During
heart development of a human
embryo
An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...
, 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 foramen secundum, or ostium secundum is a in the septum primum, a precursor to the interatrial septum of the human heart.
It is not the same as the foramen ovale, which is an opening in the septum secundum.
Development
The foramen sec ...
(). The septum primum will eventually form part of the
fossa ovalis.
Blood flow
Hemodynamics or haemodynamics are the dynamics of blood flow. The circulatory system is controlled by homeostatic mechanisms of autoregulation, just as hydraulic circuits are controlled by control systems. The hemodynamic response continuousl ...
between
atria will continue through the
foramen ovale (heart)
In the fetal heart, the foramen ovale (), also foramen Botalli, or the ostium secundum of Born, allows blood to enter the left atrium from the right atrium. It is one of two fetal cardiac shunts, the other being the ductus arteriosus (which al ...
.
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
Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with child development, physical growth delays, mild to moderate ...
. 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
Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It is distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number.Updated by Linda J ...
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