muscular organ that pumps blood throughout the body
Chambers of the Heart
Upper: right atrium and left atrium
Lower: right ventricle and left ventricle
interatrial septum and interventicular septum
divide the heart into right and left portions
open and close to maintain the one-way flow of blood through the heart
Three Layers of the Heart
1. Epicardium- outer membrane
2. Myocardium- thick, muscular layer
3. Endocardium- lines the interior cavities of the heart
loose, protective sac enclosing the heart
Circulation of Blood
1. Deoxygenated blood from the body enters the heart through the superior vena cava and inferior vena cava into the right atrium.
2. During atrial contraction, the tricuspid valve opens to allow blood to flow into the right ventricle.
3. Contraction of the ventricle pushes blood through the pulmonary semilunar valve into the pulmonary artery.
4. The pulmonary artery carries the blood to the lungs and through the pulmonary circulation (a network of arteries, capillaries, air sacs, and veins in the lung), where it is oxygenated.
5. Oxygenated blood returns to the heart via the pulmonary veins into the left atrium.
6. With atrial contraction, the mitral (or bicuspid) valve opens to allow blood to flow into the left ventricle.
7. Contraction of the left ventricle pushes blood through the aortic valve into the aorta and on to all parts of the body through the systemic circulation ( a network of arteries, arterioles, capillaries, and veins throughout the body).
Cardiac Conduction: repeated electrical impulses are conducted:
from the sinoatrial (SA) node (the pacemaker of the heart) → to the atrioventricular (AV) node → to the bundle of His → to the left and right bundle branches → to the Purkinje fibers
Cardiac Conduction: impulses cause each myocardial cell to change:
from a resting state (polarized) → to a state of contraction (depolarized) → then back to a resting state by recharging (repolarizing)