Transcript 10.4 – Kidney in Detail

Kidney in Detail
Standard Grade Biology
Excretion by the Kidney
• Urea
-nitrogenous waste
-made by liver
-excess amino acids in blood
-toxic
• Why must nitrogenous waste be excreted?
1 – Filtration by the Kidney
•Supplied with blood
from renal artery
Renal
artery
•Inside it splits into
many fine capillaries
•Each capillary
supplies blood to
hundreds of
thousands of tiny
filtration units called
nephrons
Renal
vein
Ureter
Lets have a
look at a
nephron!!!
1.
Glomerulus brings a large
surface area of blood
capillaries in close contact
with Bowman’s capsule
2.
Liquid filtered from blood
under pressure (filtration)
3.
Glomerular filtrate produced
containing:
-water
-glucose
-salts
-urea
(Protein molecules and red blood
cells do not pass into tubule as
they are TOO BIG!!!!)
Blood from
renal artery
enters wide
capillary
Filtration
Glomerular
filtrate
Blood travels
through
narrow
capillary
towards rena
vein
Think…
• Which feature of the glomerulus helps the
process of filtration?
• Which 4 components of unfiltered blood
appear in the glomerular filtrate?
• Why do blood cells and protein molecules
not appear in the glomerular filtrate?
Key Words!!
Nephron:
structure in the kidney that acts as
a microscopic filtration unit
Glomerulus: dense mass of very fine
blood capillaries at the
nephron that act as a filter
Bowman’s capusle:
cup-shaped part of the
nephron that holds a
glomerulus and collects the
products of filtration from it
Glomerular filtrate: liquid removed from the blood by
filtration in the kidney
2 – Reabsorption by the Kidney
• Once the main components of glomerulur filtrate
enter the bloodstream
-they are no longer in bloodstream
• If nothing more happened in the nephron then all
the useful stuff would be lost in the urine!
• Therefore, glucose, water and some salts need
to be reabsorbed!
More water
reabsorbed
Glucose
reabsorbed
Final urine
containing:
-excess water
-unneeded salts
-waste urea
Variable amounts of water
and salts reabsorbed and
filtrate gradually turning into
urine
Think….
• Which three components of the glomerular
filtrate are reabsorbed?
• Why is it important for these to be
reabsorbed?
• Which substances are present in the final
urine?
• Summary of kidney function
2 – Controlling Water
Concentration
• Blood
-important part of internal environment
-constantly changing water concentration
-e.g.
exercising
drinking lots of water
• The body uses negative feedback control
to regulate water content of the blood
How does it work?
• Control of Water animation
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