Avalvular means to be without one or more valves and
also means not affecting valves. A valve is a natural
structure or man-made device in a passageway, tube,
vessel, or hollow organ that allows fluid or partly fluid
contents to travel in one direction, but closes to prevent
the flow of those contents in the opposite direction. For
example, some people are born without a pulmonary
valve, which is one of the heart valves. There are other
valves of the heart, namely the tricuspid valve, mitral
valve, and aortic valve which someone can be born
without. Absence of the heart valves and other valves
of the body are treated with surgery. In some cases,
without surgery, people born without certain valves will
be unable to live.
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Some capillaries and veins do not have valves and are thus avalvular. The capillaries act
as an exchange system that connects the smallest veins with the smallest arteries. Veins
carry blood to the heart whereas arteries carry blood away from the heart and to the

Avalvular comes from the Greek word "a" meaning "to do without," and the Latin word
"valva" meaning "folding door." Put the two words together and you have "to do without
(a) folding door."
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The valves of the heart.