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Anatomy of the Human Heart

Diagram of the human heart showing its chambers and major blood vessels.

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.

Structure

The heart is enclosed in a double-walled sac called the pericardium, which provides protection and lubrication. The heart wall itself is composed of three layers: the outer epicardium, the middle myocardium, and the inner endocardium.

Chambers

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, which sends it to the lungs via the pulmonary artery for oxygenation.

The left atrium receives oxygenated blood from the lungs through the pulmonary veins. This blood is then pumped into the left ventricle, which sends it throughout the body via the aorta.

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 artery.
• The mitral valve is located between the left atrium and left ventricle.
• The aortic valve is located between the left ventricle and the aorta.

Blood Supply

Coronary arteries supply blood to the heart muscle.

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

Electrical Conduction System

The heart's rhythmic contractions are controlled by its electrical conduction system. The sinoatrial node, located in the right atrium, acts as the natural pacemaker, initiating electrical impulses that cause the heart to contract. These impulses travel through the atrioventricular node, down the bundle of His, and into the Purkinje fibers, coordinating the contraction of the ventricles.

Function

The primary function of the heart is to maintain blood circulation throughout the body, delivering oxygen and nutrients to tissues and removing carbon dioxide and waste products. This is achieved through the cardiac cycle, which consists of systole (contraction) and diastole (relaxation).

Related Pages

• Cardiovascular system
• Blood pressure
• Heart disease
• Electrocardiography