Lumen (anatomy)

A 'lumen (Lat. lūmen'', an opening or light)  (pl. lumina) in biology is the inside space of a tubular structure, such as an artery or intestine. By extension, a lumen can also be the inside space of a cellular component or structure, such as the endoplasmic reticulum.

Examples of lumina

 * The interior of a vessel, such as the central space in an artery or vein through which blood flows.
 * The interior of the gastrointestinal tract
 * The pathways of the bronchi in the lungs
 * The interior of renal tubules and urinary collecting ducts
 * The pathways of the female genital tract, starting with a single pathway of the vagina, splitting up in two lumina in the uterus, both which continue through the fallopian tubes
 * Within a cell, the inner membrane space of a thylakoid, endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria or microtubule.