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.

Transluminal procedures
Transluminal procedures are procedures occurring through lumina, including:
 * Natural orifice transluminal endoscopic surgery in the lumina of, for example the stomach, vagina, bladder or colon
 * Percutaneous transluminal angioplasty in the lumina of blood vessels