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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)