There are four main types of tissue in the human body: epithelial, nervous, muscle, and connective. Connective tissues are the most diverse group of tissues. Blood and skeletal tissue, fat and cartilage are all examples of connective tissues. What do they have in common? All of them are characterized by a high percentage of intercellular substance. For example, in the blood, the intercellular substance is represented by liquid plasma, in which blood cells are located, bone tissue is a dense intercellular substance - the bone matrix, in which individual cells are detected only under a microscope. What is intercellular substance, where is it located, who created it? The answer to the question "where is it" follows from the name - "intercellular substance", i.e. located between cells. Matter is made up of molecules. But who created these molecules? Of course, the living cells themselves.

Cartilage and bone tissues belong to the skeletal connective tissues of the body, they are united by a common function - supporting, a common source of development - mesenchyme, similarity in structure – and cartilaginous and bone tissues are formed by cells and intercellular substance prevailing in volume, having significant mechanical strength, which ensures that these tissues perform a supporting function.

cartilage tissue- tissues that are part of the respiratory organs (nose, larynx, trachea, bronchi), auricle, joints, intervertebral discs. In the fetus, they form a significant part of the skeleton. Most bones in embryogenesis develop in place of the so-called cartilage models, therefore, the cartilaginous skeleton performs a provisional (temporary) function. Cartilage plays an important role in bone growth.

Cartilage tissues are divided into three types: hyaline, elastic and fibrous (collagen-fiber) cartilage.

General structural and functional properties of cartilage tissues:

1) a relatively low level of metabolism (metabolism);

2) absence of blood vessels;

3) the ability for continuous growth;

4) strength and elasticity, the ability to reversible deformation.

hyaline cartilage tissue is the most common in the body among cartilage tissues. It forms the skeleton of the fetus, the ventral ends of the ribs, cartilage of the nose, larynx (partially), trachea, large bronchi, covers the articular surfaces. The name of this tissue is due to the similarity on the macropreparation with frosted glass (from Greek hyalos - glass).

Elastic cartilage tissue forms cartilages that are flexible and capable of reversible deformation. It consists of the cartilages of the auricle, external auditory canal, Eustachian tube, epiglottis, some cartilages of the bronchi. The intercellular substance is 90% protein elastin, which forms a network of elastic fibers in the matrix.

Fibrous cartilage tissue forms cartilages with significant mechanical strength. It is found in the intervertebral discs, pubic symphysis, sites of attachment of tendons and ligaments to bones or hyaline cartilage. This tissue never appears in isolation, it always passes into dense fibrous connective tissue and hyaline cartilage tissue.

There are no blood vessels in the cartilage tissue, so any cartilage is always covered with perichondrium, with the exception of articular cartilages that lack perichondrium (they receive nutrition from the surrounding synovial - articular fluid). The perichondrium is a connective tissue sheath containing blood vessels, nerve and cambial elements of cartilage tissue, its main function is to provide nutrition to the cartilage, which occurs diffusely from her vessels. Removal of the perichondrium causes the death of the corresponding section of the cartilage, due to the cessation of its nutrition.

With aging, calcification (calcification, mineralization) of cartilage occurs, which is then destroyed by cells - osteoclasts.

An interesting fact is that operations using donor cartilage from cadaveric material do not suffer from the problem of rejection of foreign material. This also applies to operations using artificial joints made of artificial materials. This is due to the fact that there are no blood vessels in the cartilage tissue.

The location of cartilage in the body n Cartilage tissue performs a shaping function in the fetus and a support in the adult body. Cartilaginous tissue can be found: n in the area of ​​​​the joints (covering the articular surface with a relatively narrow layer), n in the metaphyses (i.e., between the epiphysis and diaphysis) of tubular bones, n in the intervertebral discs, in the anterior sections of the ribs, in the wall of the respiratory organs (larynx , trachea, bronchi), etc.

Development n Like all other tissues of the internal environment of the body, skeletal tissues develop n from mesenchyme (the cells of which, in turn, are evicted from somites and splanchnotomes

Features n The special nature of the intercellular substance gives two important properties: n elasticity and n strength. n of the intercellular substance of these tissues. n In many cases, cartilage is covered with perichondrium, a fibrous connective tissue that is involved in the growth and nutrition of cartilage.

An important feature of cartilage tissue is the absence of blood vessels. Therefore, nutrients enter the cartilage - by diffusion from the vessels of the perichondrium. In some cases, there is no perichondrium - for example, in articular cartilage, since their surface should be smooth. Here, nutrition is carried out from the side of the synovial fluid and from the side of the underlying bone.

Cell composition n Chondroblasts are young cells, located in the deep layers of the perichondrium one by one and located closer to the surface of the cartilage n - small flattened cells capable of - proliferation and - synthesis of components of the intercellular substance of the cartilage. n granular EPS, Golgi complex, mitochondria are well expressed in them n Chondroblasts, releasing the components of the intercellular substance, "immure" themselves in it and turn into chondrocytes.

Functions n The main function of chondroblasts is the production of the organic part of the intercellular substance: collagen and elastin proteins, glycosaminoglycans (GAGs) and proteoglycans (PGs). n Chondroblasts provide appositional (superficial) cartilage growth from the side of the perichondrium.

Chondrocytes n a) Chondrocytes are the main type of cartilage cells. n - lie in special cavities of the intercellular substance (lacunae) and n - can divide by mitosis, while the daughter cells do not diverge, they remain together - isogenic groups (of 2-6 cells) are formed, originating from one cell. n b) They are n-larger (compared to chondroblasts) in size and oval in shape. n Well developed granular ER and Golgi complex

Functions n Chondrocytes that have stopped dividing actively synthesize components of the intercellular substance. n Due to the activity of chondrocytes, an increase in the mass of cartilage from the inside occurs - interstitial growth.

Chondroclasts n In the cartilage tissue, in addition to cells forming the intercellular substance, there are also their antagonists - 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 - the destruction of damaged or worn sections of cartilage.

Intercellular substance n The intercellular substance of cartilage tissue contains fibers and ground substance. n many fibrous structures: n-collagen fibers, n and in the elastic cartilage - elastic fibers.

n The intercellular substance is highly hydrophilic, 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,

n The main amorphous substance contains: n-water (70-80%), -mineral substances (4-7%), -organic component (10-15%), represented by n-proteoglycans and -glycoproteins.

Proteoglycans n The proteoglycan aggregate contains 4 components. n At the heart of the aggregate is a long thread of hyaluronic acid (1). n With the help of globular binding proteins (2), n linear (fibrillar) peptide chains of the so-called. core (core) protein (3). n In turn, oligosaccharide branches (4) depart from the latter.

These complexes n are highly hydrophilic; therefore, they bind a large amount of water and n provide high elasticity of the cartilage. n At the same time, they retain permeability to low molecular weight metabolites.

n The perichondrium is a layer of connective tissue that covers the surface of cartilage. In the perichondrium, an outer fibrous (from a dense, unformed CT with a large number of blood vessels) and an inner cell layer containing a large number of half-stem cells are isolated.

Hyaline cartilage n Outwardly, this tissue has a bluish-white color and looks like glass (Greek hyalos - glass). Hyaline cartilage - covers all articular surfaces of bones, is contained in the sternal ends of the ribs, in the airways.

Distinctive features n 1. The intercellular substance of hyaline cartilage in preparations stained with hematoxylin-eosin seems to be homogeneous, not containing fibers. n 2. around the isogenic groups there is a clearly defined basophilic zone - the so-called territorial matrix. This is due to the fact that chondrocytes secrete a large amount of GAG with an acidic reaction, so this area is stained with basic colors, i.e. basophilic. Weakly oxyphilic areas between the territorial matrices are called the interterritorial matrix. n

n A large number of proteoglycan aggregates. n Glycosaminoglycans. High elasticity depends on the content of GAGs n Chondroitin sulfates (chondroitin-6-sulfate, chondroitin-4-sulfate) n Keratan sulfates fibers). n Collagen IX, VI and X n Chondronectin protein

Cellular composition n a) Immediately below the perichondrium are n young chondrocytes (3) - n are somewhat larger in size and more oval in shape. n b) Deeper are n mature chondrocytes n large oval cells with light cytoplasm, n forming isogenic groups (4) of 2-6 cells.

n 1) Articular surfaces of bones. n 2) Airways. n 3) The junction of the ribs with the sternum.

Elastic cartilage n In the auricle, epiglottis, cartilages of the larynx. In the intercellular substance, in addition to collagen fibers, there are a large number of randomly located elastic fibers, which gives elasticity to the cartilage. Elastic cartilage contains less lipids, chondroitin sulfates and glycogen.

n b) in the thickness of the cartilaginous plate - isogenic groups of chondrocytes, n large, oval and n have a light cytoplasm. n Groups of chondrocytes usually have n-type chains (from 2, rarely more cells), oriented perpendicular to the surface.

Age-related changes n Due to the relatively low content of collagen fibrils and the absence of collagen X, there is no deposition of calcium salts (calcification) in the elastic cartilage n in case of malnutrition.

Fibrous cartilage n Fibrous cartilage is located at the points of attachment of tendons to bones and cartilage, intervertebral discs. In structure, it occupies an intermediate position between dense, formed connective and cartilage tissue. n

n In the intercellular substance, there are much more collagen fibers arranged oriented - they form thick bundles that are clearly visible under a microscope. Chondrocytes often lie singly along the fibers without forming isogenic groups. They have an elongated shape, a rod-shaped nucleus and a narrow rim of the cytoplasm.

n At the periphery, the fibrous cartilage gradually passes n into a dense, formed connective collagen fibers, which acquire orientation and go from one vertebra to another. tissue, oblique n b) In the central part of the disk, the fibrocartilage passes into the nucleus pulposus, which contains hyaline cartilage, type II collagen (in the form of fibrils)

Cartilage regeneration n Hyaline - insignificant. The perichondrium is mainly involved n Elastic - less prone to degeneration and does not calcify n Fibrous - weak regeneration, capable of calcification

Composition n Bone tissues consist of cells and intercellular substance. n Differenton of bone tissue includes n 1. stem and semi-stem (osteogenic) cells, n osteoblasts, n osteocytes n 2. osteoclasts.

Osteoblasts n Osteoblasts are the most functionally active cellular elements of differon during osteohistogenesis. In an adult organism, the source of cells that support the population of osteoblasts are cells of the dispersed cambium in the osteogenic layer of the periosteum. Osteoblasts have a cubic or prismatic shape. The nucleus is located eccentrically. Osteoblasts are typical actively synthesizing and secreting cells; secretion is carried out by the entire surface of the cell. The cell has a well-developed granular endoplasmic reticulum that fills almost the entire cytoplasm, many free ribosomes and polysomes,

Functions n secrete type I collagen, alkaline phosphatase, osteocalcin, osteopontin, transforming growth factors, osteonectin, collagenase, etc. n Highly differentiated osteoblasts are characterized by a gradual decrease in the activity of alkaline phosphatase, osteocalcin, osteopontin and the absence of proliferative activity.

n Role in the mineralization of the organic basis of the bone matrix. The process of mineralization of the bone matrix begins with the deposition of amorphous calcium phosphate. Calcium cations enter the extracellular matrix from the bloodstream, where they are in a protein-bound state. n In the presence of alkaline phosphatase synthesized by osteoblasts, glycerophosphates located in the intercellular substance are cleaved to form a phosphate anion. An excess of the latter leads to a local increase in Ca and P to a level at which calcium phosphate precipitates. The overwhelming fraction of the bone mineral is in the form of hydroxyapatite crystals. Crystals form on the collagen fibers of the bone matrix. The latter have structural features that contribute to this process. The fact is that the molecules of the precursor of collagen - tropocollagen are packed in a fiber in such a way that a gap remains between the end of one and the beginning of the other, called the zone of holes. It is in this zone that the bone mineral is initially deposited. Subsequently, the crystals begin to grow in both directions, and the process covers the entire fiber

n A significant role in the mineralization of the synthesized organic bone matrix belongs to matrix vesicles. Such vesicles are derivatives of the Golgi complex of osteoblasts, have a membrane structure and contain various enzymes necessary for mineralization reactions or their inhibition, as well as amorphous calcium phosphates. Matrix vesicles exit the cells into the extracellular space and release the products contained in them. The latter initiate mineralization processes.

Osteocytes n In terms of quantitative composition, the most numerous cells of bone tissue. These are process cells that lie in bone cavities - lacunae. The cell diameter reaches up to 50 microns. The cytoplasm is weakly basophilic. Organelles are poorly developed (granular EPS, PC and mitochondria). They don't share. n Function: take part in the physiological regeneration of bone tissue, produce the organic part of the intercellular substance. The thyroid hormone calcitonin has a stimulating effect on osteoblasts and osteocytes - the synthesis of the organic part of the intercellular substance increases and the deposition of calcium increases, while the concentration of calcium in the blood decreases.

Osteoclasts n n n Specialized macrophages. Their diameter reaches up to 100 microns. Different compartments of osteoclasts are specialized for specific functions. the basal zone, in it, as part of numerous (5 - 20) nuclei, the genetic apparatus of the cell is concentrated. light area in direct contact with the bone matrix. Thanks to it, the osteoclast adheres tightly to the bone along the entire perimeter, creating an isolated space between itself and the surface of the mineralized matrix. Adhesion of the osteoclast is provided by a number of receptors to the components of the matrix, the main of which are receptors for vitronectin. The selective permeability of this barrier makes it possible to create a specific microenvironment in the cell adhesion zone. the vesicular zone contains lysosomes. Enzymes, acidic substances are transported through the membrane of the corrugated border, carbonic acid H 2 CO 3 is formed; carbonic acid dissolves calcium salts, dissolved calcium is washed into the blood. carrying out demineralization and disorganization of the bone matrix, which leads to the formation of a resorption (erosive) Hausship lacunae.

Osteoclasts n osteoclasts have many nuclei and a large amount of cytoplasm; the zone of cytoplasm adjacent to the bone surface is called the corrugated border, there are many cytoplasmic outgrowths and lysosomes functions - the destruction of fibers and amorphous bone substance

n Thick collagen fibers, devoid of cementing substance, create a "brush border" appearance. Lysosomal enzymes proteolyze collagen and other matrix proteins. Proteolysis products are removed from osteoclastic lacunae by transcellular transport. In general, the process of reducing the river. H in the lacuna is carried out by two mechanisms: by exocytosis of the acidic contents of the vacuoles into the lacuna and due to the action of proton pumps - H + -ATPases localized in the membrane of the corrugated border. The source for hydrogen ions is water and carbon dioxide, which are the result of mitochondrial oxidation reactions.

Intercellular substance n 1. The inorganic part of the matrix It contains calcium (35%) and phosphorus (50%) (calcium phosphate and carbonate salts) mainly in the form of hydroxyapatite crystals (Ca 10 (PO 4) 6 (OH) 2 ) (3 Ca (OH) 2), n and a little - in the amorphous state, a small amount of magnesium phosphate - make up 70% of the intercellular substance. In plasma, inorganic phosphorus is contained in the form of anions HPO 4 -2 and H 2 PO 4 -2. n n The ratio of the organic and inorganic parts of the intercellular substance depends on age: in children, the organic part is slightly more than 30%, and the inorganic part is less than 70%, so their bones are less strong, but more flexible (not brittle); in old age, on the contrary, the proportion the inorganic part increases and the organic part decreases, so the bones become harder but more brittle - blood vessels are present:

The organic part of the bone matrix The organic part of the intercellular substance is represented by n collagen (collagen types I, X, V), very few glycosaminoglycans and proteoglycans. n - glycoproteins (alkaline phosphatase, osteonectin); n - proteoglycans (acid polysaccharides and glycosaminoglycans - chondroitin-4 - and chondroitin-6 sulfates, dermatan sulfate and keratan sulfate.); n - growth factors (fibroblast growth factor, transforming growth factors, bone morphogenetic proteins) - cytokines secreted by bone tissue and blood cells, which carry out local regulation of osteogenesis.

proteins that carry out cell adhesion n Osteonectin is a glycoprotein of bone and dentin, has a high affinity for type I collagen and hydroxyapatite, contains Ca-binding domains. It maintains the concentration of Ca and P in the presence of collagen. It is assumed that the protein is involved in the interaction of the cell and the matrix. n Osteopontin is the main component of the protein composition of the matrix, in particular interfaces, where it accumulates in the form of a dense cover called cementation lines (lamina limitans). Due to its physicochemical properties, it regulates the calcification of the matrix, specifically participates in the adhesion of cells to the matrix or matrix to the matrix. The production of osteopontin is one of the earliest manifestations of osteoblast activity. n Osteocalcin (OC) - a small protein (5800 Da, 49 amino acids) in the mineralized bone matrix, is involved in the process of calcification,

Classification n There are tubular, flat and mixed bones. The diaphyses of tubular bones and the cortical plates of flat and mixed bones are built from lamellar bone tissue covered with periosteum or periosteum. In the periosteum, it is customary to distinguish two layers: the outer one is fibrous, consisting mainly of fibrous connective tissue; internal, adjacent to the surface of the bone - osteogenic, or cambial.

Types of bone tissue Coarse-fibred (reticulofibrous) lamellar (fine-fibrous) The main feature Collagen fibers form a) Bone substance is thick bundles running in different (organized into plates). directions. b) Moreover, within the same plate, the fibers have the same direction, and within neighboring plates, they are different. Localization 1. Flat bones of the embryo. 2. Tubercles of bones; sites of overgrown cranial sutures. Almost all bones of an adult: flat (scapula, pelvic bones, skull bones), spongy (ribs, sternum, vertebrae) and tubular.

Lamellar bone tissue can have a spongy and compact organization. Cancellous bone substance Compact bone substance Localization Spongy substance consists of: the epiphyses of tubular bones, the inner layer (adjacent to the medullary canal) of the diaphysis of tubular bones, spongy bones, the inner part of flat bones. Most of the diaphyses of tubular bones and the surface layer of flat bones have a compact structure. Distinctive feature The spongy substance is built of avascular bone beams (beams), between which there are gaps - bone cells. There are practically no gaps in the compact bone substance: due to the growth of bone tissue deep into the cells, only narrow spaces for blood vessels remain - the so-called. central canals of osteons Bone marrow The cells of the spongy substance contain vessels that feed the bone, and red bone marrow is a hematopoietic organ. The medullary cavity of the diaphysis of tubular bones in adults contains yellow bone marrow - adipose tissue.

Structure They consist of bone plates a) In this case, the plates of the spongy substance are usually oriented along the direction of the bone beams, and not around the vessels, as in osteons of a compact substance. b) osteons can occur in sufficiently thick beams. The unit of structure is the bone plates. They consist of bone plates. In a compact substance, there are plates of 3 types: general (general) - surround the entire bone, osteon - lie in concentric layers around the vessel, forming the so-called. osteons; intercalary - located between osteons. osteons.

The structure of the osteon, the main structural unit of the bone In the center of each osteon is a blood vessel (1), around the latter there are several concentric layers of bone plates (2), called osteons. Osteons are delimited by a resorption (spinal) line (3). Intercalated bone plates (4) lie between the osteons, which are the remnants of previous generations of osteons. bone plates include cells (osteocytes), collagen fibers and a ground substance rich in mineral compounds. the fibers in the intercellular substance are indistinguishable, and the intercellular substance itself has a solid consistency.

BONE DEVELOPMENT FROM MESENCHYME (direct osteohistogenesis). An immature (coarse-fibered) bone is formed from the mesenchyme, which is subsequently replaced by a lamellar bone. There are 4 stages in development: n 1. formation of an osteogenic island - in the area of ​​bone formation, mesenchymal cells turn into osteoblasts n

2. formation of the intercellular substance - osteoblasts begin to form the intercellular substance of the bone, while some of the osteoblasts are inside the intercellular substance, these osteoblasts turn into osteocytes; the other part of the osteoblasts is on the surface of the intercellular substance,

3. calcification of the intercellular substance of the bone intercellular substance is impregnated with calcium salts. n a) At the third stage, so-called. matrix vesicles similar to lysosomes. They accumulate calcium and (due to alkaline phosphatase) inorganic phosphate. n b) When the bubbles burst, mineralization of the intercellular substance occurs, i.e., the deposition of hydroxyapatite crystals on the fibers and in the amorphous substance. As a result, bone trabeculae (beams) are formed - mineralized tissue areas containing all 3 types of bone cells - n n n from the surface - osteoblasts and osteoclasts, and in depth - osteocytes.

4. The formation of osteons n Subsequently, in the inner part of the flat bone n, the primary spongy tissue is replaced by a secondary one, n which is already built from bone plates oriented along the beams.

The development of lamellar bone tissue is closely related to 1. the process of destruction of individual sections of the bone and the ingrowth of blood vessels into the thickness of the reticulofibrous bone. Osteoclasts are involved in this process both during embryonic osteogenesis and after birth. 2. vessels growing to the trabeculae. In particular, around the vessels, the bone substance is formed in the form of concentric bone plates that make up the primary osteons.

BONE DEVELOPMENT IN THE SITE OF THE CARTILAGE (indirect osteogenesis) n a mature (lamellar) bone immediately forms in place of the cartilage n 4 stages are distinguished in development: n 1. cartilage formation - hyaline cartilage is formed in place of the future bone

2. perichondral ossification takes place only in the area of ​​the diaphysis in the area of ​​the diaphysis, the perichondrium turns into the periosteum, in which osteogenic cells appear, then osteoblasts, due to the osteogenic cells of the periosteum, on the surface of the cartilage, bone formation begins in the form of common plates that have a circular course, like the annual rings of a tree

3. endochondral ossification n Occurs both in the area of ​​the diaphysis and in the area of ​​the epiphysis; blood vessels grow inside the cartilage, where there are osteogenic cells - osteoblasts, due to which bone is formed around the vessels in the form of osteons, and osteoclasts. n simultaneously with the formation of bone, the destruction of cartilage occurs

zone of vesicular cartilage (4). At the border of the still preserved cartilage, the cartilage cells are in a swollen, vacuolated state, i.e., they have a bubble-shaped zone of columnar cartilage (5). In the adjacent region of the epiphysis, cartilage continues to grow and the proliferating cells line up in columns along the long axis of the bone.

n a) Subsequently, ossification of the epiphysis itself (with the exception of the articular surface) will occur - by the endochondral way. n b) That is, mineralization will also occur here, n vessels will sprout here, the cartilage substance will collapse and first coarse fibrous, n and then lamellar bone tissue will form.

n 4. restructuring and growth of the bone - the old parts of the bone are gradually destroyed and new ones are formed in their place; due to the periosteum, common bone plates are formed, due to the osteogenic cells located in the adventitia of the bone vessels, osteons are formed. Between the diaphysis and the epiphysis, a layer of cartilaginous tissue is preserved, due to which the growth of the bone in length continues until the end of the period of growth of the body in length, that is, up to 20-21 years.

Bone growth Sources of growth Until the age of 20, tubular bones grow: in width - by appositional growth from the side of the perichondrium, in length - due to the activity of the metaepiphyseal cartilaginous plate. Metaepiphyseal cartilage a) Metaepiphyseal plate - part of the epiphysis adjacent to the diaphysis and retaining (unlike the rest of the epiphysis) cartilaginous structure. b) It has 3 zones (in the direction from the epiphysis to the diaphysis): the border zone - contains oval chondrocytes, the zone of columnar cells - it is this that ensures the growth of cartilage in length due to the multiplication of chondrocytes, the zone of vesicular cartilage - borders on the diaphysis and undergoes ossification . c) Thus, 2 processes simultaneously occur - the growth of cartilage (in the columnar zone) and its replacement with bone (in the vesicular zone).

Regeneration n Regeneration and growth of the bone in thickness is carried out due to the periosteum and endosteum. All tubular bones, as well as most flat bones, are histologically fine-fibered bone.

n In the bone tissue, two oppositely directed processes constantly occur - resorption and neoplasm. The ratio of these processes depends on several factors, including age. Restructuring of bone tissue is carried out in accordance with the loads acting on the bone. n The process of bone tissue remodeling occurs in several phases, in each of which certain cells play the leading role. Initially, the area of ​​bone tissue to be resorbed is "marked" by osteocytes using specific cytokines (activation). The protective layer on the bone matrix is ​​destroyed. Precursors of osteoclasts migrate to the bare surface of the bone, merge into a multinuclear structure - a symplast - a mature osteoclast. At the next stage, the osteoclast demineralizes the bone matrix (resorption), gives way to macrophages, which complete the destruction of the organic matrix of the bone intercellular substance and prepare the surface for osteoblast adhesion (reversion). At the last stage, precursors arrive in the destruction zone, differentiating into osteoblasts, they synthesize and mineralize the matrix in accordance with the new conditions of static and dynamic load on the bone (formation).

Hello my friends!

In this article, we will explore what is cartilage of the knee. Consider what cartilage consists of and what function they have. As you understand, cartilage tissue is the same in all joints of our body, and everything described below 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 cartilage and menisci differ in the type of cartilage tissue: bone cartilage is hyaline cartilage, and the menisci fibrocartilage. This is what we will analyze now.

The thickness of the cartilage covering the ends of the bone is on average 5-6 mm, it consists of several layers. The cartilage is dense and smooth, which allows the bones to easily slide relative to each other during flexion and extension movements. With 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 cartilage (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 a type 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. The blood vessels would not withstand the loads and constant pressure, and the presence of nerves there would give off pain with each of our movements.

Cartilage is designed to reduce friction at the junctions of bones. They cover both heads of the bone and the inner side of the patella (patella). Constantly bathed in synovial fluid, they ideally reduce the processes of 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 is also made up of living cells, and they also need nutrition. They receive food due to the same synovial fluid.

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

Cartilages differ in the ratio of fibers: . All this gives the cartilage not only hardness, but also elasticity. Working like a sponge under stress, cartilage and menisci are compressed, unclenched, flattened, stretched as you wish. They constantly absorb a new portion of the liquid and give the old one, make it constantly circulate; at the same time, the liquid is enriched with nutrients and again carries them to the cartilage. We will talk about synovial fluid later.

The main components of cartilage

articular cartilage is a complex fabric. Consider 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 helixes. This structure of collagen fibers allows the cartilage to resist any kind of deformation. Collagen gives tissue elasticity. give elasticity, the ability to return to its original state.

The second important element of cartilage is water, which is found in large quantities in the intercellular space. Water is a unique natural element, it is not subject to any deformation, it cannot be stretched or compressed. This adds to the cartilage tissue stiffness and elasticity. In addition, the 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, does not perform its role in providing nutrition to the cartilage. !

Glycosamines- substances produced by the cartilaginous tissue of the joints are also part of the synovial fluid. Structurally, glucosamine is a polysaccharide that serves as an important constituent 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 help restore cartilage.

In our body, glucosamine binds cells and is part of cell membranes and proteins, making tissues 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, the cartilage becomes more susceptible to damage.

The restoration of cartilage tissue and the production of the 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 sufficiently 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 cartilage. Therefore, the restoration of cartilage tissue is so limited.

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

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

With prolonged immobilization of the joint or the entire leg (gypsum, splints, etc.), not only 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 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 the Creation of Nature" by this. On the scale of evolutionary development, we have gone too little way 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 does not benefit? They stopped walking with their feet - the legs atrophy, the bodybuilder stopped swinging (using all his muscle mass) - he was immediately blown away. Well, I digress.

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

In the meantime, my instructions are: , COMPLETE VARIOUS FOOD,.

You can start this minute.

All the best, don't worry!

The basis of the musculoskeletal system are cartilage tissues. It is also part of the structures of the face, becoming the place of attachment of muscles and ligaments. The histology of cartilage is represented by a small number of cellular structures, fibrous formations and nutrients. This ensures sufficient damping function.

What does it represent?

Cartilage is a type of connective tissue. Structural features are increased elasticity and density, due to which it is able to perform a supporting and mechanical function. Articular cartilage consists of cells called chondrocytes and the main substance, where the fibers are located, providing the elasticity of the cartilage. Cells in the thickness of these structures form groups or are placed separately. The location is usually near the bones.

Cartilage varieties

Depending on the features of the structure and localization in the human body, there is such a classification of cartilage tissues:

• Hyaline cartilage contains chondrocytes, placed in the form of rosettes. The intercellular substance is larger in volume than the fibrous substance, and the filaments are represented only by collagen.
• Elastic cartilage contains two types of fibers - collagen and elastic, and the cells are arranged in columns or columns. This type of fabric has a lower density and transparency, having sufficient elasticity. This matter makes up the cartilages of the face, as well as the structures of the middle formations in the bronchi.
• Fibrous cartilage is a connective tissue that performs the functions of strong shock-absorbing elements and contains a significant amount of fibers. Localization of the fibrous substance is located throughout the musculoskeletal system.

Properties and structural features of cartilage tissue

On the histological preparation, it is seen that the tissue cells are located loosely, being in an abundance of intercellular substance.

All types of cartilage are able to take on and resist the compressive forces that occur during movement and load. This ensures an even distribution of gravity and a reduction in the load on the bone, which stops its destruction. The skeletal zones, where friction processes constantly occur, are also covered with cartilage, which helps protect their surfaces from excessive wear. The histology of this type of tissue differs from other structures in a large amount of intercellular substance, and the cells are located loosely in it, form clusters or are located separately. The main substance of the cartilaginous structure is involved in the processes of carbohydrate metabolism in the body.

This type of material in the human body, like the rest, is composed of cells and intercellular substance of cartilage. A feature in a small number of cellular structures, due to which the properties of the tissue are provided. Mature cartilage refers to a loose structure. Elastic and collagen fibers perform a supporting function in it. The general plan of the structure includes only 20% of the cells, and everything else is fibers and amorphous matter. This is due to the fact that due to the dynamic load, the vascular bed of the tissue is poorly expressed and therefore it is forced to feed on the main substance of the cartilage tissue. In addition, the amount of moisture that is in it performs shock-absorbing functions, smoothly relieving tension in bone tissues.

What are they made of?

The trachea and bronchi are composed of hyaline cartilage.

Each type of cartilage has unique properties due to the difference in location. The structure of hyaline cartilage differs from the rest in a smaller number of fibers and a large filling with amorphous matter. In this regard, it is not able to withstand heavy loads, since its tissues are destroyed by bone friction, however, it has a rather dense and solid structure. Therefore, it is characteristic that the bronchi, trachea and larynx consist of this type of cartilage. Skeletal and musculoskeletal structures are formed mainly by fibrous matter. Its variety includes part of the ligaments connected to hyaline cartilage. The elastic structure occupies an intermediate location relative to these two tissues.

Cellular composition

Chondrocytes do not have a clear and ordered structure, but are more often located completely randomly. Sometimes their clusters resemble islets with large areas of absence of cellular elements. At the same time, a mature cell type and a young one, which is called chondroblasts, are located together. They are formed by the perichondrium and have interstitial growth, and in the process of their development they produce various substances.

Chondrocytes are a source of components of the intercellular space, it is thanks to them that there is such a chemical table of elements in the composition of an amorphous substance:

Hyaluronic acid is contained in an amorphous substance.

• proteins;
• glycosaminoglycans;
• proteoglycans;
• hyaluronic acid.

In the embryonic period, most bones are hyaline tissues.

The structure of the intercellular substance

It consists of two parts - these are fibers and an amorphous substance. At the same time, fibrillar structures are randomly located in the tissue. The histology of cartilage is affected by the production by its cells of chemicals responsible for the density, transparency and elasticity. The structural features of hyaline cartilage are the presence of only collagen fibers in its composition. If an insufficient amount of hyaluronic acid is released, then this destroys tissues due to degenerative-dystrophic processes in them.

Blood flow and nerves

Cartilage tissue structures do not have nerve endings. Pain reactions in them are presented only with the help of bone elements, while the cartilage will already be destroyed. This causes a large number of untreated diseases of this tissue. Few nerve fibers are present on the surface of the perichondrium. The blood supply is poorly represented and the vessels do not penetrate deep into the cartilage. Therefore, nutrients enter the cells through the main substance.

Struct functions

The auricle is formed from this tissue.

Cartilage is the connecting part of the human musculoskeletal system, but is sometimes found in other parts of the body. The histogenesis of cartilage tissue goes through several stages of development, due to which it is able to provide support, at the same time being fully elastic. They are also part of the external formations of the body such as the cartilages of the nose and auricles. They are attached to the bone ligaments and tendons.

Age-related changes and diseases

The structure of cartilage tissue changes with age. The reasons for this lie in the insufficient supply of nutrients to it, as a result of a violation of trophism, diseases arise that can destroy fibrous structures and cause cell degeneration. A young body has a much larger supply of fluid, so the nutrition of these cells is sufficient. However, age-related changes cause "drying" and ossification. Inflammation due to bacterial or viral agents can cause cartilage degeneration. Such changes are called "chondrosis". At the same time, it becomes less smooth and unable to perform its functions, as its nature changes.

Signs that the tissue has been destroyed are visible during histology analysis.

How to eliminate inflammatory and age-related changes?

To cure cartilage, drugs are used that can restore the independent development of cartilage tissue. These include chondroprotectors, vitamins and products that contain hyaluronic acid. The right diet with enough protein is important, because it is a stimulator of body regeneration. It is shown to keep the body in good shape, because excess body weight and insufficient physical activity cause the destruction of structures.

Which helps to ensure its mobility, or as a separate anatomical formation outside the skeleton. In direct connection with the bone are articular cartilages (the most representative group), intervertebral discs, cartilages of the ear, nose, pubic symphysis. Separate anatomical formations make up a group of cartilages of the airways (larynx, trachea, bronchi), stroma of the heart.

Cartilages perform integrative-buffer, shock-absorbing, form-supporting functions, participate in the development and growth of bones. Biomechanical functions are carried out due to the elastic properties of cartilage.

The bulk of the cartilage is represented by cartilaginous tissue. It consists of non-cellular and cellular elements. Non-cellular elements are the defining functional link of the cartilaginous tissue and constitute the main part. This part is conditionally divided into fibrous collagen and elastic structures and. The basis of collagen structures is collagen protein, from which all fibrous cartilage structures are built: molecules, microfibrils, fibrils, fibers. Elastic structures are present in some cartilages (auricle, epiglottis, perichondrium) in the form of elastin and elastic glycoprotein molecules, elastic fibrils and fibers, plastic glycoprotein microfibrils, amorphous elastin.

Fibrous structures and cellular elements of the cartilage are surrounded by the main substance of the integrative-buffer metabolic environment of the connective tissue, which has a gel-like consistency. Its main components are proteoglycans and the water they retain, through which all metabolic processes are carried out. It also provides the shock-absorbing function of the cartilage.

An important part of the cartilaginous tissue is the interstitial space (interfibrous and intercellular), which is a single system of peculiar channels, the walls of which are formed by fibrous structures. This channel is filled with the main substance and is the second link in the microcirculation. The interstitial fluid moves along it under the action of mechanical pressure, capillary and osmotic forces, which also provides the biomechanical function of the cartilage tissue. The channels are in the form of tubes, slits of rounded cavities.

Cellular elements of cartilage create cartilage, carry out its constant renewal and restoration. Cartilage cells include cambial cartilage cells, chondroblasts and chondrocytes.

There are three types of cartilage - hyaline, elastic and fibrous. The basis for the isolation of hyaline cartilage is their external - reminiscent. This group includes cartilage articular, airways, nose. Elastic cartilage is distinguished by the qualitative composition of fibrous structures, although outwardly they are identical to hyaline cartilage. These are the cartilages of the ear and epiglottis. Fibrous cartilages are distinguished on the basis of structural organization. Their connective tissue backbone is mainly built of collagen fibers, unlike other cartilages, where collagen fibrils form the basis.

H.'s damages note as a result of action of physical (mechanical, thermal, etc.), chemical and other traumatic agents. With mechanical damage to H., the integrity of the perichondrium may be disturbed (see Perichondritis), parts of the cartilaginous covering of the articular end of the bone, for example, transchondral (see Knee joint) , cartilaginous zone of bone growth (- see Fractures) , individual cartilages (nose, larynx, ear, ribs, etc.). X. can be damaged as a result of prolonged action of weak mechanical agents (see Microtrauma) .

H.'s defeats are noted at many dystrophic processes (see. Osteoarthrosis , Osteochondrosis , Osteochondropathy (Osteochondropathy) , metabolic disorders (for example, Kashin - Beka disease (Kashina - Beka disease) , Ochronose) . In some cases (, sepsis of various etiologies) are accompanied by damage to cartilaginous structures.

Chondroma accounts for 10-15% of all benign bone tumors. It occurs mainly at the age of 20-30 years in both sexes. It can be located both in the central and in the peripheral part of the bone and, accordingly, is designated as "" and "". Favorite - metacarpal and metatarsal bones, less often - long tubular bones and pelvic bones. In most cases, chondromas are multiple. Solitary tumors are more common in long bones and pelvic bones. Chondroma causes few clinical symptoms due to its slow growth. With the defeat of the hands and feet, there are small, slowly increasing thickening of the bones. When localized in the distal extremities, there are pathological ones.

Osteochondroma ( osteo-cartilaginous) consists of a bone outgrowth covered with a layer of cartilage. Usually localized in the metaphysis of long bones, on the ribs, pelvic bones. may be solitary or multiple, sometimes hereditary. They may not show up clinically. When large sizes are reached, deformation of the affected bone and pain occur due to pressure on.

Chondroblastoma is extremely rare, mainly in young people. It is localized in the area of ​​the epiphyseal-cartilaginous plate of long tubular bones and in the diaphysis. atypical - moderate pain, slight swelling in the area of ​​the affected bone, (restriction of movement in the adjacent joint.

Chondromyxoid fibroma is rare. It occurs in young people. More often located in the bones that form. It is clinically manifested by minor pain, movement restrictions, less often by a palpable tumor.

The leading diagnostic method is radiological. Recognition of multiple chondromas of the hands and feet usually does not cause difficulties. It is more difficult to diagnose chondromas of long bones, chondroblastomas and chondromyxoid fibromas. They have to be differentiated from slow-onset chondrosarcomas, giant cell tumors, and other bone lesions. Diagnostic difficulties are overcome with the help of histological examination of the material obtained from the lesion. The only method of treatment of these neoplasms is surgical. Chondromas of long bones and osteochondromas require special attention, since they are more likely to undergo malignancy after non-radical operations than other benign tumors. With enchondroma of a long tubular bone, segmental is shown. Small bone chondromas require removal of the entire affected bone. favorable after a radical operation.

Of great importance for resolving the issue of the onset of malignancy is the observation of the dynamics of clinical and radiological signs. The main symptom of malignant chondroma is a sudden increase in the size of a previously long-existing tumor. In doubtful cases, repeated X-ray examinations should be carried out monthly.

Chondrosarcoma is relatively common, accounting for 12-18% of all bone sarcomas. It is observed mainly at the age of 25-60 years, in men 2 times more often. The predominant localization is the bones of the pelvis, belts of the upper limbs, ribs. The proximal articular cones of the femur and humerus are often affected. In 8-10% of patients, chondrosarcoma develops secondarily from previous pathological processes: chondromas, osteochondral exostoses, dyschondroplasia (Ollier), deforming osteosis (Paget's disease) .

The main symptoms in primary chondrosarcoma are the presence of a tumor and pain, which increase as the tumor grows. According to the clinical course, X-ray morphological manifestations, chondrosarcomas differ significantly from each other, which is due to the peculiarities of the microscopic structure. Highly differentiated tumors are characterized by long-term with low severity of symptoms, which is typical for people over 30 years of age. With anaplastic chondrosarcomas (more often in young people), the duration of symptoms does not exceed 3 months.

The diagnosis is established taking into account clinical and radiological signs and morphological data. The volume of surgical intervention depends on the location and degree of malignancy of the tumor. With 1-2 degrees of malignancy, segmental resection of the tubular bone with endoprosthetics is possible. In the case of the anaplastic variant, especially in young people, the limbs are shown. With highly differentiated chondrosarcomas, the 5-year survival rate is up to 90%. In the case of the anaplastic variant, the prognosis is unfavorable - 5% of patients survive for 5 years.

Bibliography: Histology, ed. Yu.I. Afanasiev and N.A. Yurina, p. 310, M., 1989; Clinical, ed. N.N. Blokhin and B.E. Peterson, p. 250, M., 1971; Knysh I.T., Korolev V.I. and Tolstopyatov B.A. from cartilaginous tissue, Kyiv, 1986; Pavlova V.N. etc. Cartilage. M., 1988; Pathological human tumors, ed. ON THE. Kraevsky and others, p. 397, M., 1982; Trapeznikov N.N. etc. Tumors of bones, M., 1986; Ham A. and Cormac D. Histology, . from English, vol. 3, M., 1983.

II (cartilago)

anatomical formation consisting of cartilaginous tissue and performing a supporting function.

1. Small medical encyclopedia. - M.: Medical Encyclopedia. 1991-96 2. First aid. - M.: Great Russian Encyclopedia. 1994 3. Encyclopedic dictionary of medical terms. - M.: Soviet Encyclopedia. - 1982-1984.

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