The surrounding mesocardium degenerates to leave the primitive heart attached only by its arterial and venous ends, which are anatomically fixed to the pharyngeal arches and the septum transversum, respectively.
2.
In a developing embryo " JAG1 " expression is concentrated around the pulmonary artery, mesocardium, distal cardic outflow tract, major arteries, metanephros, branchial arches, pancreas, the portal vein, and otocyst.