lumen - the central opening within a tube or hollow organ.
The central opening in a vessel through which fluid flows is called a lumen. Examples of Lumina in the body are the inside of arteries and veins or the inside of the gastrointestinal tract.
It is a tunnel-like opening at the vessel's stern, through which the propeller or tail shaft passes, in order to connect the propeller to the engine.
A vessel is a ship or boat, or a tube in a body that carries fluids.
well it has a tube, and that tube is within a tube. therefore, the tube is somehow within the tube. that explains it
Phloem as it transports sugars two ways
Hounslow Central tube station was created in 1886.
Hendon Central tube station was created in 1923.
Finchley Central tube station was created in 1867.
ya it is a vain