Cells & SystemsThe 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– Excess salt– Solid waste (poop) – Etc …

• So how do we break them down and get rid of them?

GROSS!!!!

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 & Systems4 Down – 1 More To Go!