• 11 parts
  • Checked October 2026

Capillary Exchange Diagram

One capillary, the two pressures across its wall, and where fluid leaves and returns.

Capillary Exchange Diagram

Name Date

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

  1. Arterial end
  2. Venous end
  3. Capillary wall
  4. Direction of blood flow
  5. Hydrostatic pressure of the blood
  6. Colloid osmotic pressure of the blood
  7. Net filtration
  8. Net reabsorption
  9. Interstitial fluid
  10. Tissue cells
  11. Lymphatic capillary

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 Next: the vessels of a whole capillary bed

All 11 parts on the diagram

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  1. Arterial end The end of the capillary nearest the arteriole. Blood pressure is highest here.
  2. Venous end The end of the capillary nearest the venule. Blood pressure has fallen by here.
  3. Capillary wall A single layer of thin endothelial cells. Fluid and small solutes cross it; most proteins do not.
  4. Direction of blood flow Blood moves from the arteriole to the venule. Flow is slow here, which gives time for exchange.
  5. Hydrostatic pressure of the blood Blood pressure pushing fluid out through the wall. It is higher at the arterial end.
  6. Colloid osmotic pressure of the blood The pull of the plasma proteins that draws fluid in. It is about the same at both ends.
  7. Net filtration Fluid leaves the capillary near the arterial end. There the outward push is greater than the inward pull.
  8. Net reabsorption Fluid returns to the capillary near the venous end. There the inward pull is greater than the outward push.
  9. Interstitial fluid The fluid between the blood vessels and the cells. Filtered fluid joins it.
  10. Tissue cells The cells the capillary serves. They take what they need from the fluid around them.
  11. Lymphatic capillary A closed-ended vessel that takes up excess interstitial fluid. It returns the fluid to the blood as lymph.

How this list was compiled: Every name and direction read on 2026-10-03 and kept only where two independent sources give it. (1) Wikipedia, text only: Capillary, Microcirculation, Starling equation, Oncotic pressure, Extracellular fluid and Lymphatic system, https://en.wikipedia.org/wiki/Microcirculation : filtration mainly on the arteriolar side and reabsorption mainly on the venular side, hydrostatic pressure pushing out and colloid osmotic pressure of the plasma proteins pulling in, interstitial fluid, lymphatic capillaries with closed ends that return excess fluid. (2) U.S. National Cancer Institute, SEER Training Modules, Physiology of Circulation, https://training.seer.cancer.gov/anatomy/cardiovascular/blood/physiology.html : fluid movement across the capillary wall set by hydrostatic and osmotic pressure, so that substances leave the blood at one end of the capillary and return at the other; blood flow slowest in the capillaries. (3) Two books read by full-text search at archive.org: Arthur C. Guyton, Dynamics and Control of the Body Fluids (1975), https://archive.org/details/dynamicscontrolo0003guyt (the arterial end, the middle and the venous end of a capillary, capillary pressure and plasma colloid osmotic pressure), and an illustrated review of physiology (1993), https://archive.org/details/illustratedrevie0000bast (net filtration near the arterial end, reabsorption at the venule end). 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. Not to scale. Licence: own work

How it works

Capillary exchange is how fluid crosses the capillary wall. In the classic textbook model, blood pressure pushes fluid out near the arterial end and the pull of the plasma proteins draws most of it back near the venous end.

Read the full guide

Two pressures, two ends

The solid arrows are the hydrostatic pressure of the blood, which pushes fluid out. The outlined arrows are the colloid osmotic pressure, which pulls fluid in. At the arterial end the push is greater, so there is net filtration. At the venous end the pull is greater, so there is net reabsorption.

What is left over

Filtered fluid joins the interstitial fluid around the tissue cells. The lymphatic capillary takes up the excess.

  • Arrow lengths show which pressure is greater at each end. They are not measured values.

Questions and answers

What is capillary exchange?

The movement of fluid, gases, nutrients and wastes between the blood in a capillary and the fluid around the tissue cells. Fluid crosses the wall by filtration and reabsorption; gases cross by diffusion.

What is the difference between filtration and reabsorption?

Filtration is fluid leaving the capillary for the interstitial fluid, mainly near the arterial end. Reabsorption is fluid moving back into the capillary, mainly near the venous end.

What are hydrostatic pressure and colloid osmotic pressure?

Hydrostatic pressure is the pressure of the blood against the capillary wall; it pushes fluid out. Colloid osmotic pressure comes from the plasma proteins, which stay in the blood; it pulls fluid in.

Where does the fluid that is not reabsorbed go?

Into the lymphatic capillaries, which return it to the blood as lymph. Newer research finds that in most tissues little fluid is reabsorbed at the venous end and most of it returns this way.

How do I correctly label the following anatomical features of capillary fluid exchange?

Find the arterial end and the venous end first. Then name the arrow that points out, the arrow that points in, and the net movement at each end. This drawing is our own, made for practice.

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