Early Heart Development:
The cardiac primordium arises from a cardiogenic plate made up of mesoderm, lying in front of the head, and beneath the pericardial chamber (Table 2.01).. The head, or neural plate, grows forward, reversing orientation, to below the foregut, and above the pericardial coelom.
The caudal (tail) end is continuous with mesoderm, and receives veins there. The cardiac tube is composed of two longitudinal strands of mesodermal cells, each forming cavities. Thus, there are thin-walled endothelial tubes within splanchnic mesoderm, which begin fusing first at the cranial (head) end into a single tube.
The internal endothelial tissue becomes the future endothelial lining, while the external thick covering gives rise to the myocardium and epicardium. The space between the two is filled with cardiac jelly.
At the 7-16 somite stage, the cardiac tube is suspended by a dorsal mesocardium. This dorsal mesentery later disappears.
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