|
Written by Administrator
|
|
Sunday, 07 February 2010 00:43 |
|
the aorta is the main artery leaving your heart. It sends blood to your head and then curves over to run down your chest along the spine. It passes along the back of your stomach, and at the top of the legs it divides into the big arteries which send branches down to your feet. Arteries branch off the aorta supplying arms, legs and all the important organs, such as the kidneys and liver.
What are the valves?
the valves control the flow of blood into and out of your heart. They open and shut just like a tap being turned on and off. When
working normally, they act as one-way valves. The valves are on the
inside of your heart, whereas the coronary arteries are on the outside.
There are four valves – the aortic, mitral, pulmonary and tricuspid.
1) Blood returns to your heart through the veins. It has given up its oxygen to your brain, kidneys and muscle. It comes from the head region in a big vein called the superior(from the top of the body) vena cava, and from the lower body in a big vein called theinferior vena cava. It collects in a chamber called the rightatrium.
2) The tricuspid valve separates this collecting chamber from the right ventricle, which is part of your muscle pump. (Ventricle is the medical word for pump.) You will notice the use of the word ‘right’ at this stage. This is because your heart is divided into two sides. The right side(on your right) collects used-up blood and passes it to your lungs to pick up oxygen, and the left collects oxygen-rich blood from the lungs and pumps it round the body. The muscle pump on the left is called the left ventricle. This is the most important part of the heart and the one that is most often damaged in a heart attack.
3) On the left side of your heart, blood leaving the lungs has been collecting in the left atrium. Blood therefore collects in the right atrium and left atrium at the same time. Separating the left atrium from the left ventricle is the mitral valve. The mitral valve opens at the same time as the tricuspid valve so that blood enters the right and left ventricles almost
simultaneously.
4) Both the right ventricle and left ventricle contract at the same time. As the pressure builds up, the force closes the tricuspid and mitral valves (preventing any leaking backwards) and opens thepulmonaryandaortic valves. Blood is ejected through the pulmonary valve to your lungs, and the aortic valve to your body. When the pump has emptied, the pressure drops, the pulmonary and aortic valves close, and the tricuspid and mitral valves open again; the cycle is then repeated.
What keeps the right and left heart apart?
The muscle that divides your heart is called the septum. Between the right and left atrium, it is known as the atrial septum, and between the ventricles, the ventricular septum. When a hole occurs in your heart, we call it a defect. If it is between the atria (plural of atrium), it is known as an atrial septal defect(ASD) and if it is between the ventricles, it is a ventricular septal defect(VSD). |
