Fate Map - Gastrulation in Chick

All the three main germinal layers (ectoderm, mesoderm, endoderm) are made from cells initially located in the epiblast in area pellucida, hence, the entire body of chick and most parts of the extra-embryonic membranes (yolk sac, amnion, chorion, allantois) are developed from cells derived from the epiblast. Therefore, the fate maps constructed for the blastoderm of chick embryo consider to the several presumptive organ making areas in the epiblast only. This map is based on the results of a number of studies by dissimilar workers by using a variety of in ovo and in vitro techniques involving staining with vital dyes, marking with carbon particles, labelling along with tritiated thymidine and subsequent autoradiography, grafting and transplantation of specific areas etc. The map displays the location and the extent of different areas in the blastoderm (epiblast) from where the presumptive cells are derived for the three germinal layers:

1. Ectoderm (involving epidermal, neural and extra-embryonic ectoderm)
2. Mesoderm (involving mesoderm for notochord, head, somites, lateral plate and extra-embryonic mesoderm) and
3. Endoderm (involving gut and extra-embryonic yolk sac endoderm).

As a result of morphogenetic movements during gastrulation the cells from the several areas reach their respective specific destinations making the ectoderm on the surface, endoderm below and mesoderm among the two.