Final answer:
The word built using the prefix vascul/o that means pertaining to outside a vessel is 'extravascular'. This term describes areas or spaces outside the blood vessels, which include veins, arteries, and capillaries.
Step-by-step explanation:
Using the prefix vascul/o, which relates to blood vessels, we can build the word extravascular to mean pertaining to outside a vessel. The term extravascular is utilized to describe an area or space that is outside the blood vessels. When we break down the word, 'extra-' means outside, and 'vascular' pertains to blood vessels, which include structures like veins, arteries, and capillaries.
Blood vessels are hollow, tube-like structures through which blood flows as part of the cardiovascular system. Arteries carry blood away from the heart, while veins direct blood back towards the heart. The extravascular space is important as it is involved in various physiological processes and may also be referenced in the context of diseases or medical procedures.