Artery
Because the heart pumps blood right into the arteries, the arteries are under a lot of pressure.  Unlike the veins, the arteries are always stretching and then squeezing to push blood through them to the body.  Because of this, an arterial bleed - bleeding from an artery - can be a medical emergency, especially if the artery is big.  Arterial bleeding can happen very quickly.  For example, if a person's femoral artery is cut, they can bleed to death.