2.63a Heart Structure

1. If blood is going into the heart, the blood vessel is called a vein. If blood is going out of the heart that kind of blood vessel in called an artery.
2. The technical word for lung is polmonary. We have the polmonary artery which takes the blood from the heart to the lung.
3. The polmonary vein takes the blood from the lung to the heart.
4. The major artery in the body is the aorta which takes blood from the heart to around the body.
5. The major vein in the body is Vena cava.
6. These two are our major blood vessels.
7. The heart has two small chambers: the left atrium and the right atrium.
8. The large chambers are known as the keft and rught ventricles.
9. What separeates the right and lift side of the heart is the septum.
10. The valves on the left side are called the bicuspid valves which open and close, allowing blood to flow through.
11. The valves in the right side are called the tricuspid valves.
12. The valves beneath the aorta and polmonary artery are called the semilunar valves.
13. The bicuspid valves: When the pressure is high above the valves, the blood forces down through the valves, forcing the cusps open. The blood then flows to a region of low pressure. 
14. When the ventricle contracts we get high pressure below the bicuspid/tricuspid valves, causing it to close. This makes a sound 'lub' or 'lup'
15. The semilunar valves react in the same way. When the high pressure is below the valves, the blood is forced upwards into the arteries, opening the cusps. However, when the the heart relaxes the blood flows back down, closing the semi lunar valves. This is the second sound known as 'dub'.
16. This overall, gives a lub dub sound. 'Lub' is the sound caused by the closure of atrial ventricular valves whereas 'dub' is caused by the closure of the semilunar valves.