Urine becomes more concentrated
• Osmoregulation in case of too much water

  1. Hypothalamus detects high water in blood

  2. Pituitary gland releases less ADH

  3. Less water reabsorbed in collecting duct

  4. Urine is diluted
• Urinary system

  Kidney, ureter, bladder and urethra
• Structure of the Nephron

  • Bowman's Capsule surrounds glomerulus
  • High pressure in glomerulus forces blood out into Bowman's Capsule
  • Basement Membrane filters blood, allowing small molecules to pass
  • Fluid entering nephron is glomerular filtrate
  • Filtering in Bowman's Capsule is ultrafiltration
  • Proximal convoluted tubule reabsorbs all glucose via active transport
  • Loop of Henle reabsorbs most water, sodium and chloride via diffusion
  • Collecting duct reabsorbs remaining water via osmosis
• The urine contains urea, water and ions like chloride