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Excretion

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Excretion Section 39.3 Excretion Process that rids the body of substances: toxic chemicals excess water salts carbon dioxide Maintains osmotic (water) and pH ... – PowerPoint PPT presentation

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Title: Excretion


1
Excretion Section 39.3
2
Excretion
  • Process that rids the body of substances
  • toxic chemicals
  • excess water
  • salts
  • carbon dioxide
  • Maintains osmotic (water) and pH balance

3
Excretion
  • Lungs
  • Excrete CO2 and water vapor in exhaled air
  • Kidneys
  • Excretes nitrogen wastes, salts, water, and other
    substances in urine
  • Skin
  • Excretes water, salts, small amounts of nitrogen
    wastes, and other substances in sweat

4
Excretion
  • Urea
  • Main nitrogenous waste of body
  • Produced in liver from ammonia (NH3
  • Formed during metabolism of proteins and nucleic
    acids

5
How the Kidney Works
6
The Kidneys
  • Maintains balance of salt, water, minerals,
    vitamins, pH, and volume of blood
  • Each Kidney composed of 1 million microscopic
    units called a nephron that filter the blood
  • Three phases occur as blood flows through a
    nephron
  • Filtration
  • Reabsorption
  • Secretion

7
Nephron Structure
8
Filtration
  • Occurs in Bowmans capsule where there is a
    network of arteries called a glomerulus
  • Blood pressure inside the capillaries forces
    fluid containing water, salt, glucose, amino
    acids, and urea into the hollow interior of
    Bowmans capsule.
  • This fluid is called filtrate.
  • Blood cells, proteins, and other molecules too
    large to cross the membrane remain in the blood.

9
Filtration
10
Filtration
11
Reabsorption
  • Filtrate passes from the Bowmans capsule into
    the renal tubules.
  • As the filtrate passes through the renal tubules
    useful molecules glucose, ions, and some water,
    is reabsorbed.
  • These substances reenter the bloodstream through
    capillaries that wrap around the tubule
  • About 99 of water is returned to blood by
    osmosis

12
Reabsorption
13
Reabsorption
14
Secretion
  • When substances pass from the blood into the
    filtrate
  • Eliminate toxic substances from blood

15
(No Transcript)
16
Some Interesting Facts!
  • Blood passes through kidneys 300 times a day.
  • Nephrons clean all your blood in 45 minutes
  • Every day the nephrons send about six cups of
    urine to the bladder

17
Urine Formation
  • Filtrate contained in nephron is urine
  • Formed from the water, urea, and salts that are
    left after the absorption and secretion processes
  • Urine leaves the kidneys through the ureters and
    travels to the urinary bladder
  • Urinary bladder stores urine and expands as more
    urine enters

18
Excretion
  • Stretch receptors send nerve impulses to spinal
    cord
  • Spinal cord returns impulses to bladder and
    urethra simultaneously
  • Impulses cause contractions of bladders muscular
    wall and relaxes muscle of urethra
  • Urine is emptied through the urethra

19
Animation
  • Click here for Urinary System Animation

20
Review Questions
  1. Identify how the carbon dioxide in your body is
    produced and excreted.
  2. Relate the following terms to the formation of
    urine filtration, reabsorption, and secretion.
  3. Summarize how urine is stored and eliminated from
    the body.
  4. Concept Generalization circulatory system,
    respiratory system, and excretory system
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