Atria

Atria (singular: atrium) are the upper chambers of the heart in anatomy. They are responsible for receiving blood from the veins and pumping it into the ventricles, which then send it to the rest of the body. The human heart has two atria: the right atrium and the left atrium.

Structure

The atria are located at the top of the heart, above the ventricles. The right atrium receives deoxygenated blood from the superior vena cava, inferior vena cava, and the coronary sinus. The left atrium receives oxygenated blood from the pulmonary veins.

Right Atrium

The right atrium is a thin-walled chamber that receives deoxygenated blood from the body. It has a smooth posterior wall and a rough anterior wall due to the presence of pectinate muscles. The right atrium also contains the sinoatrial node (SA node), which is responsible for initiating the heart's electrical impulses.

Left Atrium

The left atrium is also a thin-walled chamber but receives oxygenated blood from the lungs. It has a smooth interior surface and is connected to the left ventricle via the mitral valve.

Function

The primary function of the atria is to act as receiving chambers for blood returning to the heart. They play a crucial role in the cardiac cycle by ensuring that the ventricles are filled with blood before contraction. The atria contract to push blood into the ventricles, a process known as atrial systole.

Clinical Significance

Atrial function is vital for maintaining efficient blood circulation. Disorders of the atria, such as atrial fibrillation, can lead to significant health issues. Atrial fibrillation is a common type of arrhythmia that can cause blood clots, stroke, and heart failure.

Related Structures

• Ventricles
• Heart valves
• Cardiac muscle
• Coronary circulation

See Also

• Cardiovascular system
• Electrocardiogram
• Heart disease