Excretion Notes WHAT YOU SHOULD KNOW

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					                           WHAT YOU SHOULD KNOW ABOUT EXCRETION


Excretion is the process by which harmful wastes are removed from an organism.
Harmful Wastes that are removed include:
Carbon Dioxide
Excess Water
Nitrogenous Wastes
        a. Urea in humans
        b. Ammonia in fish
        c. Uric acid in birds
Oxygen in plants and other photosynthetic organisms
Excess Heat
Mineral Salts

Where do wastes come from?
Wastes come from the Metabolic Activities of living organisms.




                                 NITROGENOUS WASTES result from
                            the breakdown of proteins and nucleic acids.


                             PROTEIN AMINO ACIDS




In humans, excess amino acids are processed by the liver.
They undergo a chemical reaction called DEAMINATION which removes the amino group from each

amino acid.
                          WHAT YOU SHOULD KNOW ABOUT EXCRETION



But this part is converted into AMMONIA, a toxic substance




                                                                    (NH3)




   1. Organisms that live in a watery environment can excrete ammonia directly into the
      environment by diffusion. In addition, single celled organisms such as a protest can remove
      excess water through its contractile vacuoles.

   2. In humans and other mammals, ammonia is converted into UREA by chemical reactions in the
      liver. It is moderately toxic. Urea is soluble in water, and can be eliminated in urine and
      sweat.

   3. Some organisms, such as birds, convert ammonia to URIC ACID. URIC ACID is insoluble in
      water and can be excreted as a dry waste. This helps organisms conserve water. Uric acid in
      our gouts can cause a painful disorder called gout.

Gas Excretion
   1. Oxygen through the stomates in leaves, lenticels in stems, and root hairs in plants
   2. Carbon dioxide through our lungs, a worms skin and the cell membrane of the cells in hydra
       and protist.
                      WHAT YOU SHOULD KNOW ABOUT EXCRETION




  Organism                  Where Nitrogenous Wastes are Removed
  Protist                   Cell membrane
  Hydra                     Cell membrane
  Earthworm                 Nephridia to skin
  Grasshopper               Malpighian tubules


                         The metabolic wastes of humans include
                          carbon dioxide, water, salts, and urea.
Excretory wastes pass from the cells into the blood, and are carried to the excretory organs
                             that expel them from the body.
                         The human excretory organs include the
                                           LUNGS
                                            LIVER
                                          KIDNEYS
                                             and
                                      SWEAT GLANDS
                  WHAT YOU SHOULD KNOW ABOUT EXCRETION


                  In humans, carbon dioxide and water vapor are
                      excreted by the LUNGS when we exhale.




The LIVER is a large organ that performs many functions essential to human survival.




                 1. One of the functions of the liver is DEAMINATION,
                   which is used to eliminate excess amino acids.
                    In the LIVER, the amino groups are removed
                    from amino acids and converted into UREA.
                   2. The liver is also responsible for the breakdown
                                  of red blood cells.

           Water, salts, and UREA are excreted by the URINARY SYSTEM.
       WHAT YOU SHOULD KNOW ABOUT EXCRETION


       Human KIDNEYS remove urea from the blood.




The working unit of the human kidney is called the NEPHRON.




          As blood flows through the GLOMERULUS,
      water, salts, urea, glucose, and some amino acids
     diffuse out of the blood into BOWMAN'S CAPSULE.

             This process is called FILTRATION.
           The liquid that results is the FILTRATE
                 WHAT YOU SHOULD KNOW ABOUT EXCRETION


Most of the water is REABSORBED from the filtrate and returned to the bloodstream
                in the capillaries surrounding the LOOP OF HENLE.




                        As water is reabsorbed by the kidney,
                                  URINE is formed.
The urine passes through the URETERS to the URINARY BLADDER where it is stored.
             Urine is eliminated from the body through the URETHRA.
WHAT YOU SHOULD KNOW ABOUT EXCRETION

				
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posted:11/9/2011
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