- 1. Originally applied to a group of cells on the dorsal lip of the blastopore, which induce differentiation of cells in the embryo and control growth and development of adjacent parts. 2. Any group of cells having such a controlling influence, the effects being brought about through the action of an evocator.- nucleolar o. the region of the satellites on the acrocentric chromosomes that is active in nucleolus formation. SYN: nucleolar zone, nucleolus o..
* * *or·ga·niz·er also Brit or·ga·nis·er -.nī-zər n1) one that organizes2) a region of a developing embryo (as the chordamesoderm of the dorsal lip of the vertebrate blastopore) or a substance produced by such a region that is capable of inducing a specific type of development in undifferentiated tissue called also inductor
* * *or·ga·niz·er (orґgə-nīz″ər) a part of an embryo that so influences some other part as to bring about and direct its histological and morphological differentiation. Parts developing as a result of induction, and inducing in their turn are classified as organizers of the second grade, third grade, and so on. Cf. activator (def. 2) and inductor.
Medical dictionary. 2011.