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Heart Development - Anatomy & Physiology (view source)
Revision as of 16:01, 8 July 2008
, 16:01, 8 July 2008no edit summary
Septation of the tubular heart begins in the atrioventricular canal. Two masses of cardiac mesenchymal tissue, known as endocardial cushions, extend towards each other and fuse. The fused endocardial cushions form the septum intermedium, which divides the common atrioventricular canal into left and right atrioventricular canals.
Septation of the tubular heart begins in the atrioventricular canal. Two masses of cardiac mesenchymal tissue, known as endocardial cushions, extend towards each other and fuse. The fused endocardial cushions form the septum intermedium, which divides the common atrioventricular canal into left and right atrioventricular canals.
During proliferation of the endocardial cushions the initial atrial septum forms inside the common atrial chamber as a crescent-shaped ridge called the septum primum. The septum primum emerges from the dorsal wall of the common foetal atrium and extends towards the endocardial cushions. The septum primum becomes progressively smaller as the septum primum advances and disappears altogether when the septum primum fuses with the endocardial cushions. Before closure of the foramen primum, however, apoptosis in the central part of the septum primum results in the formation of a new foramen between the left and right atria, the foramen secundum. A second membrane, the septum secundum, arises from the dorsal wall of the right atrium and extends towards the septum intermedium. The opening which persists between the free edge of the septum secundum and the foramen secundum is known as the foramen ovale.