cartilage tissue.

Cartilage tissue plays a supporting role. It does not work in tension, like a dense connective tissue, but due to internal tension, it resists compression well. This tissue forms the basis of the larynx and bronchi, serves to immobile the bones, forming synchondrosis. Covering the articular surfaces of the bones, softens the movement in the joints. Cartilage tissue is quite dense and at the same time quite elastic. Its intermediate substance is rich in dense amorphous substance. Cartilage develops from mesenchyme. At the site of the future cartilage, mesenchymal cells multiply intensively, their processes shorten, and the cells are in close contact with each other. Then an intermediate substance appears, due to which mononuclear sections are clearly visible in the rudiment, which are the primary cartilage cells - chondroblasts. They multiply and give more and more masses of the intermediate substance.

The amount of the latter begins to prevail over the mass of cells. Breeding rate cartilage cells by this time, it slows down, and due to the large amount of intermediate substance, they are far removed from each other. Soon, cells lose the ability to divide by mitosis, but still retain the ability to divide amitotically. However, now the daughter cells do not diverge far, as the intermediate substance surrounding them has condensed. Therefore, cartilage cells are located in the mass of the main substance in groups of 2-5 or more cells. All of them come from one initial cell. Such a group of cells is called isogenic (isos - equal, identical, genesis - occurrence). Cells of the isogenic group do not divide by mitosis, they give little intermediate substance of a slightly different chemical composition, which forms cartilaginous capsules around individual cells, and fields around the isogenic group. The cartilage capsule, as revealed by electron microscopy, is formed by thin fibrils concentrically located around the cell.

Thus, in the beginning, the development of cartilage is accompanied by the growth of the entire mass of cartilage from the inside. Later, the oldest part of the cartilage, where cells do not multiply and no intermediate substance is formed, ceases to increase in size, and cartilage cells even degenerate. However, the growth of cartilage as a whole does not stop. Around the obsolete cartilage, a layer of cells separates from the surrounding mesenchyme, which become chondroblasts.
They secrete around themselves the intermediate substance of the cartilage and are gradually walled up with it. Soon chondroblasts lose the ability to divide by mitosis, form less intermediate substance and become chondriacs. On the layer of cartilage formed in this way, due to the surrounding mesenchyme, more and more layers of it are superimposed. Consequently, cartilage grows not only from the inside, but also from the outside.

Mammals have: hyaline (vitreous), elastic and fibrous cartilage.

Young cells contain a large amount of RNA, a well-developed lamellar complex, and a cytoplasmic reticulum, which, apparently, is associated with their ability to form protein products that enter the intermediate substance of the cartilage. In mature chondroblasts there are protofibrils - thin threads. It is assumed that these are the beginnings of fibers that are finally formed into collagen (chondriac) fibers already outside the cell. Chondroblasts lying in the mass of cartilage are older. They are round, triangular or semi-oval. Each chondroblast is surrounded by a cartilaginous capsule, which is a compacted layer of intermediate substance. The cytoplasm of chondroblasts contains a lot of water and often contains inclusions of fat and glycogen. As cells mature, the amount of glycogen increases, especially in chondrocytes. Chondroblasts divide by amitosis and are arranged either singly or in isogenic groups.

Chondrocytes are the final link in the transformation of chondroblasts. These cells are not capable of further differentiation. They do not divide and almost do not form an intermediate substance. They are located in special cavities. The shape of the cells is the most diverse (round, elongated, oval, angular, disc-shaped), and it depends on the state of the intermediate substance. Electron microscopic studies have shown that the surface of the cells is not smooth, it has a jagged contour due to the formation of microvilli. Chondrocytes in most cases are single-nuclear, rarely with two nuclei. The nucleus is poor in chromatin, while the cytoplasm is rich in water.

Intermediate hyaline cartilage consists of an amorphous substance and fibers. home component amorphous substance - chondromucoid. This is a combination of proteins with chondroitin sulfuric acid. In older areas, the intermediate substance also contains free chondroitinsulfuric acid, due to which the intermediate substance begins to stain with basic dyes, that is, it becomes basophilic, while in young areas of the cartilage closest to the perichondrium and in cartilage capsules, it is oxyphilic. The second component of the intermediate substance, chondrin fibers, is close to collagen fibers and, when boiled, also gives glue. The fibers give cartilage its strength. The thickness of the fibers (fibrils) in different animals and different age groups is not the same. Their smallest diameter is 60 A, and the largest is 550. Since the refractive indices of the fibers and the amorphous substance are close, the fibers can be detected only after a special treatment of the cartilage. In the outer layers of the cartilage, the fibers lie parallel to the surface, and in the deep ones -
more or less perpendicular to it. In old parts of the cartilage, as well as where the cartilage experiences a significant mechanical load, the structure of the intermediate substance of the hyaline cartilage becomes somewhat more complicated. In the oldest parts of the cartilage, complete cell atrophy occurs, and the ground substance becomes opaque and calcified.

Elastic cartilage (B) is yellowish in color and completely opaque. It is very elastic, with repeated bending, it returns to its original position. Elastic are the cartilages of the auricle, epiglottis and some cartilages of the larynx. In its structure, this cartilage is similar to hyaline, but unlike it, in the intermediate substance of the elastic cartilage, in addition to chondrin, there is a large number of elastic fibers. There are fewer isogenic groups in this cartilage.

fibrocartilage(B) forms intervertebral discs, pubic fusion; it is also present at the site of attachment of the tendon and ligaments to the bones. It differs from hyaline cartilage in the strong development of collagen fibers, which form bundles that lie almost parallel to each other, as in tendons. There is less amorphous substance in fibrous cartilage than in hyaline. Rounded light cells of fibrocartilage lie between the fibers in parallel rows. In places where fibrocartilage is located between hyaline cartilage and formed dense connective tissue, a gradual transition from one type of tissue to another is observed in its structure. Yes, closer to connective tissue collagen fibers in cartilage form coarse parallel bundles, and cartilage cells lie in rows between them, like fibrocytes of dense connective tissue. Closer to the hyaline cartilage, the bundles are divided into individual collagen fibers that form a delicate network, and the cells lose their correct location.

7. Bone tissue.

Function bone tissue, primarily associated with the implementation of mechanical tasks, and, on the one hand, bone tissue, due to its density, is a reliable support and protection for soft organs and tissues, and, on the other hand, due to its internal organization, it provides mitigation of shocks and tremors, then there is depreciation. In addition, bone tissue is actively involved in mineral metabolism. The dry matter of the bone tissue contains about 60% of minerals, the main of which are calcium, phosphorus, magnesium, etc., in the bone in a state of mobile equilibrium. They are vigorously washed out of the bone during pregnancy, in laying hens during oviposition, in dairy cows during lactation. In order for this process not to go beyond the limits of the norm, the livestock specialist must pay Special attention mineral nutrition. Bone minerals are involved in creating a normal concentration of minerals, especially calcium and phosphorus, in the blood, which creates a constancy of the internal environment of the body.

Finally, bone tissue is inextricably linked both in development and in the process of functioning with the bone marrow, in which either hematopoiesis takes place (red bone marrow) or fat is reserved (yellow bone marrow). The nature of this connection has not yet been elucidated.

Chemically bone tissue is composed of organic and inorganic matter. Main organic compounds are ossein and osseomucoid. Ossein is similar in chemical composition to collagen and also gives glue when boiled. Due to ossein, bone fibers are built. Osseomucoid glues the fibers together. In addition, there are elastin, mucoprotein and glycogen.
Inorganic substances are mainly in the form of apatite Ca 10 (P0 4) 6 CO 3 . Especially a lot in the bones of calcium (21-25%) and phosphorus (9-13%), less magnesium (1%), carbonic acid (5%) and other elements. The mineral substance of the bone on electron micrographs has the form of needle-shaped or lamellar particles, the length of which reaches 1500 A at a thickness of 15-75 A. The size of the crystals increases with age. The ratio of organic and inorganic compounds in the bones with the age of the animal changes towards an increase in the amount of inorganic substances. Therefore, the bones of old animals become brittle. If the diet of young animals is low in vitamin D or minerals, the animals
get rickets. With rickets, the deposition of salts in the intermediate substance of the bone is disturbed, and they begin to bend under the weight of their own body. The ratio of the organic and inorganic complex is also determined by the position of the bone in the skeleton. Thus, in the distally located bones of the extremities, the compact layer of bone is less mineralized than in the proximal ones.

Classification and structure. known coarse fibrous and lamellar bone tissue , which form the skeleton, as well as dentin, which forms the basis of the teeth. What is common to varieties of skeletal tissue is that, like all supporting-trophic tissues, they consist of cells and an intermediate substance, and the latter contains a large amount of mineral substances. Cellular forms of bone tissue - osteoblasts, osteocytes and osteoclasts.

osteoblasts- young bone cells develop from the mesenchyme. They are large, with an eccentrically located juicy core. Their shape is mostly cylindrical. Osteoblasts have short processes with which they come into contact with neighboring cells.

In their cytoplasm, the cytoplasmic reticulum, lamellar
complex and mitochondria. This indicates a high synthetic activity of osteoblasts. It is believed that they provide material for the intermediate substance of the bone. Electron microscopy confirmed this assumption. Osteoblasts contain a large amount of alkaline phosphatase, which is involved in the process of mineralization.

Osteocytes occur in pre-existing bone and develop from osteoblasts. They have a relatively small body and numerous long processes. The nucleus is small, dense; the cytoplasmic reticulum, lamellar complex and mitochondria are poorly developed. This is due to the fact that osteocytes are not able to produce an intermediate substance. Not observed in them
mitoses.

osteoclasts- large multinucleated cells, rather, representing a symplast (cytoplasm with numerous nuclei). Their sizes reach 80 and more microns. The shape of the cell is very diverse, which is associated with its active movement. On the cell body, on the side of the resorbed bone, there are numerous processes (outgrowths). The cytoplasm is poorly stained, slightly basophilic. The cytoplasm contains numerous vacuoles, which, according to some authors, are lysosomes that lyse the intercellular substance during bone remodeling.

Intermediate bone tissue, like other musculoskeletal tissues, consists of an amorphous substance and fibers. The main mass of the latter is ossein fibers, close to collagen. It is found in the bone and a small amount of elastic fibers.

coarse fibrous bone tissue forms the skeleton in lower vertebrates - fish and amphibians. In mammals, it exists only in the early stages of intrauterine life, and in an adult animal, it exists at the points of attachment of muscle tendons and ligaments. In the coarse fibrous bone that has completed its development, cells (osteocytes) and elements of the intermediate substance (amorphous substance), as well as randomly located ossein and a small amount of elastic fibers, are distinguished. Ossein fibers have a significant thickness, since they contain a large number of fibrils.

lamellar bone tissue is characteristic of more highly organized terrestrial animals. In mammals, all the bones of the skeleton consist of lamellar bone tissue. Lamellar bone differs from coarse-fibred bone in that the cells, amorphous substance, and especially ossein fibers are arranged in it in an orderly manner, and the latter form plates. The plates, together with the cells in the lamellar bone, form the following systems: osteons, intercalary plates, general plates; in pigs and ruminants, systems of circular-parallel plates are also well developed.

The structure of the osteon (Fig. 9-A). More or less in the center of the osteon there is an osteon canal. It contains one or two blood vessels with a poorly differentiated surrounding fabric.

The canal wall is composed of osteocytes and an intermediate substance. The latter forms, as already mentioned, bone plates in the form of cylinders, which are, as it were, nested one inside the other. Their number, depending on the size of the osteon, ranges from several units to several tens. Each plate is made of glued not large quantity amorphous substance parallel and closely adjacent to each other ossein fibers with hydroxyapatite crystals deposited on them. If within one plate the fibers lie strictly parallel, then with the ossein fibers of adjacent plates they form an angle of about 90 °. This is reminiscent of the principle underlying the construction of plywood. Part of the ossein fibers passes from one plate to another, which determines their density. Due to this, osteons provide strength to bone tissue. Therefore, in places subject to shock loading, there are more osteons in the tissue. Between the plates there is a small layer of amorphous substance in which the bodies of osteocytes lie, while their processes penetrate the bone plates adjacent to them. The intermediate substance around the body and cell processes is slightly modified and is designated as a cell capsule. Osteons are delimited from the surrounding structures by a more developed layer of amorphous substance that forms cleavage lines. Osteons branch, anastomose with each other, forming a complex network in the compact bone substance. They have different size and rounded cross section.

Insert plates are located between osteons and by origin are the remains of the wall of pre-existing osteons (Fig. 9, 10). Therefore, they also consist of plates and bodies of osteocytes located between them, the processes of which penetrate a number of bone plates. However, intercalary plates differ from osteon in that their bone plates do not form a complete cylinder, but are only its fragments. In addition, the intercalated plates are more mineralized, harder and do not contain blood vessels. They give rigidity to bone tissue, and therefore there are more of them in the middle of the diaphysis, especially in the long bones of large animals.

General records encircle the compact bone substance from the outside (outer general plates) and from the side of the medullary cavity of tubular bones (internal general plates) (Fig. 10, 11). They also consist of bony plates alternating with rows of osteocyte bodies. But these plates cover, if not entirely, then most of the surface of the entire bone from the outside or from the inside. The general plates are pierced by nutrient channels (Fig. 10-5), which do not have their own wall.

Vessels pass through them from the periosteum, communicating
with vessels of osteon channels.

Circular-parallel structures reminiscent of general plates, they are separated from each other by circular canals and penetrated by a system of more or less short radial canals. These are the most mineralized and solid formations. Most often they are located in the outer layers of the compact substance of tubular bones. Sometimes in the mass of these structures there are poorly expressed osteons.

Developing bone tissue from mesenchyme. Mesenchymal cells, undergoing a series of transformations, become osteoblasts.

They produce material that forms the intermediate substance, in particular the ossein fibers of the bone. In mammals, at first
coarse fibrous bone tissue is formed, for more late stages Ontogenesis, it is replaced by a lamellar one, and osteons are formed, and after their partial destruction during bone restructuring, insertion plates are formed.

At osteon development osteoblasts secrete the intermediate, mainly towards the blood vessel. As a result, a cylindrical bone plate is formed around the vessel from closely spaced ossein fibers close to each other. A new layer of osteoblasts forms the second bone plate, and its main component, the osseomucoid, is small in the bone plates. A layer of intermediate substance formed by the same osteoblasts, which is richer in osseomucoid, but poorer in fibers, is adjacent to the outer surface of the bone plate and is called the commissure line. Osteoblasts are immured in it, gradually losing the ability to give an intermediate substance and turning into osteocytes. In the bones of different animals and in different bones of the same animal, the size, number of osteons, and the number of bone plates in them fluctuate. A. A. Maligonov and Bednyagin found that in cows of the Simmental breed, the bones per unit area of ​​the cut have more, although smaller, osteons than the bones of Kuban cattle. The authors attribute this difference to the greater precocity of Simmental cattle. A number of studies have found that the more osteons in the bone, the better it resists the load. Studies have shown that in ungulates, the number of osteons in the proximal links of the limbs is minimal, while their number increases in the distal (lower) links. The cross-sectional shape of the osteons of different bones is somewhat different, but, in general, it is more or less rounded.

Formation and structure of intercalary plates. Once formed, primary osteons do not remain unchanged throughout the life of the animal. The microstructure of the bone changes depending on the operating conditions, such as load. At the same time, old osteons are destroyed, and new osteons are built from the mesenchyme, the size, shape, and location of which turn out to be different. The destruction of old osteons is carried out due to the activity of another cell form, extremely characteristic of the bone, the osteoclast. They destroy osteons, but only partially, resulting in a cavity (lacuna). Following this, osteoblasts are formed from undifferentiated tissue, which are located along the walls of this cavity. Thanks to their activity, the first (counting from the periphery) bone plate arises, and due to the activity of new generations of osteoblasts, subsequent osteon plates are formed, located closer and closer to its center. The newly formed osteon turns out to be adjacent to the remnants of the former osteon. These residues are insert systems. From the path of their origin, it is clear that they are built in the same way as the wall of the osteon.

Formed bone tissue is the strongest, it is second only to tooth enamel.

The development of tubular bone. The process of bone development has been described above.
tissue that always develops from the mesenchyme. An organ is built from bone and other tissues, which is called bone . In the process of bone development as an organ, there are certain patterns. They are especially well studied for the tubular bones of the skeleton. Most of the bones of the mammalian skeleton undergo three stages ; connective tissue, cartilage
and bone. Only the integumentary bones of the skull and clavicle develop in situ
connective tissue, bypassing the cartilaginous stage. The development of cartilage at the site of the connective tissue germ occurs due to mesenchymal tissue. The development of bone in place of cartilage also occurs due to the mesenchyme. However, cartilage tissue has a significant effect on osteogenesis. With the development of the bone in place of the cartilage, a coarse-fibred bone is first formed, later replaced by a lamellar one. At the stage of the cartilaginous germ, the shape of the future bone is already quite clearly outlined. The cartilaginous rudiment is covered on all sides by the perichondrium, in which there are cambial
cellular elements and pass through blood vessels and nerves. Due to the undifferentiated cellular elements of the perichondrium,
cartilage growth.

The ossification process begins in the middle part of the diaphysis. In this place, from the side of the perichondrium, a layer of cells is separated, turning
into osteoblasts, which build coarse fibrous bone. As a result, a bone cuff of coarse fibrous bone is formed around the middle part of the diaphysis. Since the cuff develops by layering from the periphery, the bone is called perichondral (Fig. 12). After the formation of the bone cuff, restructuring processes rapidly develop in the cartilage, and a large amount of glycogen is concentrated in its cells. The basic substance of the cartilage is destroyed and probably serves as a source of phosphate, which later, during calcification, together with calcium forms bone tissue apatite. Blood vessels and mesenchyme grow into the cartilage through the pores of the cuff. Polysaccharides released from cartilage cells also come here. There is reason to believe that this is one of the factors causing the transformation of the mesenchyme into osteogenic tissue. At the same time, part of the mesenchymal cells turns into two types of cells typical for bone tissue: osteoblasts(bone builders) and osteoclasts(bone breakers).

osteoclasts destroy the calcified cartilage, and in its place a primary bone cavity is formed. It is filled with mesenchyme, osteoblasts, cartilage fragments and blood vessels. osteoblasts settle around fragments of cartilage and begin to build bone. In accordance with the shape of the cartilage fragments, the resulting bone has the character of a sponge. Spongy bone initially fills the entire middle part (diaphysis) of the bone rudiment.

Unlike the cuff, which was layered on the outside, this bone develops from the inside- endochondral bone. Inside each crossbar of the endochondral bone, sections of cartilage remain. The perichondral bone cuff in the middle of the diaphysis of the future bone thickens and grows towards both ends (epiphyses) of the future bone. As it covers the cartilaginous bud, it gets bigger and bigger. most of cartilage is replaced by cancellous bone. As a result, the amount of enchondral cancellous bone increases. Closer to the epiphyses, in the place where the cuff is thin, there is still an increased growth of cartilage in length, but it no longer grows in thickness. There are two such zones of increased cartilage growth: above and below. Each of these zones borders on one side with the cartilage of the epiphysis, and on the other side with the endochondral bone of the diaphysis.

Due to the fact that in these zones the cartilage grows only in the direction of the long axis of the rudiment, the cartilage cells diverge from each other only in the longitudinal direction, located right rows in the form of coins. The zone of coin columns from the side of the diaphysis is gradually destroyed, and the cartilage cells swell and vacuolize, and its intermediate substance calcifies. This altered cartilage from the side of the diaphysis is destroyed by osteoclasts, and endochondral bone is created in place of the destroyed areas. Histochemical and electron microscopic methods have been able to show that some substances of the collapsing cartilage are used in the construction of the endochondral bone. Thus, the preexistence and destruction of cartilage is a condition for the development of bone. From the side of the proximal and distal epiphyses, the layer of coin columns continuously grows, so the entire bone rudiment grows in length. Later, from the side of the periosteum, a new layer of perichondral bone is superimposed on top of the bone cuff, which, unlike the endochondral bone cuff, is not porous, but solid. This is a compact substance.

In the spongy substance of the diaphysis, at a certain stage, bone-destructive processes begin, as a result of which an extensive cavity appears in the center of the bone diaphysis. A very small amount of spongy enchondral substance remains in the diaphysis, only along its walls. The bone cavity is filled with mesenchyme, which forms the bone marrow. Later, ossification processes begin in the epiphyses, where the endochondral and then the perichondral bones form first. Between the ossified epiphysis and diaphysis, long after the birth of the animal, layers of cartilage remain, which are called the epiphyseal cartilage. Due to it, the bone continues to grow in length; in thickness, it increases due to the cambial elements of the periosteum. When the epiphyseal cartilages are finally replaced by bone, the
bone growth in length and linear growth of the animal. The perichondral and endochondral bones are initially built of coarse fibrous bone tissue, later it is replaced by lamellar.

Thus, in the formed bone, a periosteum and a compact substance are distinguished, which is covered with articular cartilage at the places of articulation with other bones, spongy substance and a bone cavity filled with bone marrow. The periosteum covers the entire bone, except for the articular surfaces. Through the vessels of the periosteum, the bone receives nutrients
substances and oxygen. Nerves located in the periosteum connect the bone with the central nervous system, and through it - with the whole organism. Finally, the presence of poorly differentiated cellular elements in the periosteum makes it possible to restore the bone in case of damage. The compact substance is built from lamellar bone. It is most strongly developed in the middle part of the diaphysis, decreasing towards the epiphyses. The crossbeams of cancellous substance are also constructed from lamellar bone. The spongy substance is most strongly developed in the epiphyses and very little in the diaphysis. The voluminous bone cavity in the center of the diaphysis in adult animals is filled with yellow bone marrow, which is the result of fatty degeneration of the red bone marrow. In the loops of the spongy substance, mainly the epiphyses, there is a red bone marrow, which performs
the role of the hematopoietic organ. It develops erythrocytes, granular forms of leukocytes and platelets.

cartilage type	INTERCELLULAR SUBSTANCE		Localization
	fibers	Base substance
hyaline cartilage	collagen fibers (collagen II, VI, IX, X, XI types)	glycosaminoglycans and proteoglycans	trachea and bronchi, articular surfaces, larynx, connections of the ribs with the sternum
elastic cartilage	elastic and collagen fibers		auricle, horn-shaped and sphenoid cartilages of the larynx, cartilages of the nose
fibrocartilage	parallel bundles of collagen fibers; fiber content is greater than in other types of cartilage		places of transition of tendons and ligaments into hyaline cartilage, in intervertebral discs, semi-movable joints, symphysis
	in the intervertebral disc: the fibrous ring is located outside - it contains mainly fibers that have a circular course; and inside there is a gelatinous nucleus - it consists of glycosaminoglycans and proteoglycans and cartilage cells floating in them

cartilage tissue

It consists of cells - chondrocytes and chondroblasts and a large amount of intercellular hydrophilic substance, characterized by elasticity and density.

In fresh cartilage tissue contains:

70-80% water,

10-15% organic matter

4-7% salts.

50-70% of the dry matter of cartilage tissue is collagen.

The cartilage itself does not have blood vessels, and nutrients diffuse from the surrounding perichondrium.

Cartilage tissue cells are represented by chondroblastic differen:

1. Stem cell

2. Semi-stem cell (prechondroblasts)

3. Chondroblast

4. Chondrocyte

5. Chondroclast

Stem and semi-stem cell- poorly differentiated cambial cells, mainly localized around the vessels in the perichondrium. By differentiating, they turn into chondroblasts and chondrocytes, i.e. needed for regeneration.

Chondroblasts- young cells are located in the deep layers of the perichondrium singly, without forming isogenic groups. Under a light microscope, chondroblasts are flattened, slightly elongated cells with basophilic cytoplasm. Under an electron microscope, granular EPS, the Golgi complex, and mitochondria are well expressed in them; protein-synthesizing complex of organelles main function of chondroblasts- production of the organic part of the intercellular substance: collagen and elastin proteins, glycosaminoglycans (GAGs) and proteoglycans (PGs). In addition, chondroblasts are capable of reproduction and subsequently turn into chondrocytes. In general, chondroblasts provide appositional (superficial, neoplasms from the outside) cartilage growth from the side of the perichondrium.

Chondrocytes- the main cells of cartilage tissue are located in the deeper layers of cartilage in cavities - lacunae. Chondrocytes can divide by mitosis, while the daughter cells do not diverge, they remain together - the so-called isogenic groups are formed. Initially, they lie in one common gap, then an intercellular substance is formed between them, and each cell of this isogenic group has its own capsule. Chondrocytes are oval-round cells with basophilic cytoplasm. Under an electron microscope, granular ER, Golgi complex, mitochondria are well expressed; protein-synthesizing apparatus, tk. main function of chondrocytes- production of the organic part of the intercellular substance of cartilage tissue. Cartilage growth due to the division of chondrocytes and their production of intercellular substance provides interstitial (internal) cartilage growth.

There are three types of chondrocytes in isogenic groups:

1. Type I chondrocytes predominate in young, developing cartilage. They are characterized by a high nuclear-cytoplasmic ratio, the development of vacuolar elements of the lamellar complex, the presence of mitochondria and free ribosomes in the cytoplasm. In these cells, patterns of division are often observed, which allows us to consider them as a source of reproduction of isogenic groups of cells.

2. Type II chondrocytes are distinguished by a decrease in the nuclear-cytoplasmic ratio, a weakening of DNA synthesis, and the preservation of high level RNA, intensive development of the granular endoplasmic reticulum and all components of the Golgi apparatus, which provide the formation and secretion of glycosaminoglycans and proteoglycans into the intercellular substance.

3. Type III chondrocytes are characterized by the lowest nuclear-cytoplasmic ratio, strong development and an ordered arrangement of the granular endoplasmic reticulum. These cells retain the ability to form and secrete protein, but the synthesis of glycosaminoglycans decreases in them.

In the cartilage tissue, in addition to the cells forming the intercellular substance, there are also their antagonists - the destroyers of the intercellular substance - these are chondroclasts(can be attributed to the macrophage system): rather large cells, there are many lysosomes and mitochondria in the cytoplasm. Function of chondroclasts- Destruction of damaged or worn parts of cartilage.

Intercellular substance of cartilage tissue contains collagen, elastic fibers and ground substance. The ground substance consists of tissue fluid and organic substances:

GAGs (chondroethin sulfates, keratosulfates, hyaluronic acid);

10% - PG (10-20% - protein + 80-90% GAG);

The intercellular substance has a high hydrophilicity, the water content reaches 75% of the mass of the cartilage, which leads to a high density and turgor of the cartilage. Cartilaginous tissues in the deep layers do not have blood vessels, nutrition is carried out diffusely due to the vessels of the perichondrium.

perichondrium is a layer of connective tissue that covers the surface of cartilage. In the perichondrium secrete external fibrous(from a dense, unformed CT with a large number of blood vessels) layer and inner cell layer containing a large number of stem, semi-stem cells and chondroblasts.



Cartilage tissue plays a supporting role. It does not work in tension, like a dense connective tissue, but due to internal tension, it resists compression well. This tissue forms the basis of the larynx

Nbrinlcho, serves for a fixed connection of bones, forming synchondrosis. Covering the articular surfaces of the bones, softens the movement in the joints. Cartilage tissue is quite dense and at the same time quite elastic. Its intermediate substance is rich in dense amorphous substance. Cartilage develops from mesenchyme. At the site of the future cartilage, mesenchymal cells multiply intensively, their processes are shortened and the cells are in close contact with each other. Then an intermediate substance appears, due to which mononuclear sections are clearly visible in the rudiment, which are primary cartilage cells - chondroblasts. They multiply and give more and more masses of the intermediate substance.

The amount of the latter begins to prevail over the mass of cells. The rate of reproduction of cartilage cells by this time slows down, and due to the large amount of intermediate substance, they are far removed from each other. Soon, cells lose the ability to divide by mitosis, but still retain the ability to divide amitotically. However, now the daughter cells do not diverge far, as the intermediate substance surrounding them has condensed. Therefore, cartilage cells are located in the mass of the main substance in groups of 2-5 or more cells. All of them come from one initial cell. Such a group of cells is called iso-genius (isos - equal, identical, genesis - occurrence). Cells

Rice. 56. Different kinds cartilage:

A - hyaline cartilage of the trachea; B - elastic cartilage of the auricle of the calf; B - fibrous cartilage intervertebral disc calf a - perichondrium; b ~ cartilage; in - an older section of cartilage; 1 - chondroblast; 2 - chondrocyte; 3 - isogenic group of chondrocytes; 4 - elastic fibers; 5 - bundles of collagen fibers; 6 - basic substance; 7 - chondrocyte capsule; 8 - basophilic and 9 - oxyphilic zone of the main substance around the isogenic group.

The isogenic group does not divide by mitosis, they give little intermediate substance of a slightly different chemical composition, which forms cartilage capsules around individual cells, and fields around the isogenic group. The cartilage capsule, as revealed by electron microscopy, is formed by thin fibrils concentrically located around the cell.

Thus, in the beginning, the development of cartilage is accompanied by the growth of the entire mass of cartilage from the inside. Later, the oldest part of the cartilage, where cells do not multiply and no intermediate substance is formed, ceases to increase in size, and cartilage cells even degenerate. However, the growth of cartilage as a whole does not stop. Around the obsolete cartilage, a layer of cells separates from the surrounding mesenchyme, which become chondroblasts. They secrete around themselves the intermediate substance of the cartilage and are gradually walled up with it. Soon chondroblasts lose the ability to divide by mitosis, form less intermediate substance and become chondrocytes. On the layer of cartilage formed in this way, due to the surrounding mesenchyme, more and more layers of it are superimposed. Consequently, cartilage grows not only from the inside, but also from the outside.

In mammals, there are: hyaline (vitreous), elastic and fibrous cartilage.

Hyaline cartilage (Fig. 56-A) is the most common, milky white and somewhat translucent, which is why it is often called vitreous. It covers the articular surfaces of all bones; costal cartilages, cartilages of the trachea and some cartilages of the larynx are formed from it. Hyaline cartilage consists, like all tissues of the internal environment, of cells and an intermediate substance.

Cartilage cells are represented by chondroblasts (on different stages differentiation) and chondrocytes. It differs from hyaline cartilage in the strong development of collagen fibers, which form bundles that lie almost parallel to each other, as in tendons! There is less amorphous substance in fibrous cartilage than in hyaline. Rounded light cells of fibrocartilage lie between the fibers in parallel rows. In places where fibrocartilage is located between hyaline cartilage and formed dense connective tissue, a gradual transition from one type of tissue to another is observed in its structure. Thus, closer to the connective tissue, collagen fibers in cartilage form coarse parallel bundles, and cartilage cells lie in rows between them, like fibrocytes of dense connective tissue. Closer to the hyaline cartilage, the bundles are divided into individual collagen fibers that form a delicate network, and the cells lose their correct location.

Bone and cartilage make up the human skeleton. These tissues have a supporting function, at the same time they protect internal organs, organ systems from adverse factors. For the normal functioning of the human body, it is necessary that all the cartilage laid down by nature be in anatomically correct places, so that the tissues are strong and regenerating as needed. Otherwise, a person is faced with many unpleasant diseases that lower the standard of living, or even completely depriving them of the opportunity to move independently.

Fabric Features

Tissue, like any other structural elements of the body, is formed from special cells. Cartilage tissue cells in science are called differons. This concept is complex, it includes several types of cells: stem cells, semi-stem cells, combined within the framework of anatomy into a group of unspecialized ones - this category is characterized by the ability to actively divide. Chondroblasts are also isolated, that is, cells that can divide, but at the same time are able to produce intercellular compounds. Finally, there are cells whose main task is to create an intermediate substance. Their specialized name is chondrocytes. These cells contain not only cartilage fibers, the functions of which are to ensure stability, but also the main substance, which scientists call amorphous. This compound is able to bind water, thanks to which the cartilage tissue resists compressive loads with firmness. If all the cells of the joint are healthy, it will be elastic and durable.

In science, there are three types of cartilage tissue. For division into groups, the features of the intercellular connecting component are analyzed. It is customary to talk about the following categories:

• elastic;
• hyaline;
• fibrous.

How about more details?

As is known from anatomy, all types of cartilage tissue have their own characteristics. Thus, elastic tissue is distinguished by the specific structure of the intercellular substance - it is characterized by a rather high concentration of collagen fibers. At the same time, such tissue is rich in amorphous matter. At the same time, this tissue exhibits high percent elastic fibers, which gave it its name. The functions of cartilage tissue of an elastic type are associated with this feature: providing elasticity, flexibility, and lasting resistance. external influence. What else interesting anatomy can tell? Where is this type of cartilage located? Usually - in those organs that by nature are provided for bending. For example, the laryngeal cartilages, the nose and ear shells, and the center of the bronchi are made of elastic cartilage.

Fibrous tissue: some features

At the point from which hyaline cartilage begins, fibrous connective tissue ends. Typically, this tissue is found in the discs between the vertebrae, as well as at the junctions of bones where mobility is not important. The structural features of this type of cartilage tissue are directly related to the specifics of its location. Tendons, ligaments at the point of contact with cartilage provoke an actively developed system of collagen fibers. The peculiarity of such tissue is the presence of cartilage cells (instead of fibroblasts). These cells form isogenic groups.

What else do you need to know

The course of human anatomy allows you to clearly understand what cartilage tissue is for: to ensure mobility while maintaining elasticity, stability, and safety. These fabrics are dense and guarantee mechanical protection. Modern anatomy as a science is characterized by an abundance of terms, including those that complement and mutually replace each other. So, if we are talking about the vitreous cartilaginous tissue of the spine, then it is assumed that they are talking about hyaline. It is this tissue that forms the ends of the bones that make up the rib cage. Some elements of the respiratory system are also created from it.

The functions of cartilage tissue from the connective tissue category are the combination of tissue and hyaline vitreous cartilage, which has a completely different structure. But the mesh cartilage tissue ensures the normal functioning of the epiglottis, the hearing system, and the larynx.

Why is cartilage needed?

Nature does not create anything just like that. All tissues, cells, organs have a fairly extensive functionality (and some tasks are still hidden from scientists). As is already known from anatomy today, the functions of cartilage tissue include a guarantee of the reliability of the connection of elements that provide a person with the ability to move. In particular, the bone elements of the spine are interconnected precisely by cartilage tissue.

As it has been established in the course of studies on aspects of cartilage tissue nutrition, it takes Active participation in carbohydrate metabolism. This explains some of the features of regeneration. It is noted that in childhood restoration of cartilage tissue is possible by 100%, but over the years this ability is lost. If an adult is faced with cartilage damage, he can only count on partial restoration of mobility. At the same time, the restoration of cartilage tissue is one of the tasks that attract the attention of the advanced minds of medicine of our time, so it is expected that an effective pharmaceutical solution to this problem will be found in the near future.

Joint problems: there are options

Currently, medicine can offer several methods for restoring organs and tissues damaged for various reasons. If the joint has received a mechanical injury or some disease has provoked the destruction of biological material, in most cases the most effective solution problems becomes prosthetics. But injections for cartilage tissue will help when the situation has not yet gone so far, degenerative processes have begun, but are reversible (at least partially). As a rule, they resort to products that contain glucosamine, sodium sulfate.

Understanding how to restore cartilage tissue on early stages diseases, usually resort to exercise, strictly monitoring the load level. A good effect is shown by therapy using inflammation-blocking drugs. As a rule, most patients are prescribed drugs that are rich in calcium in a form that is easily absorbed by the body.

Cartilaginous connective tissue: where do the problems come from?

In most cases, the disease is provoked by previous injuries or infection of the joint. Sometimes the degeneration of the cartilaginous connective tissue is provoked by increased loads falling on it for a long time period. In some cases, problems are associated with genetic prerequisites. Hypothermia of body tissues can play a role.

With inflammation, a good result can be given by the use of both topical preparations and tablets. Modern medicines are formed taking into account the hydrophilicity characteristic of the cartilaginous tissue of the spine and other organs. This means that topical agents can quickly “get” to the affected area and have a therapeutic effect.

Structural features

As can be seen from the anatomy, hyaline cartilage, other cartilage tissues, as well as bone tissues are combined into the skeletal category. In Latin, this group of tissues received the name textus cartilaginus. Up to 80% of this tissue is water, from four to seven percent is salt, and the rest is organic components (up to 15%). The dry part of the cartilage tissue is half or more (up to 70%) formed from collagen. The matrix produced by tissue cells is a complex substance that includes hyaluronic acid, glycosaminoglycans, proteoglycans.

Tissue cells: some features

As scientists have found out, chondroblasts are such young cells that usually have an irregularly elongated shape. Such a cell in the process of life generates proteoglycans, elastin, and other components indispensable for the normal functioning of the joint. The cytolemma of such a cell is microvilli, presented in large numbers. The cytoplasm contains an abundance of RNA. Such a cell is characterized by an endoplasmic reticulum of a high level of development, presented both in a non-granular form and in a granular one. The cytoplasm of chondroblasts also contains glycogen granules, the Golgi complex, and lysosomes. Typically, the nucleus of such a cell has one or two nuclei. Education contains a large amount of chromatin.

A distinctive feature of chondrocytes is their large size, since these cells are already mature. They are characterized by a round shape, oval, polygonal. Most chondrocytes are equipped with processes, organelles. Typically, such cells occupy gaps, and around them there is an intercellular connective substance. When a lacuna contains one cell, it is classified as primary. Predominantly observed isogenic groups, consisting of a pair or triple of cells. This allows us to speak of a secondary lacuna. The wall of such a formation has two layers: on the outside it is made of collagen fibers, and on the inside it is lined with proteoglycan aggregates interacting with the cartilage glycocalyx.

Biological features of tissue

When the cartilaginous tissue of a joint is the focus of attention of scientists, it is usually studied as an accumulation of chondrons - this is the name given to the functional, structural units of biological tissue. A chondron is formed from a cell or a combined group of cells, a matrix surrounding the cell, and a lacuna in the form of a capsule. Each of the three types of cartilage tissue listed above has its own unique structural features. For example, hyaline cartilage, which got its name from Greek word"glass", has a bluish tint and is characterized by the cells of the different shapes, buildings. Much depends on exactly what place the cell occupies inside the cartilage tissue. Usually hyaline cartilage is formed by groups of chondrocytes. Such tissue creates joints, cartilage of the ribs, larynx.

If we consider the process of bone formation in the human body, we can see that at the initial stage, most of them consist of hyaline cartilage. Over time, the articular tissue is transformed into bone.

What else is special?

But fibrocartilage is very strong, as it consists of thick fibers. Its cells are characterized by an elongated shape, a rod-shaped nucleus and a cytoplasm that forms a small rim. Such cartilage usually creates the fibrous rings characteristic of the spine, menisci, discs inside the joints. Cartilage covers some joints.

If we consider the elastic cartilage tissue, we can see that it is quite flexible, since the matrix is ​​rich not only in collagen, but also in elastic fibers. This tissue is characterized by rounded cells enclosed in lacunae.

Cartilage and cartilage tissue

These two terms, despite their similarities, should not be confused. Cartilage tissue is a type of connective biological tissue, while cartilage is an anatomical organ. In its structure there is not only cartilage tissue, but also there is a perichondrium covering the tissues of the organ from the outside. In this case, the perichondrium does not cover the articular surface. This element of cartilage is formed by a connective tissue consisting of fibers.

The perichondrium consists of two layers: fibrous, covering it from the outside, and cambial, with which the organ is lined inside. The second is also known as sprout. The inner layer is an accumulation of poorly differentiated cells. These include chondroblasts in the inactive stage, prechondroblasts. These cells first form chondroblasts, then they progress to chondrocytes. But the fibrous layer is distinguished by a developed circulatory network, represented by an abundance of blood vessels. The perichondrium is both a protective layer and a storage of material for regenerative processes, and a tissue through which the trophism of cartilage tissue is realized, in the structure of which there are no vessels. But if we consider hyaline cartilage, then in it the main tasks for trophism fall on the synovial fluid, and not just on the vessels. The blood supply system of bone tissue plays a very important role.

How it works?

The basis for the formation of cartilage, cartilage tissue is mesenchyme. The process of tissue growth in science is called chondrohistogenesis. Mesenchymal cells at points where nature provides for the presence of cartilaginous tissue multiply, divide, grow, round. This results in a cell clump called a foci. Science usually refers to such places as chondrogenic islets. As the process moves forward, differentiation into chondroblasts occurs, due to which the production of fibrillar proteins that enter the medium between living cells becomes real. This leads to the formation of the first type of chondrocytes, capable of not only producing specialized proteins, but also a number of other compounds indispensable for the normal activity of the organs.

As cartilage tissue develops, chondrocytes differentiate, which leads to the formation of the second and third types of cells in this tissue. At the same stage, gaps appear. The mesenchyme, located around the cartilaginous island, becomes the source of cells to create the perichondrium.

Features of tissue growth

Cartilage development is usually divided into two stages. First, tissues go through a period of interstitial growth, during which chondrocytes actively multiply and produce intercellular substance. Then comes the stage of oppositional growth. Here the main characters"- chondroblasts of the perichondrium. In addition, tissue overlays located on the periphery of the organ provide indispensable assistance for the formation and functioning of cartilage tissue.

With the aging of the body as a whole, cartilage tissue in particular, degenerative processes are outlined. The hyaline cartilages are most prone to such. Elderly people often experience pain caused by salt deposits in the deep cartilage layers. More often, calcium compounds accumulate, which leads to tissue shrinkage. Vessels grow into the affected area, cartilage gradually transforms into bone. In medicine, this process is called ossification. But elastic tissues are not damaged by such changes, they do not stiffen, although they lose elasticity over the years.

Cartilage tissue: problems of degeneration

It so happened that from the point of view of human health, cartilage tissue is one of the most vulnerable, and almost all elderly people, and often the younger generation, suffer from joint-related diseases. There are many reasons for this: it is the environment, and the wrong way of life, and improper nutrition. Of course, very often we get injured, encounter infections or inflammations. A one-time problem - an injury or illness - passes, but at an older age it returns with echoes - joint pains.

Cartilage is quite sensitive to many diseases. Problems with the musculoskeletal system arise if a person is faced with a hernia, dysplasia, arthrosis, arthritis. Some suffer from a lack of natural collagen synthesis. With age, chondrocytes degenerate, and cartilage tissue suffers greatly from this. In many cases, the best therapeutic effect comes from surgery, when the affected joint is replaced with an implant, but this solution is not always applicable. If there is a possibility of restoring natural cartilage tissue, this chance should not be neglected.

Joint diseases: how are they manifested?

Most of those suffering from such pathologies can predict weather changes more accurately than any forecast: joints affected by the disease respond to the slightest changes in the surrounding space with excruciating, pulling pain. If the patient suffers from damage to the joints, he should not move sharply, as the tissues react to this with a sharp, severe pain. As soon as similar symptoms begin to appear, you should immediately make an appointment with a doctor. It is much easier to cure a disease or block its development if you start the fight at an early stage. Delay leads to the fact that regeneration becomes completely impossible.

Quite a few drugs have been developed to restore the normal functionality of cartilage tissue. Mostly they belong to the category of non-steroidal and are designed to block inflammation. Painkillers are also produced - tablets, injections. Finally, in recent times special chondroprotectors have become widespread.

How to treat?

The most effective drugs against degenerative processes in cartilage affect cellular level. They block inflammatory processes, protect against negative impact chondrocytes, and also stop the degenerative activity of various aggressive compounds that attack cartilage tissue. If inflammation has been effectively blocked, the next step in therapy is usually to restore the intercellular junction. For this, chondroprotectors are used.

Several agents of this group have been developed - they are built on different active components, which means that they differ in the mechanism of action on human body. For all the means of this group, efficiency is characteristic only when taken in a long course, which makes it possible to achieve really good results. Particularly widespread are preparations made on chondroitin sulfate. This is glucosamine, which is involved in the formation of cartilage proteins and allows you to restore the structure of the tissue. By supplying a substance from external source in all types of cartilage tissue, the process of production of collagen, hyalic acid is activated, and the cartilage is independently restored. With proper use of medications, you can quickly restore joint mobility and get rid of pain.

Another a good option- products containing other glucosamines. They restore tissue from various kinds of damage. Under the influence of the active component, the metabolism in the cartilaginous tissues of the joint is normalized. Also recently used drugs of animal origin, that is, made from biological material obtained from animals. Most often, these are tissues of calves, aquatic creatures. Nice results shows therapy with the use of mucopolysaccharides and medicines built on them.

In the human body, cartilage tissues serve as a support and connection between the structures of the skeleton. There are several types of cartilage structures, each of which has its own location and performs its tasks. Skeletal tissue undergoes pathological changes due to intense physical activity, congenital pathologies, age and other factors. To protect yourself from injuries and diseases, you need to take vitamins, calcium supplements and not be injured.

The value of cartilage structures

Articular cartilage holds skeletal bones, ligaments, muscles and tendons together. musculoskeletal system. It is this type of connective tissue that provides cushioning during movement, protecting the spine from damage, preventing fractures and bruises. The function of cartilage is to make the skeleton elastic, elastic and flexible. In addition, cartilage forms a supporting frame for many organs, protecting them from mechanical damage.

Features of the structure of cartilage tissue

The specific gravity of the matrix exceeds the total mass of all cells. Overall plan cartilage structure consists of 2 key elements: intercellular substance and cells. During the histological examination of the sample under the lenses of a microscope, the cells are located on a relatively smaller percentage of the area of ​​space. The intercellular substance contains about 80% water in the composition. The structure of hyaline cartilage provides it leading role in the growth and movement of joints.

intercellular substance

The strength of cartilage is determined by its structure.

The matrix, as an organ of cartilaginous tissue, is heterogeneous and contains up to 60% amorphous mass and 40% chondrin fibers. Fibrils histologically resemble human skin collagen, but differ in more chaotic placement. The ground substance of cartilage consists of protein complexes, glycosaminoglycans, hyaluronan compounds and mucopolysaccharides. These components provide durable cartilage properties, keeping it permeable to essential nutrients. There is a capsule, its name is perichondrium, it is a source of cartilage regeneration elements.

Cellular composition

Chondrocytes are located in the intercellular substance rather chaotically. The classification divides cells into undifferentiated chondroblasts and mature chondrocytes. The precursors are formed by the perichondrium, and as they move into deeper tissue balls, the cells differentiate. Chondroblasts produce matrix ingredients that include proteins, proteoglycans, and glycosaminoglycans. Young cells by division provide interstitial growth of cartilage.

Chondrocytes located in deep tissue spheres are grouped by 3-9 cells, known as "isogenic groups". This mature cell type has a small nucleus. They do not divide, and their metabolic rate is greatly reduced. The isogenic group is covered by intertwined collagen fibers. The cells in this capsule are separated by protein molecules and have a variety of shapes.

With degenerative-dystrophic processes, multinucleated chondroclast cells appear, which destroy and absorb tissues.

The table presents the main differences in the structure of cartilage tissue types:

View	Peculiarities
Hyaline	Thin collagen fibers
	Has basophilic and oxyphilic zones
elastic	Made up of elastin
	Very flexible
	Has a cellular structure
Fibrous	Formed from a large number of collagen fibrils
	Chondrocytes are comparatively larger
	Lasting
	Able to withstand high pressure and compression

Blood supply and nerves

The tissue is not supplied with blood from its own vessels, but receives it by diffusion from adjacent ones.

Due to the very dense structure, cartilage does not have blood vessels of even the smallest diameter. Oxygen and all the nutrients necessary for life and functioning come by diffusion from nearby arteries, perichondrium or bone, and are also extracted from synovial fluid. Decay products are also excreted diffusely.

In the upper balls of the perichondrium there are only a small number of individual branches of nerve fibers. Thus, the nerve impulse is not formed and does not spread in pathologies. The localization of the pain syndrome is determined only when the disease destroys the bone, and the cartilage tissue structures in the joints are almost completely destroyed.

Varieties and functions

Depending on the type and relative position of fibrils, histology distinguishes the following types of cartilage tissue:

• hyaline;
• elastic;
• fibrous.

Each type is characterized by a certain level of elasticity, stability and density. The location of the cartilage determines its tasks. The main function of cartilage is to ensure the strength and stability of the joints of the parts of the skeleton. The smooth hyaline cartilage found in the joints makes it possible for the bones to move. Due to its appearance, it is called vitreous. The physiological conformity of the surfaces guarantees a smooth glide. The structural features of hyaline cartilage and its thickness make it integral part ribs, upper rings respiratory tract.

The shape of the nose is formed by an elastic type of cartilage.

Elastic cartilage forms appearance, voice, hearing and breathing. This applies to the structures that are in the skeleton of the small and medium-sized bronchi, auricles and the tip of the nose. The elements of the larynx are involved in the formation of a personal and unique voice timbre. Fibrous cartilage connects skeletal muscles, tendons, and ligaments to vitreous cartilage. Intervertebral and intra-articular discs and menisci are built from fibrous structures; they cover the temporomandibular and sternoclavicular joints.