1. The primordial cellular mass (precursor) from which an organ or part is formed.
2. A cluster of cells competent to initiate the regeneration of a damaged or ablated structure.
The definition information for blastema is provided by Stedman's. You can search our medical dictionary here.
Stedman's, part of Lippincott Williams & Wilkins, provides a comprehensive line of health-science publications for healthcare professionals and medical students.