Foramen ovale is a small opening located in the bone of the skull, specifically in the interatrial septum, which separates the left and right atria of the heart. It is present in the fetal stage of human development and serves as an important structure in fetal circulation.
Structure
Foramen ovale is a small opening in the interatrial septum of the heart that measures about 8-10 mm in diameter. It is surrounded by a fibrous ring, which is composed of connective tissue and collagen fibers. The opening is covered by a thin, flexible membrane called the septum primum, which is made up of fibrous tissue and endothelial cells.
The septum primum is attached to the inner surface of the interatrial septum and extends towards the left atrium. It is thinner at the edges and thicker in the center, where it is perforated by a small opening called the foramen secundum. The foramen secundum is located between the septum primum and the septum secundum, which is a thin, muscular structure that separates the left and right atria.
Location
Foramen ovale is located in the interatrial septum, which is the wall that separates the left and right atria of the heart. It is situated between the left and right atria and is located just above the atrioventricular valves, which regulate the flow of blood between the atria and ventricles.
Function
In the fetal stage of human development, foramen ovale serves as an important structure in fetal circulation. During fetal development, the fetus relies on the mother’s circulatory system for oxygen and nutrients. Oxygen-depleted blood from the fetus returns to the right atrium of the heart, where it is then pumped into the right ventricle and sent to the lungs for oxygenation.
However, the lungs of the fetus are not yet functional and do not participate in gas exchange. To bypass the non-functioning lungs, the oxygen-depleted blood from the fetus is directed to the left atrium through the foramen ovale, which allows it to enter the left ventricle and be pumped out to the rest of the body.
This arrangement allows the fetus to receive oxygenated blood from the mother’s circulatory system, which helps to sustain fetal growth and development. After birth, the foramen ovale closes, and the circulation of blood in the body changes to the adult pattern.
Clinical significance
In some cases, foramen ovale may fail to close properly after birth, leading to a condition called patent foramen ovale (PFO). PFO is a common cardiac abnormality that occurs in about 25% of the population. It is characterized by the persistence of the foramen ovale in the interatrial septum, which allows the flow of blood between the left and right atria.
PFO is usually asymptomatic and does not cause any noticeable symptoms in most individuals. However, in some cases, it may be associated with an increased risk of stroke, particularly in younger individuals. PFO may also be associated with other cardiovascular conditions, such as atrial fibrillation and pulmonary embolism.
The diagnosis of PFO is usually made through imaging tests, such as echocardiography or transesophageal echocardiography, which can visualize the opening in the interatrial septum. Treatment for PFO may include medications such as blood thinners to reduce the risk of stroke or closure of the foramen ovale through a medical procedure called transcatheter closure.
PFO closure involves the insertion of a small device into the foramen ovale, which seals the opening and prevents the flow of blood between the left and right atria. The procedure is usually performed through a catheterization procedure and is performed under local anesthesia. PFO closure is generally safe and effective, with a success rate of about 95%.
