Capillary blood is composed of which components?

• A. Interstitial fluid and intracellular fluids, arterial and venous blood
• B. Plasma and platelets
• C. Lymph
• D. Cerebrospinal fluid

Answer: (A)

Capillary blood isn’t a pure arterial or venous sample; it’s a blend that comes from the capillary bed. As blood passes through capillaries, plasma can mix with the surrounding tissue fluid (interstitial fluid), and that tissue fluid can become part of the capillary sample. So capillary blood contains components from arterial and venous blood plus interstitial (tissue) fluid. Intracellular fluid stays inside cells, and fluids like lymph or cerebrospinal fluid are separate from the bloodstream, not part of capillary blood. That combination—arterial and venous blood with interstitial fluid—best captures what capillary samples typically contain.