A river carrying dirt into a lake
Organelles exist within cells, which exist within tissues. Communities exist within ecosystems, which exist in the biosphere.
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In biology, the inner lining of tubular structures is called a lumen.
This can refer to numerous tubular structures in the body, such as the lumen of the veins and arteries, the lumen of the intestines or the tubes in the kidneys.
This term can also be used to describe a space defined by membranes of cell organelles such as the lumen of the mitochondria, the Golgi apparatus, and others.
