Search results
Results from the WOW.Com Content Network
A defect in the ostium primum is occasionally classified as an atrial septal defect, [17] but it is more commonly classified as an atrioventricular septal defect. [18] [19] Ostium primum defects are less common than ostium secundum defects. [20] This type of defect is usually associated with Down syndrome. [21]
Foramen secundum atrial septal defects are the most common atrial septal defects. This defect can arise as a result of defects of the septum primum and the septum secundum. For the septum primum, the problem can arise as a result of excess resorption of the septum during the process of apoptosis in order to form the foramen secundum.
The ostium primum atrial septal defect is a defect in the atrial septum at the level of the tricuspid and mitral valves. This is sometimes known as an endocardial cushion defect because it often involves the endocardial cushion, which is the portion of the heart where the atrial septum meets the ventricular septum and the mitral valve meets the tricuspid valve.
Before it does so, bloodflow from the inferior vena cava wears down a portion of the septum primum, forming the ostium secundum. Some embryologists postulate that the ostium secundum may be formed through programmed cell death. [4] The ostium secundum provides communication between the atria after the ostium primum closes completely.
Before the ostium primum is completely occluded, a second opening called the ostium secundum begins to form in the septum primum. The ostium secundum allows continued shunting of blood from the right atrium to the left. To the right of the septum primum, the septum secundum begins to form. This thick, muscular structure initially takes on the ...
The septum primum, a septum which grows down to separate the primitive atrium into the left atrium and right atrium, grows in size over the course of heart development. The primary interatrial foramen is the gap between the septum primum and the septum intermedium , which gets progressively smaller until it closes.
This opening is closed by the union of the septum primum with the septum intermedium, and the communication between the atria is re-established through an opening which is developed in the upper part of the septum primum; this opening is known as the foramen ovale (ostium secundum of Born) and persists until birth.
The gap below it is known as the ostium primum (from Latin 'first opening'), and becomes increasingly small. The septum primum eventually fuses with the endocardial cushion, closing the ostium primum off completely. Meanwhile, perforations appear in the superior part of the septum primum, forming the ostium secundum (from Latin 'second opening').