Читать книгу Understanding Anatomy and Physiology in Nursing - John Knight - Страница 87

The atria (sometimes known by the older term auricles) are the two superior (upper) chambers of the heart. These are thin-walled, elastic structures that function primarily as simple collecting chambers. The right atrium collects deoxygenated blood from the two great veins (the superior vena cava and the inferior vena cava). The left atrium receives highly oxygenated blood directly from the lungs via the pulmonary veins. Following collection the atria rapidly deliver blood to their corresponding ventricles. During foetal development the left and right atria are connected to each other via a small opening termed the foramen ovale.

When a baby is born and takes its first breath, changes in blood pressure cause this aperture to close, forming a thin interatrial septum which permanently separates the right- and left-hand sides of the heart. Sometimes this closure does not occur or is incomplete, resulting in a patent foramen ovale (PFO) which is often referred to as a ‘hole in the heart’. This is a common congenital birth defect (affecting around 25 per cent of the population) and frequently seen in babies with chromosomal abnormalities such as Down syndrome. Septal defects such as PFO allow abnormal mixing of oxygenated and deoxygenated blood which can lead to reduced blood oxygen saturation and also may increase the risk of stroke in later life. Such congenital defects, if severe, often require surgery to correct.