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Bone is a complex matter; it is a complex anisotropic, uneven living material with elastic and viscous properties, as well as a good adaptive function. All the excellent properties of bones are inextricably unified with their functions.

The function of bones mainly has two sides: one is the formation of the skeletal system, which is used to support the human body and maintain its normal shape, as well as to protect its internal organs. The skeleton is the part of the body to which muscles are attached and which provides the conditions for their contraction and body movement. The skeleton itself performs an adaptive function by consistently changing its shape and structure. The second side of the function of bones is to, by regulating the concentration of Ca 2+, H +, HPO 4 + in the blood electrolyte, maintain the balance of minerals in the human body, that is, the function of hematopoiesis, as well as the preservation and exchange of calcium and phosphorus.

The shape and structure of bones vary depending on the functions they perform. Due to their functional differences, different parts of the same bone have different shapes and structures, for example, the diaphysis of the femur and the head of the femur. Therefore, a complete description of the properties, structure and functions of bone material is an important and challenging task.

Bone structure

“Tissue” is a combined formation consisting of special homogeneous cells that perform a specific function. Bone tissue contains three components: cells, fibers and bone matrix. Below are the characteristics of each of them:

Cells: There are three types of cells in bone tissue: osteocytes, osteoblast and osteoclast. These three types of cells interchange and combine with each other, absorbing old bones and generating new bones.

Bone cells are found within the bone matrix, these are the main cells of bones in normal condition, they have the shape of a flattened ellipsoid. In bone tissue, they provide metabolism to maintain the normal state of bones, and under special conditions they can turn into two other types of cells.

Osteoblast is cube or dwarf column shaped, they are small cellular projections arranged in a fairly regular pattern and have a large and round cell nucleus. They are located at one end of the cell body, the protoplasm has alkaline properties, they can form intercellular substance from fibers and mucopolysaccharide proteins, as well as from alkaline cytoplasm. This results in the precipitation of calcium salts into needle-shaped crystals located among the intercellular substance, which is then surrounded by osteoblast cells and gradually turns into osteoblast.

Osteoclasts are multinucleated giant cells, their diameter can reach 30–100 µm, they are most often located on the surface of absorbed bone tissue. Their cytoplasm is acidic in nature; inside it contains acid phosphatase, which is capable of dissolving bone inorganic salts and organic substances, transferring or throwing them to other places, thereby weakening or removing bone tissue in a given place.

The bone matrix is ​​also called the intercellular substance and contains inorganic salts and organic substances. Inorganic salts are also called inorganic bone constituents, their main component being hydroxyl apatite crystals about 20-40 nm long and about 3-6 nm wide. They mainly consist of calcium, phosphate radicals and hydroxyl groups that form, on the surface of which there are ions Na +, K +, Mg 2+, etc. Inorganic salts make up approximately 65% ​​of the total bone matrix. Organic substances are mainly represented by mucopolysaccharide proteins that form collagen fiber in bone. Crystals of hydroxyl apatite are arranged in rows along the axis of collagen fibers. Collagen fibers are arranged unequally, depending on the heterogeneous nature of the bone. In the interlacing reticular fibers of bones, the collagen fibers are bundled together, but in other types of bones they are usually arranged in orderly rows. Hydroxyl apatite binds together with collagen fibers, which gives the bone high compressive strength.

Bone fibers are mainly composed of collagen fiber, so it is called bone collagen fiber, the bundles of which are arranged in layers in regular rows. This fiber is closely connected to the inorganic constituents of the bone to form a board-like structure, hence it is called lamella or lamellar bone. In the same bone plate, most of the fibers are located parallel to each other, and the layers of fibers in two adjacent plates intertwine in the same direction, and the bone cells are sandwiched between the plates. Due to the fact that the bone plates are located in different directions, the bone substance has quite high strength and plasticity, it is able to rationally perceive compression from all directions.

In adults, almost all bone tissue is presented in the form of lamellar bone, and depending on the shape of the location of the bone plates and their spatial structure, this tissue is divided into dense bone and spongy bone. Dense bone is located on the superficial layer of abnormal flat bone and on the diaphysis of a long bone. Its bone substance is dense and strong, and the bony plates are arranged in a fairly regular order and closely connected to each other, leaving only a small space in some places for blood vessels and nerve canals. Spongy bone is located in its deep part, where many trabeculae intersect, forming a mesh in the form of a honeycomb with different sizes of holes. The holes of the honeycomb are filled with bone marrow, blood vessels and nerves, and the location of the trabeculae coincides with the direction of the lines of force, so although the bone is loose, it is able to withstand a fairly large load. In addition, cancellous bone has a huge surface area, which is why it is also called bone, which is shaped like a sea sponge. An example is the human pelvis, the average volume of which is 40 cm 3, and the surface area of ​​dense bone is on average 80 cm 2, while the surface area of ​​trabecular bone reaches 1600 cm 2.

Bone morphology

In terms of morphology, bones vary in size and can be classified into long bones, short bones, flat bones and irregular bones. Long bones are tube-shaped, the middle part of which is the diaphysis, and both ends are the epiphysis. The epiphysis is relatively thick, has an articular surface formed together with neighboring bones. Long bones are mainly located on the limbs. Short bones have an almost cubic shape, most often found in parts of the body that experience quite significant pressure, and at the same time they must be mobile, for example, these are the bones of the wrists and the tarsal bones of the legs. Flat bones have the shape of plates; they form the walls of bone cavities and play a protective role for the organs located inside these cavities, for example, like the bones of the skull.

Bone consists of bone substance, marrow and periosteum, and also has an extensive network of blood vessels and nerves, as shown in the figure. The long femur consists of a diaphysis and two convex epiphyseal ends. The surface of each epiphyseal end is covered with cartilage and forms a smooth articular surface. The coefficient of friction in the space between the cartilages at the joint junction is very small, it can be below 0.0026. This is the lowest known frictional force between solid bodies, allowing cartilage and adjacent bone tissue to create a highly efficient joint. The epiphyseal plate is formed from calcified cartilage connected to cartilage. The diaphysis is a hollow bone, the walls of which are formed from dense bone, which is quite thick along its entire length and gradually thins towards the edges.

Bone marrow fills the medullary cavity and cancellous bone. In fetuses and children, the medullary cavity contains red bone marrow; it is an important hematopoietic organ in the human body. In adulthood, the marrow in the bone marrow cavity is gradually replaced by fats and yellow bone marrow is formed, which loses its ability to form blood, but the bone marrow still contains red bone marrow that performs this function.

The periosteum is a compacted connective tissue closely adjacent to the surface of the bone. It contains blood vessels and nerves that perform a nutritional function. Inside the periosteum there is a large amount of highly active osteoblast, which during the period of human growth and development is able to create bone and gradually make it thicker. When bone is damaged, the dormant osteoblast within the periosteum becomes active and becomes bone cells, which are essential for bone regeneration and repair.

Bone microstructure

The bone substance in the diaphysis is mostly dense bone, and only near the medullary cavity there is a small amount of cancellous bone. Depending on the arrangement of the bony lamellae, dense bone is divided into three zones, as shown in the figure: annular lamellae, Haversian (Haversion) lamellae and interosseous lamellae.

Annular plates are plates arranged circumferentially on the inner and outer sides of the diaphysis, and they are divided into outer and inner annular plates. The outer ring-shaped plates have from several to more than a dozen layers, they are located in orderly rows on the outer side of the diaphysis, their surface is covered with periosteum. Small blood vessels in the periosteum penetrate the outer ring-shaped plates and penetrate deep into the bone substance. The channels for blood vessels passing through the outer annular plates are called Volkmann's Canal. The internal ring-shaped plates are located on the surface of the medullary cavity of the diaphysis; they have a small number of layers. The inner ring-shaped plates are covered by the internal periosteum, and Volkmann's canals also pass through these plates, connecting small blood vessels with the vessels of the bone marrow. The bony plates concentrically located between the inner and outer ring-shaped plates are called Haversian plates. They have from several to more than a dozen layers located parallel to the axis of the bone. The Haversian plates have one longitudinal small canal, called the Haversian canal, which contains blood vessels, as well as nerves and a small amount of loose connective tissue. Haversian plates and Haversian canals form the Haversian system. Due to the fact that there are a large number of Haversian systems in the diaphysis, these systems are called osteons. Osteons are cylindrical in shape, their surface is covered with a layer of cementin, which contains a large amount of inorganic components of bone, bone collagen fiber and an extremely small amount of bone matrix.

Interosseous plates are irregularly shaped plates located between osteons, they do not have Haversian canals and blood vessels, they consist of residual Haversian plates.

Intraosseous circulation

Bone has a circulatory system, for example, the figure shows a model of blood circulation in a dense long bone. The diaphysis contains the main feeding artery and veins. In the periosteum of the lower part of the bone there is a small hole through which a feeding artery passes into the bone. In the bone marrow, this artery divides into upper and lower branches, each of which further diverges into many branches that form capillaries at the final section that nourish brain tissue and supply dense bone with nutrients.

The blood vessels in the terminal part of the epiphysis connect to the feeding artery entering the medullary cavity of the epiphysis. The blood in the vessels of the periosteum flows out from it, the middle part of the epiphysis is mainly supplied with blood from the feeding artery and only a small amount of blood enters the epiphysis from the vessels of the periosteum. If the feeding artery is damaged or cut during surgery, it is possible that the blood supply to the pineal gland will be replaced by nutrition from the periosteum, since these blood vessels communicate with each other during fetal development.

Blood vessels in the epiphysis pass into it from the lateral parts of the epiphyseal plate, developing, turning into epiphyseal arteries that supply blood to the brain of the epiphysis. There are also a large number of branches that supply blood to the cartilage around the epiphysis and its lateral parts.

The upper part of the bone is articular cartilage, under which is the epiphyseal artery, and even lower is the growth cartilage, after which there are three types of bone: intracartilaginous bone, bony plates and periosteum. The direction of blood flow in these three types of bone is not the same: in the intracartilaginous bone the blood moves upward and outward, in the middle part of the diaphysis the vessels have a transverse direction, and in the lower part of the diaphysis the vessels are directed downward and outward. Therefore, the blood vessels throughout the dense bone are arranged in the shape of an umbrella and diverge in a radial manner.

Because the blood vessels in bone are very thin and cannot be observed directly, studying the dynamics of blood flow in them is quite difficult. Nowadays, with the help of radioisotopes introduced into the blood vessels of the bone, judging by the amount of their residues and the amount of heat they generate in comparison with the proportion of blood flow, it is possible to measure the temperature distribution in the bone to determine the state of circulation.

In the process of treating degenerative-dystrophic diseases of the joints using a non-surgical method, an internal electrochemical environment is created in the head of the femur, which helps restore impaired microcirculation and actively remove metabolic products from tissues destroyed by the disease, stimulates the division and differentiation of bone cells, which gradually replace the bone defect.

Bone tissue is a supporting tissue characterized by special mechanical properties, which consists of bone cells and a special intermediate substance. The composition of the intermediate substance includes (bone matrix) and various inorganic compounds. In addition, bone tissue has a lacunar-canalicular system, consisting of a network of microscopic lacunae and tubules and providing intraosseous metabolism.

There are three types of bone cells: osteoclasts, osteoblasts and osteocytes. Osteoclasts are multinucleated large cells of monocyte origin, the size of which can reach 190 microns. These cells are involved in the resorption (destruction) of bones and cartilage. In the process of reparative and physiological regeneration of bone tissue, osteoclasts carry out its resorption. The activity of osteoclasts directly depends on the amount of synthesis of which entails activation of osteoclast function, leading to bone destruction.

Osteoblasts are young polygonal cubic bone cells that lie in the superficial layers of bone and are surrounded by thin collagen microfibrils. The main function of osteoblasts is to synthesize the components of the intercellular substance - bone collagen, as well as regulate its mineralization.

Osteocytes are located in lacunae and are mature spindle-shaped multi-processed bone cells that regulate intraosseous metabolism.

There are two types of bone tissue: coarse-fiber and lamellar. In an adult, coarse-fibrous bone tissue is located in the sutures of the skull and areas of attachment of bones to tendons, and also contains disordered thick bundles of collagen fibers. The composition of lamellar bone tissue includes bone plates 4-15 microns thick made of osteocytes, ground substance and thin collagen fibers.

Bone tissue, like other organs of the human body, is susceptible to various inflammations and diseases. Inflammatory agents can be introduced into it through the bloodstream, i.e., hematogenously, if the patient has a purulent focus. tissues are called osteomyelitis, the predisposing factors for the occurrence of which may be vitamin deficiency, trauma, overwork, cooling, etc. Depending on the intensity and speed of development of osteomyelitis, chronic, subacute and acute forms of this disease are distinguished.

The result of a long-term inflammatory process of bone tissue is blockage of blood vessels (thrombosis). Thus, deprived of adequate nutrition, bone tissue begins to die and collapse, as a result, necrosis (death) and destruction of bone tissue occurs. In addition, the dead areas of the bone are rejected and the connection with healthy bone tissue is lost, so-called sequesters are formed.

The main causes of tissue infection) are pyogenic microbes: streptococci, staphylococci and pneumococci, as well as intestinal, typhoid bacilli and other microbes. A type of osteomyelitis is considered to be inflammatory diseases such as bone panaritium and bone tuberculosis.

It consists of destroying the infection with the help of antibiotics, which are selected individually depending on the type of bacteria. Taking antibiotics lasts about two months. During the first days, the drugs are taken in the form of tablets; if after four days no improvement is observed, the drugs continue to be administered intravenously or directly into the site of osteomyelitis.

Bone cells (bone):

* osteoblasts,

* osteocytes,

* osteoclasts.

The main cells in formed bone tissue are osteocytes. These are process-shaped cells with a large nucleus and weak cytoplasm (nuclear type cells). Cell bodies are localized in bone cavities - lacunae, and processes - in bone tubules. Numerous bone tubules, anastomosing with each other, penetrate the entire bone tissue, communicating with the perivascular spaces, and form the bone tissue drainage system. This drainage system contains tissue fluid, through which the exchange of substances is ensured not only between cells and tissue fluid, but also with intercellular substance. The ultrastructural organization of osteocytes is characterized by the presence in the cytoplasm of a weakly defined granular endoplasmic reticulum, a small number of mitochondria and lysosomes, and no centrioles. Heterochromatin predominates in the nucleus. All these data indicate that osteocytes have insignificant functional activity, which consists in maintaining metabolism between cells and the intercellular substance. Osteocytes are the definitive cell form and do not divide. They are formed from osteoblasts.

Osteoblasts are found only in developing bone tissue. They are absent in formed bone tissue (bone), but are usually contained in an inactive form in the periosteum. In developing bone tissue, they cover the periphery of each bone plate, tightly adjacent to each other, forming a kind of epithelial layer. The shape of such actively functioning cells can be cubic, prismatic, or angular. The cytoplasm of osteoblasts contains a well-developed granular endoplasmic reticulum and a lamellar Golgi complex, and many mitochondria. This ultrastructural organization indicates that these cells are synthesizing and secreting.

Indeed, osteoblasts synthesize collagen protein and glycosaminoglycans, which are then released into the intercellular space. Due to these components, the organic matrix of bone tissue is formed. Then these same cells provide mineralization of the intercellular substance by secreting calcium salts. Gradually, releasing intercellular substance, they become walled up and turn into osteocytes. In this case, intracellular organelles are significantly reduced, synthetic and secretory activity is reduced, and the functional activity characteristic of osteocytes is preserved. Osteoblasts, localized in the cambial layer of the periosteum, are in an inactive state, synthetic and transport organelles are poorly developed. When these cells are irritated (in the case of injuries, bone fractures, and so on), a granular endoplasmic reticulum and lamellar complex quickly develop in the cytoplasm, active synthesis and release of collagen and glycosaminoglycans occurs, the formation of an organic matrix (bone callus), and then the formation of definitive bone tissue (bones). In this way, due to the activity of osteoblasts of the periosteum, bone regeneration occurs when they are damaged.

Oteoclasts are bone-destructive cells and are absent in formed bone tissue. But they are contained in the periosteum and in places of destruction and restructuring of bone tissue. Since local processes of bone tissue restructuring are continuously carried out during ontogenesis, osteoclasts are necessarily present in these places. During the process of embryonic osteohistogenesis, these cells play an important role and are found in large numbers.

Osteoclasts have a characteristic morphology:

* these cells are multinucleated (3-5 or more nuclei);

* these are quite large cells (about 90 microns in diameter);

* they have a characteristic shape - the cell is oval in shape, but the part of it adjacent to the bone tissue is flat.

In this case, two zones are distinguished in the flat part:

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

* the peripheral (transparent) part is in close contact with the bone tissue.

In the cytoplasm of the cell, under the nuclei, there are numerous lysosomes and vacuoles of different sizes. The functional activity of the osteoclast is manifested as follows: in the central (corrugated) zone of the cell base, carbonic acid and proteolytic enzymes are released from the cytoplasm. The released carbonic acid causes demineralization of bone tissue, and proteolytic enzymes destroy the organic matrix of the intercellular substance. Fragments of collagen fibers are phagocytosed by osteoclasts and destroyed intracellularly. Through these mechanisms, resorption (destruction) of bone tissue occurs and therefore osteoclasts are usually localized in the recesses of bone tissue. After the destruction of bone tissue, due to the activity of osteoblasts moving out of the connective tissue of blood vessels, new bone tissue is built.

The intercellular substance of bone tissue consists of:

* basic substance

* and fibers that contain calcium salts.

The fibers consist of type I collagen and are folded into bundles, which can be arranged in parallel (ordered) or disordered, on the basis of which the histological classification of bone tissue is based.

The main substance of bone tissue, like other types of connective tissues, consists of:

* glycosaminoglycans

* and proteoglycans.

However, the chemical composition of these substances is different. In particular, bone tissue contains less chondroitinsulfuric acids, but more citric and other acids that form complexes with calcium salts. In the process of bone tissue development, an organic matrix-ground substance and collagen (ossein, type II collagen) fibers are first formed, and then calcium salts (mainly phosphates) are deposited in them. Calcium salts form hydroxyapatite crystals, deposited both in the amorphous substance and in the fibers, but a small part of the salts is deposited amorphously. Providing bone strength, calcium phosphate salts are also a depot of calcium and phosphorus in the body. Therefore, bone tissue takes part in mineral metabolism.

Note in the body (literary data):

1. From 208 to 214 individual bones.

2. Native bone is composed of 50% inorganic material, 25% organic matter, and 25% water associated with collagen and proteoglycans.

3. 90% of organic matter consists of collagen type 1 and only 10% of other organic molecules (glycoprotein osteocalcin, osteonectin, osteopontin, bone sialoprotein and other proteoglycans).

4. Bone components are represented by: organic matrix - 20-40%, inorganic minerals - 50-70%, cellular elements 5-10% and fats - 3%.

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

6. The average weight of the skeleton is 5 kg (weight greatly depends on age, gender, body structure and height).

7. In an adult body, the cortical bone accounts for 4 kg, i.e. 80% (in the skeletal system), while cancellous bone makes up 20% and weighs on average 1 kg.

8. The total volume of skeletal mass in an adult is approximately 0.0014 m³ (1,400,000 mm³) or 1,400 cm³ (1.4 liters).

9. The surface of the bone is represented by periosteal and endosteal surfaces - a total of about 11.5 m² (11,500,000 mm²).

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

11. The internal (endosteal) surface consists of three components - 1) the intracortical surface (surface of the Haversian canals), which is 30.4% or roughly 3.5 m² (3,500,000 mm²); 2) the surface of the inner side of the cortical bone is about 4.4% or roughly 0.5 m² (500,000 mm²) and 3) the surface of the trabecular component of the cancellous bone is 60.8% or roughly 7 m² (7,000,000 mm²).

12. Spongy bone 1 g. on average has a surface area of ​​70 cm² (70,000 cm²: 1000 g), while cortical bone is 1 g. has about 11.25 cm² [(0.5+3.5+0.5) x 10000 cm²: 4000 g], i.e. 6 times less. According to other authors, this ratio may be 10 to 1.

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

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And especially in deep-sea waters, the mineral content is relatively low, and they have a soft fibrous structure.

The surface of the bone can present various depressions (grooves, pits, etc.) and elevations (corners, edges, ribs, ridges, tubercles, etc.). The irregularities serve to connect bones to each other or to attach muscles and are more developed the more developed the muscles. On the surface there are so-called “nutrient openings” (Foramina nutritiva), through which nourishing and blood vessels enter the bone.

The bones are divided into dense and spongy bone matter. The first is characterized by uniformity, hardness and makes up the outer layer of bone; it is especially developed in the middle part of the tubular bones and becomes thinner towards the ends; in wide bones it consists of 2 plates, separated by a layer of spongy substance; in short ones, it covers the bone from the outside in the form of a thin film. The spongy substance consists of plates that intersect in different directions, forming a system of cavities and holes that merge into a large cavity in the middle of the long bones.

The outer surface of the bone is dressed in the so-called periosteum(Periosteum), a sheath of connective tissue containing blood vessels and special cellular elements and serving for nutrition, growth and repair of bone. The internal cavities of the bone are filled with a special soft tissue called bone marrow.

Cellular structure

According to its microscopic structure, bone substance is a special type of connective tissue (in the broad sense of the word), bone tissue, the characteristic features of which are: solid fibrous intercellular substance impregnated with mineral salts and stellate cells equipped with numerous processes.

Bone marrow

The internal cavities of the bone contain a soft, delicate, cell-rich and blood-vascular mass called bone marrow (in birds, some of the cavities are filled with air). There are three types of it: mucous (only in some developing bones), red or lymphoid (for example, in the epiphyses of tubular bones, in the spongy substance of the vertebrae), and yellow or fatty (the most common). The main form is red bone marrow, in which there is a delicate connective tissue base, rich in blood vessels, bone marrow or lymph cells very similar to leukocytes, cells stained with hemoglobin and considered to be the transition to red blood cells, colorless cells containing red balls inside, and multinucleated large (“giant”) cells, so-called. myeloplasts.

When the fat base is deposited in the cells (usually star-shaped) and the number of lymphatic elements decreases, the red marrow turns into yellow, and when the fat disappears and the lymphatic elements decrease, it approaches the mucous membrane.

Bone development and growth

Bone development occurs in 2 ways: either from connective tissue or cartilage. The first way to develop is the vault and lateral parts of the skull, the lower jaw and, according to some, the collarbone (and in lower vertebrates, some others) - this is the so-called. integumentary or enclosing bones. They develop directly from connective tissue; its fibers thicken somewhat, bone cells appear between them and lime salts are deposited in the spaces between them; Islands of bone tissue are first formed, which then merge with each other. Most skeletal bones develop from a cartilaginous base that has the same shape as the future bone. Cartilage tissue undergoes a process of destruction, absorption, and instead of it, bone tissue is formed, with the active participation of a special layer of educational cells (osteoblasts); This process can occur both from the surface of the cartilage, from the shell that covers it, the perichondrium, which then turns into the periosteum, and inside it. Usually, the development of bone tissue begins at several points; in tubular bones, the epiphyses and diaphysis have separate points of ossification.

Bone growth in length occurs mainly in parts that have not yet ossified (in the tubular bones between the epiphyses and diaphysis), but partly also through the deposition of new tissue particles between existing ones (“intussusception”), which is proven by repeated measurements of the distances between nutritive points driven into the bone holes, etc.; Bone thickening occurs through the deposition of new layers on the bone surface (“apposition”) due to the activity of periosteal osteoblasts. This latter has a high ability to reproduce destroyed and removed parts of the bone. Its activity also determines the healing of fractures. In parallel with bone growth, there is destruction, absorption (“resorption”) of some areas of bone tissue, and an active role is played by the so-called osteoclasts (“cells that destroy bone”), multinuclear elements that are observed on the walls of the brain cavities, in the periosteum and the walls of large cavities in the bones (eg maxillary sinus, etc.).

Bone connections

Syndesmology - the study of bone joints

• Synarthrosis is a continuous connection of bones, earlier in development, immobile or sedentary in function.
  • Syndesmosis - bones are connected through connective tissue.
    • interosseous membranes (between the bones of the forearm or lower leg)
    • ligaments (in all joints)
    • fontanelles
    • seams
      • serratus (most bones of the cranial vault)
      • scaly (between the edges of the temporal and parietal bones)
      • smooth (between the bones of the facial skull)
  • Synchondrosis - bones are connected by cartilage tissue.
    • according to the properties of cartilage tissue:
    • hyaline (between the ribs and sternum)
    fibrous
    • According to the duration of their existence, synchondrosis is distinguished:
    • temporary
  • permanent
• Synostosis - bones are connected through bone tissue.
  • Diarthrosis is a discontinuous joint, later in development and more mobile in function.
  • joint classifications:
• by the number of articular surfaces

in form and function

Hemiarthrosis is a transitional form from continuous to discontinuous or vice versa.

• see also

Form

long, short, flat, sesamoid

Wikimedia Foundation. 2010. See what “Bone tissue” is in other dictionaries:

BONE - Rice. 1. Bone cells (surface view). Rice. 1. Bone cells (surface view): 1 nucleus; 2 cytoplasm; 3 shoots. bone tissue, one of the types of connective tissue; hard calcified tissue that is part of... ...

Veterinary encyclopedic dictionary- one of the types of connective tissue. It is characterized by high mineralization of the intercellular substance. Mineral structures are formed on the protein collagen, the tripartite helical structure of which is a matrix for the deposition of minerals... ... Physical Anthropology. Illustrated explanatory dictionary.

Wikimedia Foundation.- a type of connective tissue that forms the basis of the bones of the vertebrate skeleton; consists of cells and mineralized intercellular substance. There are roughly fibrous and lamellar K. t. In the first (present in embryos, and in adults only... ... Psychomotorics: dictionary-reference book

Bone tissue is a specialized type of connective tissue with high mineralization of the intercellular substance (73% bone tissue consists of calcium and phosphorus salts). The bones of the skeleton, which perform a supporting function, are built from these tissues. Bones protect the brain and spinal cord (bones of the skull and spine) and internal organs (ribs, pelvic bones). Bone tissue is composed of cells Andintercellular substance .

Cells:

- Osteocytes– the predominant number of bone tissue cells that have lost the ability to divide. They have a process form and are poor in organelles. Located in bone cavities, or gaps, which follow the contours of the osteocyte. Osteocyte processes are located in tubules bones, through which nutrients and oxygen diffuse from the blood deep into the bone tissue.

- Osteoblasts– young cells that create bone tissue. In bone, they are found in the deep layers of the periosteum, in places of formation and regeneration of bone tissue. In their cytoplasm, the granular endoplasmic reticulum, mitochondria and Golgi complex are well developed for the formation of intercellular substance.

- Osteoclasts– simplasts that can destroy calcified cartilage and bone. They are formed from blood monocytes, are large in size (up to 90 microns), contain up to several dozen nuclei . The cytoplasm is slightly basophilic, rich in mitochondria and lysosomes. To destroy bone tissue, they secrete carbonic acid (to dissolve salts) and lysosome enzymes (to destroy organic bone substances).

Intercellular substance comprises:

- main substance (osseomucoid), impregnated with calcium and phosphorus salts (calcium phosphate, hydroxyapatite crystals);

- collagen fibers , forming small bundles, and the hydroxyapatite crystals lie in an orderly manner along the fibers.

Depending on the location of collagen fibers in the intercellular substance, bone tissue is divided into:

1. Reticulofibrous bone tissue. It contains collagen fibers disorderly location. Such tissue occurs during embryogenesis. In adults, it can be found in the area of ​​cranial sutures and in the places where tendons attach to bones.

2. Lamellar bone tissue. This is the most common type of bone tissue in the adult body. It consists of bone plates , formed by osteocytes and mineralized amorphous substance with collagen fibers located inside each plate parallel. In adjacent plates, the fibers usually have different directions, due to which greater strength of the lamellar bone tissue is achieved. Made from this fabric compact And spongy substances of most flat and tubular bones of the skeleton.

Bone as an organ (structure of tubular bone)

Tubular bone consists of epiphyses and diaphysis. The outside of the diaphysis is covered periosteum , or periostomy. The periosteum has two layers: outer(fibrous) – formed mainly by fibrous connective tissue, and interior(cellular) – contains stem cells and young osteoblasts . From the periosteum through perforating channels vessels and nerves supplying the bone pass through . The periosteum connects the bone with surrounding tissues and takes part in its nutrition, development, growth and regeneration. The compact substance that forms the bone diaphysis consists of bone plates that form three layers:

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

– Middle, osteonic layer, formed by concentrically layered bone plates around the vessels . Such structures are called osteons (Haversian systems) , and the concentric plates that form them are osteon plates. Between the records in gaps the bodies of osteocytes are located, and their processes run across the plates, are interconnected and are located in bone tubules. Osteons 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.” Osteons are a functional and structural unit of the compact substance of tubular bone. Each osteon is delimited from neighboring osteons by the so-called cleavage line. IN central channel osteon ( Haversian Canal) pass blood vessels with accompanying connective tissue . All osteons are mainly located along the long axis of the bone. The osteon canals anastomose with each other. The vessels located in the osteon canals communicate with each other, with the vessels of the periosteum and bone marrow. All the space between our osteos is filled insert plates(remains of old destroyed osteons).

– Inner layer of common plates – 2-3 layers of plates bordering the endosteum and the medullary cavity.

The inside of the compact substance of the diaphysis is covered endostome , containing, like the periosteum, stem cells and osteoblasts.