The septum secundum is a
muscular
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle ...
flap that is important in
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 ...
. It is semilunar in shape, and grows downward from the upper wall of the
atrium immediately to the right of the
septum primum and
ostium secundum. It is important in the closure of the
foramen ovale after
birth
Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the f ...
.
Structure
Development
At the end of the fifth week of development, the septum secundum grows from the upper wall of the
primitive atrium.
It grows to the right of the
septum primum, which has already started growing.
It grows down towards the
septum intermedium
Endocardial cushions project into the atrial canal
The proper development of the atrioventricular canal into its prospective components (The heart septum and associated valves) to create a clear division between the four compartments of the heart ...
formed from the
endocardial cushions.
Before
birth
Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the f ...
, it does not fuse with the septum intermedium, leaving a gap to form the
foramen ovale.
Shortly after birth, it fuses with the
septum primum to form the
interatrial septum
The interatrial septum is the wall of tissue that separates the right and left atria of the heart.
Structure
The interatrial septum is a that lies between the left atrium and right atrium of the human heart. The interatrial septum lies at angl ...
, and the foramen ovale is closed.
The
fossa ovalis denotes the free margin of the septum secundum after birth.
Clinical significance
Sometimes, the fusion of the septum secundum to the
septum intermedium
Endocardial cushions project into the atrial canal
The proper development of the atrioventricular canal into its prospective components (The heart septum and associated valves) to create a clear division between the four compartments of the heart ...
is incomplete, and the upper part of the foramen remains patent.
This creates an
atrial septal defect
Atrial septal defect (ASD) is a congenital heart defect in which blood flows between the atria (upper chambers) of the heart. Some flow is a normal condition both pre-birth and immediately post-birth via the foramen ovale; however, when this d ...
(ASD).
References
External links
*
*
Overview at edu.mt*
Embryology of cardiovascular system
{{Portal bar, Anatomy