In biology, a lumen (from Latin lumen, meaning 'an opening'; plural lumina) is the inside space of a tubular structure, such as an artery or intestine. - ppt download
Molecular Regulation of Lumen Morphogenesis - ScienceDirect
Växter | Biologi
Forum OSN | Gudang Soal OSN/KSN Biologi - SMA
What is the function of a lumen in a cell? - Quora