• 13 parts
  • Checked October 2026

Countercurrent Multiplier Diagram

The nephron loop in the medulla: what leaves each limb, and how concentrated the fluid gets.

Countercurrent Multiplier Diagram

Name Date

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1 2 3 4 5 6 7 8 9 10 11 12 13
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Write the name of each numbered part.Answer key

  1. Descending limb
  2. Thick ascending limb
  3. Thin ascending limb
  4. Collecting duct
  5. Vasa recta
  6. Water leaving by osmosis
  7. Sodium and chloride pumped out
  8. Interstitial fluid of the medulla
  9. Filtrate entering the loop
  10. Filtrate at the bend
  11. Filtrate leaving the loop
  12. Interstitial fluid, outer medulla
  13. Interstitial fluid, inner medulla

Drawn for this site on 2026-10-03 from plain geometry. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Zoom out: the whole nephron

All 13 parts on the diagram

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The loop 8

  1. Descending limb Its wall lets water out and holds most salt in.
  2. Thick ascending limb It pumps salt out and lets no water follow.
  3. Thin ascending limb Water cannot leave here; some salt passes out.
  4. Collecting duct Water leaves it as it runs down through the medulla.
  5. Vasa recta Hairpin blood vessels that keep the gradient from washing out.
  6. Water leaving by osmosis Water moves out of the descending limb by osmosis.
  7. Sodium and chloride pumped out Active transport moves sodium and chloride into the interstitial fluid.
  8. Interstitial fluid of the medulla The fluid around the tubes, saltier toward the inner medulla.

How concentrated 5

  1. Filtrate entering the loop About 300 mOsm/L, as concentrated as blood plasma.
  2. Filtrate at the bend The most concentrated filtrate, about 1,200 mOsm/L.
  3. Filtrate leaving the loop Dilute, about 100 mOsm/L.
  4. Interstitial fluid, outer medulla About 600 mOsm/L, outer medulla.
  5. Interstitial fluid, inner medulla About 1,200 mOsm/L, inner medulla.

How this list was compiled: Every name, movement and figure was read on 2026-10-03 and kept only where two independent sources give it. (1) Wikipedia, text only: Countercurrent multiplication, Loop of Henle, Ascending limb of loop of Henle, Descending limb of loop of Henle, Vasa recta (kidney), Renal medulla and Collecting duct system, https://en.wikipedia.org/wiki/Loop_of_Henle . (2) Active salt transport and countercurrent exchange as the basis of urine concentration, Pflügers Archiv (2026), open access, read in full through Europe PMC, https://europepmc.org/article/PMC/PMC12904963 . (3) Textbook passages found by archive.org's full-text search: Human Anatomy and Physiology (2011), https://archive.org/details/isbn_9780133889550 ; Essentials of Renal Physiology (1999), https://archive.org/details/essentialsofrena0000redd ; Textbook of Nephrology (1989), https://archive.org/details/isbn_0683056204_1 ; Practical Fluids and Electrolytes (1991), https://archive.org/details/practicalfluidse00krie ; Renal Physiology (1992 and 1997 editions), https://archive.org/details/renalphysiology00koep_0 ; Renal Physiology: A Clinical Approach (2012), https://archive.org/details/renalphysiologyc0000danz ; Bucket Diagrams: A Problem-Solving Approach to Renal Physiology (1994), https://archive.org/details/bucketdiagramspr0000jans . The drawing is our own. Licence: own work

The drawing: Drawn for this site on 2026-10-03 from plain geometry. Own original drawing; nothing traced or copied. Licence: own work

How it works

The same drawing twice. The first view names the limbs of the nephron loop, the vasa recta, the collecting duct and what leaves each limb. The second marks five places and how concentrated the fluid is there.

Read the full guide

The loop

Filtrate comes down the descending limb, turns at the bend and goes up the thin, then the thick ascending limb. Water leaves the descending limb by osmosis. The thick ascending limb pumps sodium and chloride out and lets no water follow. Textbooks call the arrangement the countercurrent multiplier.

How concentrated

Each large dot stands for about 100 mOsm/L. Filtrate enters at about 300, as concentrated as blood plasma, reaches about 1,200 at the bend and leaves at about 100. The fluid around the tubes rises from about 600 in the outer medulla to about 1,200 in the inner medulla.

  • Descending limb: water out. Ascending limb: salt out.

Questions and answers

What is the countercurrent multiplier?

It is the textbook name for the way the two limbs of the nephron loop, carrying fluid in opposite directions, build a concentration gradient in the medulla: the thick ascending limb pumps salt out, and water leaves the descending limb.

Why is the filtrate dilute when it leaves the nephron loop?

The ascending limb moves sodium and chloride out and does not let water follow. The fluid falls from about 1,200 mOsm/L at the bend to about 100, which is why this limb is called the diluting segment.

What do the vasa recta do?

They are hairpin blood vessels beside the loop. Blood runs down and back up in them, and this countercurrent exchange keeps the concentration gradient of the medulla from being washed out.

Is this the art-labeling activity: osmotic and solute concentrations in the nephron loop?

No. That is a publisher’s activity with a figure of its own. This drawing is ours and is no answer key. It names the same loop, the water and salt that leave it, and the concentrations that two sources give.

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