The heart
The heart in humans is located in the thorax between the lungs. When you place your fingers on the left side of the chest between the fifth and sixth ribs, you can feel the heart pulsate each time it beats.
The wall of the heart is richly supplied with nerves, blood vessels and lymph vessels. From the inside out, the layers of the heart are the endocardium, myocardium ( lots of problems like hyperthrophy of the heart is caused in this area) and pericardium.
The heart has four chambers and it works as a double pump. The right and left sides of the heart are copletely separated by a wall called septum. These four chambers are: a right atrium and right ventricle and a left atrium and left ventricle.
function
The right atrium receives oxygen-poor blood returning from the tissues and gets into the right atrium through vena cava superior and vena cava inferior. Then the right atrium pumps the blood to the right ventricle through valve tricuspidalis ( has three cusps) and after that blood goes to pulmonary artery, so as the blood comes back to the heart after passing from lungs where it's oxygenated, and comes as oxygenated blood through pulmonary veins to left atrium. There it passes the valve bicuspidalis and blood is pumped into the left ventricle. Lastly, left ventricle pumps the blood into the aorta and blood goes to all body systems and tissues. After that, it comes back, low oxyganated and enters the heart from vena cava superior and vena cava inferior again.
note: remember that the blood is following a closed network and that why we do not lose blood and we see this process going on and on involing the heart.
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