part of develops from develops into germ band mesoderm trunk mesoderm FBbt:00000128 Region of mesoderm of that forms a layer interior to the ectoderm of the germ band (Campos-Ortega and Hartenstein, 1997). Following its invagination during ventral furrow formation in stages 6 and 7, it remains a coherent structure with no morphologically apparent subdivisions, apart from transient metamery during stage 9, until stage 11 (Campos-Ortega and Hartenstein, 1997). Its cells divide following invagination and it loses its epithelial integrity, forming a monolayer of cuboidal cells by stage 9 (Campos-Ortega and Hartenstein, 1997). A further division happens during stage 10 leading to two distinct layers by stage 11 (Campos-Ortega and Hartenstein, 1997). P2 TrMes UBERON:6000128 mesoderm of the germ layer AtrunkMes TrMes fly_anatomy.ontology developing embryonic structure trunk mesoderm anlage primordium trunk mesoderm derivative