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. In fact, most embryologists use the term mesenchyme only for those cells that develop from the mesoderm. The term mesenchyme essentially refers to the morphology of embryonic cells. Mesenchymal cells can migrate easily, unlike epithelial cells, which do not show great mobility and which are polygonal in shape, polarized in an apical-basal orientation, and organized into closely adherent sheets. Mesenchyme is characterized morphologically by a prominent ground substance matrix containing a loose aggregate of reticular fibrils and unspecialized cells. The cells are capable of developing into connective tissue, such as bone, and cartilage, the lymphatic system, and the circulatory system.