Dense connective tissues.

Comparing to LICT the dense connective tissues have more fibers that cells. The cells are mainly fibrocytes. The fibers may be organized and disordered. That is why two following variants of the dense connective tissues exist: regular and irregular. The regular connective tissue is located in tendons, ligaments fascia, aponevrosis. Sometimes, elastic and collagen regular connective tissues are concerned. In the collagen connective tissue the main fibers are collagen fibers. The elastic tissue has more elastic fibers. The elastic dense regular tissue is found in vocal folds, yellow ligaments of vertebrae. The irregular dense connective tissue is in the reticular layer of skin dermis.

As it was said above, the following structures are made of dense regular connective tissue as tendons, ligaments, fascia, aponevrosis.

Let describe the structure of tendon. It is made of thick, parallel collagen fibres. Such fibres are separated one from another by single layer of fibrocytes and they are called bundles of first grade. Fibrocytes have many processes. They are lack of protein synthesis organelles. However, they are capable to produce intercellular ground substance. This ability depends on functional load on the tendon. All fibrocytes are connected with eachother by processes making entire three dimentional network. The cells junctions are communicating junctions (nexuses). Perhaps, the cells are united not only mechanically, but electrically and chemically as well. In it’s turn, the cell membrane of the processes is connected with ground substance with help of the cell adhesion molecules. That is why even slight change of mechanical load on tendon leads to changing of synthetic activity of fibrocytes.

Bundles of first grade stay together surrounded by LICT. All together they are called bundles of second grade. Surronding LICT is called endotenonium. It has trophic function because of having vessels. It plays the role in regeneration because it contains stem cells (dense regular connective tissue has no stem cells, because fibrocytes are irreversibly differentiated cells).

Several bundles of second grade unite to the bundles of third grade. They are surrounded by thicker layer of LICT called perytenonium. It has functions similar to endotenonium. Some tendons are bundles of third grade. Although, there are tendons, which are the bundles of fourth or even fifth grade. Functions of dense regular connective tissue are support, transmitting mechanical load from muscle to bone, joints strengthening and etc.

Dense irregular connective tissue is located in reticular layer of the skin dermis and it makes capsules of many organs. It has cells and ground substance. The cells are mainly fibrocytes, but some fibroblasts also present. Some mast cells, plasma cells, macrophages may be found. Intercellular ground substance consists of fibers directed irregularly and amorphous substance. There is LICT around vessels in DICT.

Function of dense irregular connective tissue is mechanical support. Regeneration ability of dense connective tissues is low. They have no cambial cells. The cells which are able to division are located in inserted LICT layers. They have insignificant volume in compare with dense tissue volume.

Дата добавления: 2015-08-05