1. 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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2. 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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3. Nephrons There are about _______________ in each mammalian kidney

4. 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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5. Excellent! There are about one million nephrons in each kidney.
BOM CHICKA WOW WOW
Excellent! There are about one million nephrons in each kidney.
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6. Not quite. Try re-watching the videos or check your textbook!
Errr…
Not quite. Try re-watching the videos or check your textbook!
TRY AGAIN

7. Label the nephron A H G D B E C F Label A, B & C Label D, E & F
Label G & H

8. 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

9. Ohh yeah!
On to the next one…

10. Not quite… Try again!

11. 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

12. Ohh yeah!
On to the next one…

13. Not quite… Try again!

14. 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

15. Not quite… Try again!

16. Finito!
(except not)

17. 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

18. (Hint: It’s the other one)
Not quite…
(Hint: It’s the other one)

19. Ohh yeah!
On to the next one…

20. Blood Blood comes to the kidneys via the:
Renal vein
Renal artery
The ____________ arteriole brings blood to the glomerulus.
Efferent
Afferent

21. One down… one to go!

22. (Hint: it’s the other one)
Not quite.
(Hint: it’s the other one)

23. Ohh yeah!
On to the next one…

24. (Hint: it’s the other one)
Not quite.
(Hint: it’s the other one)

25. 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

26. Let’s give it another whirl!
Not quite.
Let’s give it another whirl!

27. 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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28. 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
Water K+
NaCl
Drugs e.g. aspirin
Bicarbonate ions
Hydrogen ions
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29. Amino acids are actively transported into transported from the proximal tubule into the blood. This is reabsorption.
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30. Glucose is actively transported into transported from the proximal tubule into the blood. This is reabsorption.
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31. As salt moves out of the tubule, water passes by osmosis back into the blood. This is reabsorption.

32. Sodium ions are actively transported back into the blood and chloride ions follow passively. This is absorption.
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33. 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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34. Drugs such as aspirin and penicillin and poisons identified by the liver are actively secreted into the tubule.
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35. Some hydrogen ions are secreted into the proximal tubule
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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36. Potassium ions are actively transported into the blood
Potassium ions are actively transported into the blood. This is absorption.
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37. 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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38. 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
Diffusion
Osmosis

39. Ohh yeah!
On to the next one…

40. (Hint: it’s the other one)
Not quite.
(Hint: it’s the other one)

41. 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

42. Ohh yeah!
On to the next one…

43. (Hint: it’s the other one)
Not quite.
(Hint: it’s the other one)

44. Loop of Henle
What part of the kidney does the loop of Henle mostly sit?
cortex
medulla
pyramid
pelvis
Cortex
Medulla
Pelvis
Pyramid
Source:

45. Ohh yeah!
On to the next one…

46. Let’s try again, shall we?
Not quite.
Let’s try again, shall we?

47. Loop of Henle
As 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

48. BOO YAH! On to the next one...

49. (Hint: it’s the other one)
Not quite.
(Hint: it’s the other one)

50. Ohh yeah!
NEXT!

51. (Hint: it’s the other one)
Not quite
(Hint: it’s the other one)

52. 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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53. 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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54. 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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55. 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!