In the developing
heart
The heart is a muscular Organ (biology), organ found in humans and other animals. This organ pumps blood through the blood vessels. The heart and blood vessels together make the circulatory system. The pumped blood carries oxygen and nutrie ...
, the
atria are initially open to each other, with the opening known as the primary interatrial foramen or ostium primum (or interatrial foramen primum). The foramen lies beneath the edge of
septum primum and the
endocardial cushions
Endocardial cushions, or atrioventricular cushions, refer to a subset of cells in the development of the heart that play a vital role in the proper formation of the heart septa.
They develop on the atrioventricular canal and conotruncal region of ...
. It progressively decreases in size as the septum grows downwards, and disappears with the formation of the
atrial septum.
Structure
The foramen lies beneath the edge of
septum primum and the
endocardial cushions
Endocardial cushions, or atrioventricular cushions, refer to a subset of cells in the development of the heart that play a vital role in the proper formation of the heart septa.
They develop on the atrioventricular canal and conotruncal region of ...
. It progressively decreases in size as the septum grows downwards, and disappears with the formation of the
atrial septum.
Closure
The septum primum, a which grows down to separate the
primitive atrium
The primitive atrium is a stage in the embryonic development of the human heart. It grows rapidly and partially encircles the bulbus cordis; the groove against which the bulbus cordis lies is the first indication of a division into right and left ...
into the
left atrium
The atrium (; : atria) is one of the two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular mitral and tricuspid heart valves.
...
and
right atrium
The atrium (; : atria) is one of the two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular mitral and tricuspid heart valves.
...
, grows in size over the course of
heart development
Heart development, also known as cardiogenesis, refers to the prenatal development of the heart. This begins with the formation of two endocardial tubes which merge to form the tubular heart, also called the primitive heart tube. The heart is ...
. The primary interatrial foramen is the gap between the septum primum and the
septum intermedium
Endocardial cushions project into the atrial canal, and, meeting in the middle line, unite to form the septum intermedium which divides the canal into two channels, the future right and left atrioventricular orifices.
References
External links ...
, which gets progressively smaller until it closes.
Clinical significance
Failure of the septum primum to fuse with the endocardial cushion can lead to an ostium primum
atrial septal defect
Atrial septal defect (ASD) is a congenital heart defect in which blood flows between the atrium (heart), atria (upper chambers) of the heart. Some flow is a normal condition both pre-birth and immediately post-birth via the Foramen ovale (heart) ...
.
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 condition may be asymptomatic, however, over time pulmonary hypertension
Pulmonary hypertension (PH or PHTN) is a condition of increased blood pressure in the pulmonary artery, arteries of the lungs. Symptoms include dypsnea, shortness of breath, Syncope (medicine), fainting, tiredness, chest pain, pedal edema, swell ...
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. Although hypertro ...
of the right side of the heart will lead to a reversal of this shunt. This reversal is called Eisenmenger syndrome.
References
External links
*
Overview and diagram at um.edu.mt
*
{{Authority control
Embryology of cardiovascular system