Answer:In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including aerodynamics (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion).
Explanation:
It's mainly because your arteries pump a lot of blood so a few things could happen, you could tear the artery or the needle could pop out, they're usually harder to get to, and it's just very dangerous.