From Big Medical Encyclopedia

CARTILAGINOUS TISSUE [textus cartilagineus (LNH)] — a kind of connecting fabric, performs basic function.

X. t. is a part of a skeleton (see) in the form of cartilaginous coverings of joint surfaces of bones (a joint cartilage), a cartilage of intervertebral disks, costal cartilages, and also creates extra skeletal basic structures (cartilages of a throat, a trachea, bronchial tubes, a cartilaginous part of an Eustachian tube, cartilaginous plates of an auricle, nose, etc.).

In an embryogenesis of X. t. it is formed of a mesenchyma (see). Predecessors of chondrocytes are the small differentiated prokhondrobla-sta and chondroblasts. They make the ground mass of a bookmark X. t. in the course of a histogenesis, and further are present at a nadkhryashchnitsa. At early stages of pre-natal development almost all skeleton of the highest vertebrata and the person is cartilaginous. During this period of X. t. makes up to 45% of the weight (weight) of a body. In the course of antenatal and early post-natal development of X. t. it is generally replaced with a bone tissue (see the Bone) therefore at the adult a lot of all cartilaginous educations does not exceed 2% of body weight.

All cartilaginous educations except for a joint cartilage are covered by the nadkhryashchnitsa consisting of the dense fibrous connecting fabric rich with vessels. Nadkhryashchnitsa provides growth and food of a cartilage. Besides, food of a joint cartilage is carried out with active participation of the synovial fluid (see) which is in a joint cavity.

X. t. consists of chondrocytes (cartilaginous cells) and a cartilaginous matrix. Chondrocytes represent large cells of oval or rounded shape with small shoots. Depending on degree of a maturity distinguish chondrocytes of several types. A chondrocyte of the I type — the young active cell with high rates of synthesis of DNA having ability to a mitosis (see). Mature chondrocytes II and III types contain well developed cytoplasmic reticulum and Golgi's complex in cytoplasm, actively produce and cosecrete collagen, glycoproteins, proteoglycans. The ami-totichesky type of division is characteristic of them (see Amitotic division).

At a mature cartilage there are also bubbly strongly vacuolated collapsing cells which ended the life cycle. Chondrocytes are in cavities (lacunas) of a matrix separately or the groups formed as a result of division of one cell (isogenic groups). Walls of a lacuna represent a dense fibrous collagenic framework (a so-called pericellular basket), to-ry protects cells from mechanical influences. In a lacuna chondrocytes are surrounded with the tonkofibrillyarny main substance rich with water.

In a cartilaginous matrix distinguish fibers and the main substance. Fibrous components of a cartilaginous matrix are collagen II of type, elastin, proteins of not collagenic nature, glycoproteins, proteoglycans. Macromolecules of collagen form fibrous structures at interaction with glycoproteins and proteoglycans.

The main substance consists of proteoglycans and glycoproteins and is not amorphous. Strict orientation, orderliness in an arrangement of macromolecules and their units is revealed; vectors of orientation are both the direction of fiber of collagen, and an arrangement of chondrocytes.

Accurate orderliness in a relative positioning of cells and a matrix is inherent to cartilaginous tissue. In it it is accepted to distinguish territorial and interterritorial sites. Territorial sites are formed by isogenic groups of the cells surrounded with the main substance and narrow by a fibrous framework tsirkulyarno of the located collagenic fibers. Interterritorial sites are presented by yarns with layers of the main substance, the power lines of distribution of loading oriented according to a vector.

Depending on dominance of these or those fibrous components and extent of masking by their homogeneous main substance it is accepted to distinguish hyaline, fibrous and elastic cartilages. Most often in an organism the hyaline cartilage meets. Joint and costal cartilages, and also cartilages of a nose, a throat (thyroid and cricoid), an epiphyseal cartilage of long tubular bones, cartilages of a trachea and bronchial tubes are hyaline. The native hyaline cartilage — dense, elastic, pearl-white (vitreous) that is connected with considerable contents in it the homogeneous main substance rich with proteoglycans, during removal to-rykh comes to light a fibrous collagenic framework.

Existence of the expressed bunches of collagenic fibers, and also heterogeneity of cells (along with chondrocytes at it there are also fibroblasts) is characteristic of a fibrous cartilage. Intervertebral disks, continuous connections (synchondroses), and also sites of sinews and sheaves in the place of their attachment are constructed of a fibrous cartilage.

The elastic cartilage is found in an auricle, an epiglottis, corniculatus and arytenoid cartilages of a throat. It differs in high content in a matrix of elastic fibers and is not exposed to calcification.

Peculiar kind of X. t. the chondroid fabric of a stroma of heart remaining in certain sites of fibrous rings at adults is.

Regeneration of X. t. it is carried out at the expense of the low-differentiated cells of a nadkhryashchnitsa, and also, apparently, thanks to ability of chondrocytes under certain conditions to mitotic division.

Biochemistry cartilaginous is woven and. Chemical composition of X. t. in connection with poverty almost completely is defined cells by structure of its matrix, or intercellular substance (see). Cartilaginous tissue is rich with water (more than 70%); the solid residue makes apprx. 30%, it contains about 50% of collagen (see), and specific to X. t. collagen II of type is, molecules to-rogo consist from three identical polypeptide and - chains. Besides, in X. t. several peculiar contains, so-called minor, kollagen. In a normal hyaline cartilage collagen II of type makes the ground mass of collagen, along with collagen II ti ~ the pas is present at elastic and fibrous cartilages also

collagen 144 HUNDADZE I of type. In joint cartilages concentration of collagen is highest in a surface layer.

Other component X. t. glikozaminoglikana are (see Mucopolysaccharides), the summary contents to-rykh in the embryonal period reaches 25% of a solid residue, then gradually decreases and at advanced age makes 14%. The sulphated glikozaminoglikana — hondroitinsulfata (see. Chondroitinsulphuric acids) and ke-ratansulfat — are attached to so-called rod protein and form macromolecules of proteoglycans (proteinpolisakharid, hondro-mucoproteins) of Ltd company weighing 1 Ltd company — 3 OOO OOO. Feature of X. t. the fact that proteoglycans connect to the help of hyaluronic acid (see is. Hyaluronic acids) in units weighing up to 50 Ltd companies of Ltd company — 100 OOO OOO. Units of proteoglycans hold in the connected state the main part contained in X. t. water and solutions of electrolytes, thanks to osmotic effect promote maintenance of a collagenic framework in the straightened state and provide diffusion of substances in cartilaginous tissue, free of blood vessels.

Proteins of not collagenic nature make 10 — 20% of a solid residue, including the proteins connected with glycose-minoglikanami of 7 — 13%, structural glycoproteins (see) and lipoproteids (see) 3 — 7%, lipids (see)

and deoxyribonucleic acid (see) 1,3 — 1,8%. Cells and matrix of X. t. contain also a glycogen (see), and cartilaginous tissue of epiphyseal departments of bones — phosphorus-calcium salts.

A metabolism in X. t. due to the lack of vascularization it is carried out by chondrocytes (thanks to physical properties and a specific structure of a matrix) and provided with energy due to the glycolysis (see) proceeding preferential on anaerobic type. The metabolism is very intensive in a growth period, especially in epiphyseal cartilages, but then is sharply slowed down, and mature X. t. it is characterized by the expressed metabolic inertness. X. t. has ability to reversible deformation in the conditions of considerable mechanical loadings, and also a weak immune responsiveness in connection with ability of the hydrated matrix to detain and isolate antigens.

In the course of aging of an organism in X. t. concentration of proteoglycans and consequently, and ste-laziness of a gidratirovannost of a matrix decreases.

In chondrocytes the glycogen and lipids collect, the sizes of a complex of Golgi (see Golgi a complex) and a cytoplasmic reticulum decrease (see. An endoplasmic reticulum), and also number of mitochondrions (see). Cells vakuoliziruyut-sya also perish, and lacunas are filled with the main substance. In a matrix salts of calcium are laid and water content decreases that leads to loss by a cartilage of elastodinamichesky properties.

In patol. conditions a metabolism in X. t. it is broken: activity of proteolytic enzymes increases, catabolic and biosynthetic processes are intensified, there is a disturbance of structure and aggregation of proteoglycans, X appear unusual. t. kollagena, are noted adjournment of pigments and surplus of lipids.

Pathology H.T. includes malformations (see the Chondrogenesis imperfect, Hondas a sort an isplaziya);

damages (see. Knee joint, M of an ikrotravm, Backbone, Radiculitis, Joints); diseases (see Arthritises, Arthroses, the Arthropathy, Bekhtereva a disease, Keniga a disease, the Osteoarthritis, the Osteochondritis, the Perichondritis, Rickets, the Chondritis)', tumors (see Hondroblastom, the Chondroma, Chondromyxoid fibroma, the Chondrosarcoma).

Bibliography: Zhadenov. And. also

V. B tel Grazed. Exchange processes in a joint cartilage normal (age aspect) and at pathology (osteoarthrosis), Ortop. and travmat., No. 3, page 65, 1982, bibliogr.; The multivolume guide to orthopedics and traumatology, under the editorship of N. P. Novachenko, t. 1, page 427, 606, M., 1967; The Multivolume guide to pathological anatomy, under the editorship of A. I. Strukov, t. 5, page 234, 433, M., 1959; Pavlova V. N. Synovial environment of joints, page 155, M., 1980; R e y-N e r S. A. Radiodiagnosis of diseases of bones and joints, book 1, M., 1964; Slutsky JI. I. Biokhimiya normal and patholologically the changed connecting fabric, L., 1969; T and e r I. L. Radiodiagnosis of diseases of a backbone, page 101, M., 1983; F r and N to e To. Sports traumatology, the lane with it., page 74, M., 1981; Ham A. and Kormakd. Histology, the lane with English, t. 3, M., 1983; KneseK. - H. Stiitzgewebe und Skelett-system, V. u. and., 1979;

Thompson R. Page of a. R o b i n s o n H. J. Articular cartilage matrix metabolism, J. Bone Jt. Surg. v. 63-A, p. 327, 1981.

Century of H. Pavlova (An., gist., embr.), L. I. Slutsky (biochemical).