The heart is a muscular organ with four chambers. Located just behind and slightly left of the breastbone, it pumps blood through the network of arteries and veins called the cardiovas- cular system.

Medically reviewed by Jeffrey S. Lander, MDMedically reviewed by Jeffrey S. Lander, MD The cardiovascular system, also known as the circulatory system, includes the heart and blood vessels. It plays ...

Your venous system is a network of veins that carry blood back to your heart from other organs. We’ll explain the basic structure of a vein before diving into different types of veins and their ...