The cardiovascular system consists of your heart, arteries, veins, and blood vessels. This system is probably the most important system of the human body. Without your heart, you couldn't live. The cardiovascular system works like a train. Just picture it. The train picks people up at the stops and delivers them to a station that they need to go to for work in the morning. The same train picks up the people at the end of the day and brings them back to their home station. The heart pumps blood through it and brings oxygen and other important nutrients to all of the parts of your body. After your body uses the oxygen and takes in the nutrients the leftover waste is brought back by the blood so your body can dispose of it or throw it out like garbage.

Your heart is an organ and it is also a muscle. If you are not sure how big it is, just take a look at your fist. It's not very big, but it does a very BIG job for your body. It pumps over 4,000 gallons of blood daily and it beats 30 million times a year. It never takes a vacation. It pumps about 70 times a minute when you are relaxing. If you exercise, your heart works harder and pumps much faster. The heart contains chambers or little rooms for the blood to go in and out. The chambers are connected to valves. When you hear your heart beating or feel it beating, do you know what is happening? Your heart is passing the blood through the chambers. Connected to the heart are the arteries and veins. If you look at some types of pasta, they that look like tubes. This is what your arteries and veins look like. They are like tubes that carry the blood to different parts of your body like the bones, skin, and the other organs of your body. The arteries bring the blood out. Veins are responsible for returning the blood.

Now, let's talk about the blood. When you get a cut you see the color red. Did you know that blood really isn't red? It's colorless. Can you believe it? Then, why do you see red? Well, you see a red color because blood is made up of red blood cells. These cells make the blood look red.