The microvilli are about 1 micron high and 0.08 micron wide and are covered by the plasma membrane. In the trachea, the epithelial lining is composed of ciliated cells. Connective These tissues are responsible for cushioning, supporting and maintining form within the body and include adipose, cartilage, bone, tendons and ligaments. The major constituent of connective tissue is the ground substance or extracellular matirix which is composed of protein fibers, ground substance and tissue fluid. The cells make and are embedded in the matrix.
Most connective tissue is derived from the mesoderm.
Structural glycoproteins and glycosaminoglycans make up the transparent and colorless ground substance of connective tissue. Glycosaminoglycans are long polysaccharide chains composed of uronic acid and hexosamines like glucosamine or galactosamine. The polysaccharide chains are usually bound to a protein core forming a proteoglycan. These molecules interact with collagen, are very hydrophillic and can bind a huge number of cations due to a great degree of sulfation. Examples include heparin sulfate, chondroitin sulfate, hyaluronic acid and keratin sulfate.