Author: Gordana Sendi MDLast reviewed: July 07, 2022Reading time: 1 minute Mesenchymal cells are small spindle-shaped cells with large nuclei, prominent nucleoli and fine chromatin.These are multipotent stem cells that differentiate as progenitor cells for all types of connective tissue, such as fibroblasts, osteoblasts, chondroblasts and preadipocytes. Mesenchymal cells produce an extracellular matrix (ECM) that consists mainly of a simple ground substance rich in hyaluronic acid.The mesenchymal cells, together with their ECM, compose the mesenchyme, a type of embryonic connective tissue that gives rise to all other connective tissues of the body during early development. In adults, mesenchymal cells are present in small quantities as part of loose connective tissue mainly in the umbilical cord, bone marrow and adipose tissue. Adult mesenchymal stem cells serve to give rise to fibroblasts and new blood vessels. Learn more about the loose connective tissue with the study unit below: Mescher, A