The connective tissues bind, protect and support the body. All connective tissues have three characteristics in common:
1. Cells such as fibrocytes, chondrocytes and osteocytes.
2. Three principal types of fiber found in connective tissues.
A. Collagen - abundant in tendons and bones.
B. Elastic fiber - found in the walls of arteries and in
flexible cartilage like the epiglottis.
C. Reticular fiber is the support material of soft organs
like the spleen and liver.
3. Ground substance, a complex mixture of organic and
inorganic materials, fills the spaces between the cells and
fibers.
Mesenchyme
Mesenchyme is the first connective tissue to appear in the embryo. All other connective tissues arise from mesenchyme by a process known as differentiation. The image to the right shows a very early fetal stage. The asterisk labels a region filled with mesenchyme.