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Overview

Diagram of the human heart

The human heart is a muscular organ responsible for pumping blood through the circulatory system. It is located in the thoracic cavity, between the lungs, and is roughly the size of a fist. The heart is composed of four chambers: the left and right atria and the left and right ventricles.

Structure

The heart is enclosed in a protective sac called the pericardium, which also contains a small amount of fluid. The heart wall itself is made up of three layers: the epicardium, the myocardium, and the endocardium.

Chambers

The heart has four chambers:

• Right Atrium: Receives deoxygenated blood from the body through the superior vena cava and inferior vena cava.
• Right Ventricle: Pumps deoxygenated blood to the lungs via the pulmonary artery.
• Left Atrium: Receives oxygenated blood from the lungs through the pulmonary veins.
• Left Ventricle: Pumps oxygenated blood to the body through the aorta.

Valves

Heart valves

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

• Tricuspid Valve: Located between the right atrium and right ventricle.
• Pulmonary Valve: Located between the right ventricle and the pulmonary artery.
• Mitral Valve: Located between the left atrium and left ventricle.
• Aortic Valve: Located between the left ventricle and the aorta.

Function

The primary function of the heart is to maintain a continuous flow of blood throughout the body. This is achieved through a coordinated sequence of contractions known as the cardiac cycle. The heart's electrical conduction system, including the sinoatrial node, atrioventricular node, and Purkinje fibers, regulates the timing of these contractions.

Blood Supply

The heart itself requires a constant supply of oxygenated blood, which is provided by the coronary arteries. These arteries branch off from the aorta and encircle the heart muscle.

Related pages

• Cardiovascular system
• Blood pressure
• Electrocardiography
• Heart disease