Right Atrium

Right AtriumĀ is one of the four chambers of the human heart. The heart is divided into four chambers, two are called atria, and the other two are ventricles. These chambers help to keep the oxygenated blood separate from deoxygenated blood and maintain the circulation of the blood in the entire body.

Deoxygenated blood enters the heart through two atria, and oxygenated blood exits the heart through two ventricles.

The blood enters the right atrium through inferior and superior vena cava.


The right atrium is located in the upper right corner of the heart above the right ventricle. There is a tricuspid valve present between the right atrium and right ventricle.


Diagram of Right Atrium

The right atrium muscular walls are much thinner than the ventricles. On the medial side, there is a muscular wall present known as the interatrial septum which separates the left and right atria. It forms a barrier so that the blood cannot pass between them.


The right atrium contains the sinoatrial node(SA node) which helps the heart in regulating its rhythm. It acts as a pacemaker and contracts the cardiac muscles. The SA node is connected to the brain via the autonomic nerves which control the heart rate in maintaining blood pressure, oxygen and carbon dioxide homoeostasis.

The deoxygenated blood enters the right atrium through superior vena cava, inferior vena cava and coronary sinus. The superior vena cava returns blood to the heart from the head, neck, arms and upper thorax region.

The blood is returned back to the heart from legs, abdomen and lower thorax region by the inferior vena cava.

Blood from the exterior of the heart is returned to the interior of the heart by the coronary sinus.


As a developing baby inside the womb, there is a small hole present in the interatrial septum called the foramen ovale. This hole allows the flow of blood from right to left atrium, so there is less blood flow to inactive lungs. By the time of birth, a small flap of tissues has covered the foramen ovale to prevent the flow of blood between two atria. By adulthood, a small indentation or marking remains where the foramen ovale once existed and is now called the foramen ovale.

In some babies, the foramen ovale fails to close and the baby is born with a hole in the heart at birth. This condition is known as patent foramen ovale.

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