Wound healing in the early chick embryo studied by scanning electron microscopy.

A simple incision was made in the early chich embryo (stages 3-5) are pellucida endoderm and its subsequent healing studied by scanning electron microscopy (SEM). Initially the wounded edges of the endoderm layer curl towards the ectoderm creating a gaping slit. The endoderm cells adjacent to the slit from large mounds probably in response to a loss of substrate and the trauma of the incision. Healing begins as the endoderm cells direct processes across the underlying cell layers and the two cut edges move towards one another. Many intervening mesoderm cells have cup-shaped processes. As the two endoderm edges meet in the corners of the wound, the wound outline changes to an oval shape. After 2 hours the wound outline is changed to a slit with the cut edges contracting in one or two areas. The cup-shaped mesoderm processes remain in the slit until the wound is healed primarily by endoderm cell movement.