Blastema

A blastema (Greek βλάστημα, "offspring"[1]) is a mass of cells capable of growth and regeneration into organs or body parts.

Then, during the early nineteenth century, the definition broadened to include growth zones (still considered acellular) in healthy, normally developing plant and animal embryos.

In short, the term blastema started being used to refer to what modern embryologists increasingly began calling a rudiment or Anlage.

Importantly, the term blastema did not yet refer to a mass of undifferentiated-looking cells that accumulates relatively early in a regenerating body part.

Currently, the old usage of blastema to refer to a normal embryological rudiment has largely disappeared (except for describing aspects of development of the kidney and, to a lesser extent, the adrenal gland).

In the first few days after the injury, this wounded epidermis transforms into a layer of signaling cells called the Apical Epithelial Cap (AEC), which has a vital role in regeneration.

[7] An important model organism for studying limb regeneration is Ambystoma mexicanum, a neotenic salamander with exceptional regenerative capabilities.

In flatworms, the formation of a blastema needs adult stem cells that are called neoblasts for any type of regeneration to occur.

[12] In urodele amphibians, studies suggest that dedifferentiation of cells leads to the formation of a blastema that is able to form multiple tissue types after the amputation of their tails and wound healing occurs.