And especially deep-water content of minerals is relatively small, and they are distinguished by a soft fibrous structure.

The surface of the bone can represent different deepening (grooves, pits, etc.) and elevations (corners, edges, ribs, ridges, tubercles, etc.). Reliability serve to connect bones among themselves or to attach muscles and are the stronger than developed, the more developed muscles. The surfaces are the so-called "nutrient holes" (ForaMina Nutritiva) through which the feed and blood vessels are included in the bone.

In the bones distinguish the dense and spongy bone substance. The first is distinguished by homogeneity, hardness and constitutes the outer layer of the bone; It is especially developed in the middle of the tubular bones and is sophisticated to the ends; In wide bones, it is 2 plates separated by a layer of spongy substance; In short, it in the form of a thin film clothes the bone outside. The spongy substance consists of plates intersecting in various directions, forming a cavity system and holes, which in the middle of long bones merge into a large cavity.

The outer surface of the bone is dressed so-called perceivers (Periosteum), a shell of connective tissue containing blood vessels and special cellular elements and employees for nutrition, growth and bone recovery. Internal bone cavities are made of a special soft cloth called bone marrow.

Cellular structure

According to the microscopic structure, the bone substance represents a special type of connective tissue (in a broad sense of the word), bone tissue, characteristic features of which: solid, soaked with mineral salts, fibrous intercellular substance and star, equipped with numerous process, cells.

Bone marrow

Internal bone cavities contain soft, gentle, rich cells and supplied with blood vessels, a mass called bone marrow (in birds, part of the cavities is filled with air). There are three types of it: mucous (only in some emerging bones), red or lymphoid (eg in epiphyses of tubular bones, in the spongy vertebrae substance), and yellow or fat (most common). The main form is a red bone marrow, it observes a tender connecting and wannaya base, rich in vessels, very similar to leukocytes bone marrow or lymphatic cells, cells painted with hemoglobin and considered to go to red blood cells, colorless cells containing in red balls, and Multi-core large ("giant") cells, so calling. Mieloplasts.

When depositing in the cells (usually star-shaped) bases of fat and reduce the number of lymphatic elements, the red brain goes into yellow, and when the fat disappears and the reduction of lymphatic elements is approaching the mucous membrane.

The development and growth of bones

The development of the bone occurs in 2 ways: or from connective tissue, or cartilage. The first way to develop K. Vault and side departments of the skull, lower jaw and, according to some, the clavicle (and the lower vertebrates and some others) are so called. Cooking or tight bones. They develop directly from the connecting tissue; Its fibers are somewhat condensed, bone cells appear between them and lime salts are deposited between the latter; The islands of bone tissue are first form, which are then merged with each other. Most skeleton bones develop from the cartilage foundation that has the same form as the future bone. The cartilage tissue is subjected to the process of destruction, suction and instead of it is formed, with the active participation of a special layer of educational cells (osteoblasts), bone tissue; This process can go both from the surface of the cartilage, from the dressing of its shell, the perichondria that turns into the perichduction, and inside it. Commodably the development of bone tissue begins at several points, epiphysis and diaphysis have separate points in the tubular bones.

The length of the bone in length occurs mainly in parts of not yet soldered (in tubular bones between epiphyses and diaphysia), but partly and by depositing new tissue particles between existing ("intussusceptition"), which prove repeated measurements of the distances between the epipsets into the bone, nutrition holes, etc.; The thickening of the bones occurs by postponement on the surface of the bone of the new layers ("Apposition") thanks to the activities of Osteoblasts periosteum. This latter has a highly ability to reproduce destroyed and remote parts of the bone. It is determined by the action of fractures. In parallel with increasing bone, the suction ("resorption") of some areas of bone tissue, and the so-called osteoclasts are played with an active role ("cells that destroy the bone"), multi-core elements that are observed on the walls of the brain cavities, in the periosteum and the walls of large cavities In the bone (for example, the Gaimores of the sinus, etc.).

Bone compounds

Syndesology - the doctrine of bone connections

  • Synartrosis - continuous bone joints, earlier development, fixed or low-modular function.
    • Syneximum - bones are connected by means of connective tissue.
      • inter-emergency membrane (between bones of forearm or leg)
      • bundles (in all joints)
      • rodniki
      • seam
        • protectors (most bones of the skull
        • scaly (between the edges of temporal and dark bones)
        • smooth (between the bones of the facial skull)
    • Synchondrosis - bones are connected by cartilage tissue. For cartilage fabric:
      • hyaline (between ribs and sternum)
      • fibrous
      The duration of its existence differences synchronosis:
      • temporary
      • permanent
    • Synostosis - bones are connected by bone tissue.
  • Diarrosis is interrupted compounds, later development and more movable functions. Classifications of joints:
    • by the number of articular surfaces
    • in form and function
  • Gemiarrosis is a transitional form from continuous to be interrupted or back.

see also

Links

  • Medical tools for skin plastic and bone treatment
Musculoskeletal system, connecting fabric: bone and cartilage
Cartilage
Crying growth soup, bone corner, epiphysear plate
Cells chondroblast, Chondrocyte
Types of cartilage fabric hyalin, elastic, fibrous
Bones
Ospecification endesmal, endochondral
Cells osteoblast, osteocyte, osteoclast
Types of bone tissue spongy, compact
Departments subchondral bone, epiphysis, metaphiz, diaphysis
Structure osteon, Gaverca Channels, Folkman Canals, Endost, Vescar, bone marrow
The form long, short, flat, sesamovoid

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Watch what is "bone tissue" in other dictionaries:

    BONE - Fig. 1. Bone cells (view from the surface). Fig. 1. Bone cells (surface view): 1 - core; 2 - cytoplasm; 3 - processes. bone tissue, one of the types of connective tissue; A solid occurrend fabric, which is part of ... ... Veterinary Encyclopedic Dictionary

    See bone ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

    Bone - One of the varieties of connective tissue. Differs in high mineralization of the intercellular substance. Mineral structures are formed on protein collagen, the three-part spiral structure of which is a matrix for depositing mineral ... ... Physical anthropology. Illustrated Dictionary.

    BONE - a type of connective tissue, which makes up the base of the bones of the vertebrate skeleton; Consists of cells and a mineralized intercellular substance. They distinguish roughly fibrous and lamellar K. t. In the first (available in the embryos, and in adults only ... ... Psychomotorika: Slovar-Directory

The bone is complex matter, it is a complex anisotropic uneven vital material with elastic and viscous properties, as well as a good adaptive function. All excellent bone properties are inseparable unity with their functions.

Bone functions mainly has two sides: one of them is the formation of a skeletal system used to maintain the human body and maintaining its normal form, as well as to protect its internal organs. The skeleton is part of the body to which the muscles are attached and which provides conditions for their reduction and body movement. The skeleton itself performs an adaptive function by consistently changing its form and structure. The second side of the bone function is that by regulating the Ca 2+, H +, HPO 4 + concentration in the blood electrolyte maintain the balance of mineral substances in the human body, that is, the function of the blood formation, as well as the conservation and exchange of calcium and phosphorus.

The shape and structure of bones are different depending on the functions performed. Different parts of the same bone due to their functional differences have different shapes and structure, for example, the aqueous of the femoral bone and the head of the femoral bone. Therefore, a complete description of the properties, structures and functions of bone material is an important and challenging task.

Bone fabric structure

"Fabric" is a combined formation consisting of special homogeneous cells and performing a specific function. In bone tissues contain three components: cells, fibers and bone matrix. Below are the characteristics of each of them:

Cells: There are three types of cells in bone tissues, these are osteocytes, osteoblast and osteoclast. These three types of cells are mutually converted and mutually combined with each other, absorbing old bones and generating new bones.

Bone cells are inside the bone matrix, these are the main bone cells in the normal state, they have the shape of a flattened ellipsoid. In bone tissues, they provide metabolism to maintain the normal state of the bones, and in much conditions they can turn into two other types of cells.

Osteoblast has the shape of a cube or a dwarf column, they are small cell ledges, located in a rather right order and have a large and round cell core. They are located at one end of the body of the cell, protoplasm has alkaline properties, they can form an intercellular substance from fibers and mucopolysaccharide proteins, as well as from alkaline cytoplasm. This leads to precipitation of calcium salts in the idea of \u200b\u200bneedle-shaped crystals located among the intercellular substance, which is then surrounded by Osteoblast cells and gradually turns into an osteoblast.

Osteoclast is multi-core giant cells, diameter can reach 30 - 100 μm, they are most often located on the surface of the absorbed bone tissue. Their cytoplasm is acidic, inside it contains acid phosphatase capable of dissolving bone inorganic salts and organic substances, transferring or throwing them into other places, thereby weakening or removing bone tissues in this place.

Bone matrix is \u200b\u200balso called an intercellular substance, it contains inorganic salts and organic matter. Inorganic salts are also called inorganic components of bones, their main component are hydroxyl apatite crystals with a length of about 20-40 Nm and about 3-6 Nm wide. They mainly consist of calcium, phosphorous radicals and hydroxyl groups forming, on the surface of which are Na +, K +, Mg 2+ ions, and others. Inorganic salts are approximately 65% \u200b\u200bof the total bone matrix. Organic substances are mainly represented by mucopolysaccharide proteins forming collagen fibers in the bone. The crystals of hydroxyl apatite are located rows along the axis of collagen fibers. Collagen fibers are located unequal, depending on the inhomogeneous nature of the bone. In the intertwing reticular fibers of bones, collagen fibers are connected together, and in the bones of other types, they are usually located slender rows. The hydroxyl apatite is connected together with collagen fibers, which gives the bone high compressive strength.

Bone fibers mainly consists of collagen fiber, so it is called bone collagen fiber, the beams of which are located in layers in the right rows. This fiber is tightly connected to inorganic components of the bone, forming a bone-shaped structure, so it is called the bone plate or lamellar bone. In the same bone plate, most of the fibers are located in parallel to each other, and the layers of fibers in two adjacent plates are intertwined in one direction, and bone cells are cleaned between the plates. Due to the fact that the bone plates are located in different directions, the bone substance has quite high durability and plasticity, it is able to rationally perceive compression from all directions.

In adults, the bone tissue is almost completely represented in the form of a lamellar bone, and, depending on the form of the arrangement of bone plates and their spatial structure, this fabric is divided into dense bone and spongy bone. The dense bone is located on the surface layer of abnormal flat bone and on the diaphysis of long bone. Its bone substance is dense and durable, and bone plates are located in a rather right order and are closely connected to each other, leaving only a small space in some places for blood vessels and nervous channels. The spongy bone is located in its deep part, where many trabeculs intersect, forming a mesh in the form of bee honeycombs with different types of holes. The openings of the cells are filled with bone marrow, blood vessels and nerves, and the location of the Trabecus coincides with the direction of power lines, so although the bone and loose, but it is able to withstand a fairly large load. In addition, the spongy bone has a huge surface area, so it is also called a coat having the shape of the sea sponge. As an example, a human pellet can be cited, the average volume of which is 40 cm 3, and the surface of the dense bone is 80 cm 2, while the surface area of \u200b\u200bthe spongy bone reaches 1600 cm 2.

Morphology of bone

From the point of view of morphology, the size of the bones of unequal, they can be divided into long, short, flat bones and bones of the wrong shape. Long bones have a tube shape, the middle part of which is a diaphone, and both ends - epiphysis. Epiphesis is relatively thick, has a joint surface formed with neighboring bones. Long bones are mainly located on the limbs. Short bones have almost a cubic shape, most often are in parts of the body, experiencing quite significant pressure, and at the same time they must be mobile, for example, it is the bones of the wrist and bones are repulsed. Flat bones have the form of plates, they form the walls of the bone cavity and perform a protective role for organs inside these cavities, for example, as a skull bone.

The bone consists of bone substance, bone marrow and periosteum, and also has an extensive network of blood vessels and nerves, as shown in the figure. The long femoral bone consists of a diaphysis and two convex epiphyseal ends. The surface of each epiphyseal end is covered with cartilage and forms a smooth joint surface. The friction coefficient in the space between cartilage in the junction area is very small, it may be below 0.0026. This is the lowest well-known friction force between solid bodies, which allows the finishing and neighboring bone tissues to create a highly efficient joint. The epiphysear plate is formed from calcined cartilage connected to cartilage. The diaphysis is a hollow bone, the walls of which are formed from dense bone, which is rather thick along its entire length and gradually thinning towards the edges.

The bone marrow fills the bone production cavity and spongy bone. The fetus and children in the bone marrow cavity there is a red bone marrow, this is an important blood formation organ in the human body. In the mature age, the brain in the bone marrow cavity is gradually replaced by fats and a yellow bone marrow is formed, which loses the ability to bleeding, but in the bone marrow there is still a red bone marrow that performs this function.

The periosteum is a compacted connecting fabric, closely adjacent to the bone surface. It contains blood vessels and nerves that perform the nutritional function. Inside the perception, there is a large number of Osteoblast, which has high activity, which in the period of growth and human development is capable of creating a bone and gradually make it thicker. When the bone is damaged, the Osteoblast, which is at rest inside the periosteum, begins to be activated and turns into bone cells, which is important for regeneration and bone recovery.

Microstructure of the bone

The bone substance in diaphysia is mostly dense, and only near the bone marrow cavity there is a small amount of spongy bone. Depending on the location of the bone plates, the dense bone is divided into three zones, as shown in Figure: Round-shaped plates, Gavercovy (Haversion) bone plates and inter-care plates.

The ring-shaped plates are plates located around the circumference on the inner and outer side of the diaphysis, and they are divided into external and internal ring-shaped plates. External ring-shaped plates have from several to more than a dozen layers, they are located slender rows on the outer side of the diaphysis, their surface is covered with periosteum. Small blood vessels in the periosteum permeate the outer ring-shaped plates and penetrate the bone substance. Channels for blood vessels passing through external ring-shaped plates are called Volkmann's Canal. Internal ring-shaped plates are located on the surface of the bone margin of diaphysis, they have a small number of layers. Internal ring-shaped plates are covered with internal periostellitus, and through these plates also pass folkman channels connecting small blood vessels with bone marrow vessels. The bone plates concentricly located between the inner and external ring-shaped plates are called gaverca plates. They have from several to more than a dozen layers, located parallel to the axis of the bone. In the Gavers plates there is one longitudinal small channel, called the gaverc channel, in which there are blood vessels, as well as the nerves and a small amount of loose connective tissue. Gavercovy plates and Gaverca Channels form Gavers system. Due to the fact that in diaphysis there is a large number of gavers systems, these systems are called osteon (Osteon). Osteons have a cylindrical shape, their surface is covered with a layer of cementine, which contains a large number of inorganic component parts of the bone, bone collagen fiber and an extremely minor amount of bone matrix.

Inter-plate plates are plates of irregular shapes located between osteon, there are no gavers and blood vessels in them, they consist of residual gaverca records.

Intraight blood circulation

There is a circulatory system in the bone, for example, in the figure shows the blood circulation model in a dense long bone. In diaphysis there is a main supply of artery and veins. In the periosteum of the bottom of the bone there is a small hole through which the feeding artery passes inside the bone. In the bone marrow, this artery is divided into the upper and lower branches, each of which is further diverged into a plurality of branches forming on the final portion of capillaries that feed the tissue of the brain and the tight bone supplying tissues.

Blood vessels in the final part of the epiphyse are connected to the feeding artery included in the bone marrow cavity of the epiphyse. Blood in the vessels of the periosteum comes out of it, the middle part of the epiphyse is mainly supplied with blood from the feeding artery and only a small amount of blood enters the epiphis from the vessels of the periosteum. If the nutritional artery is damaged or cut during the operation, it is possible that the supply of epiphysees will be replaced by power from the periosteum, since these blood vessels are mutually associated with each other when developing the fetus.

The blood vessels in the epiphysis pass into it from the side parts of the epiphysear plate, developing, turn into epiphyseal arteries, supplying blood epiphyse brain. There are also a large number of branches that supply blood cartilage around the epiphyse and its side parts.

The upper part of the bone is the articular cartilage, under which the epiphyseal artery is located, and even lower the growth cartilage, after which there are three types of bones: intravenous bone, bone plates and periosteum. The direction of blood flow in these three types of bones is Nonodynakovo: In the intravenous bone, the blood movement takes up and outward, in the middle part of the diaphysis of the vessels have a transverse direction, and at the bottom of the diaphysis of the vessels are directed down and outward. Therefore, the blood vessels in all dense bones are located in the form of an umbrella and diverge is rape.

Since the blood vessels in the bone are very thin, and they cannot be observed directly, so the study of the dynamics of blood flow in them is quite difficult. Currently, with the help of radioisotopes introduced into the blood vessels, judging by the amount of their residues and the amount of heat released in comparison with the proportion of blood flow, the temperature distribution in the bone can be measured to determine the state of blood circulation.

In the process of treating degenerative-dystrophic joint diseases, the internal electrochemical medium is created in the head of the femoral bone, which contributes to the restoration of the impaired microcirculation and the active removal of the exchange products of the tissue destroyed by disease, stimulates the division and differentiation of bone cells, gradually replacing the bone defect.

Bone tissue cells (bones):

* Osteoblasts,

* Osteocytes,

* Ostoclasts.

The main cells in the formed bone tissue are osteocytes. These are the cells of the process shape with a large core and a low-heated cytoplasm (nuclear-type cells). The cells of the cells are localized in bone catering - lacuna, and processes in bone canalians. Numerous bone tubules, anatomosing among themselves, permeate all bone tissue, reported with perivascular spaces, and form a bone drainage system. This drainage system contains a tissue fluid, through which the metabolism is provided not only between the cells and the tissue fluid, but also the intercellular substance. For the ultrastructural organization of osteocytes, the presence in the cytoplasm of a low-rise grainy endoplasmic network, a small number of mitochondria and lysosomes, there are no centriots. Heterochromatin prevails in the kernel. All these evidence suggests that osteocytes have insignificant functional activity, which is to maintain metabolism between cells and an intercellular substance. Osteocytes are definitive forms of cells and are not divided. They are formed from Osteoblasts.

Osteoblasts are contained only in developing bone tissue. In the formed bone tissue (bone) they are missing, but is usually contained in inactive form in the periosteum. In the developing bone tissue, they embrace each bone plate on the periphery, nourishing each other, forming the similarity of the epithelial reservoir. The shape of such active functioning cells can be cubic, prismatic, angular. The Cytoplasm of Osteoblasts contains a well-developed grainy endoplasmic network and a lamellar complex of Golgi, many mitochondria. Such an ultrastructural organization suggests that these cells are synthesizing and secreting.

Indeed, the osteoblasts synthesize protein collagen and glycosocaminoglycans, which are then isolated into the intercellular space. Due to these components, organic matrix bone tissue is formed. The same cells then provide the mineralization of the intercellular substance by separating calcium salts. Gradually, highlighting the intercellular substance, they seem to be meditated and turn into osteocytes. At the same time, intracellular organelles are largely reduced, synthetic and secretory activity decreases and functional activity peculiar to osteocytes. Osteoblasts, localized in the cambial layer of periosteum, are in inactive condition, synthetic and transport organelles are weakly developed. In case of irritation of these cells (in case of injuries, bone fractures, and so on), a grainy endoplasmic network and a plate complex is rapidly developing in the cytoplasm, the active synthesis and the selection of collagen and glycosoaminoglycans, the formation of an organic matrix (bone corn), and then the formation of definitive bone tissue (bones). In this way, due to the activities of the Osteoblasts of the periosteum, the regeneration of bones occurs when they are damaged.

Oclasts - boostering cells, in the formed bone tissue are missing. But it is contained in the periosteum and in the places of destruction and restructuring of bone tissue. Since the local processes of bone tissue rebuilding are continuously carried out in ontogenesis, and osteoclasts are also necessarily present in these places. In the process of embryonic osteohythogenesis, these cells play an important role and are determined in large quantities.

Osteoclasts have a characteristic morphology:

* These cells are multi-core (3-5 or more nuclei);

* these are rather large cells (with a diameter of about 90 microns);

* They have a characteristic form - the cell has an oval shape, but part of it, adjacent to the bone tissue, is flat.

At the same time, two zones are distinguished in a flat part:

* The central part is corrugated, contains numerous folds and islands;

* Peripheral (transparent) Part closely comes into contact with bone tissue.

In the cytoplasm of cells, under the kernels, numerous lysosomes and vacuoles of different magnitude are located. The functional activity of osteoclast is manifested as follows: in a central (corrugated) zone of the base of the cell from the cytoplasm, coalic acid and proteolytic enzymes are distinguished. The separated coalic acid causes bone demineralization, and proteolytic enzymes destroy the organic matrix of the intercellular substance. Fragments of collagen fibers are phagocycled with osteoclasts and destroyed intracellularly. Through these mechanisms, resorption occurs (destruction) of bone tissue and therefore osteoclasts are usually localized in bone deepening. After the destruction of bone tissue, due to the activities of osteoblasts, eating vessels from the connective tissue, there is a construction of a new bone tissue.

The intercellular substance of bone fabric consists of:

* Basic substance

* And fibers in which calcium salts are contained.

Fibers consist of type I collagen and fold in bundles, which can be placed in parallel (ordered) or disordered, based on which the histological classification of bone tissues is built.

The main substance of bone tissue, as well as other varieties of connecting tissues, consists of:

* Glycosoaminoglykanov

* and proteoglycans.

However, the chemical composition of these substances is different. In particular, the bone tissue contains less chondroitrine acids, but more lemon and other acids, which form complexes with calcium salts. In the process of the development of bone tissue, an organic matrix-basic substance and collagen (ossein, collagen II) fibers are formed first, and then calcium salts (mainly phosphorous) are minimized. Calcium salts form hydroxyapatitis crystals that are deposited in both amorphous substances and in the fibers, but the small part of the salts is postponed by amorphous. By ensuring the strength of the bones, the phosphate calcium salts are at the same time calcium depot and phosphorus in the body. Therefore, bone tissue takes part in mineral exchange.

Notice in the body (literary data):

1. From 208 to 214 individual bones.

2. Native bone consists of 50% of inorganic material, 25% organic substances and 25% of water associated with collagen and proteoglycans.

3. 90% of the organic compositions of type 1 collagen and only 10% other organic molecules (osteokalcin glycoprotein, osteurectin, osteopontin, bone sialoprotein and other pretoglycans).

4. The bone components are presented: organic matrix - 20-40%, inorganic minerals - 50-70%, cell elements 5-10% and fats - 3%.

5. Macroscopically skeleton consists of two components - compact or cortical bone; and mesh or spongy bone.

6. On average, the weight of the skeleton is 5 kg (weight highly depends on age, gender, body structure and growth).

7. In an adult body, 4 kg accounts for a cortical bone, i.e. 80% (in the skeletal system), while the spongy bone is 20% and weighs an average of 1 kg.

8. The entire skeletal mass in an adult is approximately 0.0014 m³ (1400000 mm³) or 1400 cm³ (1.4 liters).

9. The bone surface is represented by periosal and endosteal surfaces - a total of 11.5 m² (11500000 mm²).

10. The periosteal surface covers the entire outer perimeter of the bone and is 4.4% roughly 0.5 m² (500,000 mm²) of the entire bone surface.

11. The inner (endosal) surface consists of three components - 1) an intricultural surface (the surface of the gavers channels), which is 30.4% or rude 3.5 m² (3500000 mm²); 2) The surface of the inside of the cortical bone of about 4.4% or roughly 0.5 m² (500,000 mm²) and 3) the surface of the trabecular component of the spongy bone is 60.8% or roughly 7 m² (7000000 mm²).

12. Sponge dice 1 gr. On average, there is a surface of 70 cm² (70,000 cm²: 1000 gr.), while the cortical bone is 1 gr. It has about 11.25 cm² [(0.5 + 3.5 + 0.5) x 10000 cm²: 4000 gr.], i.e. 6 times less. According to other authors, this ratio can be 10 to 1.

13. Typically, with normal metabolism, 0.6% cortical and 1.2% of the spongy bone surface is destroyed (resorption) and, accordingly, 3% cortical and 6% of the spongy bone surface are involved in the formation of a new bone tissue. The remaining bone tissue (more than 93% of its surface) is in a state of rest or rest.

The article is provided by Edektbiofarm LLC

Teeth are located in bone wells - separate cells of alveolar processes of the upper and lower jaws. Bone tissue is a type of connective tissue, developing from mesoderm and consisting of cells, an intercellular non-mineralized organic matrix (osteoid) and the main mineralized intercellular substance.

5.1. Organization and structure of bone tissue of alveolar processes

Alveolar's bone surface is covered perceivers(periost) Formed mainly dense fibrous connective tissue, in which 2 layers are distinguished: outer - fibrous and internal - osteogenic, containing osteoblasts. From the osteogenic layer of vessels in the bone, vessels and nerves pass. Thick bundles of triggering collagen fibers bind the bone with the periosteum. The periosteum carries out not only a trophic function, but also participates in the growth and regeneration of the bone. As a result, the bone tissue of alveolar processes has a high regenerative ability not only in physiological conditions, with orthodontic influences, but also after damage (fractures).

Mineralized matrix is \u200b\u200borganized in Trabez - structural-functional units of spongy bone tissue. In the lacuna of the mineralized matrix and on the surface of the trabeculus there are bone cells - osteocytes, osteoblasts, osteoclasts.

In the body, the processes of refreshing bone tissue are constantly occurring by the time of costh formation and resorption (resorption) of the bone. Various bone cells are actively involved in these processes.

Bone Fabric Cell Composition

Cells occupy only 1-5% of the total volume of the bone of the skeleton of an adult. Distinguished 4 types of bone cells.

Mesenchymal undifferentiated bone cells they are mainly in the composition of the inner layer of the periosteum, covering the surface of the bone outside - periosta, as well as in the composition of the endosta, the lining contours of all internal bones, the inner surface of the bone. They are called lining, or contour, cells. New bone cells can be formed from these cells - osteoblasts and osteoclasts. In accordance with this function, they are also called them osteogeniccells.

Osteoblastov- Cells located in the costh formation zones on the outer and internal surfaces of the bone. Osteoblasts contain a sufficiently large amount of glycogen and glucose. With age, this amount decreases by 2-3 times. ATP synthesis is 60% connected with glycolysis reactions. As the osteoblasts agrees, the glycolysis reaction is activated. The cells of the citrate cycle proceeds in the cells, and citrate citnesintase has the greatest activity. The synthesized citrate is used further on the binding of Ca 2+ necessary for mineralization processes. Since the function of Osteoblast is the creation of an organic intercellular bone matrix, these cells contain a large amount of RNA required for protein synthesis. Osteoblasts are actively synthesized and highlighted in extracellular space a significant amount of glyceluphospholipids that are able to bind CA 2+ and participate in mineralization processes. Cells communicate with each other by desplaomoms that allow CA 2+ and CAMF to pass. Osteoblasts are synthesized and separated into the environment of collagen fibrils, proteoglycans and glycosaminoglycans. They also provide a continuous growth of hydroxyapatite crystals and act as intermediaries when binding mineral crystals with a protein matrix. As aging, the Osteoblasts turn into osteocytes.

Osteocytes- bone-eyed bone tissue cells included in the organic intercellular matrix that contact each other through the proof. Osteocytes also interact with other bone tissue cells: osteoclasts and osteoblasts, as well as with mesenchymal bone cells.

Osteoclasts- cells performing the function of bone destruction; Frame from macrophages. They carry out a continuous managed process of reconstruction and renewal of bone tissue, ensuring the necessary growth and development of the skeleton, structure, strength and elasticity of bones.

Intercellular and base bone tissue

Intercellular substance presented by an organic intercellular matrix constructed from collagen fibers (90-95%) and the main mineralized substance (5-10%). Collagen fibers are mainly located in parallel to the direction of the level of the most likely mechanical loads on the bone and ensure the elasticity and elasticity of the bone.

Main substance the intercellular matrix consists mainly of extracellular fluid, glycoproteins and proteoglycans involved in the movement and distribution of inorganic ions. Mineral substances placed in the composition of the base substance in the organic dice matrix are represented by crystals, mainly hydroxyapatite Ca 10 (PO 4) 6 (OH) 2. Calcium / phosphorus ratio is 1.3-2.0. In addition, the ions of Mg 2+, Na +, K +, SO 4 2-, HCO 3-, hydroxyl and other ions that can take part in the formation of crystals were found in the bone. Mineralization of bones is associated with the peculiarities of the glycoproteins of bone tissue and the activity of osteoblasts.

The main proteins of the extracellular bone matrix are collagen type I proteins that make up about 90% of the organic bone matrix. Along with the type I collagen, there are traces of other types of collagen, such as V, XI, XII. It is possible that these types of collagen belong to other tissues, which are in bone tissue, but are not included in the bone matrix. For example, type V collagen is usually found in vessels that permeate the bone. The type XI collagen is in the cartilage tissue and can correspond to the remains of the calcified cartilage. The source of collagen XII type can be "blanks" of collagen fibrils. In bone tissue of type I, contains derivatives of monosaccharides, has a smaller number of transverse bonds than in other types of connective tissue, and these bonds are formed by allyzine. Another possible difference is that the N-terminal seppetide of the type I type I phosphorylated and this peptide is partially stored in a mineralized matrix.

Bone tissue contains about 10% of noncallant proteins. They are represented by glycoproteins and proteoglycans (Fig. 5.1).

Of the total number of noncallant proteins, 10% falls on the proportion of proteoglycans. Initially, great chondroititin is synthesized.

Fig. 5.1.The content of noncallant proteins in the intercellular matrix of bone tissue [by Gehron R. P., 1992].

containing proteoglycan, which, as bone fabric, is destroyed and replaced by two small proteoglycans: decorine and biiglikan. Small proteoglycans are introduced into a minimalized matrix. Decolar and Biglikan activate the differentiation and proliferation processes, and also involved in the regulation of deposits of minerals, crystal morphology and combining the elements of an organic matrix. The first is the synthesized Biglican containing dermatansulfate; It affects cell proliferation processes. A biglikan associated with chondroitin sulfate appears in the mineralization phase. Decolar is synthesized later than Biglikan, in the stage of sediments of proteins for the formation of an intercellular matrix; It remains in the mineralization phase. It is assumed that the decoration "seals" collagen molecules and regulates the fibril diameter. During the formation of bone, both proteins are produced by osteoblasts, but when these cells become osteocytes, they are synthesized only by Biglikan.

From bone matrix in small quantities, other types of small proteoglycans were highlighted, which act as

receptors and facilitate the binding of growth factors with a cell. These types of molecules are in the membrane or are attached to the cell membrane by phosphoinositol bonds.

In bone tissue is also present hyaluronic acid. It is likely that it plays an important role in the morphogenesis of this fabric.

In addition to proteoglycans in the bone, a large number of diverse proteins belonging to glycoproteins are determined (Table 5.1).

As a rule, these proteins are synthesized by osteoblasts and are able to bind phosphates or calcium; Thus, they participate in the formation of a mineralized matrix. Combining with cells, collagen and proteoglycans, they ensure the formation of supramolecular complexes of bone matrix (Fig. 5.2).

Proteoglycans are present in osteoid: fibromodulin, biglican, decorine, collagen proteins and morphogenetic bone protein. In the mineralized matrix, osteocytes are closed, which are associated with collagen. In collagen, hydroxyapatite, osteocalcin, osteoeeerine are fixed. In mineralized intercellular

Fig. 5.2.Participation of various proteins in the formation of bone matrix.

Table 5.1.

Uncoated bone tissue proteins

Protein

Properties and functions

OsteEnectin

Glyco phosphoprotein capable of binding Ca 2+

Alkaline phosphatase

Splits phosphate from organic compounds with alkaline pH values

Thrombospondin

Protein with mol. Weighing 145 kDa, consisting of three identical subunits associated with each other disulfide bonds. Each subunit has several different domains that give protein the ability to bind to other proteins of bone matrix - heparans-containing proteoglycans, fibronectin, laminin, collagen I and V types and osteonectin. In the N-Control Area, the thrombospondin contains a sequence of amino acids that ensures the attachment of cells. The binding of thromboopondin with receptors on the cell surface is affected by the CA 2+ concentration. In bone tissue, thromboospondin is synthesized by Osteoblasts

Fibronctin

Binds to the surface of cells, fibrin, heparin, bacteria, collagen. In bone tissue, fibronectin is synthesized in the early stages of osteogenesis and is stored in a mineralized matrix

Osteopontin

Glicophosphoprotein containing N- and O-related oligosaccharides; Participates in adhesion cells

Bone sour glycoprotein-75

Protein with mol. Weighing 75 kDa, contains sialic acids and phosphate residues. It is capable of binding ions Ca 2+, inherent in bone, dentin and cartilage sprout record. Inhibits bone resorption processes

Bone sialoprotein

Adhesive glycoprotein containing up to 50% carbohydrates

Matrix GLA protein

Protein containing 5 residues of 7-carboxygluto-new acid; It is capable of binding to hydroxyapatite. Appears in the early stages of bone development; Protein also found in lungs, heart, kidney, cartilage

osteoeerine matrix is \u200b\u200bassociated with osteonectin, and osteocalcin with collagen. The morphogenetic bone protein is located in the border zone between the mineralized and non-mineralized matrix. Osteopontin regulates the activity of osteoclasts.

Properties and functions of bone proteins are presented in Table. 5.1.

5.2. Physiological regeneration of bone tissue

In the process of vital activity, the bone is constantly updated, that is, it is destroyed and restored. At the same time, it occurs two opposite directed process - resorption and recovery. The ratio of these processes is called bone remodeling.

It is known that every 30 years bone tissue varies almost completely. Normally, the bone "grows" to 20 years of age, reaching the peak of the bone mass. During this period, the bone growth is up to 8% per year. Next to 30-35 years of age there is a period of more or less sustainable state. Then the natural gradual reduction of bone mass begins, which is usually not more than 0.3-0.5% per year. After the occurrence of menopause in women, the maximum speed of loss of bone tissue, which reaches 2-5% per year and continues at such a pace to 60-70 years. As a result, women lose from 30 to 50% of bone tissue. In men, these losses usually make up 15-30%.

The process remodeling of bone tissue occurs in several steps (Fig. 5.3). At the first stage, the area of \u200b\u200bbone tissue is subject to

Fig. 5.3.Stages of bone remodeling [according to Martin R.B., 2000, as amended].

osteocytes are launched by osteocytes. To activate the process, the participation of the parathyroid hormone, an insulin-like growth factor, interleukinov-1 and -6, prostaglandins, calcitriol, tumor necrosis factor is necessary. It is inhibited by this stage of remodeling estrogen. At this stage, surface contour cells change their shape, converting from flat rounded cells into cubic.

Osteoblasts and T-lymphocytes secrete ligands of the capppon nucleation factor in (Rankl) as a certain moment of the Rankl molecule can remain associated with the surface of osteoblasts or stromal cells.

Ostoclast precursors are formed from bone marrow stem cell. They have membrane receptors called the capppon nucleation activator activator receptors in (Rank). At the next stage, Rank Ligands (RANKL) are associated with Rank receptors, which is accompanied by a merger of several precursors of osteoclasts into one large structure and mature multi-core osteoclasts are formed.

The forming active osteoclast creates a corrugated edge on its surface and mature osteoclasts begin to resorbate

bone tissue (Fig. 5.4). On the side of the junction of the osteoclast to the destroyed surface distinguish between two zones. The first zone is the most extensive, called brush cut, or corrugated edge. Corrugated edge is a twisted membrane spiral with multiple cytoplasmic folds, which are facing resorption on the bone surface. Through the osteoclast membrane, lysosomes are exempt, containing a large amount of hydrolytic enzymes (Katpsins K, D, B, acid phosphatase, esterase, glycosidase, etc.). In turn, Cathepsin K activates the matrix metalloproteinase-9, which is involved in the degradation of collagen and proteoglycans of the intercellular matrix. During this period in osteoclasts, carbathyndase activity is growing. NSO 3 ions - CL - which accumulate in a corrugated region; H + ions are transferred there. The secretion of H + is carried out due to the N + / K + -ATFases very active in osteoclasts. Developing acidosis contributes to the activation of lysosomal enzymes and contributes to the destruction of the mineral component.

The second zone surrounds the first and, as it were, seals the area of \u200b\u200bthe action of hydrolytic enzymes. It is free from organelle and

Fig. 5.4.Activation of the Rankl Pre-Simtoclast and the formation of an active osteoblastic corrugated border, leading to the resorption of bone tissue [according to Edwards P. A., 2005, as amended].

it is a clean zone, therefore bone resorption occurs only under the corrugated edge in a closed space.

At the stage of formation of osteoclasts from predecessors, the process can be blocked by protein osteoprotegery, which, fluently moving, is able to bind Rankl and thus prevent RANKL interaction with Rank receptors (see Fig. 5.4). Osteoprotegery - glycoprotein with mol. Weighing 60-120 kDa, belonging to the FFF receptor family. Inhibiting Rank binding with Rank ligand, osteoprotegeryin thereby suppresses mobilization, proliferation and activation of osteoclasts, so an increase in Rankl synthesis leads to bone resorption and, therefore, to loss of bone mass.

The nature of bone remodeling is largely determined by the balance between Rankl products and osteoprotegery. The undifferentiated stromal bone marrow cells are largely synthesized by Rankl and to a lesser extent osteoprotegery. The resulting imbalance of the RANKL / Osteoprotegery system with an increase in Rankl leads to bone resorption. This phenomenon is observed in postmenopausal osteoporosis, peonge disease, bone losses in cancer metastases and rheumatoid arthritis.

Ripe osteoclasts begin to actively absorb the bone, and the destruction of the organic matrix of the intercelred of the bone of the macrophages is completed. Resorption lasts about two weeks. The osteoclasts are then dying in accordance with the genetic program. Apptosis of osteoclasts can linger with the lack of estrogen. At the last stage, pluripotent stem cells arrive in the destruction zone, which are differentiated into osteoblasts. In the future, the osteoblasts are synthesized and the matrix mineralizes in accordance with the new conditions of the static and dynamic burden on the bone.

There are a large number of factors that stimulate the development and functions of osteoblasts (Fig. 5.5). Involvement in the process of restructuring the bone of Osteoblasts is stimulated by various growth factors - TFR- (3, morphogenetic bone protein, an insulin-like growth factor, a factor in the growth of fibroblasts, platelets, colony positive and hormones - paratyrin, calcitrilar, and the binding factor of the α-1 kernel and is inhibited by the protein leptin . Leptin - protein with mall. Weighing 16 kDa is formed mainly in adipocytes; its action implements through an increase in cytokine synthesis, epithelium growth factors and keratinocytes.

Fig. 5.5.Remodeling bone tissue.

Active secretioning osteoblasts create osteoid layers - non-mineralized bone matrix and slowly replenish the resorption cavity. At the same time, they secrete not only various growth factors, as well as proteins of the intercellular matrix - osteopontin, osteocalcin and others. When a formed osteoid reaches a diameter of 6-10 -6 m, it begins to mineralize. The rate of mineralization process depends on the content of calcium, phosphorus and a number of trace elements. The mineralization process is controlled by osteoblasts and is inhibited by pyrophosphate.

The formation of crystals of the mineral island of bone induces collagen. The formation of a mineral crystal lattice begins in a zone located between collagen fibrils. Then they, in turn, become centers for deposit in space between collagen fibers (Fig. 5.6).

The formation of the bone occurs only in the immediate vicinity of osteoblasts, and mineralization begins in cartilage,

Fig. 5.6.Deposition of hydroxyapatitis crystals on collagen fibers.

which consists of collagen located in proteoglycan matrix. Proteoglycans increase the extensibility of the collagen network. In the calcification zone, the protein-polysaccharide complexes are destroyed as a result of protein matrix hydrolysis by lysosomal bone cell enzymes. As the crystals are growing, not only proteoglycans, but also water. Dense, fully mineralized bone, practically dehydrated; Collagen is 20% of the mass and 40% of the volume of such tissue; The rest falls on the share of the mineral part.

The beginning of mineralization is characterized by reinforced absorption of osteoblasts O 2 molecules, activation of redox processes and oxidative phosphorylation. In mitochondria, CA 2+ and PO 4 3- ions are accumulated. The synthesis of collagen and noncallant proteins begins, which then after post-transmission modification is secreted from the cell. Various vesicles are formed, in which collagen, proteoglycans and glycoproteins are transferred. Osteoblasts buds special formations, called matrix bubbles, or membrane vesicles. They contain at large concentrations of Ca 2+ ions, which exceeds 25-50 times the content of them in osteoblasts, as well as glyceluphospholipids and enzymes - alkaline phosphatase, pyrophosphatase,

adenosinerphosphatase and adenosine monophosphatase. Ca 2+ ions in membrane vesicles are connected mainly with a negatively charged phosphatidylserine. In the intercellular matrix, membrane vesicles are destroyed with the release of Ca 2+ ions, pyrophosphates, organic compounds associated with phosphoric acid residues. Present in the membrane vesicles phosphoghydrolase, and primarily alkaline phosphatase, cleave the phosphate from organic compounds, and pyrophosphate is hydrolyzed with pyrophosphatase; Ca 2+ ions are connected to PO 4 3, which leads to the appearance of calcium amorphous phosphate.

At the same time, partial destruction of proteoglycans associated with type I collagen occurs. Released fragments of proteoglycans, charged negatively, begin to bind Ca 2+ ions. A certain number of Ca 2+ and PO 4 3 ions form pairs and triplets that bind to collagen and non-core proteins forming the matrix, which is accompanied by the formation of clusters, or nuclei. The ions Ca 2+ and PO 4 3 osteenectin and matrix GLA proteins are most actively associated from the bone tissue proteins. The collagen of the bone tissue binds ions PO 4 3 through the ε-amino group of lysine with the formation of phosphoamide communication.

In the resulting core, spiral-like structures arise, the growth of which goes on the usual principle of adding new ions. The step of such a spiral is equal to the height of one structural unit of the crystal. The formation of one crystal leads to the emergence of other crystals; This process is called epitaxis, or epitaxic nucleation.

The crystal growth is highly sensitive to the presence of other ions and molecules that inhibit crystallization. The concentration of these molecules may be small, and they affect not only the speed, but on the shape and direction of growth of crystals. Supports that such compounds are adsorbed on the surface of the crystal and inhibit the adsorption of other ions. Such substances are, for example, sodium hexametompham, which inhibits calcium carbonate precipitation. Pyrophosphates, polyphosphates and polyphosphonates also inhibit the growth of hydroxyapatitis crystals.

After a few months, after the resorption cavity is filled with bone tissue, the density of the new bone increases. Osteoblasts begin to turn into contour cells that are involved in continuous elimination of calcium from the bone. Some

osteoblasts are converted to osteocytes. Osteocytes remain in the bone; They are connected with each other long cellularity and are able to perceive mechanical effects on the bone.

With differentiation and aging cells, the nature and intensity of metabolic processes changes. With age 2-3 times the amount of glycogen is reduced; The released glucose in young cells by 60% is used in the reactions of anaerobic glycolysis, and in older by 85%. Synthesized ATP molecules are necessary for the livelihoods and mineralization of bone cells. In osteocytes, only glycogen traces remain and the main supplier of ATP molecules is only glycoliz, due to which the constancy of organic and mineral composition is maintained in the already mineralized bone sections.

5.3. Regulation of metabolism in bone tissue

Bone remodeling is regulated by systemic (hormones) and local factors that ensure the interaction between osteoblasts and osteoclasts (Table 5.2).

System factors

The formation of bones to a certain extent depends on the number and activity of Osteoblasts. The process of formation of Osteoblasts affect

Table 5.2.

Factors regulating bone remodeling processes

somatotropin (growth hormone), estrogens, 24.25 (OH) 2 D 3, which stimulate the division of osteoblasts and the transformation of the presenters in Osteoblasts. Glucocorticoids, on the contrary, suppress the division of osteoblasts.

Parathyrin (parathgorom) it is synthesized in parathyroid glands. Parastrine molecule consists of one polypeptide chain containing 84 amino acid residues. Parastrine synthesis stimulates adrenaline, so in conditions of acute and chronic stress, the amount of this hormone increases. Parathyrine activates the proliferation of Osteoblast precursor cells, prolongs the time of their half-life and inhibits apoptosis of Osteoblasts. In bone tissue, the receptors for paratyrin are present in the membranes of osteoblasts and osteocytes. Osteoclasts are devoid of receptors for this hormone. Hormone binds to Osteoblast receptors and activates adenylate cyclase, which is accompanied by an increase in quantity of 3 " 5" cAMF. Such an increase in the content of CAMP contributes to the intensive flow of Ca 2+ ions from extracellular fluid. The calcium received forms a complex with a calmoduline and further activates calcium-dependent protein kinase, followed by phosphorization of proteins. Binding to osteoblasts, paratyrin causes the synthesis of osteoclast-activating factor - Rankl, capable of binding to premostoclasts.

The introduction of large doses of parasitis leads to the death of osteoblasts and osteocytes, which is accompanied by an increase in the resorption zone, an increase in the level of calcium and phosphates in the blood and urine with a simultaneous increase in the excretion of hydroxyproline due to the destruction of collagen proteins.

Parathyrine receptors are located in renal tubules. In the proximal departments of the renal channels, the hormone inhibits the reabsorption of phosphate and stimulates the formation of 1.25 (it) 2 D 3. In the distal departments of the renal tubules, Parathyrin enhances the reabsorption of Ca 2+. Thus, paratyrin provides an increase in the level of calcium and the decrease in phosphates in the blood plasma.

Parotine -glycoprotein, highlighted by the parole and lobby-jewish salivary glands. The protein consists of α-, β -, and γ subunits. The active beginning of the paryotine is the γ-subunit that affects the mesenchymal fabrics - cartilage, tubular bones, dentin tooth. Parotine enhances the proliferation of hondronogenic cells, stimulates the synthesis of nucleic acids and DNA in odontoblasts,

mineralization Cesses Dentin and Bones. These processes are accompanied by a decrease in calcium content and glucose in blood plasma.

Calcithonin- polypeptide consisting of 32 amino acid residues. Secrets parapolycular n-cells of the thyroid gland or C-cells of parachite glazes in the form of a high-molecular precursor protein. The secretion of calcitonin increases with increasing concentration of C C 2+ ions and decreases with a decrease in the concentration of Ca 2+ ions in the blood. It also depends on the level of estrogen. With a lack of estrogen, the secretion of calcitonin decreases. This causes strengthening calcium mobilization in bone tissue and promotes osteoporosis. Calcithonine is associated with specific receptors of osteoclasts and kidney channel cells, which is accompanied by activation of adenylate cyclase and an increase in the formation of the CAMF. Calcitonine affects the transport of Ca 2+ ions through cell membranes. It stimulates the absorption of CA 2+ ions by mitochondria and thereby delays the outflow of Ca 2+ ions from the cell. This depends on the amount of ATP and the ratio of Na + and K + ions in the cell. Calcitonine oppresses collagen disintegration, which is manifested by a decrease in excretion with urine hydroxyproline. In the cells of the kidney channels, calcitonin inhibits hydroxylation 25 (it) D 3.

Thus, calcitonin suppresses the activity of osteoclasts and inhibits the release of Ca 2+ ions from bone tissue, and also reduces the reabsorption of CA 2+ ions in the kidneys. As a result, the resorption of bone tissue is inhibited, the mineralization processes are stimulated, which is manifested by a decrease in the level of calcium and phosphorus in the blood plasma.

Iodine-containing hormones thyroid gland - thyroxine (T4) and triiodothyronine (T3) provide optimal growth of bone tissue. Thyroid hormones are able to stimulate the secretion of growth hormones. They increase both synthesis of MRNA insulin-like growth factor 1 (IFR-1) and the products of the IFR-1 itself in the liver. With hyperthyroidism, the differentiation of osteogenic cells and protein synthesis in these cells is suppressed, alkaline phosphatase activity is reduced. Due to the reinforced secretion of osteocalcin, chemotaxis osteoclasts is activated, which leads to resorption of bone tissue.

Semi-steroids hormones participate in bone remodeling processes. The impact of estrogen on bone tissue is manifested in the activation of osteoblasts (direct and indirect action), the oppression of osteoclasts. They also contribute to the suction of CA 2+ ions in the gastrointestinal tract and its deposit in bone tissue.

Women's sex hormones stimulate the products of calcitonin by the thyroid gland and reduce the sensitivity of the bone tissue to parasirine. They also displacing corticosteroids from their receptors in bone tissue on a competitive basis. Androgens, having an anabolic effect on bone tissue, stimulate protein biosynthesis in osteoblasts, as well as flavored in adipose tissue in estrogens.

In conditions of lack of genital steroids, which takes place in menopause, bone resorption processes begin to prevail over the processes of bone remodeling, which leads to the development of osteopia and osteoporosis.

Glucocorticoids synthesized in adrenal cortex. The main glucocorticoid person is cortisol. Glucocorticoids are coordinated to act on different tissues and different processes - both anabolic and catabolic. In bone tissue, cortisol is inhibits the synthesis of type I collagen, some non-body proteins, proteoglycans and osteopontin. Glucocorticoids also reduce the amount of fat cells that are the formation of the formation of hyaenuronic acid. Under the influence of glucocorticoids, the decay of proteins is accelerated. Glucocorticoids suppress the absorption of Ca 2+ ions in the intestine, which is accompanied by a decrease in it in serum. This decrease leads to emission of paratyrin, which stimulates the formation of osteoclasts and bone resorption (Fig. 5.7). In addition, cortisol in muscles and bones stimulates the decay of proteins, which also disrupts the formation of bone tissue. Ultimately, glucocorticoids leads to loss of bone tissue.

Vitamin D 3 (cholecalciferol) it comes with food, and also formed from the predecessor of 7-dehydroholezterol under the influence of ultraviolet rays. In the liver, the cholecalciferol is converted to 25 (OH) D 3, and further hydroxylation 25 (OH) D 3 is further hydroxylation, 2 hydroxylized metabolites are formed - 1.25 (O) 2 D 3 and 24.25 (OH) 2 D 3. Vitamin D 3 metabolites regulate hondrogenesis and osteogenesis already in the process of embryonic development. In the absence of vitamin D 3, the mineralization of the organic matrix is \u200b\u200bimpossible, and the vascular network is not formed, and the metaphizar bone is not capable of forming properly. 1.25 (OH) 2 D 3 binds to chondroblasts in an active condition, and 24.25 (it) 2 D 3 - with cells at rest. 1.25 (O) 2 D 3 regulates growth zones through the formation of a complex with a nuclear receptor for this vitamin. It is also shown that 1.25 (it) 2 D 3 is capable of

Fig. 5.7.Scheme of glucocorticoids on metabolic processes, resulting in loss of bone tissue

wanted with a membrane-nuclear receptor, which leads to the activation of phospholipase with and the formation of inositol-3-phosphate. In addition, the resulting complex is activated by phospholipase A 2. Prostaglandin E 2 is synthesized from an instant arachidonic acid, which also affects the response of chondroblasts when they are binding to 1.25 (it) 2 D 3. On the contrary, after binding 24.25 (it) 2 D 3 with its membrane-binding receptor, phospholipase C, and then proteinkinase C.

In the cartilage zone of the growth of epiphysis of bone tissue 24.25 (OH) 2 D 3 stimulates the differentiation and proliferation of prechondoblasts, which contain specific receptors to this metabolite. Vitamin D 3 metabolites affect the formation and functional state of the temporomandyl adhesive joint.

Vitamin A. With a lack and redundant arrival of vitamin A, bone growth is disturbed to the organism of children and their deformation occurs. Probably, these phenomena are due to the depolymerization and hydrolysis of chondroitin sulfate, which is part of the cartilage.

Vitamin C. With a lack of ascorbic acid in mesenchumal cells, it does not hydroxylation of lysine residues and proline, which leads to a violation of the formation of mature collagen. The resulting immature collagen is not capable of binding Ca 2+ ions and thus violate mineralization processes.

Vitamin E.. With a deficiency of vitamin E in the liver, 25 (O) D 3 is not formed - the precursor of the active forms of vitamin D 3. The deficiency of vitamin E can also lead to a decrease in magnesium level in bone tissue.

Local factors

Prostaglandinsaccelerate the yoy of Ca 2+ ions from the bone. Exogenous prostaglandins increase the generation of osteoclasts, which are separated by the bone. A catabolic impact on the exchange of proteins in bone tissue and inhibits their synthesis.

Laktorrin- Iron-containing glycoprotein, in physiological concentration stimulates the proliferation and differentiation of osteoblasts, as well as inhibits osteoclastogenesis. The mitogenic effect of Laktorrin on osteoblast-like cells is carried out through specific receptors. The resulting complex by endocytosis enters the cell, and the lactoferrin phosphorylates mitogen - activating protein kinases. Thus, Laktorinrin acts as a factor of the growth of bone and its health. It can be used as an anabolic factor in osteoporosis.

Cytokines- low molecular weight polypeptides that determine the interaction of the cells of the immune system. They provide a response to the introduction of alien bodies, immune damage, as well as inflammation, reparations and regeneration. They are represented by five large groups of proteins, one of which is interleukins.

Interleukins(Il.) - proteins (from IL-1 to IL-18), synthesized mainly by T-cell lymphocytes, as well as mononuclear phagocytes. Functional functions are associated with the activity of other physiologically active peptides and hormones. In physiological concentration, growth, differentiation and life expectancy of cells are suppressed. Connect the products of collagenase, adhesion of endothelial cells to neutrophilas and eosinophils, NO products and, as the concern, there is a decrease in the degradation of cartilage tissue and bone resorption.

The process of resorption of bone tissue can be activated with acidosis and large amounts of integrins, yl and vitamin A, but is inhibited by estrogens, calcitonine, interferon and morphogenetic bone protein.

Bone Metabolic Marketers

Biochemical markers provide information on the pathogenesis of the skeleton diseases and the phases of the remodeling of bone tissue. Biochemical markers of the formation and resorption of bones characterizing the functions of osteoblasts and osteoclasts.

Prognostic significance of the determination of bone metabolism markers:

The screening using these markers allows you to identify patients with a high risk of osteoporosis; High levels of bone resorption markers may be associated with

increasing risk of fractures; Increasing the level of markers of bone metabolism in patients with osteoporosis more than 3 times compared with the indicators of the norm implies other bone pathology, including malignant; Recorption markers can be used as additional criteria in solving the issue of the appointment of special therapy in the treatment of bone pathology. Bone resorption markers . During the renewal of the bone tissue of the type I collagen, which is more than 90% of the organic bone matrix and is synthesized directly in the bones, degrades, and small peptide fragments fall into blood or highlighted by the kidneys. Collagen degradation products can be determined both in the urine and serum. These markers can be used in therapy with drugs that reduce bone resorption, in patients with diseases associated with bone metabolic disorders. As criteria for resorption of bone tissue, the products of the degradation of collagen I types are performed: N- and C-Telopeptides and tartrate-resistant acid phosphatase. With primary osteoporosis and nasty disease, a distinct increase in the C-terminal telopeptide of type I collagen and the amount of this marker increases in serum 2 times.

Collagen disintegration is the only source of free hydroxyproline in the body. Prevailing part of hydroxyproline

catabases, and part is distinguished with urine, mainly as part of small peptides (di- and tripipeptides). Therefore, the content of hydroxyproline in the blood and the urine reflects the balance of catlagen catabolism. In an adult per day, 15-50 mg of hydroxyproline is excreted, at a young age of up to 200 mg, and in some diseases associated with collagen damage, for example: hyperparathyroidism, diseases of the pedage and hereditary hyperhydroxyprolinemia, the cause of which is the enzyme defect hydroxyprolinoxidase, the amount of blood and blood and Hydroxyproline allocated with urine increases.

The glasses secrete tartrate-resistant acid phosphatase. As an increase in the activity of osteoclasts, an increase in the content of tartrate-resistant acid phosphatases occurs and it enters into an increased amount in the bloodstream. In the blood plasma, the activity of this enzyme increases with the disease of the pedez, oncological diseases with metastases in the bone. The definition of the activity of this enzyme is especially useful in monitoring the treatment of osteoporosis and oncological diseases accompanied by bone lesion.

Marketers of the formation of bone . The formation of bone tissue is estimated by the amount of osteocalcin, the bone isoenzyme of alkaline phosphatase and osteoprotegery. Measuring the amount of serum osteocalcin allows you to determine the risk of osteoporosis in women, monitor bone metabolism during menopause and hormonal replacement therapy. Rickets in young children is accompanied by a decrease in the blood of the osteocalcin content and the degree of reduction of its concentration depends on the severity of the ricketical process. In patients with hypercorticism and patients receiving prednisone, the content of osteocalcin in the blood is significantly reduced, which reflects the suppression of costh formation processes.

Alkaline phosphatase isoenzyme is present on the cell surface of Osteoblasts. With an increased synthesis of the enzyme with bone tissue cells, its amount in the blood plasma increases, therefore, the determination of alkaline phosphatase activity, especially the bone isoenzyme, is an informative indicator of bone remodeling.

Osteoprotegeryne acts as a FNF receptor. Combining with premostoclasts, it inhibits mobilization, proliferation and activation of osteoclasts.

5.4. Bone tissue reaction to dental

Implants

With various forms of adventure, an alternative to removable prosthetics are intraoscience dental implants. The reaction of bone tissue on the implant can be viewed as a special case of reparative regeneration.

There are three types of connection of dental implants with bone cloth:

Direct enrollment - osteo integration;

Fibrozno-ossal integration, when a layer of fibrous tissue is formed around a dental implant with a thickness of about 100 μm;

Periodontal compound (the very rarest form), sampled in the case of a periodontal binder-like battle with perimplemental collagen fibers or (in some cases) cementing of an intraosseous dental implant.

It is believed that in the process of osteo-integration after the decree of dental implants, a thin zone of proteoglycans is formed, which is deprived of collagen. The zone of gluing a dental implant with a bone is provided by a double layer of proteoglycans, including decorine molecules.

With fibrous-sole integration, the numerous components of the extracellular matrix are also involved in the compound of implant with bone tissue. The stability of the implant in its capsule is responded by collagen I and III types, and fibronectin plays a major role in binding elements of connective tissue with implants.

However, after a period of time, the activity of collagenase, cathepsin to and acid phosphatases grows under the action of mechanical load. This leads to loss of bone tissue in the perimplementation area and disintegration of the dental implant occurs. Early disintegration of intraosseous dental implants occurs on the background of a reduced amount of fibronectin, GLA protein bone, fabric inhibitor of matrix metalloproteinase (TIMP-1).

66562 1

Bone It is a very perfect specialized variety of internal wednesday tissues.

In this system, such opposite properties are harmoniously combined as mechanical strength and functional plasticity, neoplasm and destruction processes.

The bone tissue consists of cells and intercellular substances, which are characterized by a certain histochitectonics. The main cells of bone tissue are osteoblasts, osteocytes and osteoclasts.

Osteoblastov Have an oval or cubic form. A large bright core is not located in the center, it is somewhat shifted to the periphery of the cytoplasm. Often, several nucleolies are found in the kernel, which indicates the high synthetic activity of the cell.

Electron microscopic studies have shown that a significant part of the osteoblast cytoplasm is filled with numerous ribosomes and polysomas, a granular endoplasmic network channel, a Golgi complex, mitochondria, as well as special matrix bubbles. Osteoblasts have proliferative activity, are produced by the intercellular substance and play a major role in the mineralization of the bone matrix. They synthesize and secrete chemical compounds such as alkaline phosphatase, collagen, osteurectin, osteopontin, osteocalcin, bone morphogenetic proteins, etc. In the matrix bubbles of osteoblasts, numerous enzymes are contained, which, released outside the cell, initiate bone mineralization processes.

The organic matrix of bone tissue synthesized by Osteoblasts consists mainly (90-95%) from the type I collagen, collagen III-V and other types, as well as from noncallant proteins (osteocalcin, osteopontin, osteonectin, phosphoprotein, bone morphogenetic proteins) and glycosaminoglycan substances. The proteins of noncallagenic nature possess the properties of regulators of mineralization, osteoinductive substances, mitogenic factors, regulators of the rate of formation of collagen fibrils. Thrombospondin contributes to the adhesion of Osteoblasts to the subprove osteoid of the human bone. Osteocalcin is considered a potential indicator of the function of these cells.

The ultrastructure of Osteoblasts indicates that their functional activity is different. Along with functionally active osteoblasts, having high synthetic activity, there are inactive cells. Most often, they are localized on the periphery of the bone from the bone marrow channel and are part of the periosteum. The structure of such cells is characterized by a small content of organelles in the cytoplasm.

Osteocytesare more differentiated cells than osteoblasts. They have a processful shape.

Osteocyte processes are located in the tubules that penetrate the mineralized bone matrix in various directions. The glued bodies of osteocytes are in special cavities - lacunas - and from all sides is surrounded by a mineralized bone matrix. A significant part of the osteocyte cytoplasm occupies a oscillatory core. Organelles of synthesis in cytoplasm are developed weakly: there are a few polisoms, the short tubes of the endoplasmic network, single mitochondria. Due to the fact that the tubules of neighboring lacuna anastomize each other, the osteocyte processes are interconnected using specialized slot contacts. In a small space around the bodies and the osteocyte processes, the tissue fluid containing a certain concentration of Ca 2+ and Po 4 3- may contain non-mineralized or partially mineralized collagen fibrils.

The osteocyte function is to maintain the integrity of the bone matrix due to participation in the regulation of mineralization of bone tissue and providing an answer to mechanical incentives. Currently, more and more data is accumulating that these cells are actively involved in metabolic processes occurring in the bone intercellular substance, in maintaining the constancy of the ion balance in the body. The functional activity of osteocytes largely depends on the stage of their life cycle and the action of hormonal and cytokine factors.

Osteoclasts- These are large multi-core cells with sharp oxificial cytoplasm. They are part of the phagocytic-macrophage system of the body, blood monocytes derivatives.

On the periphery of the cell is determined by corrugated brush cut. In the cytoplasm there is a lot of ribosomes and polis, mitochondria, the channels of the endoplasmic network, the Golgji complex is well developed. A distinctive feature of the ultrastructure of osteoclasts is the presence of a large number of lysosomes, phagosomes, vacuoles and vesicles.

Osteoclasts have the ability to create locally in its surface with a sour medium as a result of the glycolysis processes intense in these cells. The acidic medium in the area of \u200b\u200bdirect contact of the cytoplasm of osteoclasts and the intercellular substance contributes to the dissolution of mineral salts and creates optimal conditions for the action of proteolytic and a number of other Lizosoma enzymes. The cytochemical marker of osteoclasts is the activity of an acidic phosphatase isoenzyme, which is called sour nitrophenyl phosphatase. The functions of osteoclasts are to resorption (destruction) of bone tissue and participation in the process of remodulation of bone structures during embryonic and postnatal development.

The intercellular substance of bone tissues consists of organic and inorganic components. The organic compounds are represented by collagen I, III, IV, V, IX, XIII types (about 95%), non-colated proteins (bone morphogenetic proteins, osteocalcin, osteopontin, thromboopondin, bone syialoprotein, etc.), glycosaminoglycans and proteoglycans. The inorganic part of the bone matrix is \u200b\u200brepresented by crystals of hydroxyapatitis containing in a large number of calcium and phosphorus ions; In a significantly smaller amount, it consists of salts of magnesium, potassium, fluorides, bicarbonates.

The intercellular substance of the bone is constantly updated. The destruction of the old intercellular substance is quite complicated and not yet clear in many details, in which all types of bone cells and a number of humoral factors take part, but osteoclasts play a particularly noticeable and important role.

Types of bone tissue

Depending on the microscopic structure, two main varieties of bone tissue are distinguished by reticulo-fibrous (coarse-fiber) and lamellar.

Reticulosophy bone tissue It is widely represented in embryogenesis and early postnatal histogenesis of the skeleton bones, and adults meet in places attaching tendons to the bones, along the ingrowth of the cranial seams, as well as in the field of fractures.

Both in embryogenesis and during regeneration, the reticulosophybrusky bone tissue is always replaced by a plate. Characteristic in the structure of the reticulophibroid bone tissue is the disordered, diffuse arrangement of bone cells in the intercellular substance. Powerful bunches of collagen fibers are weakly mineralized and go in different directions. The density of the location of osteocytes in the reticulophibroid bone tissue is higher than in a plate, and they do not have a certain orientation relative to collagen (osseinov) fibers.

Plate bone fabric It is the main cloth in almost all bones of man. In this variety of bone tissue, the mineralized intercellular substance forms special bone plates with a thickness of 5-7 microns.

Each bone plate is a combination of parallel collagen fibers, impregnated with hydroxyapatitis crystals. In adjacent fiber plates are located at different angles, which gives the bone additional strength. Bone cells are ordered between bone plates in the lacunas - osteocytes. Osteocyte processes on bone canalians penetrate the surrounding records, entering into intercellular contacts with other bone cells. There are three bone plate systems: surrounding (generals, external and internal), concentric (included in the osteon structure), insertion (represent the remains of collapsed osteonov).

The bone differ in the compact and spongy substance. Both are formed by a lamellar bone tissue. The features of the histoarchitectonics of the plate bone will be presented later when describing the bone as an organ.

Diseases of Justov
IN AND. Mazurov