Study of upper extremity growth and development using human embryos and computer-reconstructed models.

This study investigated the apical ectodermal ridge and early vasculature of the human limb bud by use of histologic techniques and a new method of computer modeling. Fourteen human embryos were studied (more than 10,000 sections) microscopically and the embryonic limbs were reconstructed three-dimensionally by use of a serialized programming method. The apical ectodermal ridge consists of an extensive band of specialized cells, located over the rim of the limb surmounting a strip of rapidly-dividing mesenchymal cells. It is consistently supplied by a large vessel that shows extensive central branching.