The Cardiovascular System
Every living thing, from tiny bacteria, to giant oak trees, to you and me, is made of tiny things called cells. When groups of cells work together, they form structures called tissues.
When groups of tissues work together, they form structures called organs. Your brain, lungs, and heart, are all examples of organs.
When groups of organs work together, they make organ systems, which are sometimes just called systems. Your body has many systems, including the cardiovascular system.
In this lesson, you will learn more about the cardiovascular system, and the important things it does to keep you alive.
