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					Chapter 19
Excretion
   in
Humans
       Excretion
Theremoval of metabolic
wastes from an organism.
(I) Human Excretory Organs
          Lungs
          Liver
           Skin
         Lungs
Ridthe body of CO2 and excess
  H2O from the blood during
  exhalation (breathing out).
              Liver
 Largest  internal organ
 Major function is the removal of
  toxins (poisons) from the blood.
  This process is know as
  detoxification and therefore, the
  liver helps in purifying the blood.
 Produces bile which is used for the
  breakdown of fats (emulsification) in
  the small intestine.

The coronary ligament of the liver refers to parts of the peritoneal reflections that hold the
                       liver to the inferior surface of the diaphragm.
The falciform ligament is a broad and thin antero-posterior peritoneal fold, falciform (Latin
"sickle-shaped") in shape, its base being directed downward and backward, its apex upward
                                        and backward.

                     Is a remnant of the ventral mesentery of the fetus.
             Skin
Largest   external organ of the
 body.
In contact with the external
 environment.
Composed of two layers:
       epidermis
       dermis
     Skin Cross-section
 Epidermis-
  outer layer of
  the skin used
  for protection.
 Dermis- lower
  layer of the skin
  where sweat
  glands are
  found.
   Sweat Glands
 Consist of tiny coiled tubes that
  open to the surface of the skin
  through pores.
 Perspiration (sweat) is excreted
  by these glands.
 Perspiration consists mostly of
  water (98%), salts, and urea.
          Function of Skin
1.   Protects internal tissue of the body from injury
     and the entrance of foreign materials and
     microorganisms.
2.   Excretes a small amount of urea and salt in the
     form of perspiration.
3.   Nerve endings in the skin detects stimuli like
     heat, and pain.
4.   The skin is also involved in the regulation of
     body temperature (homeostasis).
         - sweating cools the body
 A Closer look
    at the
Liver and Skin
               Skin
 Sweat  glands secrete wastes in the
  form of water, urea, and salt
  (perspiration).
 These wastes pass by diffusion from
  capillaries and into sweat glands and
  then through ducts that transport
  the waste to the pores in the surface
  of the skin.
                Liver
A)   Detoxification- removal of toxins
     from the blood.
B)   Urea- is formed in the liver from
     the breakdown of amino acids in a
     process known as Deamination.
     -urea then diffuses into the blood
     and is transported to the kidneys
     and excreted in the form of urine.
      Urinary System
A   group of organs whose sole purpose is
  to perform excretion.
 The urinary system consists of:
               Kidneys
               Ureters
               Urinary bladder
               Urethra
Urinary System
      
             Kidneys
 Bean-shaped   organs located below and
  toward the back of the diaphragm.
 Perform two major functions:
    1. Remove wastes from blood.
    2. Controls the concentration of
  various substances in the body.
 The functional units of the kidneys are
  known as nephrons.
Cross section of a human kidney
          Nephrons
 Each  kidney contains approximately
  1.25 million nephrons.
 The nephron begins with a cluster of
  capillaries called the glomerulus.
 The glomerulus is surrounded by a
  cup-like structure called Bowman’s
  capsule.
Nephron

     The way the nephron works:
1.    Blood is carried to each kidney by the
      Renal artery.
2.    The renal artery subdivides into smaller
      arterioles and then subdivides into a ball
      of capillaries known as the glomerulus.
3.    Each glomerulus is part of the nephron.
4. Through diffusion (passive
  transport), wastes are filtered out
  (urea, water, and salt) and enter the
  Bowman’s capsule.
5. From the Bowman’s capsule, the
  filtrate (waste) passes through a long
  tubule surrounded by capillaries.
6. Through active transport, useful
  substances are reabsorbed into the
  capillaries from the Loop of Henle.
7. The remaining liquid, called urine,
  pass into the collecting tubule and
  then pass out of the kidney and into
  the ureter.
8. Urine is composed of urea, water,
  and salt.
9. Urine then travels down the ureter,
  into the urinary bladder, and out of
  the body through the urethra.
             Ureter
Structurethat carries urine from
 the kidneys and into the urinary
             bladder.
Urinary Bladder

Temporarily   store urine.
           Urethra
  Urine  is excreted from the
bladder, through the urethra and
         out of the body.
(III) Diseases of the Kidneys

 Diseases of the kidneys affects the
   ability of the body to eliminate
   normal amounts of metabolic
                wastes.
Kidney Stones
      Kidney  stones
       are hardened
       crystal clumps
       that can
       develop in the
       urinary system .
             Gout
 Produces   symptoms similar to
              arthritis.
Caused by deposits of uric acid in
             the joints.
Victims of gout suffer severe pain
     and stiffness in the joints.


				
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posted:11/18/2011
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