Cartilage belongs to which tissue. Cartilage tissue

CARTILAGE TISSUE

General characteristics: relatively low metabolic rate, lack of blood vessels, hydrophilicity, strength and elasticity.

Structure: chondrocyte cells and intercellular substance (fibers, amorphous substance, interstitial water).

Lecture: CARTILAGE TISSUE

Cells ( chondrocytes) constitute no more than 10% of the cartilage mass. The main volume in cartilage tissue is accounted for intercellular substance. The amorphous substance is quite hydrophilic, which allows it to deliver nutrients to cells by diffusion from the capillaries of the perichondrium.

Chondrocyte differon: stem, semi-stem cells, chondroblasts, young chondrocytes, mature chondrocytes.

Chondrocytes are derivatives of chondroblasts and the only population of cells in cartilage tissue, located in the lacunae. Chondrocytes can be divided according to their maturity into young and mature. Young retain the structural features of chondroblasts. They have an oblong shape, developed GREPS, a large Golgi apparatus, and are capable of forming proteins for collagen and elastic fibers and sulfated glycosaminoglycans and glycoproteins. Mature chondrocytes have an oval or round shape. The synthetic apparatus is less developed when compared to young chondrocytes. Glycogen and lipids accumulate in the cytoplasm.

Chondrocytes are capable of dividing and form isogenic groups of cells surrounded by a single capsule. In hyaline cartilage, isogenic groups can contain up to 12 cells, in elastic and fibrous cartilage - smaller number cells.

Functions cartilaginous tissues: supporting, formation and functioning of joints.

Classification of cartilage tissues

There are: 1) hyaline, 2) elastic and 3) fibrous cartilaginous tissue.

Histogenesis . During embryogenesis, cartilage is formed from mesenchyme.

1st stage. Formation of a chondrogenic island.

2nd stage. Differentiation of chondroblasts and the beginning of the formation of fibers and cartilage matrix.

3rd stage. The growth of cartilage anlage in two ways:

1) Interstitial growth– caused by an increase in tissue from the inside (formation of isogenic groups, accumulation of the intercellular matrix), occurs during regeneration and in the embryonic period.

2) Appositional growth– caused by tissue layering due to the activity of chondroblasts in the perichondrium.

Cartilage regeneration . When cartilage is damaged, regeneration occurs from the cambial cells in the perichondrium, and new layers of cartilage are formed. Complete regeneration occurs only in childhood. Adults are characterized by incomplete regeneration: PVNST is formed in place of the cartilage.

Age-related changes . Elastic and fibrous cartilage are resistant to damage and change little with age. Hyaline cartilage tissue can undergo calcification, sometimes transforming into bone tissue.

Cartilage as an organ consists of several tissues: 1) cartilage tissue, 2) perichondrium: 2a) outer layer - PVNST, 2b) inner layer– PBCT, with blood vessels and nerves, and also contains stem cells, semi-stem cells and chondroblasts.

1. HYALINE CARTILAGE TISSUE

Localization: cartilages of the nose, larynx (thyroid cartilage, cricoid cartilage, arytenoid, except vocal processes), trachea and bronchi; articular and costal cartilages, cartilaginous growth plates in tubular bones.

Structure: cartilage cells, chondrocytes (described above) and intercellular substance, consisting of collagen fibers, proteoglycans and interstitial water. Collagen fibers(20-25%) consist of type II collagen and are arranged randomly. Proteoglycans, making up 5-10% of the mass of cartilage, they are represented by sulfated glycosaminoglycans, glycoproteins that bind water and fiber. Proteoglycans of hyaline cartilage prevent its mineralization. Interstitial water(65-85%) ensures the incompressibility of cartilage and acts as a shock absorber. Water promotes efficient metabolism in cartilage, transports salts, nutrients, and metabolites.

Articular cartilage is a type of hyaline cartilage, does not have perichondrium, and receives nutrition from synovial fluid. In articular cartilage there are: 1) a superficial zone, which can be called acellular, 2) a middle (intermediate) zone - containing columns cartilage cells and 3) the deep zone where cartilage interacts with bone.

I suggest watching the video from YouTube " ARTHROSIS OF THE KNEE JOINT»

2. ELASTIC CARTILAGE TISSUE

Localization: auricle, cartilages of the larynx (epiglottic, corniculate, sphenoid, as well as the vocal process at each arytenoid cartilage), eustachian tube. This type of tissue is necessary for those areas of organs that are capable of changing their volume, shape and have reversible deformation.

Structure: cartilage cells, chondrocytes (described above) and intercellular substance, consisting of elastic fibers (up to 95%) fibers and amorphous substance. For imaging, dyes that reveal elastic fibers, such as orcein, are used.

3. FIBROUS CARTILAGE TISSUE

Localization: fibrous rings of intervertebral discs, articular discs and menisci, in the symphysis (symphysis pubis), articular surfaces in the temporomandibular and sternoclavicular joints, in places of attachment of tendons to bones or hyaline cartilage.

Structure: chondrocytes (usually singly) of an elongated shape and intercellular substance, consisting of a small amount of amorphous substance and a large number of collagen fibers. The fibers are arranged in orderly parallel bundles.

In the human body, cartilage tissue serves as a support and connection between skeletal structures. There are several types of cartilaginous structures, each of which has its own location and performs its own 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 get injured.

The importance of cartilaginous structures

Articular cartilage holds skeletal bones, ligaments, muscles and tendons together into a single musculoskeletal system. It is this type of connective tissue that provides shock absorption 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. The general plan of the structure of cartilage consists of 2 key elements: intercellular substance and cells. During histological examination of a sample under a microscope lens, cells are located in a relatively smaller percentage of the space. The intercellular substance contains about 80% water in the composition. The structure of hyaline cartilage provides it main role in the growth and movement of joints.

Intercellular substance

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

Cellular composition

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

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

During degenerative-dystrophic processes, multinucleated chondroclast cells appear, which destroy and absorb tissue.

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

Blood supply and nerves

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

In the superior balls of the perichondrium there is only small quantity individual branches of nerve fibers. Thus, nerve impulse does not form and does not spread in pathologies. Localization pain syndrome It is determined only when the disease destroys the bone and the structures of cartilage tissue in the joints are almost completely destroyed.

Types and functions

Depending on the type and relative position of the 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 skeletal parts. The smooth hyaline cartilage found in joints makes bone movements possible. Thanks to his appearance it is called vitreous. The physiological conformity of the surfaces guarantees smooth gliding. The structural features of hyaline cartilage and its thickness make it integral part ribs, upper rings respiratory tract.

Elastic cartilage forms the appearance, voice, hearing and breathing. This applies to structures that are located in the framework of the small and medium-caliber bronchi, the ears and the tip of the nose. Elements of the larynx are involved in the formation of a personal and unique timbre of the voice. Fibrous cartilage binds skeletal muscles, tendons and ligaments with vitreous cartilage. Intervertebral and intraarticular discs and menisci are built from fibrous structures; they cover the temporomandibular and sternoclavicular joints.

Cartilage tissue is a type of connective tissue consisting of cartilage cells (chondrocytes) and a large amount of dense intercellular substance. Serves as a support. Chondrocytes have a variety of shapes and lie singly or in groups within cartilaginous cavities. The intercellular substance contains chondrinic fibers, similar in composition to collagen fibers, and the ground substance, rich in chondromucoid.

Depending on the structure of the fibrous component of the intercellular substance, three types of cartilage are distinguished: hyaline (vitreous), elastic (mesh) and fibrous (connective tissue).

Pathology of cartilage tissue - see Chondritis, Chondrodystrophy.

Cartilaginous tissue (tela cartilaginea) is a type of connective tissue characterized by the presence of a dense intercellular substance. In the latter, a basic amorphous substance is distinguished, which contains compounds of chondroitinsulfuric acid with proteins (chondromucoids) and chondrinum fibers, similar in composition to collagen fibers. Fibrils of cartilage tissue belong to the type of primary fibers and have a thickness of 100-150 Å. Electron microscopy in the fibers of cartilage tissue, in contrast to collagen fibers themselves, reveals only a vague alternation of light and dark areas without clear periodicity. Cartilage cells (chondrocytes) are located in the cavities of the ground substance individually or in small groups (isogenic groups).

The free surface of the cartilage is covered with dense fibrous connective tissue - perichondrium, in the inner layer of which poorly differentiated cells - chondroblasts - are located. The cartilaginous tissue covering the articular surfaces of the bones does not have perichondrium. The growth of cartilage tissue is carried out due to the proliferation of chondroblasts, which produce the ground substance and subsequently turn into chondrocytes (appositional growth) and due to the development of a new ground substance around the chondrocytes (interstitial, intussusceptive growth). During regeneration, the development of cartilage tissue can also occur by homogenizing the ground substance of fibrous connective tissue and converting its fibroblasts into cartilage cells.

Nutrition of cartilage tissue goes the way diffusion of substances from the blood vessels of the perichondrium. Nutrients penetrate into the tissue of articular cartilage from the synovial fluid or from the vessels of the adjacent bone. Nerve fibers are also localized in the perichondrium, from where individual branches of the soft nerve fibers can penetrate into the cartilage tissue.

In embryogenesis, cartilaginous tissue develops from mesenchyme (see), between the contiguous elements of which layers of the main substance appear (Fig. 1). In such a skeletogenic rudiment, hyaline cartilage is first formed, temporarily representing all the main parts of the human skeleton. In the future, this cartilage can be replaced bone tissue or differentiate into other types of cartilage tissue.

The following types of cartilage tissue are known.

Hyaline cartilage(Fig. 2), from which in humans the cartilages of the respiratory tract, thoracic ends of the ribs and articular surfaces of bones are formed. In a light microscope, its main substance appears homogeneous. Cartilage cells or isogenic groups of them are surrounded by an oxyphilic capsule. In differentiated areas of cartilage, a basophilic zone adjacent to the capsule and an oxyphilic zone located outside of it are distinguished; Collectively, these zones form the cellular territory, or chondrin ball. The complex of chondrocytes with the chondrinic ball is usually taken to be the functional unit of cartilage tissue - the chondrone. The main substance between chondrons is called interterritorial spaces (Fig. 3).

Elastic cartilage(synonym: reticular, elastic) differs from hyaline in the presence of branching networks of elastic fibers in the ground substance (Fig. 4). The cartilage of the auricle, epiglottis, Wrisberg and Santorini cartilages of the larynx are built from it.

Fibrous cartilage(synonym for connective tissue) is located in the places of transition of dense fibrous connective tissue into hyaline cartilage and differs from the latter in the presence of real collagen fibers in the ground substance (Fig. 5).

Pathology of cartilage tissue - see Chondritis, Chondrodystrophy, Chondroma.

Rice. 1-5. The structure of cartilage tissue.
Rice. 1. Histogenesis of cartilage:
1 - mesenchymal syncytium;
2 - young cartilage cells;
3 - layers of the main substance.
Rice. 2. Hyaline cartilage (low magnification):
1 - perichondrium;
2 - cartilage cells;
3 - main substance.
Rice. 3. Hyaline cartilage (high magnification):
1 - isogenic group of cells;
2 - cartilaginous capsule;
3 - basophilic zone of the chondrin ball;
4 - oxyphilic zone of the chondrin ball;
5 - interterritorial space.
Rice. 4. Elastic cartilage:
1 - elastic fibers.
Rice. 5. Fibrous cartilage.

The bone marrow that fills the bone marrow cavities contains mainly fats (up to 98% of the dry yellow marrow) and smaller amounts of choline phosphatides, cholesterol, proteins and minerals. The composition of fats is dominated by palmitic, oleic, and stearic acids.
In accordance with the characteristics of the chemical composition, bone is used for the production of semi-finished products, jellies, brawn, bone fat, gelatin, glue, and bone meal.
Cartilage tissue. Cartilage tissue performs supporting and mechanical functions. It consists of a dense ground substance in which round-shaped cells, collagen and elastin fibers are located (Fig. 5.14). Depending on the composition of the intercellular substance, hyaline, fibrous and elastic cartilages are distinguished. Hyaline cartilage covers the articular surfaces of bones, and the costal cartilages and trachea are built from it. Calcium salts are deposited in the intercellular substance of such cartilage with age. Hyaline cartilage is translucent and has a bluish tint.

Fibrous cartilage makes up the ligaments between the vertebrae, as well as the tendons and ligaments at their attachment to the bones. Fibrous cartilage contains many collagen fibers and a small amount of amorphous substance. It has the appearance of a translucent mass.
Elastic cartilage is cream-colored, the intercellular substance of which is dominated by elastin fibers. Lime is never deposited in elastic cartilage.

Cartilage tissue

It is part of the auricle and larynx.
Average chemical composition cartilage tissue includes: 40-70% water, 19-20% proteins, 3.5% fats, 2-10% minerals, about 1% glycogen.
Cartilage tissue is characterized by a high content of mucoprotein - chondromucoid and mucogylisaccharide - chondroitinsulfuric acid in the main intercellular substance. Important property This acid is its ability to form salt-like compounds with various proteins: collagen, albumin, etc. This apparently explains the “cementing” role of mucopolysaccharides in cartilage tissue.
Cartilage tissue is used for food purposes, and gelatin and glue are also produced from it. However, the quality of gelatin and glue is often not high enough, since mucopolysaccharides and glucoproteins pass into solution from the tissue along with gelatin, reducing the viscosity and strength of the jelly.

Cartilaginous tissue is a type of supporting tissue characterized by the strength and elasticity of the matrix. This is due to their position in the body: in the joints, in the intervertebral discs, in the wall of the respiratory tract (larynx, trachea, bronchi).

Cartilaginous

○ Hyaline

○ Elastic

○ Fibrous

However general plan their structures are similar.

1. Presence of cells (chondrocytes and chondroblasts).

2. Formation of isogenic groups of cells.

3. The presence of a large amount of intercellular substance (amorphous, fibers), which provides strength and elasticity - that is, the ability to undergo reversible deformation.

4. Lack of blood vessels - nutrients diffuse from the perichondrium, due to the high water content (up to 70–80%) in the matrix.

5. Characterized comparatively low level metabolism.

Cartilage tissue

They have the ability to continuously grow.

During the development of cartilage tissue, a differentiation of cartilage cells is formed from the mesenchyme. This includes:

1. Stem cells – characterized by a round shape, high value nuclear-cytoplasmic relationships, diffuse arrangement of chromatin and a small nucleolus. The organelles of the cytoplasm are poorly developed.

2. Semi-stem cells (prechondroblasts) – the number of free ribsomes increases in them, grEPS appears, the cells become elongated, and the nuclear-cytoplasmic ratio decreases. Like stem cells, they exhibit low

proliferative activity.

3. Chondroblasts are young cells located on the periphery of cartilage. They are small flattened cells capable of proliferation and synthesis of components of the intercellular substance. In the basophilic cytoplasm, grEPS is well developed and

agrEPS, Golgi apparatus. During development they turn into chondrocytes.

4. Chondrocytes are the main (definitive) type of cartilage tissue cells. They come in oval, round or polygonal shapes. Located in special cavities

– lacunae – intercellular substance, singly or in groups. These groups are called isogenic cell groups.

Isogenic groups of cells - (from the Greek isos - equal, genesis - development) - groups of cells (chondrocytes) formed by the division of one cell. They lie in a common cavity (lacuna) and are surrounded by a capsule formed by the intercellular substance of cartilaginous tissue.

The main amorphous substance (cartilage matrix) contains:

1. Water – 70–80%

2. Inorganic compounds – 4–7%.

3. Organic matter – 10–15%

– Glycosaminoglycans:

Ø chondroitin sulfates (chondroitin-6-sulfate, chondroitin-4-sulfate,

Ø hyaluronic acid;

– Proteoglycans.

– Chondronectin – this glycoprotein connects cells to each other and to various substrates (cell connection with type I collagen).

There are many fibers in the intercellular substance:

1. Collagen (types I, II, VI)

2. And in elastic cartilage - elastic.

Ways of cartilage growth.

Interstitial growth of cartilage is an increase in the volume of cartilage tissue (cartilage) due to an increase in the number of dividing chondrocytes and the accumulation of intercellular substance components secreted by these cells.

Appositional growth of cartilage - is an increase in the volume of cartilage tissue (cartilage) due to the replenishment of cells located on the periphery (mesenchyme cells - during embryonic chondrogenesis, perichondrium chondroblasts - in postembryonic period ontogeny).

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The structure of individual human tissues, types of cartilage

Tendons and ligaments. Strength (muscle pulling or external forces) acts on tendons and ligaments in one direction. Therefore, the fibrous plates of tendons, consisting of fibroblasts (fibrocytes), ground substance and collagen fibers, are located parallel to each other. Bundles (from 10 to 1000) of fibrous plates are separated from each other by layers of unformed connective tissue. Small bundles are combined into larger ones, etc. The entire tendon is covered by a thicker layer of unformed tissue called the peritendon. It carries vessels and nerves to the tendon, ligament; There are also germ cells there.

Fascia, muscle aponeuroses, capsules of joints and organs, etc. The forces acting on them are directed towards different sides. The bundles of fibrous plates are located at an angle to each other, so the fascia and capsules are difficult to stretch and separate into separate layers.

Cartilage tissue. It can be permanent (for example, cartilage of the ribs, trachea, intervertebral discs, meniscus, etc.) and temporary (for example, in bone growth zones - metaphyses). Temporary cartilage is subsequently replaced by bone tissue. Cartilage tissue does not have connective tissue layers, vessels or nerves. Its trophism is provided only from the side of the perichondrium (a layer of fibrous connective tissue covering the cartilage) or from the side of the bone. The growth layer of cartilage is located in the lower layer of the perichondrium. When damaged, cartilage does not recover well.

There are three types of cartilage:

1. Hyaline cartilage. Covers the articular surfaces of bones, forms the cartilaginous ends of the ribs, rings of the trachea and bronchi. The elastic base substance (chondromucoid) of the cartilaginous plates contains individual collagen fibers.

2. Elastic cartilage.

Structure and functions of human cartilage tissue

Forms the auricle, wings of the nose, epiglottis, and cartilage of the larynx. The main substance of the cartilaginous plates contains predominantly elastic fibers.

3. Fibrous cartilage. Forms intervertebral and articular discs, menisci, articular lips. The cartilaginous plates are permeated a large number collagen fibers.

Bone tissue forms individual bones - the skeleton. Makes up about 17% of a person's total weight. Bones have strength with low mass. The strength and hardness of the bone is provided by collagen fibers, a special basic substance (ossein), impregnated minerals(mainly hydroxyapatite-phosphoric lime) and an ordered arrangement of bone plates. Bone plates form the outer layer of any bone and the inner layer of the medullary cavity; middle layer The tubular bone is composed of special, so-called osteon systems - multi-row, concentrically located plates around a canal in which there are vessels, nerves, and loose connective tissue. The spaces between the osteons (tubes) are filled with intercalated bone plates. Osteons are located along the length of the bone or in accordance with the load. Very thin tubules extend to the sides from the osteon canal, connecting the separated osteocytes.

There are two types of bone - cortical(compact or dense), up to 80% and trabecular(spongy or porous), constituting up to 20% of the total bone mass. If osteons and intercalary plates lie tightly, a compact substance is formed. It forms the diaphysis of tubular bones, top layer flat bones and covers the spongy part of the bone. At the ends of the bones, where a large volume is needed for joint articulation while maintaining lightness and strength, a spongy substance is formed. It consists of crossbars, beams (trabeculae), forming bone cells (like a sponge). Trabeculae are composed of osteons and intercalated bone plates, which are positioned in accordance with the pressure on the bone and the pull of the muscles.

On the outside, the bone, with the exception of the articular surfaces, is covered with periosteum (a layer of connective tissue, dense on top and loose closer to the bone). The latter contains many vessels, nerves, and contains bone-like cells - osteoblasts, which contribute to the growth of bones in width and the healing of fractures.

The rate of renewal of cortical and trabecular bone in an adult is from 2.5 to 16% per year.

Cartilage tissue

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

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.

Cartilage tissue itself does not have blood vessels, and nutrients diffuse from the surrounding perichondrium.

Cells of cartilage tissue are represented by chondroblastic differentiation:

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. necessary 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 electron microscope the granular ER, Golgi complex, and mitochondria are well expressed in them, i.e. protein-synthesizing complex of organelles because main function of chondroblasts- production of the organic part of the intercellular substance: proteins collagen and elastin, glycosaminoglycans (GAG) and proteoglycans (PG). In addition, chondroblasts are capable of reproduction and subsequently turn into chondrocytes. In general, chondroblasts provide appositional (superficial, neoplasms from the outside) growth of cartilage from 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 separate, but remain together - so-called isogenic groups are formed. Initially, they lie in one common lacuna, then an intercellular substance is formed between them and each cell of a given isogenic group has its own capsule. Chondrocytes are oval-round cells with basophilic cytoplasm. Under an electron microscope, the granular ER, Golgi complex, and mitochondria are clearly visible. protein synthesizing apparatus, because main function of chondrocytes- production of the organic part of the intercellular substance of cartilage tissue. The growth of cartilage due to the division of chondrocytes and their production of intercellular substance ensures interstitial (internal) growth of cartilage.

In isogenic groups, three types of chondrocytes are distinguished:

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, and the presence of mitochondria and free ribosomes in the cytoplasm. Division patterns are often observed in these cells, which allows them to be considered as a source of reproduction of isogenic groups of cells.

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

3. Chondrocytes III type have the lowest nuclear-cytoplasmic ratio, strong development and the ordered arrangement of the granular endoplasmic reticulum. These cells retain the ability to form and secrete protein, but their synthesis of glycosaminoglycnes is reduced.

In cartilage tissue, in addition to the cells that form the intercellular substance, there are also their antagonists - destroyers of the intercellular substance - these are chondroclasts(can be attributed to the macrophage system): quite large cells, in the cytoplasm there are many lysosomes and mitochondria. Chondroclast function- destruction of damaged or worn areas of cartilage.

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

GAGs (chondroethinsulfates, keratosulfates, hyaluronic acid);

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

The intercellular substance is highly hydrophilic, the water content reaches 75% of the cartilage mass, this determines the high density and turgor of the cartilage. Cartilaginous tissues in the deep layers do not have blood vessels; nutrition is diffuse through the vessels of the perichondrium.

Perichondrium is a layer of connective tissue covering the surface of cartilage. In the perichondrium they secrete external fibrous(from 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.

Hello my friends!

In this article we will look at what it is knee joint cartilage. Let's look at what cartilage is made of and what its function is. As you understand, in all joints of our body the cartilage tissue is the same, and everything described below also applies to other joints.

The ends of our bones in the knee joint are covered with cartilage, between them lie two menisci - these are also cartilages, but only slightly different in composition. Read about menisci in the article "". I will only say that cartilages and menisci differ in the type of cartilage tissue: bone cartilage is hyaline cartilage, and the menisci – fibrocartilage. This is what we will look at now.

The thickness of the cartilage covering the ends of the bone is on average 5-6 mm, it consists of several layers. Cartilage is dense and smooth, which allows bones to easily slide against each other during flexion and extension movements. Possessing elasticity, cartilage acts as a shock absorber during movements.

In a healthy joint, depending on its size, fluid is from 0.1 to 4 ml, the distance between cartilages (articular space) is from 1.5 to 8 mm, acid-base balance is 7.2-7.4, water is 95% , protein 3%. The composition of cartilage is similar to blood serum: 200-400 leukocytes per 1 ml, of which 75% are lymphocytes.

Cartilage is one of the types of connective tissue in our body. The main difference between cartilage tissue and others is the absence of nerves and blood vessels that directly feed this tissue. Blood vessels would not withstand the stress and constant pressure, and the presence of nerves there would be reflected in pain with every movement we made.

Cartilage is designed to reduce friction where bones connect. Cover both heads of the bone and inner side patella (kneecap). Constantly washed by synovial fluid, they ideally reduce friction in the joints to zero.

Cartilage does not have access to blood vessels and nutrition, respectively, and if there is no nutrition, then there is no growth or repair. But cartilage also consists of living cells and they also need nutrition. They receive nutrition from the same synovial fluid.

The meniscus cartilage is riddled with fibers, which is why it is called fibrocartilage and is denser and harder in structure than hyaline, therefore it has greater tensile strength and can withstand pressure.

Cartilage differs in its fiber ratio: . All this gives the cartilage not so much hardness as elasticity. Working like a sponge under load, cartilage and menisci are compressed, unclenched, flattened, stretched as you wish. They constantly absorb a new portion of liquid and give away the old one, forcing it to constantly circulate; the liquid becomes richer nutrients and again carries them to the cartilages. We'll talk about synovial fluid later.

Main components of cartilage

Articular cartilage - This is a complex fabric in its structure. Let's look at the main components of this fabric. make up almost half of the intercellular space in articular cartilage. Collagen in its structure consists of very large molecules, intertwined in triple spirals. This structure of collagen fibers allows cartilage to resist any type of deformation. Collagen gives tissue elasticity. give elasticity, the ability to return to its original state.

Second having great importance cartilage element – water, which is in large quantities contained in intercellular space. Water is unique natural element, it is not subject to any deformation, it can neither be stretched nor compressed. This adds rigidity and elasticity to the cartilage tissue. Moreover, than more water, the better and more functional the interarticular fluid. It spreads and circulates easily. With a lack of water, the joint fluid becomes more viscous, less fluid and, of course, performs its role in providing nutrition to the cartilage worse. !

Glycosamines– substances produced by the cartilage tissue of the joints are also part of the synovial fluid. By its structure, glucosamine is a polysaccharide and serves as an important component of cartilage.

Glucosamine is a precursor of glycosaminoglycans (the main component of articular cartilage), so it is believed that its additional use from the outside can contribute to the restoration of cartilage tissue.

In our body, glucosamine binds cells and is part of cell membranes and proteins, making fabrics stronger and more resistant to stretching. Thus, glucosamine supports and strengthens our joints and ligaments. With a decrease in the amount of glucosamines, the resistance of cartilage tissue to stress also decreases, and the cartilage becomes more sensitive to damage.

The issues of restoration of cartilage tissue and the production of necessary compounds and substances are dealt with chondrocytes.

Chondrocytes, by their nature, do not differ from other cells in terms of development and regeneration, their metabolic rate is quite high. But the problem is that there are very few of these same chondrocytes. In articular cartilage, the number of chondrocytes is only 2-3% of the mass of the cartilage. Therefore, the restoration of cartilage tissue is so limited.

So, nutrition of cartilage is difficult, renewal of cartilage tissue is also a very long-term process, and restoration is even more problematic. What to do?

Considering all of the above, we come to the conclusion that in order for the knee joint cartilage to recover, it is necessary to achieve high numbers and activity of chondrocyte cells. And our task is to provide them with adequate nutrition, which they can only receive through synovial fluid. But, even if the nutrition is the richest, it will not achieve its goal without moving the joint. That's why, If you move more, your recovery will be better!

With prolonged immobilization of a joint or the entire leg (plaster, splints, etc.), not only the muscles decrease and atrophy; It has been established that cartilage tissue also decreases, since it does not receive enough nutrition without movement. I will repeat myself for the hundredth time, but this is yet another proof of the need for constant movement. Man is created by nature in such a way that he must constantly run for food and run away from the mammoth, like other animals. Excuse me if I offend some of the “Crowns of Nature” by this. To scale evolutionary development, we have come too far for the body to behave differently; it has not yet adapted to other conditions of existence. And if the body feels that something in its composition is not needed or does not work well, it gets rid of it. Why feed something that is not beneficial? They stopped walking with their legs - their legs atrophied, the bodybuilder stopped pumping (using all his muscle mass) - he immediately deflated. Well, I got distracted.

In other articles, we will, of course, touch on issues (surgical and conservative methods), their nutrition and movement. This is what I, with my cartilage injury, am trying to implement. I'll tell you too.

In the meantime, my instructions: , COMPLETE VARIED NUTRITION,.

You can start right now.

All the best, don't get sick!