Development Animation - Heart Atrial Septation
atrial septation - Term describing the complex developmental formation of the interatrial septum, the wall between the right and left atria of the heart. In humans, this septation process begins in week 5 of development with the septum primum, a membranous extension on the dorso-cranial wall growing downward towards endocardial cushions. An opening remains as the foramen primum (ostium primum). The septum primum fuses with endocardial cushion, but cranially had begun to degenerate forming foramen secundum (ostium secundum). A later forming septum secundum on the ventro-cranial wall grows downward, but does not fuse with endocardial cushion, the remaining opening is the foramen ovale. Abnormalities of this process are called Atrial Septal Defects (ASD), a group of common (1% of cardiac) congenital anomalies occurring in a number of different forms and more often in females. The process of separating the ventricles is called ventricular septation.
atrial septal defect - (ASD) Heart developmental abnormality leading to an abnormal opening or hole in the septum between right and left atria. Normally allows left to right blood shunting, though additional cardiac abnormalities causing higher right side pressure (pulmonary stenosis or tricuspid atresia) allow right to left blood shunting.
atrium - The upper heart chamber receiving circulating blood and by contracting pumps this blood into the ventricle. The human heart has two atria; right atrium receiving deoxygenated venous (vena cava) circulating blood and left atrium receiving oxygenated blood from the lungs (pulmonary).
ostium primum - (primary opening, first opening) In early heart development during atrial septation, the initial septum primum is incomplete leaving this initial opening between the left and right atria. Later the septum primum begins to degenerate forming a second opening, the ostium secundum.
ostium secundum - (secondary opening, second opening) In early heart development during atrial septation, the initial septum primum begins to degenerate forming this second opening between the developing left and right atria.
septum primum - (primary septum) In early heart development in the atrial wall a superior region in the midline extends downward, forming the initial incomplete separation (septation) of the right and left atria leaving an opening the ostium primum. This initial structure partially breaks down forming the ostium secundum and later fuses with the septum secundum. Note that complete functional and anatomical separation of the right and left atria occurs after birth with activation of the pulmonary system.
septum secundum - (secondary septum) In early heart development, atrial septation is completed by an atrial wall growth to the right of the initial septum primum. Note that complete functional and anatomical separation of the right and left atria occurs after birth with activation of the pulmonary system.