Left auricle

Left Atrium

The left atrium is one of the four chambers of the heart, located on the left posterior side. It plays a crucial role in the cardiac cycle, receiving oxygenated blood from the lungs via the pulmonary veins and pumping it into the left ventricle, which then distributes it to the rest of the body. The anatomy and function of the left atrium are essential for understanding cardiac physiology and the pathophysiology of various cardiovascular diseases.

Anatomy

The left atrium is situated in the upper part of the heart, posterior to the right atrium and above the left ventricle. It has a smooth-walled interior, except for the auricle (left atrial appendage), which has a ridged surface due to pectinate muscles. The left atrium receives oxygen-rich blood from the lungs through four pulmonary veins, two from the right lung and two from the left lung. The blood then moves from the left atrium through the mitral valve into the left ventricle.

Function

The primary function of the left atrium is to act as a holding chamber for blood returning from the lungs and to act as a pump to transport blood to other areas of the heart. During the diastole phase of the cardiac cycle, the left atrium fills with oxygenated blood from the lungs. Then, during atrial systole, the left atrium contracts, increasing the pressure within the chamber and forcing blood through the open mitral valve into the left ventricle.

Clinical Significance

Several conditions can affect the left atrium, impacting its ability to function properly. Conditions such as atrial fibrillation, atrial septal defect, and mitral valve stenosis can lead to increased pressure and volume in the left atrium, potentially causing left atrial enlargement. This enlargement is associated with an increased risk of stroke and heart failure.

See Also

• Heart
• Cardiac cycle
• Pulmonary veins
• Mitral valve