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 notesThe 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! NEXT

NephronsThere are about _______________ in each

mammalian kidney

10 000 nephrons

100 000 nephrons

1 000 000 nephrons2 000 000 nephrons

Formation of urineThe 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 nephronA

B

C

D

E

F

GH

Label A, B & C

Label D, E & F Label G & H

Label the nephronThe parts of the nephron labelled A, B and C,

respectively, are:

Return to diagram

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

Ohh yeah!On to the

next one…

Not quite… Try again!

Label the nephronThe parts labelled D, E and F, respectively, are:

Return to diagram

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

Ohh yeah!On to the

next one…

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Label the nephronThe parts labelled G and H, respectively, are:

Return to diagram

Afferent arteriole, efferent arteriole

Affluent arteriole, efferent arteriole

Efferent arteriole, afferent arteriole

Efferent duct, afferent duct

Not quite… 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 bloodThe body actively transporting substances from the blood into the

nephron

Not quite…(Hint: It’s the other

one)

Ohh yeah!On to the next

one…

BloodBlood 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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one)

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next one…

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one)

The GlomerulusThe 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 ureaNEXT

Proximal tubuleReabsorption 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.

Bicarbonate ions

Hydrogen ions

Water

NaClK+

Amino acids

Glucose

Drugs e.g. aspirin

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Amino acids are actively transported into transported from the proximal tubule into

the blood. This is reabsorption.

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Glucose is actively transported into transported from the

proximal tubule into the blood. This is reabsorption.

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As salt moves out of the tubule, water passes by osmosis back

into the blood. This is reabsorption.

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Sodium ions are actively transported back into the blood

and chloride ions follow passively. This is absorption.

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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.

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Drugs such as aspirin and penicillin and poisons identified

by the liver are actively secreted into the tubule.

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Some hydrogen ions are secreted into the proximal tubule. This is done to maintain the constant

pH of blood and body fluids

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Potassium ions are actively transported into the blood.

This is absorption.

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Reabsorption checkpointSurrounding 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 HenleThe 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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one…

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one)

Loop of HenleIn 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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next one…

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one)

Loop of HenleWhat part of the kidney does the loop of Henle

mostly sit?

cortex

medulla

pelvis

pyramid

Source: http://www.comprehensive-kidney-facts.com/kidney-anatomy.html

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next one…

Not quite.Let’s try again, shall

we?

Loop of HenleAs water is removed from the loop of Henle in the

descending limb, the concentration of salt in the medulla:

As salt is removed from the loop of Henle in the ascending limb, the concentration of salt:

Decreases

Increases

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)

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.

Source: http://www.colorado.edu/intphys/iphy3410saul/resources/kidney.html

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Distal tubuleIn 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 DuctThe 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!