Synonym
Atrium dextrumThe right atrium is one of the four inner chambers of the heart, which is connected to the large circulation. In it, blood flows in through the vena cava and is passed on to the right ventricle.
Anatomy
The right atrium is spherical and has the right auricle on the front. The heart muscle is about 3 mm thick in the right atrium. The right atrium is separated from the right ventricle by the right sail valve (tricuspid valve).
It receives the oxygen-poor blood from the lower half of the body via the inferior vena cava; from the shoulder, chest and head region via the superior vena cava. The common inflow path of the two veins is called the sinus venarum cavarum and represents the smooth part of the atrial wall. Within the cavar sinus there is a slight protrusion of the posterior wall of the atrium, the tuberculum intervenosum, which delimits the vein entrances.
The other part of the atrial wall is characterized by the so-called musculi pectinati, which, as parallel heart muscle balls, also line the right heart ear. The border between these two structurally different parts is called the crista terminalis. The right atrium is separated from the left atrium by the atrial septum.
On the right side of this dividing wall a faint depression is visible, fossa ovalis. This is the place where there was a short circuit between the two atria during embryonic development. The fossa ovalis is bordered at the bottom by a bulge (Valvula venae cavae inferioris), which ensures in the embryonic circulation that blood is channelled through the fossa ovalis into the left atrium.
In front of the Valvula venae cavae inferioris is the junction of the coronary arteries, the ostium sinus coronarii. The right atrium also contains two important components of excitation formation and conduction: the sinus node and the AV node. The sinus node is located next to the junction of the superior vena cava and is considered the primary pacemaker.
This means that it determines the heart rate in healthy individuals. It gives 60-80 pulses per minute, which are then transmitted further via the heart muscle and lead to the contraction of the heart. The AV node is the next station of the excitation line.
It is located at the base of the interatrial septum. The AV node has a natural frequency of 40-60 excitations per minute. Its main function is to delay the transmission of excitation, thus preventing simultaneous atrial and ventricular contraction. If the sinus node fails, the pacemaker function is taken over by the AV node and the heart therefore beats more slowly.
