The HEART

The heart is one of the most complicated systems in the human body. For beginners, there are four chambers of the heart: right ventricle (bottom), left ventricle (bottom), right atrium (top), left atrium (top). It seems easy enough. Just wait and see, soon enough I will get trapped and tangled in my own words. There are different ways on transporting blood.
The blood that comes back to the heart, the deoxygenated blood, comes through veins and venules. It is a complicated network of twisting and thinning tubes. These tubes have valves. They have these valves because since gravity is pulling down at 9.8 meters per seconds squared they need some where to stop every once in a while. It is like throwing a ball 100 feet, or you have a ladder with 50 people on the ladder, and slowly hand the ball up.
The blood that is leaving the heart travels though another complex system of arteries and arterioles, oxygenated blood. These unlike the veins and venules do not have valves. The blood gets pushed around by the pressure of the pumping heart. In-between the venules and arterioles are the capillaries that connect these two tubes.
In the heart, there are valves to control the blood flow through the different chambers in the heart. I am going to trace a drop of blood through your body from the femur (your thigh bone) and back. It stats be going thought the femoral vein and then travels though other veins and connects to the inferior vena cava. The vena cava leads and empties into the right atrium. It passes through the tricuspid valve and into the right ventricle. It gets squeezed though the pulmonary semi-lunar valve and into the pulmonary artery. (If you noticed before I stated that arteries carries oxygenated blood, this is the only exception). The pulmonary arteries and empties the blood into the lungs and then out through the pulmonary vein. (This is another exception; it now has oxygenated blood not deoxygenated). Through the pulmonary vein it empties into the left atrium. The blood goes through the mitral valve and into the left ventricle with all the heart might pushes it out and though the aortic semi-lunar valve and into the aorta. After the aorta it travels through various arteries and back down to the femur.
As you can see, the heart is a very complex and confusing. There are many more things that go along with the heart such as disease, EKG's, cardiac output, and stroke volume. I could go on and on and on but probably by now you aren’t even reading this so I am going to stop.