Wednesday 6 June 2012

Heart Wallpaper

Heart Wallpaper Biography
Mammals have a double circulation, which means that the right hand side of the heart pumps deoxygenated blood to the lungs in the pulmonary artery to pick up oxygen and release carbon dioxide. The oxygenated blood then returns to the left hand side of the heart in the pulmonary vein.
From there the blood is pumped to the body in the aorta, eventually returning to the right hand side of the heart in the vena cava to start the cycle again.
Since the right side pumps to the lungs which are situated close to the heart, the walls are much thinner than the left side which has to pump blood out of the heart to the body.
The heart has 4 chambers; 2 on the right hand side (the left as you look at it in the screen) and 2 on the left. The top chamber on each side is called the atrium; the bottom is called the ventricle. The atria receive blood as it enters the heart and pumps it into the ventricles. The ventricles pump blood out of the heart.
Due to this, the walls of the atria are much thinner than the walls of the ventricles.
Inside the heart and at the base of the vessels that leave the heart are valves. These valves only open one way, which ensures that there is no backflow of blood.
The valves are held open or closed by tendons (chordae tendinae or perhaps better known as heart strings), which are attached at the other end to the papillary muscles in the ventricle walls. The valves open to let blood through and then snap shut. This sound of the valves closing is the 'lub dub' sound of the heartbeat.
The muscle of the heart is called cardiac muscle and is made of tightly connecting cells. This close contact allows rapid ion transport from cell to cell. This then allows smooth, efficient waves of depolarisation to produce contractions (and repolarisation to bring about relaxation), which pass through the heart.
Heart Wallpaper
Heart Wallpaper
Heart Wallpaper
Heart Wallpaper
Heart Wallpaper
Heart Wallpaper
Heart Wallpaper

Heart Wallpaper
Heart Wallpaper

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Heart Wallpaper
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