bone depressions
A capillary is hollow. It is the smallest of the blood vessels, the tubes that carry blood.
vessel elements, tracheids, fibres, and parenchyma
It better not be. It is filled up with brain tissues and blood vessels.
Smooth muscle (involuntary)lines ducts and vessels.
To become a hollow, another hollow must eat your soul. Once they have taken your soul, you become a hollow. :D
sound
Smooth muscle activity is responsible for involuntary body activities and the contractility of hollow organs. Hollow organs include the bladder gastrointestinal tract blood vessels, and the uterus.
multiunit smooth muscle are found in those areas and a few more.
It's found mainly in the wall of hollow viscera e.g. gut, ureters and many blood vessels
Arteries are hollow tubes that carry blood away from the heart. In that senses, they are a type of tunnel, as are all blood vessels.
swamp swale
Valves are hollow shaped devices that regulate the flow of afluid opening or closing or by just obstructing various passageways. Their importance in the human is to prevent back flow of blood in the veins. By doing this it also stops blood from clotting in the veins.