Connective and supporting tissue

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The connective and supporting tissue is one of the four basic tissue types of the animal body (in addition to muscle tissue , nerve tissue and epithelium ). This group includes a number of types of fabric that differ greatly in form and function, but have crucial similarities in terms of development and structural design. Examples are loose and tight collagenous connective tissue, cartilage, bones or adipose tissue.

properties

The connective and supporting tissue is characterized primarily by two properties: The fixed (stationary) cells, called fibrocytes , are not close together in the cell structure , but often have a large space between them. This interstitial space is in turn filled with extracellular matrix (ECM, ECM, also intercellular substance ), which varies greatly depending on the type of connective tissue: from the fibers of the loose connective tissue to the mineralized matrix of the bone. The extracellular matrix largely determines the properties of the connective tissue type.

In addition to the fibrocytes, there are also numerous free (mobile) cells in the connective tissue, called histiocytes , which perform various tasks and are largely assigned to the immune system .

Classification

Differences between the individual types of tissue are u. a. due to the type and quantity of the components present in the intercellular substance. First, the division into the two groups of connective tissue in the narrower sense and into the supporting tissue . The connective tissue is then mainly determined by the type of predominant fibers, while the supporting tissue is divided into cartilage and bone.

construction

Cells

All types of connective and supporting tissue arise from the mesenchyme , the embryonic connective tissue. Mesenchymal cells are accordingly pluripotent and can differentiate into the later connective tissue-specific cells.

In the nomenclature it is common to identify active, matrix-secreting or building cells with the ending -blast and resting or inactivated cells with -cytes: osteoblasts and osteocytes of the bone, chondroblasts and chondrocytes of the cartilage, fibroblasts and fibrocytes in the case of collagen connective tissue ( the latter cannot always be consistently differentiated and are often used synonymously).

Extracellular matrix

In general, the EZM consists of two main components:

Cells + formed part (fibers) + armorphic basic substance (chemical composition see above) = intercellular substance In addition, various connection and adhesive proteins are present.

All of these components are not limited to the connective and supporting tissue, but also occur in other tissue types. However, only here do they play such a crucial role for the properties of the tissue and only here do they take up such a proportion of volume and mass. For a more detailed discussion of the above examples, reference is made to the article on the extracellular matrix .

literature

  • H.-G. Liebich: Functional histology of domestic mammals . 4th edition. Schattauer, Stuttgart 2003, ISBN 3-7945-2311-3 .
  • U. Welsch: Sobotta textbook histology . Urban & Fischer, Munich 2002, ISBN 3-437-42420-3 .