The right atrium is one of the four chambers of the heart and plays a key role in the circulatory system. It is located in the upper right portion of the heart and is responsible for receiving deoxygenated blood from the body and pumping it into the right ventricle. Here’s a breakdown of its structure and function:

Structure:

• Shape and Size: The right atrium is a thin-walled, somewhat triangular chamber that receives blood from various parts of the body.
• Internal Features:
  • Interatrial septum: This is the wall that separates the right atrium from the left atrium.
  • Tricuspid valve: Located between the right atrium and the right ventricle, it prevents backflow of blood into the atrium when the ventricle contracts.
  • Fossa ovalis: This is a depression in the interatrial septum, a remnant of the fetal foramen ovale.
  • Pectinate muscles: These are ridges of muscle within the atrium that help with contraction and blood flow.
  • Crista terminalis: A ridge that divides the smooth-walled posterior part of the atrium from the anterior, muscular part.
• Venous Return: The right atrium receives deoxygenated blood from three major veins:
  • Superior vena cava (SVC): Carries blood from the upper body (head, neck, arms).
  • Inferior vena cava (IVC): Carries blood from the lower body.
  • Coronary sinus: Drains blood from the heart muscle itself.

Function:

• Receiving Deoxygenated Blood: The right atrium receives deoxygenated blood from the body through the superior and inferior vena cava, and the coronary sinus. This blood is low in oxygen and high in carbon dioxide and metabolic waste.
• Pumping Blood to Right Ventricle: Once the right atrium fills, it contracts (atrial systole) to push the blood through the tricuspid valve into the right ventricle. This is the beginning of the process that will eventually lead to the oxygenation of the blood in the lungs.
• Atrial Contraction: The contraction of the right atrium helps to complete the filling of the right ventricle, which is necessary for the efficient pumping of blood to the lungs for oxygenation.

In summary, the right atrium’s primary function is to collect deoxygenated blood from the body and pump it into the right ventricle, which then sends it to the lungs for oxygenation. Its structural features, such as valves and the muscular ridges, ensure efficient blood flow and prevent backflow.