Ectomesenchyme has similar properties to mesenchyme

Mesenchyme

Mesenchyme, or mesenchymal connective tissue, is a type of undifferentiated loose connective tissue that is derived mostly from mesoderm, although some are derived from other germ layers; e.g. some mesenchyme is derived from neural crest cells and thus originates from the ectoderm...

. The major difference is that ectomesenchyme is usually considered to arise from neural crest cells, which are a critical group of cells that form in the cranial region during early vertebrate development. Thus, ectomesenchyme plays a critical role in the formation of the hard and soft tissues of the head and neck such as bones, muscles, teeth, and, most important, the branchial arches.