Excretory System
Section 3.4 p. 141-145
Learning Outcomes
• I can describe the role and function of the excretory System
• I can list and describe the individual organs that make up the
excretory system
• I can describe how the excretory system responds to changing
conditions
Where does it all go
• P. 141
• In a day you consume an average of 2.5L of water from what you eat
and drink
• Match the mechanisms with the correct volume lost
• A)Sweat
• B) Urine and Feces
• C) Breathed Out Air
a) 0.5L
b) 0.8L
C) 1.2L
What is our Excretory System
• So far we’ve learned about how our cell get the
molecules they need to survive, and perform
things like cellular respiration
• Many of the life processes produce waste
products that must be removed from our body
(CO2 by the lungs)
• But how does our body remove other harmful
waste products?
• Excretory System: removes chemical and gaseous
wastes from the body
• These waste products derive from
• Breaking down of proteins creates ammonia
• Chemical processes create water & salt
The Liver
• We know that the Liver produces
Bile used by the digestive system
• But it processes almost all of the
substances entering your body
helping to purify the blood
• It helps to filter our blood of many
unwanted toxins
• Ammonia which is created by the
break down of proteins, is converted
into a much less harmful chemical
called Urea
• Urea is then released back into the
bloodstream where it can be removed
from the body
The Kidneys
• The kidneys are the main organs of excretion
• They act as filters to the blood
• They strain out the unwanted Urea, Water, and
other Salts, and produce urine
• Every drop of blood is filtered around 300 times
• Your kidneys filter around 180L of blood per day
• But yet you only excrete 1.5L of urine on average
• This is all based on how much water you consume in a
day
• Kidneys keep the proper amount of water in your
blood
• If there is too much water, you will excrete more
often
Formation of Urine
• Is a complicated process
• First- blood enters the kidney by the renal artery
• The arteries branch into smaller vessels until
becoming capillaries
• The small capillaries enter into filtering units called
Nephrons
• There are millions of the microscopic units known
as nephrons
• There job is to remove wastes from the blood
and produce urine
• “clean” filtered blood returns to the body through
the renal vein
• Urine flows out a separate vessel into the ureter
Factors affecting Amount of Urine
Production
• Diet
• Salt Consumption (causes water
retention)
• Natural Diuretics (chemicals that
increase urine production)
• i.e. Certain Citrus Fruits, Caffeine,
Alcohol)
• Fluid Consumption
• Body tries to maintain Homeostasis
• So depending on intake of fluids,
you will either excrete more or less
urine
• Climate
• Hot, sweat results in less urine
Ureters, Bladder, and Urethra
• Ureters are long tubes that connect the
kidney to the bladder
• Bladder is a sac covered in muscle
• Expands as it fills up
• Max it can hold is about 1L
• When it excretes urine the muscles contract
causing it to push the urine out through the
Urethra
• Urethra is a tube that connects the
bladder to the exterior of the body
The Skin
• Your sweat tastes salty
• This is due to the fact that your sweat
glands do more than just cool you off
• The sweat glands help to remove
excess salt from your blood
• So when you sweat you are also losing
salt
• This is why energy drinks say they are
more beneficial than water due to the
addition of electrolytes that are lost as a
result of sweating
Summary of what the Excretory System
Does
When there are problems with the
• We know the Excretory system performs a number of vital roles
• The Excretory system can also inform of us when certain diseases
might be present
• This is done by testing for certain molecules that shouldn’t be
there
• Presence of proteins can show early stages of kidney failure (can no
longer filter properly)
• Presence or glucose is an indicator of diabetes (body can no longer
regulate blood sugar levels correctly, so excess glucose is removed in
the urine)
• But how are we affected when it stops working correctly?
• Two Conditions we’ll focus on
• Kidney stones
• Renal Failure
Kidney Stones
• A kidney stone is a hard, crystalline
mineral material formed within the kidney
or urinary tract
• Kidney stones form when there is a
decrease in urine volume and/or an excess
of stone-forming substances in the urine
• Dehydration is a major risk factor for
kidney stone formation
• Most kidney stones will pass through the
ureter to the bladder on their own with
time.
• Passing of a kidney stone is extremely
painful since they are quite jagged
Kidney Stone Treatment
• The most prescribed is lots of water,
and some pain medication
• If they are bigger and won’t pass on
their own
• Drugs that cause a widening of the ureter
• Shock Wave therapy
• Ureterscopy
• Preventing future kidney stones
• Cause must be determined through
testing for chemical analysis
• But better hydration, and dietary practices
is the most common method
Renal Failure
• Renal Failure can happen for many different
reasons
• The kidneys fail to adequately filter waste
products from the blood
• When this occurs a procedure called Dialysis is
performed to remove the waste products from
the blood
• Kidney dialysis is a life-support treatment that uses a special machine
to filter harmful wastes, salt, and excess fluid from your blood. This
restores the blood to a normal, healthy balance. Dialysis replaces
many of the kidney's important functions.
• This process is performed about 3-4 times a week (for 4-6 hours), and
only prolongs a patients life for an extended period of time
Kidney Transplant
• A kidney transplant is the transfer of
a healthy kidney from one person
(the donor) into the body of a person
who has little or no kidney function
(the recipient).
• Overall, average kidney survival times
are:
• 1 year – 85-95%
• 5 years – 70-80%
• 15 years – 50-60%