The Nephron
HSC Biology: Maintaining a Balance
Syllabus link: explain how the processes of filtration and reabsorption in
the mammalian nephron regulate body fluid composition
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Instructions and notes
The nephron is one of the more difficult concepts to
understand in the Maintaining a Balance module of the
HSC Biology course.
This resource is designed to build upon your knowledge
of the kidney, test your understanding of the nephron
and be used as a study tool for your exams.
Work through the questions slowly and don’t cheat – it’s
not going to help you understand the concept!
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Nephrons
There are about _______________ in each mammalian
kidney
10 000 nephrons
100 000 nephrons
1 000 000 nephrons
2 000 000 nephrons
Formation of urine
 The nephron is a small filtering unit in which urine is
produced.
 The three processes in the formation of urine are:
filtration, reabsorption and secretion.
 The kidneys process a large amount of blood, but
produce a relatively small amount of urine.
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BOM CHICKA WOW WOW
Excellent!
There are about one million nephrons in
each kidney.
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Errr…
Not quite.
Try re-watching the videos or check your
textbook!
TRY AGAIN
Label the nephron
A
H
G
D
B
E
C
F
Label A, B & C
Label D, E & F
Label G & H
Label the nephron
The parts of the nephron labelled A, B and C,
respectively, are:
Bowman’s capsule, distal convoluted tubule, collecting duct
Bowman’s capsule, proximal convoluted tubule, collecting duct
Glomerulus, loop of Henle, collecting duct
Glomerulus, loop of Henle, urethra
Return to diagram
Ohh yeah!
On to the next
one…
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Try again!
Label the nephron
The parts labelled D, E and F, respectively, are:
Bowman’s capsule, loop of Henle, distal convoluted tubule
Bowman’s capsule, proximal convoluted tubule, loop of Henle
Glomerulus, loop of Henle, collecting duct
Glomerulus, proximal convoluted tubule, loop of Henle
Return to diagram
Ohh yeah!
On to the next
one…
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Try again!
Label the nephron
The parts labelled G and H, respectively, are:
Afferent arteriole, efferent arteriole
Affluent arteriole, efferent arteriole
Efferent arteriole, afferent arteriole
Efferent duct, afferent duct
Return to diagram
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Try again!
Finito!
(except not)
Filtration, Reabsorption and
Secretion
Filtration is the removal of wastes from blood and other
fluids through a semi permeable membrane.
Reabsorption is an active process that requires energy. It
is the movement of materials being reabsorbed into the
blood.
Secretion is:
The body actively transporting substances from the nephron into the blood
The body actively transporting substances from the blood into the nephron
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(Hint: It’s the other one)
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Blood
Blood comes to the kidneys via the:
Renal vein
Renal artery
The ____________ arteriole brings blood to the
glomerulus.
Efferent
Afferent
One down…
one to go!
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(Hint: it’s the other one)
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(Hint: it’s the other one)
The Glomerulus
The glomerulus is a ball of capillaries in which blood
pressure is so high that some of the liquid from the
blood is forced through the walls of the blood vessels
into the Bowman’s capsule.
This liquid does not have:
Blood cells
Sodium chloride (NaCl)
Large proteins
Blood cells AND large proteins
Not quite.
Let’s give it another whirl!
Great work!
 The filtrate should not contain large proteins or blood cells
but does contain:
- Blood plasma
- Water
- Solutes: NaCl, K+, HCO3- Glucose and amino acids
- Other ingested substances like penicillin and aspirin
- Hormones
- Nitrogenous waste products such as urea
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Proximal tubule
 Reabsorption is an active process that requires energy.
Click on the different substances to see if they are
secreted into the nephron or reabsorbed into the blood.
Amino acids
Glucose
K+
Drugs e.g.
aspirin
Water
NaCl
Bicarbonate
ions
Hydrogen
ions
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Amino acids are actively transported
into transported from the proximal
tubule into the blood. This is
reabsorption.
BACK
Glucose is actively transported into
transported from the proximal tubule
into the blood. This is reabsorption.
BACK
As salt moves out of the tubule, water
passes by osmosis back into the
blood. This is reabsorption.
BACK
Sodium ions are actively transported
back into the blood and chloride ions
follow passively. This is absorption.
BACK
Most of the bicarbonate ions are
actively reabsorbed in the proximal
tubule. Some hydrogen ions may be
secreted in order to keep the
constant pH of blood and body
fluids.
BACK
Drugs such as aspirin and penicillin
and poisons identified by the liver
are actively secreted into the tubule.
BACK
Some hydrogen ions are secreted into
the proximal tubule. This is done to
maintain the constant pH of blood
and body fluids
BACK
Potassium ions are actively
transported into the blood.
This is absorption.
BACK
Reabsorption checkpoint
Surrounding each tubule is a large capillary
network. As the filtrate travels through the
tubules and the loop of Henle, the substances
that the body can re-use are reabsorbed into
the blood.
These substances include glucose, amino acids,
vitamins, minerals, bicarbonate and water.
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Loop of Henle
The loop of Henle has a descending and an ascending
limb.
The walls of the loop of Henle are permeable to water but
not to salt.
Water passes across the membrane by:
Diffusion
Osmosis
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(Hint: it’s the other one)
Loop of Henle
In the ascending portion of the loop of Henle, the walls
are permeable to salt not water.
Salt passes out passively across a thin-walled section and
then ____________ across a thick-walled section.
_____________ is:
actively
passively
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(Hint: it’s the other one)
Loop of Henle
What part of the kidney does the loop of Henle mostly sit?
cortex
medulla
pyramid
pelvis
Source: http://www.comprehensive-kidney-facts.com/kidney-anatomy.html
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Let’s try again, shall we?
Loop of Henle
As water is removed from the loop of Henle in the
descending limb, the concentration of salt in the
medulla:
Decreases
Increases
As salt is removed from the loop of Henle in the
ascending limb, the concentration of salt:
Decreases as it moves towards up to the cortex
Increases as it moves up towards the cortex
BOO YAH!
On to the next one...
Not quite.
(Hint: it’s the other one)
Ohh yeah!
NEXT!
Not quite
(Hint: it’s the other one)
Source: http://www.colorado.edu/intphys/iphy3410saul/resources/kidney.html
As you can see in the diagram above, the concentration of salt is high
in the bottom of the loop of Henle in the medullary region of the kidney.
This is called an osmolarity gradient, where the solute concentration
(sodium and urea in this case) increases from the cortex down to the
inner medulla.
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Distal tubule
In the distal tubule, the pH of the blood and the
level of salts, in particular sodium and
potassium, are adjusted by selective absorption
and secretion.
In the distal tube, small amounts of NaCl and H2O
are reabsorbed and K+ and H+ ions are
secreted.
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Collecting Duct
The collecting duct transports urine to the pelvis of the
kidney which leads to the ureter.
The walls of the collecting duct are are permeable to
water, but not salt which results in water passing out of
the duct by osmosis. Urea and salt is also actively
reabsorbed in the duct.
This results in the formation of of urine.
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FIN!
Questions to ask yourself:
•What do I know?
•Where are the gaps in my knowledge? What do I need to study
in order to understand this concept?
This is a resource for you! So feel free to change it up, add
things in and build upon your knowledge. This could be a very
useful study tool for you!