Fluids are injected into the circulatory system through the veins and not arteries, why is this?

Reasons: Veins flow toward the heart. IV medications are delivered to the heart and from there are rapidly dispersed throughout the body. Arteries travel away from the heart and toward the organs and extremities. A medication delivered into an arm artery would only travel to that hand. Also, arteries are much higher pressure vessels. There are more potential complications from puncturing an artery.