Right atrium

At a glance

English

Right atrium

Latin (TA2)

Atrium dextrum

System

Heart

Region

Trunk

Side

Single, on the midline

About the right atrium

The right atrium forms the right border of the heart as seen from the front, lying between the superior and inferior venae cavae, which open into its upper and lower ends. It receives all the deoxygenated blood returning from the body: from the two venae cavae, from the heart muscle itself through the coronary sinus, and from the anterior cardiac veins and the many tiny smallest cardiac veins that open straight through its wall.

Inside, a ridge called the crista terminalis runs down the lateral wall between the openings of the two venae cavae. Behind it lies the smooth-walled sinus venarum, which develops from the embryonic sinus venosus and receives the great veins. In front of it the wall is ribbed by parallel pectinate muscles, which extend into the right auricle, a broad triangular pouch that overlaps the root of the aorta. On the outside, a shallow groove called the sulcus terminalis marks the position of the crest.

The septal wall carries the fossa ovalis, an oval hollow with a raised rim that marks where the foramen ovale allowed blood to cross from right to left before birth. Below it open the inferior vena cava, guarded by a small valve, and the coronary sinus, beside which lies the triangle containing the atrioventricular node. The sinoatrial node, the natural pacemaker, sits at the top of the crista terminalis near the opening of the superior vena cava.

Because the atria have no valves at their inlets, pressure changes in the right atrium pass back into the neck veins and can be judged as the jugular venous pressure. The chamber is entered by catheters and pacing leads, and the fossa ovalis is the spot crossed to reach the left atrium. A foramen ovale that does not close is common and usually harmless, though it can let a venous clot pass to the arterial side.

Function and supply

Function

Receives venous blood from the venae cavae, coronary sinus and cardiac veins and passes it through the tricuspid valve into the right ventricle; houses the sinoatrial and atrioventricular nodes.

Nerve supply

Sympathetic and vagal fibres from the cardiac plexus, many ending at the sinoatrial and atrioventricular nodes.

Blood supply

Mainly the right coronary artery, including its sinoatrial nodal branch in most people; drained by small veins opening directly into the chamber and into the coronary sinus.