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Learning Intentions
I can describe the role of the kidneys.
I understand and can describe the process
of filtration and reabsorption in the nephron.
Success Criteria
I can label a diagram of the urinary system.
I can name the parts of the kidney nephron.
I can describe the process of filtration and
reabsorption.
The Kidneys
The kidneys have 2 main
functions.
– Maintaining water balance.
– Cleaning of the blood- getting rid
of poisonous waste substances,
such as urea, from the body.
Urea
• Urea is a poisonous
waste product formed
from amino acids.
• It is made in the liver
and travels to the
kidneys in the blood
where it is filtered from
the blood
• If not removed its build
up causes death!
A
Kidney
B
F
Renal vein
Renal artery
C
ureter
D
bladder
E
urethra
The Kidney’s under take two functional
processes:
• Filtration of the blood
• Selective re-absorption of useful
substances e.g. Water, glucose, salts.
How the Kidneys Work
• Each kidney is made up
of about 1 million tiny
filtering units called
NEPHRONS which filter
the blood and then
allow reabsorption of
the useful substances
back into the
bloodstream.
Bowman’s
Capsule
Look at these
animations.
How the kidneys work
• Blood from the renal artery enters a knot
of capillaries called the GLOMERULUS.
• The blood is under high pressure and all
small molecules such as water, salt,
glucose & urea are forced out of the blood
and into the BOWMANS CAPSULE.
• The filtered small molecules make up glomerular
filtrate and passes into the nephron.
• Useful substances such as glucose, water & salt
are reabsorbed into the capillaries from the
Kidney tubule.
• The urea and excess water & salt are passed
into the COLLECTING DUCT.
• This is passed along the URETER and stored in
bladder as URINE.
• Urine leaves the body via the URETHRA.