If Blood Is Red, Why Are Your Veins Blue? (Tech Insider, 10/2018) Anatomy and Function of the Heart. Heart With Blood Flow. CrashCourse: Circulatory System. Circulatory system. Types of Blood Vessels (eMedTV) What is Blood? (America's Blood Centers) How Does Blood Clot (eMedTV) Electric Beats - Pacemakers and the Human Heart. The Components of Blood and Their Importance (American Society of Hematology) Is blood ever blue? (Mental Floss)