Order of Blood Flow Through the Heart

Blood flow through the heart involves contractions of the heart muscle to move blood from the right chambers of the heart to the lungs—where it receives oxygen—and then to the left chambers of the heart where it is pumped to the rest of the body through a network of blood vessels.

Involved in this process are four heart valves that are synchronized to open and shut with each heartbeat. This ensures the consistent flow of blood in one direction from the heart via arteries (which carry oxygenated blood) and back to the heart via veins (which carry deoxygenated blood along with carbon dioxide).

This article maps the order of blood flow through the heart. It also describes problems that can affect blood flow when different parts of the circulatory system malfunction.

Components of the Heart Involved in Blood Flow

The heart has two upper chambers, called the left and right atriums, and two lower chambers, called the left and right ventricles. With each heartbeat, blood moves from one chamber to the next through a series of heart valves.

The heart rate and rhythm are controlled by the cardiac conduction system which delivers electric impulses that contract and relax the heart muscle.

Several major arteries and veins are involved in this process:

• The pulmonary artery transfers blood from the heart to the lungs.
• The pulmonary vein transfers blood from the lungs to the heart.
• The aorta delivers oxygenated blood from the heart to the rest of the body.
• The superior vena cava and inferior vena cava transport deoxygenated blood from the body back to the heart.

There are four valves that control blood flow in and out of the chambers of the heart:

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

Order of Blood Flow Through the Heart: Step by Step

Right Side of Heart

Here is the path that blood takes in the right side of the heart:

1. The blood first enters the right atrium from the superior and inferior vena cava.
2. It then flows through the tricuspid valve into the right ventricle.
3. The blood then moves through the pulmonary valve into the pulmonary artery.
4. The pulmonary artery carries blood to the lungs where it takes up oxygen.

Left Side of Heart

Here is the path that blood takes in the right side of the heart:

1. Oxygenated blood returns to the heart through the pulmonary vein into the left atrium.
2. The blood then moves through the mitral valve into the left ventricle.
3. The left ventricle then pumps the blood through the aortic valve into the aorta.
4. From the aorta, the blood is transported through the network of blood vessels, delivering oxygen and nutrients to tissues and taking carbon dioxide and wastes from tissues.
5. Deoxygenated blood returns to the heart via the superior and inferior vena cava, and the cycle begins again.

Order of Blood Flow Through the Body: Step by Step

Once oxygenated blood leaves the heart, it is pumped through a network of vessels throughout the body to deliver nutrients and oxygen to cells.

Here is the path blood flows once it exits the left side of the heart:

1. Oxygenated blood from the left side of the heart gets pumped out of the aorta, the largest vessel of the body. The aorta extends from the left ventricle of the heart down into the abdomen.
2. Blood then flows through arteries that branch off from the aorta. These arteries deliver blood to different areas of the body.
3. Arteries then split into smaller vessels known as arterioles, which then carry blood to the smallest vessels in the body—the capillaries.
4. The capillaries deliver oxygen and nutrients to the tissues of your body and simultaneously remove carbon dioxide to be eliminated in the lungs.
5. Deoxygenated blood from the capillaries then flows back to the heart through small vessels known as venules.
6. The venules then gradually merge to form veins.
7. Blood enters back into the heart via large veins known as the superior and inferior vena cava.
8. Blood is then pumped through the right side of the heart, into the lungs to get oxygen, and back into the left side of the heart.

Role of Heart Valves With Blood Flow

The four heart valves prevent the backward flow of blood and keep blood moving in one direction. The valves are comprised of flaps of muscular tissues that open in one direction. The tricuspid, pulmonary, and aortic valves have three flaps, while the mitral valve has two flaps.

The tricuspid and mitral valves are located on each end of the two ventricles. They act as one-way inlets of blood on one side of a ventricle and one-way outlets of blood on the other side of a ventricle.

The pulmonary valve regulates the flow of blood in and out of the lungs, while the aortic valve regulates the flow of blood out of the heart and to the body.

The sound of your heartbeat is largely due to the opening and shutting of the valves. The low-pitched "lub" sound is due to the shutting of mitral and tricuspid valves, while the high-pitched "dub" sound is caused by the shutting of the aortic and pulmonary valves.

Conditions That Affect Normal Blood Flow

A healthy heart normally beats anywhere from 60 to 70 times per minute when you're at rest. This rate can be higher or lower depending on your general health and physical fitness. Athletes generally have a lower resting heart rate.

Your heart rate will increase when you move or engage in physical activity. This is because your muscles use oxygen while they work. In response, the heart works harder to bring oxygenated blood where it is needed.

Certain conditions can affect blood flow to and from the heart, including:

• Cardiac arrhythmia: This is a group of disorders that cause irregular heartbeats due to problems with electrical impulses. Atrial fibrillation is a common form of this.
• Heart blocks: These are problems with the cardiac conduction system. Two main types are an atrioventricular (AV) block and a bundle branch block.
• Heart valve disease: Damaged valves can leak and reduce the amount of blood delivered to tissues. The cause may be congenital (something you are born with), degenerative (in which a valve gradually wears out with age), or due to heart disease.
• Heart failure: This is when the heart is unable to pump enough blood to meet the body's needs. The causes are many, including heart disease, lung disease, genetics, and infections.
• Cardiac ischemia: This is reduced blood flow due to a partially or fully obstructed blood vessel. One common cause of this is a heart attack.

Summary

Blood flow moves in one direction through the chambers of the heart. Electrical impulses are generated to make your heart beat. Heart valves open and shut to regulate blood flow. Cardiac arrhythmia, heart blocks, heart valve disease, heart failure, and cardiac ischemia can all affect the normal flow of blood to and from the heart.