AA560

Anatomy 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: two atria and two ventricles.

Diagram of the human heart

Structure

The heart is divided into 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.

The heart is enclosed in a double-walled sac called the pericardium, which provides protection and lubrication.

Function

The primary function of the heart is to maintain a continuous flow of blood throughout the body. This is achieved through a series of coordinated contractions known as the cardiac cycle. The cycle consists of two main phases:

• Systole: The phase of contraction where blood is ejected from the ventricles.
• Diastole: The phase of relaxation where the heart chambers fill with blood.

Blood Supply

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

Electrical Conduction System

The heart's rhythm is controlled by an electrical conduction system, which includes the sinoatrial node (SA node), atrioventricular node (AV node), and the bundle of His. The SA node, located in the right atrium, acts as the natural pacemaker of the heart.

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

Related Pages

• Cardiovascular system
• Blood pressure
• Electrocardiogram
• Heart disease