Mesenchyme is a type of animal tissue comprised of loose cells embedded in a mesh of proteins and fluid, called the extracellular matrix. The loose, fluid nature of mesenchyme allows its cells to migrate easily and play a crucial role in the origin and development of morphological structures during the embryonic and fetal stages of animal life. Mesenchyme directly gives rise to most of the body’s connective tissues, from bones and cartilage to the lymphatic and circulatory systems. Furthermore, the interactions between mesenchymeand another tissue type, epithelium, help to form nearly every organ in the body.
Although most mesenchyme derives from the middle embryological germ layer, the mesoderm, the outer germ layer known as the ectodermalso produces a small amount of mesenchyme from a specialized structure called the neural crest. Mesenchyme is generally a transitive tissue; while crucial to morphogenesis during development, little can be found in adult organisms. The exception is mesenchymal stem cells, which are found in small quantities in bone marrow, fat, muscles, and the dental pulp of baby teeth.
MacCord, K. (2012). Mesenchyme. The Embryo Project Encyclopedia. Retrieved from https://embryo.asu.edu/pages/mesenchyme