Place the cursor over, or click on the images. The ECM will be highlighted in blue, and the cells in red.
Both the cells and the extracellular matrix are essential for the functions of connective tissue. They also contribute to the structure and functions of the tissues and organs in which connective tissue is present, and ultimately to the functioning of the body as a whole.
Connective tissue develops from the mesenchyme, a primitive form of connective tissue that can give rise to several types and subtypes of connective tissue, particularly during embryonic and fetal development.
Most mesenchymal cells are derived from the mesoderm, the middle germ layer of the embryo. In humans, the formation of mesenchyme begins during the first month of intrauterine development. Some mesenchymal cells in the head region, however, are derived from neural crest cells rather than from mesoderm.
Some mesenchymal cells persist throughout life. They can function as stem or progenitor cells and contribute to the formation or replacement of connective tissue cells.
In addition to providing structural support, connective tissue is present in most tissues and organs providing pathways through which blood vessels, lymphatic vessels, and nerves enter and reach the structures they supply.
Connective tissue contains several types of cells embedded in a complex extracellular matrix, which is composed of many different molecules. The different types and subtypes of connective tissue are distinguished by the types of cells they contain and by the composition and organization of their extracellular matrix.
These different combinations of cells and extracellular matrix give each type of connective tissue its characteristic structure and functions.
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Hyaline cartilage. Staining: hematoxylin and eosin. Medium magnification.
Dense non-modeled connective tissue. Staining: hematoxylin and eosin. Medium magnification. .