CONNECTIVE OR SUPPORTIVE TISSUE

Origin and Characteristics

Connective tissue (or supportive tissue) is the most abun­dant tissue in the body. As its name suggests, it connects and binds or supports the various tissues. The capsules that surround organs of the body are composed of con­nective tissue. Bone, adipose tissue, and cartilage are spe­cialized types of connective tissue that function to support the soft tissues of the body and store fat. Connective tis­sue is unique in that its cells produce the extracellular ma­trix that supports and holds tissues together. Connective tissue has a role in tissue nutrition. The proximity of the extracellular matrix to blood vessels allows it to function as an exchange medium through which nutrients and metabolic wastes pass.

Most connective tissue is derived from the embryonic mesoderm, but some is derived from the neural crest, a de­rivative of the ectoderm. During embryonic development, mesodermal cells migrate from their site of origin and then surround and penetrate the developing organ. These cells are called mesenchymal cells, and the tissue they form is called mesenchyme. Tissues derived from embryonic mes­enchymal cells include bone, cartilage, and adipose (fat) cells. Besides providing the source or origin of most con­nective tissues, mesenchyme develops into other struc­tures, such as blood cells and blood vessels. Connective tissue cells include fibroblasts, chondroblasts, osteoblasts, hematopoietic stem cells, blood cells, macrophages, mast cells, and adipocytes. The matrix of the umbilical cord is composed of a second type of embryonic mesoderm called mucous connective tissue or Wharton's jelly