Right atrium

Function

The right atrium is the heart's venous receiving hall. Deoxygenated blood returns from the entire body through the superior and inferior vena cavae and from the heart's own muscle through the coronary sinus, pooling in this thin-walled chamber at pressures of just 2–6 mmHg.

Its smooth posterior wall (the sinus venarum) contrasts with ridged pectinate muscle anteriorly — the embryological seam between the primitive sinus venosus and the true atrium, marked by the crista terminalis. In the septum, the fossa ovalis remembers the foetal foramen ovale that once shunted blood directly to the left side, bypassing the liquid-filled lungs.

Blood supply

Right coronary artery.

Nerve supply

Vagus (parasympathetic) and sympathetic cardiac nerves; the SA node sits at its superior junction with the SVC.

Clinical relevance

Atrial fibrillation

Chaotic atrial activity abolishes the atrial kick; clots form mainly in the LEFT atrial appendage — AF underlies roughly 15–20% of ischaemic strokes.

Atrial septal defect

A secundum ASD shunts blood left-to-right, overloading the right heart over decades; a patent foramen ovale (in ~25% of adults) rarely shunts much but can allow paradoxical emboli.

Related conditions

• Atrial fibrillation