Chambers of the Heart

The heart contains four chambers: the right and left atria and the right and left ventricles. The right atrium receives deoxygenated blood from the body, while the left atrium receives oxygenated blood from the lungs. The right ventricle pumps blood to the lungs, and the left ventricle pumps oxygenated blood to the rest of the body under high pressure as part of the overview of systemic and pulmonary circulation.

Internally, the interatrial septum separates the atria, while the interventricular septum separates the ventricles. Externally, the coronary sulcus marks the boundary between atria and ventricles, and the anterior and posterior interventricular sulci divide the two ventricles. These structures provide structural organization and support proper blood flow through the heart.

Auricles are wrinkled, pouch-like structures located on the anterior surface of the atria. They increase the blood capacity of the atria and contain pectinate muscles, which are ridged structures on their anterior walls. These features allow the atria to hold more blood and facilitate efficient atrial filling during the cardiac cycle.

The foramen ovale is an opening in the fetal heart that connects the right and left atria, allowing blood to flow between them during fetal development. After birth, this opening closes permanently, leaving behind a depression called the fossa ovalis. This closure redirects blood flow through the lungs for oxygenation after birth.

Trabeculae carneae are irregular muscular ridges found on the internal walls of the ventricles. These structures provide additional surface area and strength to the ventricular walls, supporting the forceful contractions needed to pump blood throughout the body and maintain adequate cardiac output.

Papillary muscles are located within the ventricular walls and connect to the chordae tendineae, which are cord-like structures that attach to the heart valves. Together, these structures regulate valve function by preventing valve backflow during ventricular contraction, ensuring one-way blood flow through the heart.

The left ventricle has thicker walls because it must pump oxygenated blood to the entire body against higher resistance, requiring greater force than the right ventricle. The right ventricle only pumps blood to the nearby lungs, which requires lower pressure. This structural difference reflects the different workloads of each ventricle.