lumen (anatomy)

A lumen (pl. lumina) is an inner space, lining or cavity.The interior of a vessel within the body, such as the small central space in an artery or vein, or any of their relating vessels through which blood flows. The inner membrane space of a chloroplast, mitochondrion, endoplasmic reticulum, golgi apparatus or even a microtubule. On a larger scale, the interior of the gastrointestinal tract may also be referred to as its lumen, and likewise the pathways of the bronchi in the lungs or the single pathway of the vagina.
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