23.4 : Chambers of the Heart

The human heart is a complex organ made up of four chambers: the right and left atria and the right and left ventricles. These internal chambers are separated by partitions known as the interatrial and interventricular septa. The exterior of the heart features a groove known as the coronary sulcus that demarcates the atria from the ventricles, while the anterior and posterior interventricular sulci distinguish between the two ventricles.

Deoxygenated blood from the body is received in the right atrium, while the left atrium receives oxygenated blood from the lungs. The atria's capacity is enhanced by wrinkled pouch-like structures called auricles. Notably, the right atrium and auricle contain pectinate muscles, which are ridged structures on their anterior walls.

In the fetal stage, an opening known as the foramen ovale allows blood to flow between the atria. This opening seals after birth, leaving a depression called the fossa ovalis.

The ventricles serve unique roles. The right ventricle pumps deoxygenated blood to the lungs, whereas the left ventricle, characterized by its thicker walls, pumps oxygenated blood to the rest of the body under high pressure.

Internally, the ventricles' walls feature muscle ridges known as trabeculae carneae. The function of the heart valves is regulated by papillary muscles and chordae tendineae located within the ventricular walls.