Editing Anatomy and Physiology (section)

=== Structure and Blood Flow ===

The heart has four chambers. Deoxygenated blood returns through the superior and inferior vena cava to the '''right atrium''', passes the '''tricuspid valve''' into the '''right ventricle''', exits through the '''pulmonic valve''' to the pulmonary arteries and lungs. Oxygenated blood returns by the pulmonary veins to the '''left atrium''', passes the '''mitral valve''' into the '''left ventricle''', and is ejected through the '''aortic valve''' into the aorta.

The left ventricle has the thickest wall because it pumps against systemic vascular resistance.

The coronary arteries fill during '''diastole''', which is why tachycardia, by shortening diastole, worsens myocardial ischemia.