Human Heart – Functions, Circulation, Diagram

The heart is a muscular fist-sized organ that is situated in the front of the chest to pump blood throughout the body. The heart is divided into four major portions (chambers) that are driven by electrical impulses. The heart’s function is controlled by the brain and neurological system. 

The human heart is one of the most important organs in charge of keeping life going. It is a four-chambered muscular organ. The human heart is one of the most strong and hardworking muscles in the human body, working continuously throughout a person’s life. 

Aside from humans, most other animals have a heart that circulates blood throughout their bodies. Even invertebrates, such as grasshoppers, have a pumping organ similar to the human heart, though it does not operate in the same manner. 

Structure of the Human Heart

The human heart is positioned in the thoracic cavity between the lungs, somewhat to the left of the sternum (breastbone). The human heart is around the size of a fist and is split into four chambers, two ventricles, and two atria. The ventricles are the blood-pumping chambers, whereas the atrium is the blood-receiving chamber. The right atrium and ventricle comprise the “right heart,” whereas the left atrium and ventricle comprise the “left heart.”  The heart anatomy also houses the largest artery in the body, the aorta. 

Heart Chambers

The number of chambers of a vertebrate heart can be used to classify it. Fish, for example, has two chambers, but reptiles and amphibians have three chambers. Whereas birds and mammals have 4 chambers. Humans also have four chambers:  

  • The left atrium 
  • The right atrium 
  • The left ventricle 
  • The right ventricle 

Atria are thinner and have less muscular walls than ventricles. These are the blood-receiving chambers that are connected by large veins. 


Ventricles are bigger and more muscular chambers that pump and push blood into circulation. These are linked to bigger arteries, which transport blood for circulation. 

The right ventricle and atrium are much smaller than the left chambers. The walls have fewer muscles than the left side, and the size difference is due to their roles. Blood from the right side goes through the pulmonary circulation, whereas blood from the left side is circulated throughout the body. 

Blood Vessels

Blood travels via channels of varied diameters in creatures with closed circulatory systems. Such type of circulation is seen in all animals, including humans. Many blood veins create a network on the heart’s exterior surface, with additional significant vessels originating from within the tissue. Blood vessels are generally made up of the following components: 


Veins provide deoxygenated blood to the heart through the inferior and superior vena cava, where it empties into the right atrium. 


Capillaries are small, tube-like that connect the arteries and veins. 


Arteries are muscular-walled tubes that transport oxygenated blood from the heart to all other regions of the body. The aorta is the major artery and branches into several smaller arteries throughout the body. 


Valves are fibrous tissue flaps located between the veins in the heart chambers. They make certain that blood flows in only one direction (unidirectional). The flaps retain blood from flowing backward. Valve types are classified according to their function: 

Atrioventricular valves

Atrioventricular valves exist between the ventricles and the atria. The tricuspid valve connects the right ventricle to the right atrium, whereas the mitral valve connects the left ventricle to the left atrium. 

Semilunar valves

Semilunar valves exist between the left ventricle and the aorta. It’s also near the right ventricle and the pulmonary artery. 

Heart Walls

The heart wall has three layers: 


The epicardium is the heart’s outermost layer. It is made up of a thin-layered membrane that lubricates and protects the outer part. 


This is a layer of muscle tissue that makes up the middle layer of the heart’s wall. It adds to the thickness and is in charge of the pumping motion. 


The endocardium is the deepest layer of the heart that borders the inner chambers and covers the heart valves. Furthermore, it keeps blood from adhering to the inner walls of the vessels, preventing potentially dangerous blood clots. 

Functions of the Human Heart

In every organism, the job of the heart is to maintain blood flowing constantly throughout the body. This replaces the oxygen supply and distributes nutrients throughout the cells and tissues. 

Human Heart Diagram

The heart’s primary functions are as follows: 

  • The human heart’s duty is to circulate blood throughout the body. 
  • Throughout the body, including the human heart, blood delivers oxygen, hormones, glucose, and other chemicals. 
  • The heart also keeps the blood pressure in the body steady. 

There are two forms of circulation within the body: pulmonary circulation and systemic circulation. 

Human Heart Blood Circulation

Pulmonary circulation

Pulmonary circulation is the component of circulation that transports deoxygenated blood from the heart to the lungs and subsequently returns oxygenated blood to the heart. 

Systemic circulation

Another kind of circulation is systemic circulation, in which oxygenated blood is pumped from the heart to every organ and tissue in the body, and deoxygenated blood returns to the heart. 

As the heart is also a muscle, even it requires a steady supply of oxygenated blood. This is when another sort of circulation, the coronary circulation, comes into action. 

Coronary circulation

Coronary circulation is a vital component of circulation that supplies oxygenated blood to the heart. This is significant since the heart is in charge of delivering blood throughout the body. 

Final Notes

Tutoroot Biology lessons can help you learn more about the construction and function of the human heart, as well as other relevant concepts. A personalized tutoring mentor can assist you in learning more about such Biology subjects. 


Where is the heart located in the human body? 

The human heart is in the chest where the sternum sits behind and slightly to the left of your breastbone. 

What is the normal heart rate of a human? 

A normal resting heart rate should be 72 beats per minute, but it can vary from 60-100 beats. 

How many chambers are there in the human heart? 

There are 4 chambers in a typical heart, two upper and two lower chambers. 

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