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Portrait of Right atrium

Anatomy · Heart & blood vessels

Right atrium

Receives all the body's deoxygenated blood

Heart · receiving chamber

The upper right chamber of the heart. It receives deoxygenated blood from the superior and inferior venae cavae and the coronary sinus, and passes it through the tricuspid valve into the right ventricle. It forms the right border of the heart and its wall contains the sinoatrial node, the heart's natural pacemaker.

How to spot them

  • ▸A smooth-walled posterior part (sinus venarum) and a rough anterior part ridged by pectinate muscles
  • ▸A shallow oval depression on the septum, the fossa ovalis
  • ▸The crista terminalis, a muscular ridge dividing the smooth and rough parts
  • ▸A small ear-shaped pouch, the right auricle, overlapping the root of the aorta

What to know

The chamber where the upper and lower great veins and the coronary sinus all empty

Right atrium — the three venous inlets.

Its septal wall carries a shallow oval hollow marking where a foetal opening once let blood bypass the lungs

Right atrium — the fossa ovalis, remnant of the foramen ovale.

It forms the right border of the cardiac silhouette on a chest X-ray

Right atrium.

Its inner wall is ridged by comb-like muscles, ending at a muscular ridge, the crista terminalis

Right atrium — pectinate muscles and crista terminalis.

In the wall near the entry of the upper great vein lies the group of cells that sets the rate of the heartbeat

Right atrium — the sinoatrial node.

Blood leaves this chamber through a three-cusped valve

Right atrium — into the right ventricle via the tricuspid valve.

A rudimentary flap guards the lower great vein's opening into this chamber and once directed foetal blood across the septum

Right atrium — the valve of the inferior vena cava (Eustachian valve).

Key ideas

  • Two embryological parts: the smooth sinus venarum (from the sinus venosus) and the rough true atrium (primitive atrium).
  • The coronary sinus opens between the inferior vena cava and the tricuspid orifice, guarded by the Thebesian valve.

Quick-fire facts

  • •Receives blood from the superior vena cava, inferior vena cava and coronary sinus.
  • •The fossa ovalis is the remnant of the foramen ovale, which lets foetal blood pass from right to left atrium.
  • •The foramen ovale stays probe-patent in roughly a quarter of adults, usually without symptoms.
  • •The crista terminalis separates the smooth sinus venarum from the rough pectinate part.
  • •The sinoatrial node sits at the junction of the superior vena cava and the right atrium.
  • •The atrioventricular node lies in the triangle of Koch, near the opening of the coronary sinus.
  • •The right auricle is the ear-shaped appendage overlapping the root of the aorta.
  • •Blood passes from it through the tricuspid valve into the right ventricle.

Drill it — 7 cards

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Sources