Foramen primum

Foramen Primum is an anatomical structure that forms during the embryonic development of the heart. It is one of the openings in the septum primum, which is the initial septum that divides the primitive atrium into left and right atria in the developing heart.

Development

The foramen primum is formed during the fourth week of embryonic development. It is initially a large opening in the septum primum, which allows blood to flow freely between the two atria. As the septum primum grows towards the endocardial cushions, the foramen primum gradually decreases in size.

Function

The primary function of the foramen primum during embryonic development is to allow oxygenated blood from the placenta to bypass the non-functional fetal lungs and flow directly into the left atrium. This is crucial for the survival of the fetus, as the lungs are not yet capable of oxygenating the blood.

Closure

The foramen primum is eventually closed off by the fusion of the septum primum with the endocardial cushions. This occurs shortly before birth, when the lungs are ready to take over the role of oxygenating the blood. The closure of the foramen primum is a critical step in the transition from fetal to postnatal circulation.

Clinical Significance

If the foramen primum fails to close properly, it can result in a type of congenital heart defect known as an atrial septal defect. This can lead to a variety of health problems, including heart failure and pulmonary hypertension.

See Also

• Septum primum
• Endocardial cushions
• Atrial septal defect