What is the movement of substances within the body in body fluids called?

• A. Permeation
• B. Circulation
• C. Perfusion
• D. Diffusion

Answer: (B)

Circulation is the movement of substances through the body via the bloodstream, delivering oxygen and nutrients to cells and carrying away wastes. This system-wide transport is driven by the heart and vessels, moving fluids through the entire body rather than just within a tiny area. Permeation means crossing a barrier, diffusion is the spreading of particles from higher to lower concentration at the cellular level, and perfusion refers to blood flow to a specific tissue. Because the question describes the broad, body-wide transport of substances in body fluids, circulation best fits. For example, blood carries oxygen from the lungs to tissues and returns carbon dioxide to be exhaled.