1) pumps the blood

2) about the size of your fist

3) layers/linings of the heart
     a) pericardium - double-walled and filled with fluid
     b) myocardium - heart muscle
     c) endocardium - lining of the heart chambers

4) chambers of the heart
     a) right atrium - takes in blood from the superior and inferior vena cavae
     b) left atrium - takes in blood from the 4 pulmonary veins
     c) right ventricle - pumps blood to the lungs
     d) left ventricle - pumps blood to the body; strongest chamber of the heart

Path of blood through the heart

deoxygenated blood from the body -> superior & inferior vena cava -> right atrium -> thru the tricuspid valve -> right ventricle -> thru the pulmonary semilunar valve -> pulmonary trunk -> pulmonary arteries -> lungs -> pulmonary veins -> left atrium -> thru the bicuspid valve -> left ventricle -> thru the aortic semilunar valve -> aorta -> body

tricuspid valve - between the right atrium and right ventricle; an atrioventricular (AV) valve

bicuspid valve - between the left atrium and left ventricle; an atrioventricular (AV) valve

aortic semilunar valve - between the left ventricle and the aorta

pulmonary semilunar valve - between the right ventricle and the pulmonary trunk

interventricular septum - dividing wall of muscle between the right and left ventricles

superior vena cava - collects deoxygenated blood from the upper body

inferior vena cava - collects deoxygenated blood from the lower body

myocardial infarction (heart attack) - a coronary artery is blocked