Cells & Systems
The Excretory System
What does it do?
• Our body produces a bunch of different
waste products
• If they were to build up we could get
seriously sick or worse
• Enter the excretory system!
– The system responsible for waste removal
Waste Products
• Example we’ve covered already…
• What waste product do we breath out?
– CO2
• Digestive system breaks down protein
we are left with ammonia
– This is very toxic!
I am
ammonia!!
Ummkay?
Noooo!!
Help!!
Waste Products Cont …
• We also have processes that create …
– Excess water
GROSS!!!!
– Excess salt
– Solid waste (poop)
– Etc …
• So how do we break them down and
get rid of them? I’m Britney
Spears. I don’t
understand
science. Don’t
ask me!
The Organs
• The Liver
– Main role is the digestive system
• Enzyme release, filter, etc …
– In the excretory system it takes the toxic
ammonia out of the blood stream
– Converts the ammonia to a substance
called urea
– Puts the less harmful urea back into the
bloodstream
The Organs
The Organs Cont …
• The Kidneys
– A filter site for the body
– Approx 10cm long &
you have 2
– Filter blood of
unwanted/unneeded
• Urea
• Water
• Salts
– They produce urine (pee!)
The Organs Cont …
The Organs Cont …
• Interesting kidney facts …
– Every drop of blood in your body on a
given day is filtered about 300 times
– This means about 180L of blood passes
through kidneys each day
– On average you produce 1.5L of urine per
day
• Why do we filter so much?
How do I make pee?
• 1) Blood enters kidney via renal artery
• 2) Artery branches to smaller & smaller
vessels
• 3) Now in capillaries they enter the filter
units called nephrons! We have
millions of them
• 4) Nephrons remove waste & produce
urine
• 5) Clean blood goes back into system
via renal vein
• 6) Waste (urine) goes down ureter
How do I make pee?
Ureters & Bladder & Urethra
• Ureters are long tubes
– Connect kidneys to bladder
• The bladder is sac covered in muscle
tissue
• Urine enters bladder it expands
– Can hold 1L of urine
• The muscles contract and push the
urine out through the urethra
Ureters & Bladder & Urethra
The Skin
• Has anyone ever tasted their sweat?
– What does it taste like?
• Below the surface of your skin there are
1000s of tiny sweat glands
• What does sweat do?
– Keeps you cool
– Removes excess salt
The Power of Urine
• Urine can tell you if you have certain
diseases
– Diseases that for example affect how the
kidneys function
• Could have protein in urine because
filtration is not happening correctly
• Glucose in the urine if you have diabetes
The Power of the Nose
Dialysis
• If your kidneys do not work properly
medicine has invented a machine to do
the work for you
• Dialysis Machine
• It can remove the waste
from the blood just as
your kidney would
• So how does it work?
Dialysis Cont…
• During dialysis
– Your blood enters a special tubing inside
the machine
– The tubing is selectively permeable
– The tube is surrounded by fluid
– Waste diffuses out of the blood into the
fluid while certain substances diffuse back
into the blood from the fluid
– Clean blood pumped back into patient
– Can take 4-6 hours to fully clean the blood
Cells & Systems
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