Connective Tissue Definition and Function

Connective Tissue

Connective tissues occur in all parts of the body. They bind structures together, provide support and protection, serve as frameworks, fill spaces, store fat, produce blood cells, provide protection against infections, and help to repair tissue damage. Connective tissue cells are usually further apart than epithelial cells, and they have an abundance of intercellular material or matrix between them. This matrix consists of fibers and a ground substance whose consistency varies from fluid to semisolid or solid.

Connective tissue cells are able to reproduce. In most cases, they have good blood supplies and are well nourished. Although some connective tissues, such as bone and cartilage, are quite rigid, loose connective tissue, adipose connective tissue, and fibrous connective tissue are more flexible.

Major Cell Types

Connective tissues contain a variety of cell types. Some of them arc called resident cells because they are usually present in relatively stable numbers. These include fibroblasts, macrophages, and mast cells. Another group known as wandering cells temporarily appear in the tissues, usually in response to an injury or infection. The wandering cells include several types of white blood cells.
 

The fibroblast is the most common kind of cell in connective tissue. It is relatively large and usually star-shaped Fibroblasts function to produce white and yellow fibers of protein in the inter cellular materials of connective tissues. The white fibers are composed of the protein collagen, which is the major structural protein of the body. 

(It is also the main ingredient of leather and gelatin). 

Ciollagcnous fibers occur in bundles and are flexible, but only slightly elastic. More importantly. they have great tensile strength—that is, they arc strong in resisting pulling forces.

Macrophages (histiocnes) are almost as numerous as fibroblasts in some connective tissues. They are usually attached to fibers, but can become detached and actively move about They are specialized to carry on phagocuosis. Since they function as scavenger cells that can clear foreign particles from tissues, macrophages represent an important defense against infectious agents. They also play a role in immunity.

Mast cells are relatively large cells that are widely distributed in connective tissues, and are usually located near blood vessels. Their function is not well understood, however. they are known to contain heparin, a composited that prevents blood clotting They also contain histamine, a substance that promotes some of the reactions associated with inflammation and allergies such as asthma and hay-fever.