Circulatory System Overview

Circulatory System I

• The circulatory system comprises the heart, blood vessels, and blood.
• The cardiovascular system refers only to the heart and blood vessels.
• The circulatory system's main function is transporting substances throughout the body via blood.
• Blood acts as the liquid medium for transporting these substances.
• Blood vessels ensure the proper routing of blood to various locations.
• The heart acts a pump to maintain blood flow.
• Without valves, the body would require more effort to circulate blood.

Pulmonary and Systemic Circuits

• The cardiovascular system has two major divisions: the pulmonary and systemic circuits.
• The pulmonary circuit carries blood to the lungs for gas exchange and returns it to the heart.
• The pulmonary circuit includes blood vessels carrying blood to and from the lungs.
• The systemic circuit supplies blood to all body organs and returns it to the heart.
• The systemic circuit encompasses arteries, capillaries, and veins throughout the entire body.

Pathway of Blood Flow

• The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs (pulmonary circuit).
• The left side of the heart receives oxygenated blood from the lungs and pumps it to the rest of the body (systemic circuit).
• Oxygen-poor blood is depicted by violet arrows and oxygen-rich blood by orange arrows.

Heart Chambers

• The heart has four chambers: two atria (right and left) and two ventricles (right and left).
• The atria receive blood returning to the heart.
• The ventricles pump blood out of the heart.
• The right and left ventricles are the heart's pumping chambers.

Heart Valves

• The atrioventricular (AV) valves (tricuspid valve on the right side and mitral valve on the left side) regulate blood flow between the atria and ventricles.
• The semilunar valves (pulmonary and aortic) control blood flow from the ventricles to the respective arteries.
• Valves prevent the backflow of blood.

The Conduction System

• The cardiac conduction system controls the timing of heart chamber stimulation.
• This ensures coordinated contractions of the atria and ventricles.
• The system features specialized nodes and conducting fibers.
• The nodal cells initiate and distribute electrical impulses, coordinating heart contractions.

Coronary Circulation

• Coronary arteries supply oxygenated blood to the heart muscle.
• The coronary sinus collects deoxygenated blood from the heart.
• Blockages in coronary arteries can result in heart attacks.

Pericardium

• The pericardium is a double-walled sac enclosing the heart.
• The fibrous pericardium acts as the outer protective layer.
• The serous pericardium forms the visceral (epicardium) layer covering the heart and the parietal layer.
• The pericardial cavity contains fluid reducing friction during heartbeats.

Heart Wall Layers

• The heart wall consists of three layers:
• The epicardium is the outer layer.
• The myocardium is the muscular middle layer.
• The endocardium lines the inner surface of the heart chambers.