How the Heart Pumps Blood

The heart is a type of muscle whose primary responsibility is to pump blood throughout the circulatory system. This system consists of of many veins and blood vessels that branch out even to the smallest organs, ensuring that all parts of the body are consistently given enough supply of oxygen to function efficiently. Without a sufficient supply of oxygen, any bodily function would fail, causing organ damage or organ death.

As the center of the circulatory system, the heart is considered an essential organ in maintaining the overall functioning of the body. Any cardiac or heart-related dysfunction, especially related to oxygen distribution, should thus be addressed immediately to avoid the development of a related co-morbid condition.

Parts of the Heart

Fully understanding the heart’s vital function in the body entails the need to first understand its anatomy. As a busy and hardworking organ, the heart needs to keep all its parts on check to ensure proper functioning, because even a minor cardiac dysfunction may result in significant functional challenges in the total body function of an affected individual

Located at the center of the chest and in the thoracic cavity, the heart can be divided into four parts (oftentimes called “chambers”) and comprises of several valves. Two of these chambers—called atria—are located in the upper portion of the heart and receive oxygen-free blood. The valves that separate these chambers are called atrioventricular valves, composed of the tricuspid valve on the left and the mitral valve on the right.

Pathway of blood flow through the heart. Image Credit: Alila Medical Media / Shutterstock

Meanwhile, ventricles are chambers found on the lower portion of the heart and pump oxygen-enriched blood into the body. Similar to the atria, the ventricular chambers are also separated by valves called semillunar valves. These valves may be further divided into two: pulmonary and aortic.

The heart is also composed of a heart wall that has three parts: the outer layer epicardium, the middle layer myocardium, and the innermost layer endocardium. Both the outer and inner layers of the heart are thin; the middle layer, meanwhile, makes up most of the heart and is made up of cardiac muscle fibers.

There are also two types of blood vessels that facilitate the distribution of blood in the body. The vessels that bring oxygen-free blood back into the heart are called veins; those that bring oxygen-rich blood away from the heart and to other body parts are called arteries. Originating in the left ventricle, the largest artery is called aorta.

All these parts function together to ensure that all organs of the body are regularly supplied with a sufficient amount of oxygen.

The Pumping Process

The heart’s blood pumping cycle — called cardiac cycle — begins when oxygen-free blood comes back into the heart, through the right atrium, after distributing oxygen and nutrients into other parts of the body. The blood then moves into the right ventricle that facilitates a transfer of blood into the lungs where it would be filled with oxygen and where waste gases (such as carbon dioxide) will be released.

The oxygen-rich blood returns to the heart through the left atrium and eventually into the left ventricle. This chamber then pumps blood towards other body parts through the aorta. The process begins again when the blood comes back to the heart. Many anatomical studies have found that about 5.6 liters of blood circulate the body, and three cardiac cycles are completed per minute.

Generating a Heartbeat

A normal heartbeat is evidence of the heart’s typical functioning, and each heartbeat is a manifestation of the oxygen-reloading process within the heart. As blood flows throughout the body in a single direction, any misdirection of the blood is avoided through the regulated closing and opening functions of the various cardiac chambers and valves.

The first phase of a heartbeat known as systole is a short period that occurs when the ventricles contract, initiating the closing of the tricuspid and mitral valves. The second phase called diastole is a relatively longer period of ventricular relaxation where the aortic and pulmonary valves close.

The heart’s “lub-dub” sound is produced by the continuous closing and opening of valves. This process occurs in a way that the entry and exit of either oxygen-rich or oxygen-free blood into and outside the heart remains synchronized.

A  successful heartbeat is made possible by electrical impulses coming from the sino-atrial (S-A) node that catalyzes each part’s function. The rate of the systole and diastole are commonly-used in quantifying the rate of an individual’s blood pressure at a certain time period. A normal heart rate of an adult is at 72 beats per minute.

Further Reading

• All Cardiology Content
• Cardiology – What is Cardiology?
• Cardiac Pharmaceutical Agents
• Cardiology Procedures
• Cardiothoracic Surgery

Written by

Gaea Marelle Miranda

Gaea graduated from the University of the Philippines, Manila, with a degree in Behavioral Sciences,cum laude . Majoring in psychology, sociology, and anthropology, she approaches writing with a multidisciplinary perspective.