The primitive heart tube

• When the  primary and secondary heart fields are established, primary heart field cells are induced to form cardiac myoblasts and blood islands
• cardiac myoblast ar precursors of cardiac muscle cells
• Blood islands consist of angioblasts
• The endocardial tubes are tubes lined by endothelial cells surrounded by cardiac myoblasts
• he intraembryonic coelom (primitive body cavity) lies over the endocardial tubes and will eventually form the pericardial cavity in which the mature heart resides
• the lateral body folds bring the right and left endocardial tubes together in the midline of the embryo, where they fuse to form a continuous, expanded tube
• The primitive heart tube exist only of primary heart field cells