BIO380H5 Lecture Notes - Lecture 31: Endocardial Cushions, Atrioventricular Canal, Atrioventricular Node
Document Summary
Atrium becomes separated from the ventricles by the formation of thickened atrioventricular cushions- thickening at the junction between ventricle and the outflow tract (functions as primitive valve to help in the forward propulsion of blood) Epithelial to messenchyme transforming of endocardium of the endocardial cushions due to the inductive action of the underlying primary myocardium on certain cells. Inductive signals from primary myocardium cells packaged together called adherons. Endocardial cushions which become dense connective tissues form dorsal and ventral walls of the atrioventricular canal. As they grow into the canal, cushions meet and separate the atrioventricular canal into right and left channels. 5th week- partitioning begins with the downgrowth of interatrial septum primum from the cephalic wall between bulging atrial chambers. Apices of the crescents merge with the endocardial cushions. Space between the edge of the septum primum and the endocardial cushions is called interatrial foramen primum which allows blood to pass directly from the right to the left atrium.
