During
heart development of a human
embryo, the single
primitive atrium becomes divided into right and left by a , the septum primum. The septum primum () grows downward into the single atrium.
Development
The gap below it is known as the
ostium primum (), 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 (). The septum primum will eventually form part of the
fossa ovalis.
Blood flow
Hemodynamics American and British English spelling differences#ae and oe, or haemodynamics are the Fluid dynamics, dynamics of blood flow. The circulatory system is controlled by homeostasis, homeostatic mechanisms of autoregulation, just as hydrau ...
between
atria will continue through the
foramen ovale (heart).
Clinical significance
Failure of the septum primum to fuse with the endocardial cushion can lead to an ostium primum
atrial septal defect.
This is the second most common type of atrial septal defect
[Diagram of Ostium Secundum Atrial Septal Defect at Mayo Clinic](_blank)
/ref> and is commonly seen in Down syndrome. Typically this defect will cause a shunt to occur from the left atrium to the right atrium. Children born with this defect may be asymptomatic, however, over time pulmonary hypertension and the resulting hypertrophy of the right side of the heart will lead to a reversal of this shunt. This reversal is called Eisenmenger's syndrome.
References
External links
Overview at um.edu.mt
Diagram at lww.com
* - "Atrial Partitioning"
Embryology of cardiovascular system
{{Portal bar, Anatomy