Excretory-System

1. The Excretory System
California 5th
Grade Science Standard covered:
2d - Students know the role of the kidney in removing cellular waste
from blood and converting it into urine, which is stored in the bladder.

2. Body Needs
●The body has certain needs if it is to stay alive:
It needs food, water and oxygen, among other
things. Three body systems work together to
gather these requirements and get them to the
right places (the respiratory, digestive & circulatory
system).
●As a result of these systems working together
to keep the body alive and functioning
properly, they also produce a lot of waste as a
by-product.

3. Body Waste
●What is body waste? Any material that the
body cannot use.
Hidden throughout your body are dangerous poisons that must be removed in order for it to survive.
●These wastes are toxic to the organism if
allowed to accumulate inside the body or
blood. It will lead to sickness and death.
●This body waste must be found, collected and
then removed from the body by the excretory
system.

4. What is the Job of the Excretory System?
●The job of the excretory system is to get rid
of body waste and to maintain water balance
(it keeps the amount of water in the body fairly constant).
●Body waste that the body must get rid of:
Carbon dioxide, solid waste (indigestible
food) , water, ammonia (cell waste), inorganic
salts and heat.

5. ●Unlike other organ
systems, the
excretory system
involves a few
different organ
systems, spread
throughout the body,
working together to
do its job.
Excretory
System
Digestive
System
Removes
solid waste
(feces)
Respiratory
System
Removes
carbon dioxide
(CO2)
Urinary
System
Removes
urine
Integumentary
System (skin)
Removes
sweat
Q: How is the Excretory
System different than the
other body systems we
have studied?

6. Excretory System:
4 systems working together to excrete waste
“I Do Understand Removal!”
●Integumentary System: Also known as the skin, this system
removes excess salt, water, and other waste in the body as sweat,
through the pores of the skin. At the same time, this process helps
to cool off the body and to maintain a healthy body temperature.
●Digestive System: Materials that the body does not take in as
nutrients is eliminated as solid waste (feces).
●Urinary System: Removes waste from the blood that has been
converted to urine (see next slide)
●Respiratory System: Carbon dioxide, a cell waste, is exited out of
the body by the lungs.

7. Q: How does the urinary system work?
●Ammonia, a cell waste, gets sent out of the cell and into the blood.
●The bloodstream takes it to the liver where ammonia is converted
to urea, because it is less toxic and can be stored more efficiently .
●Then urea is carried by the blood to the kidneys, where this cell
waste is filtered out of the blood by nephrons and converted to
urine.
●Ureters, a tube, takes the urine to your bladder where it is collected
until it starts to get full.
●Once you are ready to excrete this waste from your body, the
urethra (a tube) will carry this waste out of your body.

8. Ammonia (a cell waste, leaves cell)
v
Blood
v
Liver (changes it into urea)
v
Blood
v
Kidneys (nephrons filter out waste in the blood, turning it into urine)
v
Ureters
v
Bladder (stores urine)
v
Urethra (urine is exited out of the body)
How is ammonia excreted from the body?

9. Kidneys and the Urinary Tract:
http://kidshealth.org/misc/movie/bodybasics/Kurinary_kidneys.html

10. Organs of the Urinary System
●Kidneys (main organ)
●Ureters
●Bladder
●Urethra

11. Q: What do your kidneys do?
A: The kidneys are the body’s filtration system. They
clean out your blood of body waste and make sure that
your blood is just the right combination -- not too thin or
too thick, not too salty, or overloaded with excess
vitamins and minerals or wastes made in your body.
The kidneys work as they do because they contain
millions of very small filters called “nephrons”. The entire
blood supply passes through the kidneys once every 20-
30 minutes for a total of about 60 times a day.

12. Problems with the Kidneys
In some instances, people’s kidneys can stop
working.
●Kidney disease can occur.
●Although it’s uncommon, some children are born with
missing or damaged kidneys.
●Kidneys can also become infected.
●Older adults sometimes suffer from kidney stones,
which are masses of salt and minerals. Large kidney
stones can block ureters and be very painful.
●Kidneys can be damaged from a physical injury.

13. What happens to people
whose kidneys stop working?
●Medicines and changes in diet
help some kidney problems.
●Dialysis is needed when kidneys stop working
completely. Dialysis is an artificial cleaning of the
blood, through the use of an external machine that
filters waste and extra fluid from the blood (and then
sends it back in).
●A long-lasting treatment for faulty kidneys is get a
transplant of a new kidney.

14. Kidney Transplant
●In this procedure, a doctor cuts out the damaged kidney
and inserts a new, healthy kidney from someone else. If
all goes well, the patient can lead a normal life. (People
need only one working kidney to stay alive).
●Transplants are not always easy or successful,
however. Part of the problem is that the body tries to
reject organs and tissues that are not its own. To help
the body accept a new kidney, the doctor may prescribe
special drugs. It also helps if the kidney comes from a
close relative of the patient.

15. How does the bladder know
when it is time for you to go?
●When your bladder becomes too full, it sends a message
to your brain that communicates this.
●You feel the need to pee and start looking for a place to
do it.
●When the time and place are right (hopefully in the
restroom), your brain orders the muscles around your
bladder to start squeezing and for the circle of muscles at
the bottom of your bladder to open.

16. What’s the Recipe for Urine?
http://yucky.discovery.com
Urine:
●is 95% water – about 1 ½ quarts worth.
●The rest of it is two tablespoons of urea,
●And a tablespoon of salt; some pigments,
poisons and other chemicals.

17. The Integumentary System
●Your Integumentary System uses sweat glands in the
skin to get rid of body waste. In these glands, excess
water, salt and a small amount of waste build up.
These substances leave your body through the skin
as sweat. This process helps your body cool down.

18. Releasing Sweat
& Sweat Glands
●You have about 2.6 million sweat glands through your skin.
These glands produce sweat when your body needs to
cool down.
●When enough sweat collects in the sweat gland it is
pushed to the top of the skin (through the pores) as
droplets. Once sweat reaches the surface of your skin, the
air and your body heat causes the sweat to evaporate. The
evaporated water removes the excess heat and cools your
body down.

19. Excretory System Quiz Practice Online:
www.quia.com/quiz/796946.html