Lumen - GCSE Biology Definition

In GCSE Biology, 'lumen' refers to the inside space or cavity within a tubular structure in the body, like blood vessels or the intestines. For example, in blood vessels, the lumen is the hollow centre through which blood flows, and in the intestines, it’s where food passes through and gets digested. The size of the lumen can change in blood vessels to control blood flow and pressure, which is important for maintaining healthy body functions. In GCSE Biology, knowing what a lumen is helps students to learn how substances move through different body systems.