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connective tissue

Sunday 7 March 2004

connective tissues

WKP

Definition: Connective tissue (CT) is one of the four basic types of animal tissue, along with epithelial tissue - epithelia , muscle tissue - muscles , and nervous tissue.

Connective tissue develops from the mesoderm.

Connective tissue is found in between other tissues everywhere in the body, including the nervous system. In the central nervous system, the three outer membranes (the meninges) that envelope the brain and spinal cord are composed of connective tissue.

All connective tissue consists of three main components:
- fibers (elastic fibers and collagenous fibers),
- extracellular matrix
- cells.

Types

Connective tissue can be broadly subdivided into connective tissue proper, and special connective tissue.

Connective tissue proper consists of loose connective tissue and dense connective tissue (which is further subdivided into dense regular and dense irregular connective tissues.)

Loose and dense connective tissue are distinguished by the ratio of ground substance to fibrous tissue.

Loose connective tissue has much more ground substance and a relative lack of fibrous tissue, while the reverse is true of dense connective tissue.

Dense regular connective tissue, found in structures such as tendons and ligaments, is characterized by collagen fibers arranged in an orderly parallel fashion, giving it tensile strength in one direction. Dense irregular connective tissue provides strength in multiple directions by its dense bundles of fibers arranged in all directions.

Special connective tissue consists of reticular connective tissue , adipose tissue , cartilage , bone , and blood.

Other kinds of connective tissues include fibrous tissues , elastic tissues, and lymphoid connective tissues.

New vascularised connective tissue that forms in the process of wound healing is termed granulation tissue.

Fibroblasts are the cells responsible for the production of some CT.

Extracellular matrix

Components of the extracellular matrix in connective tissue are:

- Polysccharide chains of the class called glycosaminoglycans (GAG) which are usually found covalently linked to proteins in the form of proteoglycans.
- Fibrous proteins of two functional types which have structural and adhesive types.

  • Collagen and elastin (structural)
  • fibronectin and laminin (adhesive)

Glycoaminoglycan and proteoglycan molecules in connective tissue form a highly dydrated, gel-like ground substance in which the fibrous proteins are enbedded. The polysaccharide gel resists compressive forces on the matrix and the collagen biber provide tensile strength. The aqueous phase of the polysaccharide gel permist the rapid diffusion of nutrients, metabolites and hormornes between the blood and the tissue cells.

Subtypes

- fibrous tissue
- adipose tissue (fat)

Pathology

- connective tissue disorders

See also

- tissues