8.1. Right Atrium


Right auricle
This is not the same thing as the right atrium. The auricle is a muscular structure that is a small part of the right atrium, located on its superior aspect. It has been suggested that it functions to increase the atrial volume, although this is not fully understood.

Crista terminalis
A ridge on the internal aspect of the posterolateral wall of the atrium. The smooth part of the atrium that lies posterior to the crista terminalis is called the sinus venarum: it is linked to the embryological cavity called the sinus venosus. The part of the atrium that lies anterior to the crista terminalis is roughened with bundles of muscle fibres called musculi pectinati.

Musculi pectinati
Described above.

Fossa ovalis
This fingerprint-like impression on the left wall of the right atrium is formed after the closure of the foramen oval in the fetus. The foramen ovale allowed the flow of oxygenated blood from the right atrium to the left atrium in the fetus - this was essential for ensuring all of the fetal tissues received enough oxygen. The foramen ovale closes at (or shortly after) birth.

Opening of the coronary sinus
The coronary sinus receives deoxygenated blood from the great, middle and small cardiac veins, which then enters the right atrium.

Valve of the inferior vena cava
Helps to direct blood through the foramen ovale into the left atrium. Note that it is vestigial (unused) in adult life.

Openings of superior and inferior vena cavae

Right atrioventricular orifice
Simply refers to the communicating space between the right atrium and ventricle.