Excretion

• Excretion is the removal of metabolic waste from the body
• Egestion is the removal of undigested food from the body
• Animals excretory organs are:

  Lungs,kidneys,skin
• Animals major excretory products are:

  Carbon dioxide,water,urea,heat,bile pigments
• Plants excretory organs/parts are:

  Leaves,bark,stomata,roots
• Plants major excretory products are:

  Carbon dioxide,oxygen,water,tannis,calcium oxalate
• Skin:

  Water-released as sweat by sweat glands

  Salts-released as sweat

  Heat-diffuses out of capillaries onto skins surface
• Kidneys:

  Water-excess water removed from blood;removed in urine

  Urea-excess proteins removed from blood and removed in urine

  Salts-excess removed from blood and removed in urine
• Excretion in plants

  Leaves/bark:

  Organic waste

  Calcium oxalate
• Waste are sent to these structures and when they die and fall off,waste leaves with them
• Stomata:

  Oxygen

  Carbon dioxide

  Water
• Wastes exit via stomata in underside of leaves by diffusion or transpiration
• Roots:

  Tannis

  These poisonous wastes are excreted through the roots and into the soil.
• The functions of the kidneys are:

  Excretion

  Osmoregulation

  Control of blood ph levels

  Maintenance of solute concentration
• Urine production


  1. Ultrafiltration

  2. Selective reabsorption

  3. Secretion
• The neurons have three processes for urine production
• Ultrafiltration

  Small molecules are filtered through the gloerulus into the bowman's capsule
• Selective reabsorption

  Useful substances are reabsorbed into the blood capillaries from various points along the tube
• Secretion

  Substances from the blood join the filtrate and go on to form urine
• Dialysis

  An artificial kidney is used to filter and adjust the blood
• Osmoregulation

  The process of maintaining the water balance in the body or plant system
• Osmoregulation in plants

  Excess water is lost through the stomata in the transpiration process
• Humility

  Wind intensity

  Light intensity

  Temperature, are factors that affect the rate of transpiration
• Osmoregulation in humans

  The sensor which the brain uses to detect the amount of water in the blood is called the hypothalamus
• If there is too little or too much water in the blood the hypothalamus brings about responses that correct the balance
• The main organs responsible for osmoregulation in humans are the skin and kidneys
• The hypothalamus instructs the pituitary gland to release antidiuretic hormone(ADH) which travels in the bloodstream to the kidneys if there is less water in the blood than usual
• ADH binds to receptors on collectingduct walls and makes the wall of the collectingduct much more permeable to water
• As the urine passes down the collectingduct,lots of water can be reabsorbed into the blood by osmosis
• The urine is smaller in amount, darker and more concentrated
• If there is more water in the blood than usual:

  The hypothalamus stops signaling the pituitary gland and no more ADH is released into the bloodstream
• If there is no ADH in the Bloom, the walls of the collectingduct remain totally impermeable to water
• As the dilute urine passes down the collectingduct, the water is reabsorbed into the blood by osmosis and so a large volume of dilute urine will be produced
• The urine is greater in amount,pale and less concentrated