The heart is a
cone shaped structure the size of your fist. Located slightly
to the left of the center of the chest, the heart is protected
by the breastbone in the front, the spinal cord in the back
and the lungs on both sides. The heart has two lower ventricles,
two upper auricles, the aorta and the pulmonary artery. Also,
there are the pulmonary veins and coronary arteries to carry
oxygenated and de-oxygenated blood between the heart, lungs
and body.
The heart is covered by a thick main layer of heart muscle
called the myocardium. The myocardium is composed of individual
muscle cells called myocytes that act together to contract
and relax the heart chambers to pump blood into the lungs
and body.
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The
right side of the heart is responsible for pulmonary circulation.
"Used" blood from your body returns to the right
side of the heart via the two large veins - the superior
vena cava and the inferior vena cava.