Excretion
WASTE PRODUCTS OF BODY FUNCTIONS ARE
REMOVED BY THE KIDNEYS
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Why do animals need an excretory system?
What parts make up the excretory system?
How does a kidney work?
What can be done if the system does not function?
Learning Outcomes
know that the kidneys regulate the
water content of the blood and
remove waste products from the
blood.
 recognise and label a given diagram
of the human excretory system to
show: kidneys, renal artery, renal
vein, ureters, urethra, bladder.
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Excretion
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Waste products made in our cells need to
be removed or they would poison us. This
is excretion.
In the liver excess amino acids are
broken down to make urea.
The urea is taken from the liver to the
kidneys, where it is excreted.
The diagram below shows the
excretory organs in our body.
The Kidneys
Pupil Activity

Colouring in sheet

The Urinary System
• Colour in the diagram
• Answer the questions
The Kidney
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Kidneys help to maintain the internal
environment by: 
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Filtering the blood
Reabsorbing all the sugar
Reabsorbing the dissolved ions needed by
the body
Reabsorbing as much water as the body
needs
Releasing urea, excess ions and excess
water as urine
Learning Outcomes
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know that the waste, a solution containing urea and
excess salts called urine, passes from the kidneys
in the ureters to the bladder where it is stored
before being passed out of the body.
Interpret data about the level of substances
present in urine and during passage through the
kidney.
observe gross structure of a section through a
kidney
recognise and label a given diagram of a section
through a kidney to include: cortex, medulla, pelvis,
ureter and position of nephrons
Pupil activity

Biology Foundations pages 82 – 83
Cleaning blood and balancing water –
your kidneys
 Answer questions 1 – 4, 7
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Copy and complete the “what you
need to remember” sentences
Pupil Activity – Kidney
Dissection
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Watch the demonstration on dissecting a
kidney.
In groups – dissect a kidney – try to
identify all areas labelled in the diagram –
medulla, cortex, pyramid, pelvis, ureter.
You must wear safety goggles and a lab
coat, and wash hands with anti-septic
handwash once finished.
Learning Outcomes
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recognise and label a given simplified diagram of
a nephron and its associated blood supply to
show:
 capillary knot,
 Bowman's capsule,
 tubule,
 collecting duct,
 capillary network.
understand the process of filtration under
pressure
know that selective reabsorption of glucose,
some salts, and much of the water takes place in
the tubule.
The Nephron
As the blood passes through the capillary
knot it is filtered, small molecules, urea,
glucose, salts and water, pass out the
capillary into the nephron
The glucose, water and some of the
salts are needed by the body and are
reabsorbed back into the blood from
the nephron.
 The urea and waste salts left are
dissolved in water to form urine. It
flows down the ureter to the bladder.
 The “cleaned” blood leaves the
kidneys in the renal vein
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Activity
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Complete the diagram handed out on
the structure of the nephron
Pupil activity

colour in the formation of urine sheet.
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Answer questions 1 – 9
• TRY ANSWER ALL QUESTIONS – information
needed should all be on the side of the sheet
that you coloured in!!
• Do not write on the sheet – write out full
sentences into your book!!
• You have 25 minutes to complete this activity
Learning Outcomes
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know that the kidneys regulate the
water content of the blood by
producing dilute urine if there is too
much water in the blood or
concentrated urine if there is a
shortage of water in the blood.
ADH
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ADH is a hormone, which controls
the amount of water reabsorbed
from the nephron.
ADH is produced by the pituitary
gland in the brain.
Control of water content
The effect of ADH on the
kidney Less ADH released into
Detected by the
pituitary gland
the blood stream
Less water reabsorbed
by the nephron
More dilute urine
produced
Increase in water level
Normal blood water level
Small amount of concentrated
urine produced
decrease in water level
Detected by the
More water reabsorbed
pituitary gland
by the nephron
more ADH released into
the blood stream
Tinkle Testing
Practical Lesson
Aim: to analyse urine samples and
to draw conclusions from the
results
Urine Samples
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Forensic scientists and doctors can
discover a lot about someone from
their urine, including kidney disease,
diabetes and drug abuse.
Urine sampling in sports
Monitor hydration levels
 Test for doping
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Urine Chart
Fluid loss has a negative
effect on performance
Sweat loss varies
between different sports
Progress Questions
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Define the term homeostasis.
What is urea? Where is it made?
What is ultrafiltration? Where does it
occur?
What is selective reabsorbtion?
What are the differences in composition
between blood entering and leaving the
kidney?
What is ADH? Where is it produced?
What is it’s function?
Progress Questions - 2
What would be the effect on the
volume and concentration of urine
of drinking a lot of fluid on a cold
day?
 Explain why the regulation of water
content of the blood is an example
of negative feedback!
 If a person has kidney failure, how
can they be kept alive?
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Pupil activity
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Extension
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Handout – the kidneys and urinary
system
• Answer questions 1 – 7
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Homework
colour in the formation of urine
sheet.
 Answer questions 1 - 9
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Kidney Disease
Treatment of kidney disease using
kidney dialysis or kidney
transplants!
Learning Outcomes
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know that kidney failure may be treated
by a transplant or by a dialysis machine
and compare the advantages and
disadvantages of the use of these
methods
know that a diseased kidney may be
replaced by a healthy one by transplant
from a donor of a similar 'tissue type'
to the recipient. The donor kidney may
be rejected, attacked by the immune
system, unless anti-rejection drugs are
taken.
Learning Outcome
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understand that in a dialysis
machine a person's blood flows
between selectively permeable
membranes.
Dialysis in the Kidney
Kidney Dialysis
Dialysis removes substances from a
solution by diffusion
 This principle is put to use in a
kidney dialysis machine
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Kidney Dialysis - machine
Kidney Dialysis machine
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In a dialysis machine a person's
blood flows between selectively
permeable membranes.
It is important that useful
substances in the blood, such as
glucose and salts, are not lost.
To prevent this the dialysis fluid
contains the same concentration of
these substances as blood plasma.
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This ensures that only urea and
excess salts and water diffuse into
the dialysis fluid.
This treatment has to be carried
out at regular intervals
Transplants Vs Dialysis
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Advantages
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Disadvantages
Normal lifestyle
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Dialysis machine
available for others
to use
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Dialysis machines
expensive to buy and
maintain
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Requires a suitable donor
(tissue match)
Operation is expensive
Risk of rejection of
transplanted kidney (use
of immunosupressor drugs)
Religious beliefs