The skeleton of any adult person includes 206 different bones, they are all different in the structure and roles. At first glance, they seem solid, inflexible and lifeless. But this is an erroneous impression, various exchange processes, destruction and regeneration are continuously occurring. They, in combination with muscles and ligaments, form a special system, which is called "bone-muscular fabric", the main function of which is the musculoskeletal. It is formed from several species of special cells, which differ in structure, functional features and meaning. On bone cells, their structure and functions will be further and will be discussed.

Bone fabric structure

Features of a plate bone tissue

It is formed by bone plates having a thickness of 4-15 microns. They, in turn, consist of three components: osteocytes, basic substances and collagen thin fibers. All bones of an adult person are formed from this fabric. The collagen fibers of the first type lie in parallel relative to each other and are oriented in a certain direction, in the neighboring bone plates, they are directed in the opposite direction and crossed out almost at right angles. There are bodies of osteocytes in the lacunas. Such a structure of bone tissue provides it with the greatest strength.

Spongy bone

The name "Trabecular substance" is also found. If you pose an analogy, then the structure is comparable to a conventional sponge built of bone plates with cells between them. They are arranged ordered, in accordance with the distributed functional load. The epiphysis of long bones, part of mixed and flat and all short, are mainly built from the spongy substance. It can be seen that mostly lungs and at the same time durable part of the skeleton of a person who experience the load in different directions. The functions of bone tissue are in a direct relationship with its structure, which in this case provides a large area for metabolic processes carried out on it, gives high strength together with a small mass.

Dense (compact) bone substance: what is it?

From the compact substance, the diaphysis of tubular bones consist, in addition, it is a thin plate covers their epiphysis outside. It is permeated by narrow channels, the nerve fibers and blood vessels pass through them. Some of them are located parallel to the bone surface (central or gaverca). Others exit the surface of the bone (nutrient holes), the arteries and nerves are penetrated into the inside, and the veins are penetrated. The central channel, together with the surrounding bone plates, forms the so-called Gavers system (osteon). This is the main content of the compact substance and are considered as its morphofunctional unit.

Osteon - Structural Unit of Bone Tissue

The second name is Ghershersov system. This combination of bone plates having a kind of cylinders inserted into each other, the space between them is filled with osteocytes. In the center there is Gavers channel, through it there are blood vessels in bone cells. There are insertion (interstitial) plates between adjacent structural units. In essence, they are the remains of osteonov who have previously existed and collapsed at the moment when bone tissue has undergone restructuring. There are also general and surrounding records, they form the most inner and outer layer of the bone compact substance, respectively.

Chairman: Building and meaning

Based on the name, it can be determined that it covers the bones outside. It is attached to them with the help of collagen fibers collected in thick bundles, which penetrate and fly with the outer layer of bone plates. It has two pronounced layers:

  • outer (it forms a dense fibrous, unformed connecting tissue, the fibers are dominated in parallel to the bone surface);
  • the inner layer is well pronounced in children and less noticeable in adults (formed by a loose fibrous connective tissue, in which there are spindle-shaped flat cells - inactive osteoblasts and their predecessors).

The periosteum performs several important functions. First, trophic, that is, it provides the bone with nutrition, because the surface contains vessels that penetrate inside with nerves through special nutrients. These channels feed the bone marrow. Secondly, regenerator. It is explained by the presence of osteogenic cells, which are transformed into active osteoblasts, producing matrix and causing bone extensions providing its regeneration. Third, mechanical or reference function. That is, ensuring the mechanical communication of the bone with other structures attached to it (tendons, muscles and ligaments).

Bone fabric functions

Among the basic functions, you can list the following:

  1. Motor, reference (biomechanical).
  2. Protective. The bones are protected from damage to the brain, vessels and nerves, internal organs, etc.
  3. The hematopoietic: in the bone marrow there is a hemo - and lymphopoesez.
  4. Metabolic function (participation in metabolism).
  5. Reparator and regenerator, consisting in the restoration and regeneration of bone tissue.
  6. Morphine role.
  7. Bone tissue is a kind of depot of minerals and growth factors.

The human bone density is provided by mineral substances. The same bone tissue consists of cells of osteoblasts and osteocytes, osteoclasts, their task is to remove old, dead blood cells. There is an organic component, which is a collagen called Ossein. The bone fabric of the child immediately after his birth is represented by 270 bones, over time they are becoming 206, it is if not taken into account semovoids. The greatest femur in humans, the smallest - stirrer, located in the cavity of the middle ear.

Cell component

Like all tissues, the bone consists of several cellular varieties. It:

  • osteoblastov
  • osteocytes
  • osteoclasts
  • osteogenic cells

Each has its own unique structure, located in various sections.

Osteoblast

This cell provides the ability of the bone to restore, forms a new bone. Its value from 15 to 20 microns, its task is to form a new intercellular substance. Cubic shape with many angles, which are formed by mesenchymal cells - precursors containing Golgi complexes. In total, the cellular composition of the Osteoblast is represented by ribosomes, a grainy endoplasmic network.

There are osteoblasts in a person in the growth zone, large quantities contain their periost, endost. The cell highlights the intercellular substance, turning to the center, it harvested, forming a "trap". After that, changes occur with Osteoblast, it changes its structure, turning into an osteocyte. The latter is a full-fledged bone cell, most common.

Osteocyte
Osteocytes. Source: DRPOZVOnKov.ru.

As previously mentioned, osteocyte is the mature form of Osteoblast, has a star form. The diameter is about 15 μm, and he is not more than 7 microns height. The mature form contains in its composition one core, which is located closer to the wall of the vessel, there are two nucleoli, and all the membrane is surrounded. The distance between osteocytes may vary from 20 to 30 microns.

In an adult organism, bone tissue is 42 billion cells. On average, in 25 years, half of them changes, cell divisions does not occur. The osteocyte is located in the deepening, which is called lacuna, it is surrounded by a bone cloth on all sides.

This type of cell is responsible for maintaining a mineral matrix at a constant level. Interaction with other cells occurs through long channels located in the cytoplasm, all of them are within the bone matrix. Through the cell channels receives nutrients.

Osteogenic cells

Unlike the rest, this cell has not lost the ability to divide, can reproduce like that. It is clearly not differentiated, it has a high ability to mitosis, the process, when cells are divided, the body's restoration occurs. Located this view in the deep layer of the periosteum, the brain of the bone. The development process leads to the fact that osteogen is transformed into osteoblasts.

Osteoklast

This cell contributes to the fact that a new bone structure is developing. Osteoclast has large sizes, contains several nuclei in its composition, is responsible for the removal of the old bone. On average there are 5 nuclei, and the size ranges from 150 to 200 microns. The body similar cells are very necessary, since due to them is ensured by the restoration of bones. Old, damaged bone tissue dissolves due to the enzymes separated by the cell.

This type of cells appear not from the bone, its springchart is macrophages, monocytes, components of white blood. The recovery process looks specifically, the old, damaged bone tissue is constantly destroyed, and the osteoblasts are formed new. When the process is broken, the bone is thicker, which leads to fractures, damage with minor loads on it.

In the bone, osteoclasts are located in specific deepening, which are called the bay of resorption, Lakun Haushipa. It has osteoclast a cytoplasm, inside of which there is a foam structure due to vacuoles, bubbles contained in large quantities. In the composition of vacuoles, there are lysosomes that distinguish the enzyme, acid phosphatase, precisely at the expense of her, the old bone tissue is destroyed.

Components of the bone

From the histological point of view, the bone has several components. Any kind of presented:

  • perceivers
  • compact substance
  • endostom

The periosteum has a structure, very resembling an overtime. As part of the inner layer, osteogenic, there is a loose connective tissue with a large number of osteoclasts, osteoblasts, vessels.

Endost, the shell, which was sent to the channel from the inside. As part of this layer, the main is loose fibrous connecting fabric. There are osteoblasts, osteoclasts. The task of this bone includes its nutrition, growth in thickness, recovery.

The compact substance has three layers: the outer and inner represents the plate bone tissue, the osteon layer is located between them. Osteon is a structural and functional unit. Externally, this is a plane formation, which is represented by bone plates, concentrically directed, layered one to another, reminding cylinders that are inserted one to one.

There are recesses between the plates, lacuna, osteocytes are located in them. In the center - the cavity containing the vessel, the channel received the name of the Osteon or Gavers channel. There are dice plates between osteoni, which are called inserted osteones that are destroyed.

Bone formation

The fetus is the source of bones are the cells of mezinchim, they are evicted from sclerotomes. The bone can be formed directly from the tissue of mesenchym, similar to the name of direct osteogenesis. If the mesenchym is formed instead of cartilage growth zone, the process is called indirect osteogenesis, children have it.

Indirect option
Indirect version of bone formation. Source: DRPOZVOnKov.ru.

In the process of transforming the mesenchyma, a rough-fiber bone tissue appears, it also received the name of reticulous. As they grow, a lamellar bone fabric appears in its place. Direct osteogenesis includes four stages.

During the first, an osteogenic island is isolated, the essence of this process is that the mesenchymal cells are rapidly divided. Osteogeneic cells are gradually appearing, osteoblasts, blood vessels occur.

The essence of the second, or osteoid, stage is that the substance between cells is formed by osteoblasts. Some of the osteoblasts turns out to be inside, there is a conversion to osteocyte. Partly osteoblasts are on the surface, forming a layer outside. These cells will then form an assault.

The third stage is the mineralization of the substance, it is actively saturated with calcium, its salts, the bone becomes more compact. The mineralization process occurs due to the flow of calcium gliderophosphate. Alkaline phosphatase, acting on it, causes a chemical reaction to appear new compounds, in particular, glycerol, the remainder of phosphoric acid. The last compound reacts with calcium chloride, calcium phosphate appears. It becomes hydraulicapatite, resembles durable plastic.

The fourth stage is final, has the name of the restructuring, growth, after it, the bone can be presented in its final form. Competitions are formed by common bone plates, in the main mass consisting of ousened cells located in an adventitious vessel sheath, as well as osteon.

Direct Option
Direct version of the formation of bone. Source: DRPOZVOnKov.ru.

This situation includes an option of formation in the growth zone where it was cartilage. In the process of development, a plate bone can immediately form, the process occurs, as in the previous case, in four stages.

Initially, this type of development provides for the formation of a cartilage model that will develop. At the second stage, in the field of the body of the model, a perichondral ossification is carried out, the essence of which is that the schirler becomes an assault, it is a plastic material. In this layer stem cells that are called osteogenic, turn into osteoblasts. The increasing differentiation process is preparing for the formation of a common plate, it forms a bone cuff.

In parallel with the processes described previously, the cartilage in the ends of the bone is carried out, this process is called an enchondral osenation. The same type of transformation is observed in the articular surfaces, all people in the process of growing pass through it. Vessels are growing into the fabric of cartilage, which is important for nutrition, further conversion. Osteogenic cells are located in the Advential sheath of the vessels, which are subsequently becoming osteoblasts.

It has already been mentioned that the Osteoblast can form an intercellular substance next to him. Thus, osteon is formed around the bone plates. In parallel with chondroclasts, the cartilage component of the bone is destroyed, after which it acquires its specific appearance.

Ultimately, the bone is rebuilt, growing, the destruction of old sites, the formation of new ones. A fine-fiber bone tissue is formed by the periosteum, which becomes stronger with time.

Varieties of bones

There are two types of fabrics that have fundamental differences may occur in any site of the body.

Cortical

This cloth is formed by 80% of all bones in a human skeleton, it is distinguished by strength, located, in particular, in the gum area. The task of the cortical bone is to maintain the body in space, in the protection of organs, ensuring physical effort, this fabric is able to accumulate, release calcium. Presented content of cortical bone tightly packaged osteon.

Spongy

The distinction and less dense structure has the spongy bone tissue, it is located in small bones and the gums area. This variety is softer, weaker than cortical. This type is found at the ends of long tubular bones, inside the bodies of the vertebrae. It is a sponge view of the bone, consisting of plates, strips that are adjacent to the cavities located irregularly, they contain a red bone marrow.

If you look at the bone, the feeling arises that the plates are chaotic, without organizing themselves. However, this is not the case, the location is constructed in such a way as to ensure the strength of the construction brackets used in construction. Load lines in the bone can change their direction depending on the change in the application of force. The surface area is large, due to this, metabolic processes, exchange of calcium ions occur optimally. The opposite side is that this kind is fasterly affected by osteoporosis.

Throughout life, the bone can be updated: the tagged cells are destroyed, new ones appear. The development process, presented above, is in equilibrium, destroyed areas the body can restore. The process is regulated by the hormones of the thyroid and blocking glands. Useful, no matter what type of bone, vitamins, A, D, S. In the child after birth, the lack of vitamin D leads to the formation of such a disease as Rahit.

Bone tissue is a specialized type of connector tissue with high mineralization of the intercellular substance (bone tissue by 73% consists of calcium and phosphorus salts). Of these tissues, the bones of the skeleton performing the reference function are constructed. Bones protect the head and spinal cord (bones of the skull and spine) and internal organs (ribs, pelvic bones). Bone tissues consist of cells andintercellular substance .

Cells:

- Osteocytes - prevailing bone tissue cells that have lost the ability to divide. They have a processful shape, poor organelles. Located in bone catering or lacuna, which repeat the osteocyte contours. Osteocyte processes are in kanalzach Bones, diffusion of nutrients and oxygen from the blood of bone tissue.

- Osteoblastov - Young cells that create bone tissue. In the bones, they are found in the deep layers of the periosteum, in the places of formation and regeneration of bone tissue. In their cytoplasm, the granular endoplasmic network, mitochondria and the Golgi complex for the formation of an intercellular substance are well developed.

- Osteoclasts - Symplasts that can destroy occasionally cartilage and bone. They are formed from blood monocytes, have large sizes (up to 90 microns), contain up to several tens of cores . The cytoplasma is weakly basophilic, rich in mitochondria and lysosomes. To destroy the bone tissue, they produce coalic acid (for dissolving salts) and enzymes lysosomes (for the destruction of organic substances).

Intercellular substance comprises:

- basic substance (Osseomukoid), impregnated with calcium and phosphorus salts (calcium phosphate, hydroxyapatitis crystals);

- collagen fibers forming non-large beams, and the hydroxyapatite crystals are ordered, along the fibers.

Depending on the location of collagen fibers in the intercellular substance, bone tissues are divided into:

1. Reticulophibroid bone tissue. In it, collagen fibers have meful Location. Such a fabric is found in embryogenesis. In adults, it can be found in the field of cranial seams and in places attaching tendons to the bones.

2. Platechyuyu bone tissue. This is the most common variety of bone tissue in an adult organism. It consists of bone plates formed by osteocytes and a mineralized amorphous substance with collagen fibers located inside each plate parallel. In the adjacent plates, the wolves usually have a different direction, due to which the high strength of the plate bone tissue is achieved. From this fabric built compact and spongy Substances of most flat and tubular skeleton bones.

Bone as an organ (structure of tubular bone)

The tubular bone consists of epiphysis and diaphysis. Outside Diaphysis covered perceivers , or period. In the perception distinguish two layers: outer (fibrous) - formed mainly fibrous connective tissue, and interior (cell) - contains stem cells and young osteoblasts . From periosteum through suggesting channelspurchase bone vessels and nerves . The periosteum connects the bone with the surrounding tissues and takes part in its nutrition, development, growth and regeneration. The compact substance forms the dice diaphrability consists of bone plates that form three layers:

– Outer layer of common plates , in him the plates form 2-3 layers going around the diaphysis.

– Medium, osteon layer, Educated concentrically layered around vessels with bone plates . Such structures are called osteoni (System Gavers) , And concentric plates, their forming - osteon plates. Between plates B. lakunah The bodies of osteocytes are located, and their processes go across the plates are interconnected and located in bone canalis. Osteon can be imagined as a system of hollow cylinders inserted into each other, and osteocytes with processes look in them "like spiders with thin legs". Osteon are a functional structural unit of a tubular bone compact substance. Each osteon is derived from neighboring osteons of the so-called spying line. IN central Canal Osteon ( gaverce Canal) undergo blood vessels with the accompanying connective tissue . All osteons are mainly located along the long axis of the bone. Osteonov canals anastomosi powered with each other. The vessels located in Osteonov canals communicate with each other, with vessels of vessels and bone marrow. All space between osteo we fill insert plates(residues of old destroyed osteonov).

– Inner layer of common plates - 2-3 layers of plates bordered with endostom and bone marrow cavity.

From the inside the compact diaphyse substance is covered endostom containing as per capita, stem cells and osteoblasts.

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

Bone tissue is a specialized type of connective tissue, in the organic intercellular substance of which is contained up to 70% of inorganic compounds - salts of calcium and phosphorus and more than 30 microelements compounds. The composition of the organic matrix includes proteins of collagen type (ossein), chondroitin sulfate lipids. In addition, it includes citric acid and other acids that form complex compounds with calcium impregnating the intercellular substance.

There are 2 types of bone tissue: coarse-fiber (reticulous-protein) and a plate.

In the intercellular substance of bone tissue are located Cell elements : Osteogeneic cells, osteoblasts and osteocytes that are formed from mesenchym and represent bone differential. Another population of cells - osteoclasts.

Osteogenic cells - These are bone stem cells, isolated from mesenchyma at an early stage of osteogenesis. They are able to produce growth factors inducing hemopoies. In the process of differentiation, the osteoblasts are converted.

Osteoblastov Localized in the inner layer of periosteum, during the formation of bones are on its surface and around intraosteny vessels; Cubic cells, pyramidal, angular forms, with well-developed hydroelectric power plants and other synthesis organelles. They produce collagen proteins and amorphous matrix components, are actively divided.

Osteocytes - They are formed from osteoblasts, located inside the bone in peculiar bone lacunas, have a process. Lose the ability to divide. The secretion of the intercellular substance of the bone they are poorly expressed.

Osteoclasts - Polynuclear bone tissue macrophages are formed from blood monocytes. May contain up to 40 or more nuclei. The volume of cytoplasm is large; The zone of the cytoplasm, adjacent to the bone surface, forms a corrugated cabin formed by cytoplasmic growth, which contains a lot of lysosomes.

Functions - the destruction of the fibers and the amorphous substance of the bone.

Intercellular substance Presented by collagen fibers (collagen I, V types) and the amorphous component in which the calcium phosphate is contained (mainly in the form of hydroxyapatite crystals and a little - in amorphous state), a small amount of magnesium phosphate and very little glycosaminoglycans and proteoglycans.

For coarse-fiber (reticulophybrusina) bone tissue, the unordered location of Ossein fibers is characteristic. In the lamellar (mature) bone tissue, Ossein fibers in bone plates have a strictly ordered location. At the same time, in each bone plate, the fibers have the same parallel location, and in the adjacent bone plate they are at a right angle relative to the previous one. Cells between bone plates are localized in special lacunas, they can be closed into an intercellular substance or located on the surface of the bone and around vessels that penetrate the bone.

Bone as an organ Histologically consists of three layers: periosteum, compact substance and endosta.

Periosteum It has a structure similar to the sample, that is, consists of 2 similar layers, the inner of which is osteogenic, formed by a loose connective tissue, where there are many osteoblasts, osteoclasts and many vessels.

Endost Woven the bone marrow channel. It is formed by loose fibrous connective tissue, where there are osteoblasts and osteoclasts, as well as other cages of loose connective tissue.

Features of the periosteum and endosta: bone triqué, bone growth in thickness, bone regeneration.

Compact substance The bone consists of 3 layers. Outdoor and internal - these are general (general) bone plates, and between them is an osteon layer.

Structural and functional unit of bones as an organ is Osteon , which is a honey formation consisting of concentrically enjoying bone plates in each other in the form of several cylinders inserted one to another. Between the bone plates there are lacquers, in which osteocytes are lying. In the cavity of Osteon passes the blood vessel. The bone canal in which the blood vessel is located is called osteon channel or a gaverca channel. Between osteonov are inserted bone plates (residues of collapsed osteonov).

Bone fabric histogenesis.The source of the development of bone tissue is mezzanible cells eating from sclerotomes. At the same time, its histogenesis is carried out in two ways: directly from the mesenchym (direct osteohythogenesis) or from mesenchyma at the site of the previously formed hyaline cartilage (indirect osteohythogenesis).

Direct osteohythogenesis. Directly from the mesenchym is formed a rough fiber (reticulous-protein) bone tissue, which is subsequently replaced by a plate bone tissue. In direct osteochistogenesis distinguish 4 stages:

1. The separation of osteogenic island - in the formation of bone tissue formation of mesenchym, is actively divided and converted into osteogenic cells and osteoblasts, blood vessels are formed;

2. Osteoid stage - Osteoblasts begin to form an intercellular substance of bone tissue, while part of the osteoblasts are inside the intercellular substance, these osteoblasts are converted into osteocytes; Another part of the osteoblasts is on the surface of the intercellular substance, i.e., on the surface of the bone tissue, these osteoblasts will be included in the periosteum;

3. Mineralization of the intercellular substance (impregnating it with calcium salts). Mineralization is carried out due to the flow of calcium gliderophosphate, which, under the influence of alkaline phosphatase, is split into glycerin and the residue of phosphoric acid, reacting with calcium chloride, as a result of which calcium phosphate is formed; The latter turns into hydraulicapatite;

4. Perestroika and bone growth - old areas of coarse fiber bones are gradually destroyed and new areas of the plate bone are formed in their place; Due to the perceptions, general bone plates are formed, due to osteogenic cells located in the adventitization of bone vessels, osteons are formed.

Indirect osteochistogenesis It is carried out on the site of cartilage. At the same time, a plate bone tissue is immediately formed. In this case, 4 stages can also be distinguished:

1. Education of the cartilage model of the future bone;

2. In the area of \u200b\u200bdiaphysis of this model, a perichondral osenation occurs, while the schirler turns into an admiralion, in which stem (osteogenic) cells are differentiated into osteoblasts; Osteoblasts begin the formation of bone tissue in the form of common plates forming a bone cuff;

3. In parallel, an endochondral osenation is observed, which occurs both in the diaphysis field and in the region of epiphyse; Epiphyse osenation is carried out only by endochondral osenation; Blood vessels rotate inside the cartilage, in the Adventization of which there are osteogenic cells that turn into osteoblasts. Osteoblasts, producing the intercellular substance, form bone plates around the vessels in the form of osteonov; Simultaneously with the formation of the bone, the damage to chondroclasts;

4. Perestroika and bone growth - old areas of the bones are gradually destroyed and new ones are formed in their place; Due to the perceptions, general bone plates are formed, due to osteogenic cells located in the adventitization of bone vessels, osteons are formed.

In bone tissue throughout the life, constantly both the processes of creation and destruction occur. Normally, they bail each other. The destruction of bone tissue (resorption) is carried out by osteoclasts, and the destroyed areas are replaced by a newly built bone tissue, osteoblasts participate in the formation of which. The regulation of these processes is carried out with the participation of hormones produced by the thyroid, pancakes and other endocrine glands. The structure of bone tissue is influenced by vitamins A, D, C. Inadequate entry into the organism of vitamin D in the early postnatal period leads to the development of the disease Rickets.