Excretion

• Excretion - Flowering plans
• During respration, aygen is useful and carbon dioxide is a wave product
• During photosynthesis, carbon dioxide is weful and aygon is a waste product
• The waste products are lost via the stomaku of the wat
• Excretion-Humans
• Excretory products


  • Carbon dioxide and water (lungs)
  • Water, urea, minerals ions (kidney)
  • Water, excess minerals eg. Sodium (skin)
• Excretion in the kidney

  1. Glomerular filtration

  2. Reabsorption
• Glomerular filtration


  • Blood from the renal artery flows through the glomerulus
  • High pressure squeezes wastes, glucose out of the blood and into the Bowman's capsule
  • Membranes act as filters, so larger molecules like proteins and blood cells stay in the blood
• Reabsorption


  • Useful substances are selectively reabsorbed into the blood
  • All the glucose is reabsorbed from the proximal convoluted tubule
  • Sufficient ions and water are reabsorbed
• Osmoregulation


  Balancing the water coming in and going out of the body
• Osmoregulation


  1. ADH (Anti-Diuretic Hormone) controls water reabsorption in the kidneys

  2. Brain monitors blood water content and instructs pituitary gland to release ADH

  3. Negative feedback mechanism keeps water content normal
• Parts of the urinary system

  • Renal artery
  • Kidney
  • Renal vein
  • Ureter
  • Bladder
  • Urethra
• Functions of the nephron

  • Glomerulus responsible for blood filtration
  • Bowman's Capsule purifies blood
  • Proximal convoluted tubule reabsorbs useful substances
  • Loop of Henle reabsorbs water
  • Distal tubule reabsorbs ions and water
  • Collecting duct responsible for selective reabsorption and sending urine to bladder
• Composition of glomerular filtrate - salts, glucose, water, urea
• Water is reabsorbed from the collecting duct to balance water loss
• Selective reabsorption of glucose occurs at the proximal convoluted tubule
• ADH regulates water content of blood by affecting permeability of collecting duct
• Urine contains water, urea and ions