Blood Vessel
noun, の adjective
The pipe that holds your blood is your blood vessels.
けっかん
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. The けつ goes to けっ.
彼は血管が切れそうなぐらい怒っていた。
He was so angry that his veins were popping out.