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Structure of the Human Heart

Diagram of the human heart structure

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: two upper chambers called the atria and two lower chambers called the ventricles.

Chambers of the Heart

The heart's four chambers are crucial for its function:

• 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 rest of the body through the aorta.

Valves of the Heart

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.

Heart Wall

The heart wall consists of three layers:

• Epicardium: The outer layer, which is also part of the pericardium.
• Myocardium: The thick, muscular middle layer responsible for the heart's contractile function.
• Endocardium: The inner layer that lines the heart chambers and valves.

Conduction System

The heart's electrical conduction system controls the heartbeat:

• Sinoatrial Node (SA Node): The natural pacemaker of the heart, located in the right atrium.
• Atrioventricular Node (AV Node): Relays electrical impulses from the atria to the ventricles.
• Bundle of His: Transmits impulses from the AV node to the ventricles.
• Purkinje Fibers: Distribute the electrical impulse throughout the ventricles.

Function

The primary function of the heart is to maintain blood circulation throughout the body. It achieves this by:

• Pumping deoxygenated blood to the lungs for oxygenation.
• Pumping oxygenated blood to the tissues and organs.

Related pages

• Cardiovascular system
• Blood pressure
• Heart disease
• Electrocardiography