> All parts of the body are built like this.
Please name one other organ that arises from two separate progenitor cell types. If this is common, I have never heard of it.
Well, your heart contains both mesoderm derived cells (enervation) and ectoderm derived cells (musculature).
Bones, guts, many glands, kidneys.
Well, your heart contains both mesoderm derived cells (enervation) and ectoderm derived cells (musculature).