Histology – Wall layers
Like the other internal spaces of the heart, the wall of the right atrium consists of three layers:
- Endocardium:The endocardium forms the innermost layer and consists of a single-layer endothelium. The function of the endocardium is to improve the flow properties of the blood.
- Myocardium:The myocardium is the actual heart muscle layer and consists of two parts: the excitation conduction system and the working muscles.
- Epicardium:The epicardium is the outermost layer of the heart wall and consists of a single-layer mesopithelium, elastic fibers and fatty tissue. Its functions are to compensate for the unevenness of the heart surface, protect the coronary arteries, and facilitate the volume changes of the heart.
Vascularization and Innervation
The right atrium is supplied by the right coronary artery. The venous outflow is usually via the vena cardiaca parva. The heart is innervated by the cardiac plexus, which contains fibers from the brainstem (vagus nerve) and from the upper thoracic spinal cord segments.
Function
The right atrium pumps the oxygen-poor blood from the vena cava into the right ventricle, which conveys the blood to the lungs. There the blood is enriched with oxygen (oxygenated) and brought back to the heart via the pulmonary veins to be pumped back into the body and distributed. The contraction of the atria causes the 4th heart sound; this can be physiological in children and adolescents, while in adults it can be an indication of heart disease.
Clinical aspects
Sinus node syndrome (sick sinus syndrome) and supraventricular extrasystoles are diseases that originate from the atrium itself or structures of the atrium. The sick sinus syndrome is a group of disorders that originate from the sinus node.These include sinus bradycardia, bradycardia-tachycardia syndrome, SA block and sinus node arrest. Risk factors and causes include old age, coronary heart disease, cardiomyopathies, high blood pressure or certain medications.
The symptoms vary depending on the type of disorder. These include fainting spells or dizziness, palpitations (pulse >100/min) or chest pain. The disease can be diagnosed with the help of a long-term ECG or a stress ECG and treated depending on the symptoms.
If the heartbeat is too slow (bradycardia), the implantation of a pacemaker can be treated. If the heart is racing (tachycardia), appropriate medication can be used to lower the heart rate. Supraventricular extrasystole, also known as heart stuttering, is a disorder characterized by premature excitation of the atria.
It occurs in both healthy and cardiac patients, more frequently with increasing age. The triggering factors are many and varied, including inflammation, infection, salt balance disorders, high blood pressure, coronary heart disease, but also the consumption of certain substances such as caffeine, drugs or alcohol. Most supraventricular extrasystoles are usually experienced without symptoms, sometimes they are also perceived as heart palpitations.
The diagnosis is made by means of an ECG. Usually no treatment is necessary. If the occurrence is too frequent or too strong, ß-blockers or antiarrhythmics may be used. However, in these special cases it is more important to diagnose and treat the underlying disease.
