Cardiovascular System Basics

The cardiovascular system moves oxygen, glucose, hormones, heat, and metabolic waste between tissues and the organs that exchange or remove them. The heart provides pressure; blood vessels determine resistance and distribution; blood provides the transport medium. A patient can have a normal blood pressure for a short time while tissue perfusion is already falling, so assessment must include the patient’s appearance, mental status, urine output, skin, and symptoms rather than relying on one number. Blood returns from the body through the superior and inferior venae cavae into the right atrium. It crosses the tricuspid valve into the right ventricle, passes through the pulmonary valve, and travels through the pulmonary arteries to the lungs. Oxygenated blood returns through the pulmonary veins to the left atrium, crosses the mitral valve into the left ventricle, and leaves through the aortic valve into the aorta. The right heart serves pulmonary circulation; the left heart generates the pressure required for systemic circulation. The valves maintain one-way flow. A narrowed valve obstructs forward movement and increases the workload behind it. An incompetent valve permits backward flow,...