fabric Cartilaginous

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The cartilage tissue is an original supporting tissue mesenchymal, consists of cells, fibers and ground substance. The cartilage matrix is ​​solid and elastic. It provides a support role. The important analogies with bone tissue are mainly due to the fact that they develop in a coordinated and joint fashion until’at puberty. During the primary ossification, the vast majority of the cartilage tissue is replaced by bone tissue.

Cartilage is of solid consistency and elastic. It is of mesenchymal origin. It consists of cells, fibers and ground substance. It basically provides a support role.

The cartilage tissue is avascular. On the surface of cartilage, connective tissue is observed, formed fibroblast, mesenchymal cells and collagen fibers, called perichondrium. This ensures the nutrition and growth of cartilage.

The cartilage tissue is most of the embryonic skeleton and fetal. In children and adolescents persists between the shaft and the epiphysis of long bones where it is the growth plate. In adult cartilage is rarer.

This is an avascular tissue.

1- HISTOLOGY OF FABRIC CARTILAGINOUS :

A- CELLS :

In adults, the cartilage tissue is comprised of chondrocytes and chondroclasts. The chondrocytes are of variable shape (egg-shaped, spherical or fusiform), their diameter varies between 10 and 40 one. Electron microscopic view each cell offers an irregular plasma membrane, a basophilic cytoplasm containing a granular endoplasmic reticulum, glycogen grains, lipid vacuoles, free ribosomes, Golgi developed a device perinuclear and mitochondrial. The nucleolus is the central core. Chondrocytes are cells sending short extensions in the surrounding matrix.

In vivo, chondrocytes are molded in chondroplastes which are cavities with non clean wall matrix. However, on histological sections, attachment techniques induce a retraction of the plasma membrane artificially creating a free space between the chondrocyte and chondroplaste. The chondrocytes are responsible for the synthesis

protein precursor fibers and the ground substance of cartilage. They also synthesize cytokines and growth factors.

We also include chondroclasts are multinucleated giant cells, riches in lysosomes, having l’enzymatic and molecular equipment necessary for the resorption of cartilage tissue and in particular metalloproteases (« matrix metalloproteases : MMP »). This is called the chondroclasie.

B- FUNDAMENTAL SUBSTANCE :

The ground substance is basophil, homogeneous and translucent. It is rich in water and mineral salts (K+'Na+, Mg+).

The basic substance consists of sulphate proteoglycans whose most important glycosaminoglycans are chondroitin sulfate, kératates the sulfated hyaluronic acid and. The latter is present, in much smaller amounts than in the case of connective tissue.

C- TRAINING FIBRILLAR :

They are represented mainly by collagen fibers and elastic fibers. The collagen fibers are type I, II I IX, they are visible after enzymatic digestion of the ground substance and by observation under phase contrast microscopy.

Electron microscope collagen fibers have a periodicity of 610 at 640 A ° and a diameter of variable 200 at 600 A°.

The collagen fibers are organized in baskets, around one or more chondrocytes as chondroma. On both of these other Chondromas are intercalated inter-regional fiber.

2- CLASSIFICATION CARTILAGINOUS FABRIC :

A- CARTILAGE HYALIN :

This is the most common cartilage tissue. It is the model, bone parts, in the embryo and fetus. In adults, it takes the articular surfaces and is the larynx supporting tissue, tracheal, the nostrils, the external auditory canal and intercostal cartilages.

The elastic fibers are absent and the collagen fibers constitute a dense felting. The latter are formed of type II tropocollagen molecules organized into microfibrils not visible by light microscopy, to’standard coloring help. This feature confers an amorphous appearance to the matrix, aspect which is reinforced by the’absence of vessels and nerves.

As’set of cartilages, the basic hyaline substance, abundant in hyaline cartilage tissue, contains mainly’water. This large retention capacity of the’water is linked to the abundant presence of sulfated glycosaminoglycans, such as chondroitin sulfate and keratan sulfate, that are high in acid hydrophilic radical. These glycosaminoglycans form sulfated proteoglycans, the main one being l’aggrecan. The molecules of’aggrécan s’assemble themselves to molecules of’hyaluronic acids to form a high capacity mesh’water absorption. The abundant presence of’water and

hydrophilic proteins in the cartilage tissue is responsible for the deformability and resistance. So, when’strong pressure is exerted on articular cartilage for example, part of the’water is expelled but the’increased osmotic pressure induces an influx of’water which restores water concentration and high hydrostatic pressure. Besides the retention of’water, the role of proteoglycans of the cartilage matrix is ​​to allow the distribution and / or the attachment of many molecules (growth factors, cytokines, metabolites…) necessary to the function of chondrocytes. These molecules are most often the blood flowing through the perichondrium cartilage tissue. However, in the case of articular cartilage, all of which are free of perichondrium, the cartilage tissue is fed by molecules diffusing from the synovial fluid.

B- FIBRO-CARTILAGE :

The fibrous cartilage is a tissue intermediate between the oriented dense connective tissue and hyaline cartilage. It differs from hyaline cartilage by the presence of abundant collagen fibers, thick, de type I. These fibers form bundles oriented detectable by light microscopy after staining with Masson's trichrome. Therefore the matrix of cartilage tissue that can not be considered amorphous.

The fibrocartilage is present at the mechanical stress areas such as joint menisci, intervertebral discs, the pubic symphysis, the tendon of’Achille.

C- ELASTIC CARTILAGE :

Elastic cartilage is characterized by l’abundance of elastic fibers (fibers that l’can be detected by staining with’orcéine). These fibers are intertwined and form a dense three-dimensional network, in which meshes are housed many chondrocytes. It is located primarily in the pinna, epiglottis, the external auditory canal and some laryngeal cartilages.

D- FABRIC CARTILAGINOUS IMMATURE :

It is observed at the growth plates. In the fetus, long bones are made exclusively of cartilage tissue immature hyaline. The matrix of this tissue is different from the matrix of the adult mature hyaline cartilage. In particular, the significant presence is observed of collagen type IX.

3- perichondrium :

The perichondrium is a connective tissue sheath which surrounds the cartilage, except at the articular surfaces. It is formed from two layers :

  • A fibrous outer layer said feeder layer or tendiniforme, which contains many thick collagen fibers, elastic fibers, fibroblasts and an important vascularization. This is a dense connective tissue.
  • A so-called cellular outer layer chondrogenic layer formed by thin collagen fibers arcuate path penetrating in the ground substance of cartilage tissue. This layer is considered a loose connective tissue. It also observed that mesenchymal cells are the source of chondrocytes.

4- GROWTH CARTILAGE :

Cartilage growth takes place in a dual modality :

Einer say appositionnelle (or perichondrial) is effected by differentiation of mesenchymal cells, localized in the innermost layer of perichondrium, perichondrium chondrogenic, en chondrocytes. The appositional growth is an increase in thickness is carried out by affixing layers of cartilage substance to the surface of the workpiece cartilaginous. The appositional growth is mainly observed during fetal development.

interstitial called the growth is carried out by successive mitotic chondrocytes themselves. In that case, les filles cellules of a Hare clone cellulaire s'éloignent the mother cells in if disposant soit de manière Rectiligne soit de manière circulaire. They form what is called axial or coronary isogenic groups. These different provisions allow the axial or circumferential growth of cartilage. One can in this process observe the presence of several chondrocytes within the same chondroplaste. Interstitial growth is observed in the fetus but also during the postnatal bone growth in long bones. Indeed up to’at puberty, metaphyseal long bone contains a growth plate cartilage called conjugation and involved in bone growth.

5- NUTRITION CARTILAGE :

The cartilage nutrition is either from blood capillaries in the outer layer of the perichondrium, either through synovial fluid for articular cartilage

6- REGENERATION DU Cartilage :

Cartilage has a low power of regeneration which is very low in aging.

During the DR CHEBAB.B – Faculty’Alger