Mesenchyme is an embryonic connective tissue which gives rise to cells of all type of adult connective tissue. lathe early embryo, besides the three embryonic layers i.e. ectoderm, endoderm and mesoderm, there are loose cell floating in a fluid between the ectoderm and endoderm. These cells constitute the mesochyme. They are derived from mesoderm. Each mesenchymal cell has a big nucleaus, scanty cytoplasm and a few cytoplasmic thread like processes that radiates from the cell and give it a star-shaped appearance. The cytoplasmic processes establish contact with those of neighboring cells and form a network.
The spaces of the network are filled with a jelly like intracellular substance. Mesenchymal cells have the capacity to form various types of cells and fibers of adult connective tissue. As the development of embryo progresses the mesenchymal cells gets complete converted into several different kinds of cells which in turn give rise to various tissues. As development of embryo advances, some mesenchymal cells remain dormant in the periosterm, these dormant cells change to chondroblast and osteoblast to form cartilage or bone respectively as the occasion arises. Mesenchyme therefore, is an embryonic connective tissue whose cells have the capacity to form the various cells and fibers of adult tissues.