Described the circulation of blood to and from the heart

The blood vessels of the body are functionally divided into two distinctive circuits: pulmonary circuit and systemic circuit. The pump for the pulmonary circuit, which circulates blood through the lungs, is the right ventricle. The left ventricle is the pump for the systemic circuit, which provides the blood supply for the tissue cells of the body.

Pulmonary Circuit

Pulmonary circulation transports oxygen-poor blood from the right ventricle to the lungs, where blood picks up a new blood supply. Then it returns the oxygen-rich blood to the left atrium.

Systemic Circuit

The systemic circulation provides the functional blood supply to all body tissue. It carries oxygen and nutrients to the cells and picks up carbon dioxide and waste products. Systemic circulation carries oxygenated blood from the left ventricle, through the arteries, to the capillaries in the tissues of the body. From the tissue capillaries, the deoxygenated blood returns through a system of veins to the right atrium of the heart.

The coronary arteries are the only vessels that branch from the ascending aorta. The brachiocephalic, left common carotid, and left subclavian arteries branch from the aortic arch. Blood supply for the brain is provided by the internal carotid and vertebral arteries. The subclavian arteries provide the blood supply for the upper extremity. The celiac, superior mesenteric, suprarenal, renal, gonadal, and inferior mesenteric arteries branch from the abdominal aorta to supply the abdominal viscera. Lumbar arteries provide blood for the muscles and spinal cord. Branches of the external iliac artery provide the blood supply for the lower extremity. The internal iliac artery supplies the pelvic viscera.

Major Systemic Arteries

All systemic arteries are branches, either directly or indirectly, from the aorta. The aorta ascends from the left ventricle, curves posteriorly and to the left, then descends through the thorax and abdomen. This geography divides the aorta into three portions: ascending aorta, arotic arch, and descending aorta. The descending aorta is further subdivided into the thoracic arota and abdominal aorta.

Major Systemic Veins

After blood delivers oxygen to the tissues and picks up carbon dioxide, it returns to the heart through a system of veins. The capillaries, where the gaseous exchange occurs, merge into venules and these converge to form larger and larger veins until the blood reaches either the superior vena cava or inferior vena cava, which drain into the right atrium.

Fetal Circulation

Most circulatory pathways in a fetus are like those in the adult but there are some notable differences because the lungs, the gastrointestinal tract, and the kidneys are not functioning before birth. The fetus obtains its oxygen and nutrients from the mother and also depends on maternal circulation to carry away the carbon dioxide and waste products.

The umbilical cord contains two umbilical arteries to carry fetal blood to the placenta and one umbilical vein to carry oxygen-and-nutrient-rich blood from the placenta to the fetus. The ductus venosus allows blood to bypass the immature liver in fetal circulation. The foramen ovale and ductus arteriosus are modifications that permit blood to bypass the lungs in fetal circulation.

Blood flow through the heart and to the rest of the body involves four chambers, four valves, and many blood vessels. These work together to ensure a consistent supply of oxygenated blood gets where it needs to go.

Blood flow through the heart follows a lifelong rhythm in healthy people, though it may change due to other factors including daily activity, an underlying disorder, or a developing heart disease.

This article explains blood flow through the heart, step by step. It also discusses how this complex process might change during exercise or times of stress, as well as some of the causes of serious and life-threatening health effects when it's disrupted.

Blood Flow: Step by Step

The heart has two upper chambers—the left and right atriums—and two larger lower chambers, the left and right ventricles. Four valves act like doorways, in a sequence used to control blood flow in and out of these chambers.

The cardiac conduction system sends out electric impulses to make the heart muscle contract and relax. Those pulses set the rate and rhythm of your heartbeat.

Here is what happens as blood flows through the heart and lungs:

1. The blood first enters the right atrium.
2. The blood then flows through the tricuspid valve into the right ventricle.
3. When the heart beats, the ventricle pushes blood through the pulmonic valve into the pulmonary artery.
4. The pulmonary artery carries blood to the lungs where it “picks up” oxygen.
5. It then leaves the lungs to return to the heart through the pulmonary vein.
6. The blood enters the left atrium.
7. It drops through the mitral valve into the left ventricle.
8. The left ventricle then pumps blood through the aortic valve and into the aorta. The aorta is the artery that feeds the rest of the body through a system of blood vessels.
9. Blood returns to the heart from the body via two large blood vessels called the superior vena cava and the inferior vena cava. This blood carries little oxygen, as it is returning from the body where oxygen was used.
10. The vena cavas pump blood into the right atrium and the cycle begins all over again.

Arteries generally transport oxygen-rich blood. The pulmonary artery is unique. It is the only artery in the body that carries oxygen-poor blood.

Importance of Valves

Without valves, the ventricles of the heart couldn’t build up any force or pressure. It would be like pumping up a flat tire with a huge hole in it. No matter how much effort you put into pumping, the tire would never inflate.

In the case of the heart, blood would come into the chamber and just slosh through it. It would exit the valve at the bottom, or upward in the wrong direction each time the ventricle tried to pump blood.

All four of the heart valves open and close at just the right times to keep the blood flowing through the heart in the right direction. Part of the sound of your heartbeat is valves closing.

Blood Flow Changes

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 health and physical fitness. Athletes generally have a lower resting heart rate, for example.

Your heart rate rises when you move. That's because your muscles use oxygen while they work. The heart works harder to bring oxygenated blood where it is needed.

Disrupted or irregular heartbeats can affect blood flow through the heart. This can happen in many ways:

• Electrical pulses are impacted, causing an arrhythmia, or irregular heartbeat. Atrial fibrillation is a common form of this.
• Conduction disorders, or heart blocks, affect the cardiac conduction system. That's what regulates how electrical impulses move through the heart. The type of block—an atrioventricular (AV) block or bundle branch block—depends on where it is in the conduction system.
• Damaged or diseased valves can stop working well or leak blood in the wrong direction.
• A blocked blood vessel can disrupt blood flow gradually or suddenly. One example is a heart attack.

When to Worry About Blood Flow

If you have a sudden irregular heartbeat, or cardiac symptoms like chest pain and shortness of breath, call 911 for immediate medical help. Be sure to tell your healthcare provider about more chronic symptoms, like chest pain with exertion or swelling in your legs, that may indicate problems with blood flow.

Summary

Blood flow is a cycle that involves your lungs, heart chambers, valves, and blood vessels. Electrical pulses make your heart muscles squeeze and release. That action pushes blood through the two chambers on the right side of your heart and out to the lungs where it gathers oxygen.

A vein then carries that oxygen-rich blood into the left side of the heart. The two chambers on the left thrust the blood into arteries that carry blood and oxygen to the whole body.

When any part of that complex system breaks down, your body suffers from the lack of oxygen. Arrhythmia, valve disorders, and blockages in your heart or blood vessels can cause serious health problems. They may come on gradually or suddenly.

A Word From Verywell

Healthy blood flow is critical to overall health. Physical activity is one of the best ways to make sure your heart and lungs can function well over time. If you have health issues, ask your healthcare provider about how to keep your heart rate and rhythm—and your blood flow—healthy.

Frequently Asked Questions

• In what direction does blood flow through the heart?

  De-oxygenated blood enters the right side of the heart and is pumped toward the lungs to pick up oxygen. Then that oxygen-rich blood re-enters the heart on the left side and is pumped out to the cells of the body.

• Does exercise improve blood flow?

  Yes. Exercise strengthens your heart muscle and makes it more efficient, improving blood flow. It also reduces your risk of artery-clogging cholesterol and improves blood vessel function, among other things.

• What affects your heart rate?

  Exercise and movement force your heart to beat faster and raise your heart rate. Many factors can also affect your resting heart rate, including medication, fitness level, body position, emotions, body mass, and even air temperature.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

1. National Heart, Lung, and Blood Institute. Conduction Disorders.

2. Centers for Disease Control and Prevention. How the Heart Works.

3. National Heart, Lung, and Blood Institute. How the Heart Works.

4. Pinckard K, Baskin KK, Stanford KI. Effects of exercise to improve cardiovascular health. Front Cardiovasc Med. 2019;6:69. doi:10.3389/fcvm.2019.00069

5. American Heart Association. All About Heart Rate (Pulse).

Additional Reading

• The Texas Heart Institute at St. Luke’s Episcopal Hospital. Heart Anatomy.

• YourHeartValve.com/Edwards Lifesciences. Basic Anatomy and Function of the Heart.

By Jennifer Whitlock, RN, MSN, FN
Jennifer Whitlock, RN, MSN, FNP-C, is a board-certified family nurse practitioner. She has experience in primary care and hospital medicine.

Thanks for your feedback!

How blood flows through the heart step by step?

How would you explain blood circulation?

What are the 7 steps of the circulatory system?

How does the circulatory system work step by step?