Right atrium

The right atrium (in older texts termed the "right auricle") is one of four chambers (two atria and two ventricles) in the human heart. It receives de-oxygenated blood from the superior and inferior vena cavae and the coronary sinus, and pumps it into the right ventricle through the tricuspid valve.

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The sinoatrial node (SAN) is located within this chamber next to the vena cava. This is a group of pacemaker cells which spontaneously depolarise to create an Action Potential. The cardiac action potential then spreads across both atria causing them to contract forcing the blood they hold into their corresponding ventricles.

In early life, when a fetus is in the womb, the right atrium has a hole within its septum through to the left atrium, this makes them continuous with each other which is essential for foetal circulation. This junction is called the “Foramen Ovale”. Once born (usually within 9 month's time) the Foreman Ovale seals over. This occurs when the first breath is taken; fetal blood flow is reversed and now travels through the lungs no longer requiring the Foramen Ovale. Therefore it closes and is renamed as the “Fossa Ovalis”. The Fossa Ovalis is seen as an embryonic remnant.

In some cases, the Formane Ovale fails to close and is present in 20% of the general population, however it does not cause problems in the vast majority. This is known as "Patent Foramen Ovale"

The right atrium also holds the coronary sinus which is the opening of the vein that drains the myocardium itself. Attached to the right atrium is the right auricular appendix.

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See also

• Left atrium
• Right ventricle
• Heart