Right atrium
The right atrium is one of four chambers
Heart chamber
aHeart chamber is a general term used to refer to any chambers of the mammalian heart. The heart consists of four chambers: the right and left atrium and the right and left ventricle. The top chambers are connected to the bottom chambers by valves and are separated by the coronary sulcus...

 (two atria
Atrium (anatomy)
In anatomy, the atrium , sometimes called auricle , refers to a chamber or space. For example, the term is used for a portion of the lateral ventricle in the brain and the blood collection chamber of the heart...

 and two ventricles
Ventricle (heart)
In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The Atria primes the Pump...

) in the heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

s of mammals (including humans
Human heart
The human heart is a muscular organ that provides a continuous blood circulation through the cardiac cycle and is one of the most vital organs in the human body...

) and archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...

s (which include birds and crocodilians). It receives deoxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

ated blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 from the superior
Superior vena cava
The superior vena cava is truly superior, a large diameter, yet short, vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium...

 and inferior
Inferior vena cava
The inferior vena cava , also known as the posterior vena cava, is the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart....

 vena cava and the coronary sinus
Coronary sinus
The coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the myocardium of the heart. It is present in all mammals, including humans...

, and pumps it into the right ventricle
Right ventricle
The right ventricle is one of four chambers in the human heart. It receives deoxygenated blood from the right atrium via the tricuspid valve, and pumps it into the pulmonary artery via the pulmonary valve and pulmonary trunk....

 through the tricuspid valve
Tricuspid valve
The tricuspid valve, or right atrioventricular valve, is on the right dorsal side of the mammalian heart, between the right atrium and the right ventricle. The normal tricuspid valve usually has three leaflets and three papillary muscles. They are connected to the papillary muscles by the chordae...

. Attached to the right atrium is the right auricular appendix
Right auricular appendix
The right atrial appendage is a small conical muscular pouch attached to the right atrium of the heart.-Anatomy:Its margins present a dentated edge...



The sinoatrial node
Sinoatrial node
The sinoatrial node is the impulse-generating tissue located in the right atrium of the heart, and thus the generator of normal sinus rhythm. It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava...

 (SAN) is located within this chamber next to the vena cava. This is a group of pacemaker cells which spontaneously depolarize 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
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

 is in the womb, the right atrium has a hole within its septum
Interatrial septum
The interatrial septum is the wall of tissue that separates the right and left atria of the heart.-Development:The interatrial septum forms during the first and second months of fetal development. Formation of the septum occurs in several stages...

 through to the left atrium; this makes them continuous with each other, which is essential for fetal circulation. This junction is called the Foramen ovale
Foramen ovale (heart)
In the fetal heart, the foramen ovale , also ostium secundum of Born or falx septi, allows blood to enter the left atrium from the right atrium. It is one of two fetal cardiac shunts, the other being the ductus arteriosus...

. Once born (usually within 9 months' time) the foramen 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
Fossa ovalis (heart)
Found in the right atrium of the heart, the fossa ovalis is an embryonic remnant of the foramen ovale, which normally closes shortly after birth.In a heart specimen of a neonate, the fossa ovalis is translucent, but later in life the membrane thickens...

. The fossa ovalis is considered an embryonic remnant.

In some cases, the foramen 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 a patent foramen ovale.

Within the fetal right atrium, blood from the inferior vena cava and the superior vena cava flow in separate streams to different locations in the heart, and this has been reported to occur through the Coanda effect.


  1. Sinus Venarum: smooth-walled portion that surrounds the opening of the superior and inferior vena cava and the coronary sinus.
    a.This region is the embryological remnant of venous blood vessels that were absorbed into the formation of the right atrial wall
  2. Openings of three vessels:
    a. Superior Vena Cava
    b. Inferior Vena Cava
    c. Coronary Sinus
  3. Pectinate muscles (musculi pectinati): muscular wall of the atria
  4. Right auricle: pouch-like extension of the muscular part (pectinate muscles) of the right atrium
  5. Crista terminalis: a ridge separating the muscular and smooth walled parts of the right atrium
  6. Interatrial septum: separates right atrium from left atrium
a. Fossa Ovalis, represents the closure of an opening that was present within the interatrial septum of the fetal heart (normal) and was called the foramen ovale
i. Fossa ovalis, a depression that looks like "thumb print" within the interatrial wall

7. Tricuspid valve: Its superior surface is from the right atrium


The right atrium is supplied with oxygenated blood by the right coronary artery.

The opening of the vein that drains the myocardium itself is found on the right atrium. This is called the coronary sinus.

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