Types of connective tissue proper

There are 2 classes of connective tissue proper:

· loose connective tissue;

· dense connective tissue.

Loose Connective Tissue also called areolar tissue, is the more abundant. It fills spaces between fibers and muscle sheaths, supports epithelial tissue, and forms a layer, surrounding the lymphatic and blood vessels. Loose connective tissue is also found in the papillary layer of the dermis, in glands and the mucous membranes supporting the epithelial cells.

Characteristic of loose connective tissue:

• A major constituent of loose connective tissue is the amorphous ground substance (1).

• The most numerous cells are fibroblasts and macrophages, but a variety of all the other cell types (2) of connective tissue are present also.

• Collagen, elastic, and reticular fibers appear in this tissue, though the proportion of fibers is relatively small (3).

Fig.12. Loose connective tissue

Dense Connective Tissue. This type of tissue consists of the same components found in loose connective tissue, but there is a clear predominance of collagen fibers and fewer cells. Dense connective tissue is less flexible and far more resistant to stress than is loose connective tissue.

In Dense Irregular Connective Tissue collagen fibers are arranged in bundles without a definite orientation. They form a 3-dimensional network in this tissue and provide resistance to stress from all directions. This tissue is characteristic of the dermis and capsules of many organs.

In Dense Regular Collagenous Connective Tissue the collagen bundles are arranged according to a definite pattern.

Tendons a re the most common example of dense regular connective tissue. They have parallel, closely packed bundles of collagen separated by a small quantity of amorphous intercellular substance. Their fibrocytes contain elongated nuclei parallel to the fibers and sparse cytoplasmic folds that envelop portions of the collagen bundles. The collagen bundles of the tendons (primary bundles) aggregate into larger bundles (secondary bundles) that are enveloped by loose connective tissue containing blood vessels and nerves (endotendineum). Externally, the tendon is surrounded by a sheath of dense connective tissue.

Fig.13. Tendon

Dense Regular Elastic Tissue is composed of bundles of thick, parallel elastic fibers. The space between these fibers is occupied by thin collagen fibers and flattened fibroblasts. The abundance of elastic fibers in this tissue confers on it a typical yellow color and great elasticity. Elastic tissue, which occurs infrequently, is present in the yellow ligaments of the vertebral column and in suspensory ligament of the penis.

Дата добавления: 2015-10-31