ORG-2058

Overview

Illustration of the human heart.

The human heart is a muscular organ responsible for pumping blood through the circulatory system by rhythmic contractions. It is located in the thoracic cavity, between the lungs, and is roughly the size of a fist. The heart is a central component of the cardiovascular system, which also includes a vast network of blood vessels such as arteries, veins, and capillaries.

Anatomy of the Heart

The heart is divided into four chambers: the left and right atria and the left and right ventricles. The atria are the upper chambers that receive blood, while the ventricles are the lower chambers that pump blood out of the heart.

Right Atrium

The right atrium receives deoxygenated blood from the body through the superior vena cava and inferior vena cava. It then pumps this blood into the right ventricle.

Right Ventricle

The right ventricle pumps the deoxygenated blood into the pulmonary arteries, which carry it to the lungs for oxygenation.

Left Atrium

The left atrium receives oxygenated blood from the lungs via the pulmonary veins. It then pumps this blood into the left ventricle.

Left Ventricle

The left ventricle is the most muscular chamber of the heart, responsible for pumping oxygenated blood into the aorta and throughout the body.

Heart Valves

The heart contains four main valves that ensure unidirectional blood flow:

• The tricuspid valve is located between the right atrium and right ventricle.
• The pulmonary valve is located between the right ventricle and the pulmonary arteries.
• The mitral valve is located between the left atrium and left ventricle.
• The aortic valve is located between the left ventricle and the aorta.

Cardiac Cycle

The cardiac cycle consists of two main phases: systole and diastole. During systole, the ventricles contract, pumping blood out of the heart. During diastole, the heart muscle relaxes, allowing the chambers to fill with blood.

Electrical Conduction System

The heart's rhythmic contractions are controlled by an electrical conduction system. The sinoatrial node (SA node), located in the right atrium, acts as the natural pacemaker, initiating each heartbeat. The electrical impulse travels through the atrioventricular node (AV node), down the bundle of His, and through the Purkinje fibers, causing the ventricles to contract.

Related Pages

• Cardiovascular system
• Blood pressure
• Electrocardiogram
• Heart disease