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About bones in general (general osteology) The chemical composition of the bone and its physical properties. The structure and chemical composition of bones

From school lessons in chemistry, everyone knows that the human body contains almost all the elements from the periodic table of D. I. Mendeleev. The percentage content of some is very significant, while others are present only in trace amounts. But each of the chemical elements found in the body performs its important role. In the human body, minerals are found in organic matter as carbohydrates, proteins, and others. Deficiency or excess of any of them leads to disruption of normal life.

The chemical composition of bones includes a number of elements and their substances, to a greater extent these are calcium salts and collagen, as well as others, the percentage of which is much less, but their role is no less significant. The strength and health of the skeleton depends on the balance of the composition, which, in turn, is determined by many factors, ranging from a healthy diet to the ecological situation of the environment.

Compounds that form the skeleton

and inorganic origin. Exactly half of the mass is water, the remaining 50% is divided by ossein, fat and lime, phosphorus salts of calcium and magnesium, and the mineral part accounts for about 22%, and the organic part, represented by proteins, polysaccharides, citric acid and enzymes, fills approximately 28% . Bones contain 99% of the calcium found in the human body. Similar component composition have teeth, nails and hair.

Transformations in various media

In an anatomical laboratory, the following analysis can be performed to confirm the chemical composition of the bones. To determine the organic part, the tissue is exposed to a medium strength acid solution, for example, hydrochloric acid, with a concentration of about 15%. In the resulting medium, calcium salts dissolve, and the ossein "skeleton" remains intact. Such a bone acquires the maximum property of elasticity, it can literally be tied into a knot.

The inorganic component, which is part of the chemical composition of human bones, can be isolated by burning out the organic part, it is easily oxidized to carbon dioxide and water. The mineral core is characterized by the former form, but is extremely fragile. The slightest mechanical impact - and it will simply crumble.

When bones enter the soil, bacteria process organic matter, and the mineral part is completely saturated with calcium and turns into stone. In places where there is no access to moisture and microorganisms, tissues eventually undergo natural mummification.

Through the microscope

Any textbook on anatomy will tell you about the chemical composition and structure of bones. At the cellular level, tissue is defined as a special type of connective tissue. At the base lie surrounded by plates composed of a crystalline substance - the calcium mineral - hydroxylapatite (basic phosphate). In parallel, there are star-like voids containing bone cells and blood vessels. Due to its unique microscopic structure, this fabric is surprisingly light.

The main functions of compounds of different nature

The normal functioning of the musculoskeletal system depends on the chemical composition of the bones, whether organic and mineral substances are contained in sufficient quantities. Lime and phosphorus calcium salts, which make up 95% of the inorganic part of the skeleton, and some other mineral compounds determine the hardness and strength of the bone. Thanks to them, the fabric is resistant to serious loads.

The collagen component and its normal content are responsible for such a function as elasticity, resistance to compression, stretching, bending and other mechanical influences. But only in a coordinated "union" organic matter and the mineral component provide the bone tissue with the unique properties that it possesses.

The composition of bones in childhood

The percentage of substances that indicate the chemical composition of human bones can vary in the same representative. Depending on age, lifestyle and other factors of influence, the amount of certain compounds may vary. In particular, in children it is only formed and consists to a greater extent of the organic component - collagen. Therefore, the skeleton of the child is more flexible and elastic.

For the proper formation of the tissues of the child, the intake of vitamins is extremely important. In particular, such as D 3 . Only in its presence the chemical composition of the bones is fully replenished with calcium. A deficiency of this vitamin can lead to the development of chronic diseases and excessive fragility of the skeleton due to the fact that the tissue was not filled with Ca 2+ salts in time.

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From school lessons in chemistry, everyone knows that the human body contains almost all the elements from the periodic table of D. I. Mendeleev. The percentage content of some is very significant, while others are present only in trace amounts. But each of the chemical elements found in the body performs its important role. In the human body, mineral substances are contained in the form of salts, organic substances are presented as carbohydrates, proteins and others. Deficiency or excess of any of them leads to disruption of normal life.

The chemical composition of bones includes substances of organic and inorganic origin. Exactly half of the mass is water, the remaining 50% is divided by ossein, fat and lime, phosphorus salts of calcium and magnesium, as well as sodium chloride. The mineral part accounts for about 22%, and the organic part, represented by proteins, polysaccharides, citric acid and enzymes, fills about 28%. Bones contain 99% of the calcium found in the human body. Similar component composition have teeth, nails and hair.

Any textbook on anatomy will tell you about the chemical composition and structure of bones. At the cellular level, tissue is defined as a special type of connective tissue. It is based on collagen fibers surrounded by plates composed of a crystalline substance - a calcium mineral - hydroxylapatite (basic phosphate). In parallel, there are star-like voids containing bone cells and blood vessels. Due to its unique microscopic structure, this fabric is surprisingly light.

The percentage of substances that indicate the chemical composition of human bones can vary in the same representative. Depending on age, lifestyle and other factors of influence, the amount of certain compounds may vary. In particular, in children, bone tissue is only being formed and consists to a greater extent of an organic component - collagen. Therefore, the skeleton of the child is more flexible and elastic.

For the proper formation of the tissues of the child, the intake of vitamins is extremely important. In particular, such as D3. Only in its presence the chemical composition of the bones is fully replenished with calcium. A deficiency of this vitamin can lead to the development of chronic diseases and excessive fragility of the skeleton due to the fact that the tissue was not filled with Ca2+ salts in time.

The chemical composition of the bones of a person who has passed adolescence is significantly different from that of a child. Now the ratio of the mineral and ossein parts are roughly compared. The special flexibility of bone tissue disappears, but the strength of the skeleton due to the inorganic component increases significantly. Its physical properties are comparable to a reinforced concrete structure or cast iron, and its elasticity is even greater than that of oak wood.

It is possible to fully ensure a balanced chemical composition of human bones (the table below contains data on the normal percentage of all substances that make up the skeleton) thanks to a proper lifestyle, rational nutrition and health care.

The chemical composition of human bones is disturbed by old age, which leads to serious consequences. Elderly people complain of problems with the musculoskeletal system, they are more likely to have fractures that take longer to heal than a child or an adult. This is a consequence of an increase in the content of inorganic salts in the composition of the skeleton, their amount reaches 80%. A lack of collagen, and therefore a decrease in such a property as elasticity, leads to the fact that the bones become extremely fragile. Restoring balance is possible with the help of special medications, but still this process cannot be stopped or reversed. This is the physiological feature of the body.

For the health and normal functioning of the skeleton, it is necessary from childhood to monitor the correct filling of the bone tissue with all chemical elements and compounds, only in this case it is possible to lead a full and active lifestyle.

Bone tissue has a structure with an ingeniously embodied architecture that combines mutually exclusive characteristics: density and elasticity, lightness and the ability to withstand severe loads.

What is bone made of? From cellular elements, organic matrix and minerals.

The organic matrix, or osteoid, is 90% collagen. Collagen fibrils form plates that are either parallel to each other or concentric around the blood vessels, thus forming channels connected by smaller tubules. Against the background of endocrine, chronic inflammatory diseases, primarily rheumatic diseases, the geometry of the bone tissue is disturbed.

The mineral part of the bone is represented mainly by calcium and phosphate, trace elements (magnesium, manganese, zinc, selenium and boron). For normal bone mineralization, it is necessary to maintain certain concentrations of trace elements.

The formation of bone tissue in childhood and the maintenance of a balance between the processes of formation and resorption (resorption) of bone throughout life occur in the body under the control of various external and internal factors, depending on gender, age, heredity, diet, physical activity, health status and much more. another.

Bone remodeling (formation and resorption) is the process by which inorganic substances (minerals) are deposited in the organic matrix. Bone is formed by cells - osteoblasts, which synthesize and secrete an organic matrix and are equipped with a large number of receptors for hormones, vitamin D, prostaglandins and other biological substances necessary for its nutrition and work.

Immediately after the formation of the matrix, its mineralization begins, which ends after a few weeks. In the process of mineralization, osteoblasts turn into osteocytes - cells completely integrated into the bone and having a very low metabolic activity (ie, with a very slow metabolism compared to other cells). Bone resorption is carried out by osteoclasts, actively synthesizing and secreting into the extracellular space enzymes that dissolve and recycle dead cells. The regulation of bone remodeling occurs with the participation of the neuroendocrine system. The activity of osteoblasts and osteoclasts is directly influenced by hormones of the thyroid, parathyroid, pancreas and gonads, adrenal glands and other endocrine organs. In recent years, much attention has been paid to the study of the role of the immune system in the regulation of remodeling.

Osteoporosis- a systemic disease of the skeleton, which is characterized by a decrease in bone mass and a violation of bone tissue at the molecular level, which leads to a decrease in bone strength and, consequently, to an increased risk of fractures.

The disease occurs in all age groups, is diagnosed in both women and men, can be asymptomatic, and often its first sign is a fracture. It is the fractures associated with osteoporosis, represent a huge social and economic problem, cause a low quality of life, disability and premature death. It has been established that an increase in the proportion of older people among the population of different countries of the world will lead to an increase in the frequency osteoporosis and its complications: by 2050, a 46% increase in the incidence of hip fractures is projected in Europe compared to 1990. The World Health Organization (WHO) has officially defined osteoporosis as one of the ten most important chronic diseases of mankind. At the same time, experts point out that osteoporosis can be prevented and cured. To date, risk factors and mechanisms of pathogenesis have been identified. osteoporosis, methods of its primary and secondary prevention have been developed, methods of treatment are being improved using various groups of drugs, including genetically engineered biological preparations.

According to most gerontologists, senile osteoporosis starts in childhood. Bone remodeling is disturbed, quantitative and qualitative changes in bone tissue, fractures occur, which can cause early disability and even death. According to T.A. Korotkova, who studied indicators and factors affecting bone mineralization during the period of growth in 412 adolescents aged 15-18 living in Moscow, more than half of the surveyed adolescents were found to be deficient in vitamin D, phosphorus and calcium. It turned out that only 6.3% of boys received 1300 mg of calcium per day with food, which corresponds to the recommended age norm, and none of the girls received this trace element in the proper amount.

It should be noted that the study of the role calcium, phosphorus and vitamin D Numerous studies have been devoted to the formation of bone mineral density (BMD) in women and men at different age periods of life. At the same time, the attention of scientists is attracted by the problem of low content of trace elements in the body in various pathological conditions, including osteoporosis, diseases of bones and joints.

Most trace elements are included in biologically active compounds or have an effect on them. As part of enzymes, hormones and immune complexes, microelements are involved in metabolic and immune processes, determining the functional state of various organs and systems, including bone and cartilage tissue, their quality and structure. Sick osteoporosis, as a rule, suffer simultaneously from two or three or more chronic diseases that have a negative effect on bone tissue. In the group of diseases against which the development osteoporosis, include rheumatoid arthritis, diabetes mellitus, celiac disease, chronic renal failure, chronic obstructive pulmonary disease and bronchial asthma, diseases of the thyroid and parathyroid glands, blood, liver and pancreas. Taking anticonvulsants, glucocorticoids and many other drugs also contributes to the development osteoporosis.

The leading role in this process is played by the level of providing the body with not only vitamins and protein, but also macro- and microelements. Deficiency due to insufficient dietary intake or reduced absorption of these substances can cause a decrease in bone mineral density. Particular importance is attached to such trace elements as copper, zinc, manganese and boron. Copper, manganese and zinc, which are part of the enzymes responsible for collagen synthesis, are directly involved in the synthesis of bone matrix. In addition, zinc is part of more than 300 enzymes, is involved in the synthesis and breakdown of carbohydrates, proteins, fats, nucleic acids. Insufficient zinc intake leads to anemia, secondary immunodeficiency, liver cirrhosis, sexual dysfunction, fetal malformations. Zinc in combination with the amino acid cysteine is fundamentally important for gene metabolism. Insulin, corticotropin, growth hormone and gonadotropin are zinc-dependent hormones. Bone tissue contains the main reserve (about 30%) of zinc in the whole body. The concentration of zinc in bone tissue rapidly decreases with insufficient intake of zinc in the body or a violation of its absorption. In this regard, it is not surprising that defects in the development of the human skeletal system are due to zinc deficiency. On average, a person consumes from 7.5 to 17.0 mg of zinc per day, while the physiological need for zinc in adults is 12 mg / day, and in children - from 3 to 12 mg / day. Sources of zinc are beef, liver, seafood (oysters, herring, shellfish), grain ovaries, carrots, peas, bran, oatmeal, nuts.

Copper is part of the enzymes that have redox activity and are involved in the metabolism of iron, stimulates the absorption of proteins and carbohydrates, and is involved in the processes of providing tissues of the human body with oxygen. In addition, this microelement is necessary for the intermolecular bonding of collagen and elastin. Copper is the main component of the myelin sheath, is involved in the formation of collagen, mineralization of the skeleton, the synthesis of red blood cells, the formation of skin pigments. Clinical manifestations of copper deficiency in the body are violations of the formation and function of the cardiovascular system, the skeleton, the development of connective tissue dysplasia. Copper deficiency leads to inhibition of bone growth and OP, which is observed in Menkes syndrome (congenital inability to absorb copper). The daily requirement for copper ranges from 0.9 to 3.0 mg/day. At the same time, the physiological need for copper in adults is 1.0 mg/day, in children - from 0.5 to 1.0 mg/day.

Sources of copper include chocolate, cocoa, liver, nuts, seeds, mushrooms, shellfish, salmon, and spinach.

Insufficient intake of manganese in the body is accompanied by growth retardation, disorders in the reproductive system, increased fragility of bone tissue, disorders of carbohydrate and lipid metabolism. This is due to the fact that manganese is directly involved in the formation of bone and connective tissue, is part of the enzymes involved in the metabolism of amino acids, carbohydrates, catecholamines, and is necessary for the synthesis of cholesterol and nucleotides.

Dietary sources of manganese are green leafy vegetables, whole grain products (wheat, rice), nuts and tea. The average intake of this trace element with food ranges from 1 to 10 mg / day. Established requirement levels range from 2 to 5 mg/day, and the physiological requirement in adults is 2 mg/day.

The role of boron in the processes of osteogenesis is determined by the direct influence of this trace element on the metabolism of vitamin D, as well as the regulation of the activity of parathyroid hormone, which is known to be responsible for the exchange of calcium, phosphorus and magnesium. This suggests that the effect of boron on bone metabolism is comparable to that of vitamin D. The daily requirement for boron is 2-3 mg/day, it is found in root vegetables, grapes, pears, apples, nuts and beer.

Information on the study of the status of microelements in the pathology of the skeletal system (osteopenia, osteoporosis) is extremely limited, since, unfortunately, few studies have been carried out, but the accumulated material allows us to draw unambiguous conclusions.

A direct relationship between the content of minerals in the bones of the forearm and the absorption of zinc in postmenopausal women has been established, which indicates the effect of this microelement on the preservation of bone mass. Other studies have shown that zinc absorption declines with age, especially in women, and is associated with postmenopausal bone loss. An increase in the excretion of zinc in the urine was found in patients with osteoporosis compared with women of the same age without osteoporosis, which may be associated with increased bone resorption, which leads to the release of zinc from bone tissue.

It has been established that the concentration of zinc in the blood, as well as its absorption in elderly patients with osteoporosis statistically significantly lower than in young women. The level of zinc in blood serum in patients with postmenopausal OP is lower than in women without osteoporosis.

Of particular interest is a study of the relationship between indicators of the status of zinc in the body and biochemical markers of bone remodeling in Europeans aged 55-87 years, conducted at four research centers in France, Italy and Northern Ireland (ZENITH). The study lasted 6 months and involved 387 healthy men and women. All patients were determined the concentration of zinc in the blood and urine, the level of markers of bone formation and markers of bone resorption. In most patients, bone remodeling was normal, there were no signs of an imbalance in the processes of bone formation and resorption. After adjusting for confounding factors (age, gender, and center of study), some data have been obtained on the relationship between body zinc metabolism and bone remodeling in healthy adults.

A study by Turkish scientists was devoted to the study of the content of magnesium, zinc and copper in the blood serum of women with postmenopausal osteoporosis, osteopenia and normal bone mineral density of the femoral neck. It was found that the concentration of magnesium and zinc in patients with osteoporosis significantly lower than in women with osteopenia and healthy women, and in women with osteopenia - statistically significantly lower than in healthy women. There was no statistically significant difference between the groups in terms of copper concentration. The authors suggested that micronutrient intake, especially magnesium, zinc, and possibly copper, may have a beneficial effect on bone density. However, a number of researchers did not find a significant difference in the concentration of magnesium, zinc, selenium and manganese in the blood and erythrocytes of postmenopausal women, both with osteoporosis, and without osteoporosis.

It should be noted that in many countries the status of magnesium, copper, zinc, manganese, selenium and boron in patients with osteoporosis not described in the literature. Some researchers report a decrease in the level of these trace elements in patients with osteoporosis while others claim otherwise. The inconsistency of data on the level of magnesium, copper, zinc, manganese, selenium and boron in blood plasma in the elderly is explained by the fact that the concentration of these trace elements in plasma or blood serum is used as an indicator. However, this indicator is unreliable, since it is influenced by a number of factors that are not related to the content of substances in the body. These factors include taking hormone replacement therapy drugs, diuretics, laxatives, etc.).

In our country, interest in studying the relationship between osteotropic microelements, characteristics of bone tissue and the possibility of using drugs containing these microelements for prevention and treatment osteoporosis obvious.

Thus, domestic pediatricians studied the status of microelements and indicators of bone mineral density in various parts of the skeleton in 100 adolescents aged 11-15 years old, hospitalized for autonomic dystonia. The examined patients showed changes in the content of boron, copper, manganese and zinc, and 46 people had osteopenia. It was possible to establish the relationship between the content of microelements in the hair and bone mineral density, to analyze the possibility of its assessment based on the determination of the complex of these microelements.

Thus, people with bone and joint diseases need to understand that there are many reasons for the development of osteoporosis: comorbidities, dietary habits, consumption of foods rich in micronutrients, signs of deficiency of calcium, vitamin D, zinc, copper, manganese, selenium and boron.

Promoting knowledge about the need for prevention and treatment osteoporosis, the contribution of calcium, vitamin D and trace elements to bone health will reduce the incidence of fractures, and hence the socio-economic costs of society.

The Clinical Guidelines prepared by the Russian Association for Osteoporosis formulate provisions for the treatment and prevention of osteoporosis based on the analysis of a large number of sources from the standpoint of evidence-based medicine. The main goal of prevention osteoporosis is to improve the quality of life of patients, prevent the risk of skeletal fractures. Prevention osteoporosis should be aimed at early diagnosis and rational treatment of the disease. The arsenal of therapeutic agents includes the necessary modern anti-osteoporotic drugs. The effectiveness of various agents (calcium and vitamin D preparations in combination with osteotropic microelements, etc.) has been proven in the prevention and treatment osteoporosis found their positive effect on bone mineral density.

Based on the materials of "Effective pharmacotherapy" No. 38 2013, Special issue No. 2 Osteoporosis, Reprint I.S. Dadykina, P.S. Dadykina, O.G. Alekseeva "The contribution of trace elements (copper, manganese, zinc, boron) to bone health: prevention and treatment of osteopenia and osteoporosis"

Bone- a solid organ of a living organism. It consists of several tissues, the most important of which is bone. Bone performs musculoskeletal and protective functions, is an integral part of the vertebrate endoskeleton, produces red and white blood cells, and stores minerals. Bone tissue is one of the varieties of dense connective tissue.

Bones come in a wide variety of shapes and sizes, depending on the function of the particular bone. Each has a complex structure, so that they are quite light, but at the same time rigid and durable. The bone may include in its structure: bone marrow, endosteum, periosteum, nerves, blood vessels, cartilage.

Bones are made up of various bone cells: osteoblasts are involved in the formation and mineralization of bones, osteocytes maintain structure, and osteoclasts provide bone resorption. The mineralized matrix of bone tissue has an organic component mainly from collagen and an inorganic component of bone tissue from various salts.

There are over 270 bones in the human body at birth, but many of these fuse together during growth, leaving a total of 206 individual bones in the adult body (not counting numerous small sesamoid bones). The femur is the largest bone in the human body, the smallest is the stirrup in the middle ear.

The composition of bones includes both organic and inorganic substances; the number of the former is greater, the younger the organism; in this regard, the bones of young animals are flexible and soft, and the bones of adults are hard. The relation between the two constituents represents the difference in different groups of vertebrates; thus, in the bones of fish, especially deep-sea fish, the content of mineral substances is relatively low, and they are distinguished by a soft fibrous structure.

In an adult, the amount of mineral constituents (mainly hydroxyapatite) is about 60-70% of bone weight, and organic matter (mainly type I collagen) is 30-40%. Bones have great strength and tremendous resistance to compression, resist destruction for an extremely long time and are among the most common remains of fossil animals. When calcined, the bone loses organic matter, but retains its shape and structure; By exposing the bone to the action of an acid (for example, hydrochloric acid), minerals can be dissolved and a flexible organic (collagen) framework of the bone can be obtained.

When burned, the bone turns black with the release of carbon, which remains after the decomposition of organic matter. With further burnout of carbon, a white solid brittle residue is obtained.

In older people, the proportion of minerals in the bones increases, because of this, their bones become more fragile (osteoporosis).

Microscopic bone structure

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

The basis of the bone is collagen fibers surrounded by hydroxyapatite crystals, which form plates. These plates in the bone substance are partly located in concentric layers around long branching canals (Haversian canals), partly lie between these systems, partly embrace entire groups of them or stretch along the surface of the bone. The Haversian canal, in combination with the surrounding concentric bone plates, is considered to be the structural unit of the compact bone substance, the osteon. Parallel to the surface of these plates, they contain layers of small star-shaped voids, continuing into numerous thin tubules - these are the so-called "bone bodies", in which there are bone cells that give rise to tubules. The tubules of the bone bodies are connected to each other and to the cavity of the Haversian canals, the internal cavities and the periosteum, and thus the entire bone tissue is permeated with a continuous system of cavities and tubules filled with cells and their processes, through which the nutrients necessary for bone life penetrate. Fine blood vessels (usually an artery and a vein) pass through the Haversian canals; the wall of the Haversian canal and the outer surface of the blood vessels are covered with a thin layer of endothelium, and the spaces between them serve as the lymphatic pathways of the bone. Cancellous bone does not have Haversian canals.

The bone tissue of fish presents some differences: there are no Haversian canals here, and the tubules of the bone bodies are highly developed.

Osteoblasts are young bone-forming bone cells (diameter 15-20 microns) that synthesize the intercellular substance - the matrix. As the intercellular substance accumulates, osteoblasts become immured in it and become osteocytes. The ancestor is the adventitial cells.

Osteocytes are cells of the bone tissue of vertebrates and humans that have significantly or completely lost the ability to synthesize the organic component of the matrix.

They have a process shape, a rounded dense nucleus and a weakly basophilic cytoplasm. There are few organelles, there is no cell center - the cells have lost the ability to divide. They are located in bone cavities, or lacunae, following the contours of an osteocyte, and are 22–25 µm long and 6–14 µm wide. Slightly branching tubules of the bone cavities depart in all directions from the lacunae, anastomosing (communicating) with each other and with the perivascular spaces of the vessels running inside the bone. The space between the processes of osteocytes and the walls of the tubules contains tissue fluid, the movement of which is facilitated by "pulsating" oscillations of osteocytes and their processes. Osteocytes are the only living and actively functioning cell in mature bone tissue, their role is to stabilize the organic and mineral composition of the bone, metabolism (including the transport of Ca ions from bone to blood and vice versa). Bone tissue that does not contain living osteocytes is rapidly destroyed.

Cells of hematogenous origin, formed from monocytes. May contain from 2 to 50 cores. The organization of the osteoclast is adapted to bone destruction. In combination with osteoblasts, osteoclasts control the amount of bone tissue (osteoblasts create new bone tissue, and osteoclasts break down old bone)

Schematic diagram of the structure of the tubular bone

In the human skeleton, long, short, flat and mixed bones are distinguished in shape, there are also pneumatic and sesamoid bones. The location of the bones in the skeleton is related to the function they perform: “The bones are built in such a way that, with the least amount of material, they have the greatest strength, lightness, and, if possible, reduce the effect of shocks and concussions” (P. F. Lesgaft).

long bones, ossa longa, have an elongated, tubular middle part called diaphysis, diaphysis, consisting of a compact substance. Inside the diaphysis there is medullary cavity, cavitas medullaris, with yellow marrow. At each end of a long bone is epiphysis, epiphysis, filled with spongy substance with red bone marrow. Between the diaphysis and the epiphysis metaphysis, metaphysis. During the period of bone growth, cartilage is located here, which later ossifies. Long tubular bones make up mainly the skeleton of the limbs. Bone protrusions on the epiphyses, which are the site of attachment of muscles and ligaments, are called apophyses (apophysis).

flat bones, ossa plana, consist of a thin layer of spongy substance, covered on the outside with a compact substance. They are different in origin: the scapula and pelvic bone develop from cartilage, and the flat bones of the skull roof from connective tissue.

short bones, ossa brevia, consist of a spongy substance covered on the outside with a thin layer of compact substance. These bones do not have one large bone marrow cavity. Red bone marrow is located in small spongy cells separated by bone beams. The short bones of the wrist and tarsus contribute to greater mobility of the hands and feet.

mixed dice, ossa irregularia, are located in various parts of the skeleton (spine, skull). They combine elements of short and flat bones (the main part and scales of the occipital bone, the body of the vertebra and its processes, the petrous part and scales of the temporal bone). Such features are due to the difference in the origin and function of the parts of these bones.

Pneumatic dice, or air-bearing, - bones that have a cavity inside, lined with a mucous membrane and filled with air, which lightens the weight of the bone without reducing its strength.

Sesamoid bones- these are bones inserted into the tendons of the muscles and therefore increase the shoulder of muscle strength, contributing to the strengthening of their action.

The surface of the bone may have various depressions (striations, pits, etc.) and elevations (corners, edges, ribs, ridges, tubercles, etc.). Irregularities serve to connect bones to each other or to attach muscles and are the more developed, the more developed the muscles. On the surface are the so-called "nutritional holes" (Foramina nutricia), through which nerves and blood vessels enter the bone.

Bones are divided into compact and spongy bone. The first is homogeneous, hard and makes up the outer layer of the bone; it is especially developed in the middle part of the tubular bones and becomes thinner towards the ends; in broad bones it is 2 plates separated by a layer of spongy substance; in short ones, in the form of a thin film, it dresses the bone from the outside. The spongy substance consists of plates intersecting in various directions, forming a system of cavities and holes, which 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 connective tissue sheath containing blood vessels and special cellular elements that serve to nourish, grow and repair bones.

The internal cavities of the bone contain a soft, tender, cell-rich and vascularized mass called bone marrow (in birds, some of the cavities are filled with air). There are three types of it: mucous (gelatinous), red (or often myeloid), and yellow or fatty (the most common). The main form is the red bone marrow, it has a delicate connective tissue base rich in blood vessels, bone marrow or lymphatic 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, the so-called myeloplasts.

Red (active) bone marrow- it myeloid tissue , which, like lymphoid, consists of two main components: stromal- stroma, which serves as a microenvironment for hematopoietic (hematopoietic) cells, and hemal- formed elements of blood at different stages of development.

Stroma formed by reticular tissue, osteogenic, obese, fatty, adventitial, endothelial cells and intercellular substance.

Yellow (inactive) bone marrow- this is adipose tissue with separate islands (stromas) of reticular tissue. It is found in the medullary canals of tubular bones and in parts of the cells of the cancellous bone.

Mucous bone marrow- gelatinous, slimy, cell-poor consistency. It is formed in the developing bones of the skull and face.

When the fat base is deposited in the stromal component and the number of myeloid elements decreases, the red brain turns into yellow, and when the fat and myeloid elements disappear, it approaches the mucous.

The bone marrow has nothing to do with the brain and spinal cord. It does not belong to the nervous system and has no neurons.

The bone marrow is the most important hematopoietic organ.

Bone develops in two ways:

from connective tissue;
in place of the cartilage.

The bones of the vault and lateral parts of the skull, the lower jaw and, according to some, the clavicle (and some others in lower vertebrates) develop from the connective tissue - these are the so-called integumentary or tight-fitting bones. They develop directly from the connective tissue; its fibers thicken somewhat, bone cells appear between them, and in the intervals between the latter, lime salts are deposited; islands of bone tissue are formed first, which then merge with each other. Most of the bones of the skeleton 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 go both from the surface of the cartilage, from the sheath that dresses 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 ossification points.

The growth of the bone in length occurs mainly in parts that have not yet ossified (in the tubular bones between the epiphyses and the diaphysis), but partly by the deposition of new tissue particles between the existing ones ("intussusception"), which is proved by repeated measurements of the distances between the points driven into the bone, nutritious holes, etc.; thickening of the bones occurs by deposition of new layers on the surface of the bone ("apposition"), due to the activity of osteoblasts of the periosteum. This latter has a high degree of ability to reproduce destroyed and removed parts of the bone. Its activity is also determined by the fusion of fractures. In parallel with the growth of the bone, there is destruction, absorption (resorption) of some parts of the bone tissue, and the so-called osteoclasts (“bone-destroying cells”) play an active role.

Syndesmology is the study of the joints of bones.

Synarthrosis - continuous connections of bones, earlier in development, motionless or inactive in function.
- Syndesmosis - bones are connected by connective tissue.
  - interosseous membranes (between the bones of the forearm or lower leg)
  - ligaments (in all joints)
  - fontanelles
  - seams
    - dentate (most bones of the cranial vault)
    - squamous (between the edges of the temporal and parietal bones)
    - smooth (between the bones of the facial skull)
- Synchondrosis - the bones are connected by cartilage. according to the properties of cartilage tissue:
  - hyaline (between ribs and sternum)
  - fibrous (between vertebrae)
  According to the duration of their existence, synchondrosis is distinguished:
  - temporary
  - permanent
- Synostosis - bones are connected by means of bone tissue.
Diarthroses are discontinuous connections, later in development and more mobile in function. joint classifications:
- according to the number of articular surfaces
- in form and function
Hemiarthrosis is a transitional form from continuous to discontinuous or vice versa.

Everyone needs to know the human skeleton with the name of the bones. This is important not only for doctors, but also for ordinary people, because information about the structure of a person, his skeleton and muscles will help to strengthen him, feel healthy, and at some point can help out in emergency situations.

The skeleton and muscles together make up the human locomotor system. The human skeleton is a whole complex of bones of different types and cartilage, interconnected with the help of continuous joints, synarthroses, symphyses. Bones are divided into:

tubular, forming the upper (shoulder, forearm) and lower (thigh, lower leg) limbs;
spongy, foot (in particular, tarsus) and human hand (wrists);
mixed - vertebrae, sacrum;
flat, this includes the pelvic and cranial bones.

Important! Bone tissue, despite its increased strength, is able to grow and recover. Metabolic processes take place in it, and blood cells are even formed in the red bone marrow. With age, bone tissue is rebuilt, it becomes able to adapt to various loads.

Types of bones

How many bones are in the human body?

The structure of the human skeleton undergoes many changes throughout life. At the initial stage of development, the fetus consists of fragile cartilage tissue, which over time is gradually replaced by bone. A newborn baby has over 270 small bones. With age, some of them can grow together, for example, cranial and pelvic, as well as some vertebrae.

It is very difficult to say exactly how many bones in the body of an adult. Sometimes people have extra ribs or bones in the foot. There may be growths on the fingers, a slightly smaller or larger number of vertebrae in any of the spine. The structure of the human skeleton is purely individual. On average in an adult have from 200 to 208 bones.

Each department performs its highly specialized tasks, but the human skeleton as a whole has several common functions:

Support. The axial skeleton is a support for all soft tissues of the body and a system of levers for the muscles.
Motor. Movable joints between bones allow a person to make millions of precise movements with the help of muscles, tendons, ligaments.
Protective. The axial skeleton protects the brain and internal organs from injury, acts as a shock absorber during impacts.
Metabolic. The composition of bone tissue includes a large amount of phosphorus, calcium and iron involved in the exchange of minerals.
Hematopoietic. The red marrow of tubular bones is the place where hematopoiesis takes place - the formation of erythrocytes (red blood cells) and leukocytes (cells of the immune system).

If some functions of the skeleton are impaired, diseases of varying severity may occur.

Functions of the human skeleton

Departments of the skeleton

The human skeleton is divided into two large sections: axial (central) and additional (or limb skeleton). Each department performs its own tasks. The axial skeleton protects the abdominal organs from damage. The skeleton of the upper limb connects the arm to the torso. Due to the increased mobility of the bones of the hand, it helps to perform many precise finger movements. The functions of the skeleton of the lower extremities are to bind the legs to the body, move the body, and cushion when walking.

Axial skeleton. This department forms the basis of the body. It includes: the skeleton of the head and torso.

Head skeleton. The cranial bones are flat, immovably connected (with the exception of the movable lower jaw). They protect the brain and sense organs (hearing, sight and smell) from concussions. The skull is divided into the facial (visceral), cerebral and middle ear sections.

Torso skeleton. The bones of the chest. In appearance, this subsection resembles a compressed truncated cone or pyramid. The chest includes paired ribs (out of 12, only 7 are articulated with the sternum), the vertebrae of the thoracic spine and the sternum - an unpaired sternum.

Depending on the connection of the ribs with the sternum, true (upper 7 pairs), false (next 3 pairs), floating (last 2 pairs) are distinguished. The sternum itself is considered the central bone included in the axial skeleton.

The body is distinguished in it, the upper part is the handle, and the lower part is the xiphoid process. The bones of the chest are connection of increased strength with the vertebrae. Each vertebra has a special articular fossa designed for attachment to the ribs. This method of articulation is necessary to perform the main function of the skeleton of the body - the protection of human life support organs: the heart, lungs, parts of the digestive system.

Important! The bones of the chest are subject to external influences, prone to modification. Physical activity and proper sitting at the table contribute to the proper development of the chest. A sedentary lifestyle and stoop lead to tightness of the chest organs and scoliosis. An improperly developed skeleton threatens with serious health problems.

Spine. The department is central axis and main support the entire human skeleton. The spinal column is formed from 32-34 individual vertebrae that protect the spinal canal with nerves. The first 7 vertebrae are called cervical, the next 12 are thoracic, then come the lumbar (5), 5 fused, forming the sacrum, and the last 2-5, constituting the coccyx.

The spine supports the back and torso, ensures the motor activity of the whole organism and the connection of the lower body with the brain due to the spinal nerves. The vertebrae are connected to each other semi-mobile (in addition to the sacral). This connection is carried out through the intervertebral discs. These cartilaginous formations soften shocks and tremors during any movement of a person and provide flexibility to the spine.

Skeleton of the upper limb. Skeleton of the upper limb represented by the shoulder girdle and the skeleton of the free limb. The shoulder girdle connects the arm to the body and includes two paired bones:

The clavicle, which has an S-shaped bend. At one end it is attached to the sternum, and at the other it is connected to the scapula.
Shoulder blade. In appearance, it is a triangle adjacent to the back of the body.

The skeleton of the free limb (hand) is more mobile, since the bones in it are connected by large joints (shoulder, wrist, elbow). Skeleton represented by three subdivisions:

The shoulder, which consists of one long tubular bone - the humerus. One of its ends (epiphyses) is attached to the scapula, and the other, passing into the condyle, to the forearms.
Forearm: (two bones) the ulna, located on the same line with the little finger and the radius - in line with the first finger. Both bones on the lower epiphyses form a wrist joint with the carpal bones.
A brush that includes three parts: the bones of the wrist, metacarpus and finger phalanges. The wrist is represented by two rows of four spongy bones each. The first row (pisiform, trihedral, lunate, navicular) serves to attach to the forearm. In the second row are the hamate, trapezium, capitate and trapezoid bones facing the palm. The metacarpus consists of five tubular bones, with their proximal part they are motionlessly connected to the wrist. Finger bones. Each finger consists of three phalanges connected to each other, in addition to the thumb, which is opposed to the rest, and has only two phalanges.

Skeleton of the lower limb. The skeleton of the leg, as well as the hand, consists of a limb belt and its free part.

limb skeleton

The belt of the lower extremities is formed by paired pelvic bones. They grow together from paired pubic, iliac and ischial bones. This happens by the age of 15-17, when the cartilaginous connection is replaced by a fixed bone one. Such strong articulation is necessary for the maintenance of the organs. Three bones to the left and right of the axis of the body form along the acetabulum, which is necessary for the articulation of the pelvis with the head of the femur.

The bones of the free lower limb are divided into:

Femoral. The proximal (upper) epiphysis connects to the pelvis, and the distal (lower) to the tibia.
The patella (or patella) covers the knee joint formed at the junction of the femur and tibia.
The lower leg is represented by the tibia, located closer to the pelvis, and the fibula.
Foot bones. The tarsus is represented by seven bones that make up 2 rows. One of the largest and well developed is the calcaneus. The metatarsus is the middle part of the foot, the number of bones included in it is equal to the number of fingers. They are connected to the phalanges by means of joints. Fingers. Each finger consists of 3 phalanges, except for the first, which has two.

Important! During life, the foot is subject to modifications, calluses and growths can form on it, and there is a risk of developing flat feet. Often this is due to the wrong choice of shoes.

The structure of a woman and a man has no major differences. Only separate parts of some bones or their sizes are subject to changes. Among the most obvious, a narrower chest and a wide pelvis in a woman are distinguished, which is associated with labor. The bones of men, as a rule, are longer, more powerful than women's, and have more traces of muscle attachment. Distinguishing a female skull from a male is much more difficult. The skull of men is slightly thicker than the female, it has a more pronounced contour of the superciliary arches and the occipital protuberance.

Human anatomy. Skeleton bones!

What bones does the human skeleton consist of, a detailed story

The human structure is extremely complex, but the minimum amount of information about the functions of the skeleton, the growth of bones and their location in the body, can help maintain one's own health.

The average chemical composition of bone tissue includes 20-25% water, 75-80% solids, including 30% proteins and 45% inorganic compounds. However, the composition of the tissue varies depending on the type and age of the animal, as well as on the structure of the bone. The chemical composition of various types of cattle bones is presented in Table. 5.5.

Table 55 Chemical composition of cattle bones

Bones	Content, %
Bones	moisture	squirrel	fat	ash
Spine	30-41	14-23	13-20	20-30
breast bone	48-53	16-21	13-16	1F 17
Pelvic bone	24-30	16-20	22-24	30-33
Ribs	28 31	19-22	10-11	36-40
tubular	15-23	17-23	13-24	40-50
Fist	17 32	14-21	18 33	28-36

When treating bone tissue with acids (hydrochloric, phosphoric, etc.), minerals dissolve and a soft organic part remains - ossein. The softening of the bone as a result of the removal of minerals is called maceration. X

The structure of ossein consists mainly of protein substances - collagen (93%), ossemucoid, albumins, globulins, etc. The amino acid composition of the bone is characterized by a low content of glutamic acid, lysine, the absence of cystine, tryptophan; high content of glycine, prolen, hydroxyproline, up to 43% of the total amount of amino acids. Thus, bone proteins are not complete.

Of the organic compounds in the composition of bone tissue, there are lipids, in particular lecithin, salts of citric acid, etc.

The most characteristic components of bone tissue are minerals, which make up half of the tissue mass. They are mainly represented by phosphorus-calcium salts necessary for the life of the organism, as well as microelements - Al, Mn, Cu, Pb, etc.

With the age of the animal, along with a general increase in the content of mineral substances in the bone tissue, the content of carbonates increases and the amount of phosphates decreases. As a result of this change, the bones lose their elasticity and become brittle. A change in the properties of the bone can also be associated with a lack of certain salts in the diet, in particular, with a lack of calcium during pulp fattening. Electrostunning of such cattle leads to fragmentation of the spine and pelvic bones.

The bone marrow filling the marrow cavities contains mainly fats (up to 98% in the dry residue of the yellow marrow) and less choline phosphatides, cholesterol, proteins and minerals. The composition of fats is dominated by palmitic, oleic, stearic acids.

In accordance with the characteristics of the chemical composition, the bone is used for the production of semi-finished products, jelly, brawn, bone fat, gelatin, glue, bone meal.

cartilage tissue. Cartilage tissue performs supporting and mechanical functions. It consists of a dense ground substance, in which round-shaped cells, collagen and elastin fibers are located (Fig. 5.14). Depending on the composition of the intercellular substance, hyaline, fibrous and elastic cartilages are distinguished. Hyaline cartilage covers the articular surfaces of the bones, costal cartilages and the trachea are built from it. Calcium salts are deposited in the intercellular substance of such cartilage with age. Hyaline cartilage is translucent, has a bluish tint.

Fibrous cartilage is made up of ligaments between vertebrae, as well as tendons and ligaments where they attach to bones. Fibrous cartilage contains many collagen fibers and a small amount of amorphous matter. It has the appearance of a translucent mass.

Cream-colored elastic cartilage, in the intercellular substance of which elastin fibers predominate. Lime is never deposited in elastic cartilage. It is part of the auricle, larynx.

The average chemical composition of cartilage tissue includes: 40-70% water,

19-20% protein, 3.5% fat, 2-10% minerals, about 1% glycogen.

Cartilaginous tissue is characterized by a high content of mucoprotein - chondromucoid and mucopolysaccharide - chondroitinsulfuric acid in the main intercellular substance. An important property of this acid is its ability to form salt-like compounds with various proteins: collagen, albumin, etc. This, apparently, explains the "cementing" role of mucopolysaccharides in cartilage tissue.

Cartilage tissue is used for food purposes, and gelatin and glue are also produced from it. However, the quality of gelatin and glue is often not high enough, since mucopolysaccharides and glucoproteins pass into solution from the tissue along with gelatin, reducing the viscosity and strength of the jelly.

The structure of bone tissue. The composition of bone tissue includes, as is known, bone cells and intercellular substance, which consists of the main structureless substance and the shaped part in the form of fibers. Each bone along the periphery is built from a very dense, sometimes thin, sometimes, on the contrary, very thick wall, consisting of a compact bone substance. Inside, the bone is built of a spongy bone substance, consisting of a number of thin bone crossbars connected to the wall and to each other, which in their mass resemble a finely looped sponge.
Bone crossbars, or trabeculae, are distributed in the spongy substance along the trajectory of compression and tension, that is, as if strictly following the laws of mechanics. Thanks to this design, they respond to the "compression", "stretch" and "twisting" experienced by the bone, each crossbar has its own special meaning, and with prolonged changes in the conditions in which the bone is located, the internal architecture of the bone is rebuilt.
In the formation of bone shapes, along with other reasons (feeding, maintenance, exploitation, etc.), the conditions under which a given bone develops are also important. In this regard, the most important factors are adjacent bones and muscles adjacent to it, as well as vessels, nerves, glands and other tissue elements that affect the shaping of the bone.
It is known that the surface of the bones, where muscles, tendons and ligaments are attached, is uneven: in this place it is concave or (more often) convex. With the tendon method of attachment, tubercles develop on the bone. If the muscle bundles are directly woven into the periosteum (with the so-called periosteal method of attachment), then a flat or even concave surface (various pits) is formed on the bone.
In general, despite the variety of bone shapes, for convenience of description, they are divided according to their shape into long, short, wide, and mixed. For the question we are considering, the first two forms are most interesting - long and short bones.
In long bones, one size significantly predominates over the others. The middle part (diaphysis), or the body of such a bone, has a cylindrical or prismatic shape; the ends (epiphyses) are more or less thickened and are connected to adjacent articulating bones. Bones of this type form the basis of the limbs and play the role of levers set in motion by muscles and tendons.
In short bones, all three sizes are approximately the same. Bones of this type are found where, with the strength of the joints, at the same time, a certain flexibility is necessary; this includes the bones of the wrist and tarsus.
When examining the external shape of a bone, attention is paid to the nature of its surfaces; they can be flat, concave or convex, smooth or rough. The articular surfaces (fades articulares), which are present at the ends of long bones and at their junctions, are distinguished by the greatest smoothness. In this case, sometimes the end of one bone is rounded, forming a head, and on the other, accordingly, an articular fossa is formed, and the head can be separated from the body of the bone by an interception (neck). If the articular end represents an extensive but slightly curved surface, then it belongs to the number of articulated processes, an example of which are the articular processes of the vertebrae. Short bones consist entirely of spongy substance and are only externally covered with a relatively thin layer of compact bone substance.
The ends of long bones are built in the same way as short bones. The body is arranged differently: it is a hollow cylinder along its entire length, the wall of which is formed by a rather thick crust of dense substance, and the cavity is a bone marrow canal communicating with voids in the substantia spongiosa of the ends of the bone. The internal structure of the bones is such that with the least amount of material they have the greatest strength. In particular, long bones, which act as uprights and levers, for the most part consist of a dense substance, and their body is hollow. Such bones, being light and taking up little space, are able to withstand the greatest resistance to the mechanical force that acts on the peripheral layers of the bone. Spongy substance is found where, with a certain strength and lightness, there is also a significant volume, which is observed in short bones and at the ends of long ones; in this way, the surface of contact of the bones increases. The arrangement of the plates of the spongy substance, which at first glance seems to be disordered, generally coincides with the direction of the greatest functional compression and tension. In addition, special systems of fasteners are often formed in the bone tissue. As a result, each bone has a structure that best suits the functional conditions in which it is located, and the stretching or compression curves can form one common system in several adjacent bones. Thus, the structure and function of the bone mutually condition each other; this interaction is easily revealed when studying the architecture of spongy matter, each crossbar of which has its own special purpose. When conditions change, the location of the crossbars changes, everything unnecessary, superfluous is destroyed (dissolved), systems of new plates develop, an example of which is a change in the internal structure of bones during fracture healing.
A microscopic study of the structure of bone tissue reveals that the compact bone substance consists of closely spaced bone plates and is pierced by numerous Haversian canals, which run mostly parallel to the long section of the bone, anastomosing with each other many times. There are three types of plates: common Haversian and intermediate. The main mass of the bone is built from Haversian plates, which form concentric layers around the canals of the same name and in general represent a series of cylinders of different diameters nested in each other. The spaces between the individual Haversian systems are made with insert or intermediate plates. Common or main plates make up the outermost and innermost (limiting the medullary canal) layers of bone.
In each plate, the bundles of fibrils go predominantly in one specific direction, moreover, in such a way that in neighboring plates these directions intersect with each other.
Haversian canals contain, in addition to delicate connective tissue, blood vessels that feed the bone.
Separate crossbars of the spongy substance consist of bone plates that do not have such a regular arrangement as in the dense substance; Haversian canals are almost non-existent there.
The histological structure of the bone tissue of the tubular bones of the fore and hind limbs in a horse, as shown by the studies of prof. N. F. Bogdashev, is directly dependent on their physiological function. A characteristic difference for the metacarpal bone of the horse is the relatively rare location of the haversian canals with large areas occupied by intermediate plates.
In the compact substance of the metatarsal bone, the Haversian systems are located more densely, but with a smaller number of intermediate plates. The dependence of the bone microstructure on the thickness of its wall has been established; their degree of development depends on the unequal functional load falling on different parts of the cross section of the tube. In foals up to 2-3 months of age, the histostructure of the bone tissue of tubular bones is identical. However, at an older age, as the shape of the tubular bones themselves differentiates, functional differences begin to appear in the histological structure of the tubular bones. Already at the age of 2-3 years in horses, according to prof. N. F. Bogdasheva, “it is clearly seen that the volar part of the wall always has much denser Haversian canals compared to other parts. At the same time, the thickness of the volar wall becomes much thinner by this age.” On the dorsal wall at this age, its thickening and the rarest location of the haversian canals are noted; the fields occupied by intermediate plates are well distinguished between them.

The chemical composition of bone tissue. Structureless bone substance basically consists of mucus-like and protein-like organic substances, which are in close combination with mineral substances, mainly with phosphate salts. The fibrous part of the bone tissue consists of collagenous collagen fibers. It is known that collagens are the main component of the basic substance of loose connective tissue, tendons, fascia, ligaments, bone and cartilage ossein. Collagen is insoluble neither in water nor in weak acids and alkalis; when boiled with water, it turns into glue (glutin, gelatin).
Collagens in their composition are characterized by a high content of nitrogen (18%) and a low content of carbon (49%). They contain a very large amount of glycocol, protein and hydroxyproline and do not contain cystine, tyrosine and tryptophan at all, thus being an incomplete protein.

Fibrous substance together with mucus-like and protein-like forms the organic basis of bone tissue - ossein (or bone cartilage). The combination of ossein with inorganic matter (lime salts) creates the necessary physical properties - elasticity and strength of bone tissue. Chemical analysis of tubular bones in horses, according to prof. N. F. Bogdasheva, contains: water - 9.18%, organic matter - 28.58%. ash - 62.24%, including calcium oxide - 34.37%.

The normal quantitative ratio between ossein and inorganic matter may change under the influence of various physiological and pathological causes. As you know, at a young age, bones are much poorer in mineral salts and are distinguished by their increased flexibility and lower hardness compared to the bones of an adult animal. In old age, on the contrary, the amount of ossein contained in the bones decreases, as a result of which the bones of these animals are less resistant to mechanical stress and more susceptible to fractures.

Physical properties of bone tissue. The combination of ossein with an inorganic substance creates the necessary physical properties for bone tissue. The elasticity of bone tissue exceeds the elasticity of an oak tree. In terms of strength (strength), bone tissue is stronger than granite and approaches some metals - cast iron and iron.

The physiological properties of bones are somewhat dependent on their specific gravity. According to prof. N. F. Bogdasheva, the specific gravity of the compact substance of the air-dry bones of the metacarpus and metatarsus of a horse is on average 1.985, and he noted that the specific gravity of the metacarpal bones is somewhat greater than the specific gravity of the bones of the metatarsus. So, for example, the specific gravity of the metacarpus is 1.995, and the specific gravity of the metatarsal bones in the same horse is 1.976.

The mechanical properties (strength) of tubular bones in animals are somewhat dependent on the calcium content in them. The presence of lime salts in bone tissue increases its resistance by more than 6 times. According to prof. N. F. Bogdasheva, samples from the metacarpal bones of horses from 4 to 16 years of age are destroyed only under a load of 1840 to 2805 kg / cm2, the bones of foals up to 2 years of age can withstand a load of only 1300 to 1510 kg / aw2.

Comparing the different mechanical stability during compression of certain sections of the walls of tubular bones with their microstructure, it can be concluded that the most stable sections of the bone that collapse under the greatest load are the volar wall of MC3, which has the most densely located network of Haversian canals in the structure. The dorso-medial walls of the metacarpal bones, which have a more sparse arrangement of the Haversian systems, with large gaps in the Haversian canals and significant fields of the intermediate plates, are less resistant to compression.
It follows that the quantity and quality of the Haversian systems and bone cavities on the dorso-medial and volar walls of the metacarpal bones, on the one hand, and the degree of stability of the corresponding sections during their destruction, on the other, represent a certain pattern, which, in all likelihood, is characteristic for the anatomical and histological structure of bone tissue in general.
The resistance of tubular bones to fracture in the dorso-caudal direction is significantly lower than the resistance in the medial-lateral direction. This position is consistent with the anatomical shape of the metacarpal bones, in which the transverse diameter of the tubes is greater than their longitudinal diameter. From this we can conclude that during the life of a horse, a greater possibility of fracture of the bones of the metacarpus in the dorso-volar direction than in the lateral-medial direction is permissible, if the same mechanical force acts in these directions.

The structure of the periosteum and its role in the physiology and pathology of bone tissue
The entire outer surface of the bone, with the exception of those places where the articular cartilage is located, and the places of attachment of tendons and ligaments, is covered with periosteum. It is a fairly strong connective tissue film of pale pink color, rich in nerves, blood and lymphatic vessels. The periosteum is tightly held on the surface of the bone, due to the existence of special perforating thin connective tissue bundles or the so-called Sharpey fibers, which, separating from the periosteum, penetrate into the bone tissue and lie in it in special tubules.
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The periosteum is very sensitive to all kinds of irritants; the nutrition of the adjacent layers of bone tissue and the growth of the bone in thickness depend on it.
Microscopically, it can be found that the periosteum consists of three layers - the outer adventitia layer (tunica adventitia), the middle fibrous-elastic layer (tunica fibroblastica) and the inner osteoblastic layer (tunica osteoblastica). The outer, or superficial, layer of the periosteum is built from coarser collagen bundles. It contains a large number of nerve fibers, blood vessels and lymphatic slits that feed the bone tissue. The middle layer contains many elastic fibers, but few vessels.
The inner, or deep (osteogenic) layer is more delicate and poor in blood vessels. It consists of loose connective tissue and cells of the cambial layer. This osteoblastic layer contains numerous cambial cellular elements that retain the ability to give rise to generations of bone-forming osteoblasts. In young animals with growing bone, as well as during embryonic development, osteoblasts and the indifferent skeletal cells that give rise to them are especially numerous in this layer and form a special layer on the bone surface called the bone cambium or simply the cambial layer, which the periosteum provides growth. bones.

As the bone grows, osteoblasts multiply vigorously, produce the intermediate substance of the bone tissue, and one by one turn into real bone cells of the newly formed bone layers.

In old animals, osteoblasts are located in the periosteum no longer in a continuous layer, as in young individuals, but in separate areas. Hence, their rates of regenerative processes in bone tissue during fractures are relatively slow.
Thus, when the bones are damaged, their restoration proceeds mainly from the side of the periosteum, which, being richly supplied with blood vessels, delivers blood flow to the thickness of the bone tissue. It is known that the bone, exposed from the periosteum in a significant area, dies due to the lack of an influx of nutrients.

With mechanical, chemical or biological damage, a pathological process develops in the periosteum, which, depending on the cause, is characterized by serous, purulent, fibrous, or ossifying inflammation.
Bone marrow and its importance in the physiology and pathology of bone tissue
The bone marrow fills the medullary canal and the medullary cavities of the spongy substance. It is a very tender red mass, rich in blood vessels, which is based on reticular tissue; in the loops of the latter, mature blood elements, their young forms and special giant cells are placed.
The physiological significance of the red brain is very great and versatile. First of all, it belongs to the number of hematopoietic organs, and in young animals hematopoiesis occurs throughout the bone marrow, while in adult and old animals it occurs only in a certain part of the bone marrow. The rest is replaced by adipose tissue, which has a yellowish-reddish color and is called yellow bone marrow. In addition, the blood vessels of the brain abundantly nourish the inner layer of the bone. The red brain plays an important role in the development and growth of bone tissue. Osteoblasts take the same part as the periosteum in the formation of new bone tissue, and osteoclasts dissolve and destroy excess bone tissue. Thanks to this diametrically opposed work of osteoblasts and osteoclasts, the bone has the ability to rebuild its architectonics until a very old age in accordance with the mechanical conditions of compression, stretching or twisting.

In old age, the yellow brain turns into gelatinous or gelatinous bone marrow. It also appears in malnourished animals at a young age during starvation, various xpo-i (nic diseases (cachexia). Atrophy of the red brain and its premature replacement with yellow at a young age occur with severe nutritional disorders, infection and intoxication, and are also possible with osteosclerosis and developed neoplasms.
With injuries and fractures of bones in the bone marrow, hemorrhages are observed from small, dark red dots and spots to significant hemorrhages with destruction of the bone marrow tissue.

Inflammation of the bone marrow can occur with many infectious, toxic and traumatic diseases. The most common form of inflammation is serous osteomyelitis, characterized by hyperemia and serous swelling of the brain. With hemorrhagic osteomyelitis, severe hyperemia, hemorrhagic infiltrates and severe swelling of the brain are noticeable. Purulent osteomyelitis is characterized by the development of small or larger abscesses in the bone marrow or more diffuse, purulent infiltration of the bone marrow.

Productive inflammation of the bone marrow is observed in chronic fibrous osteomyelitis, accompanied, as is known, by the proliferation of reticuloendothelial tissue, followed by fibrous compaction of the bone marrow.

Blood supply to the bones of the horse's limbs
The great importance of vascularization in the physiology and pathology of bone tissue in animals is undeniable. It is gratifying to note that priority in the study of this important issue for veterinary medicine belongs to Soviet authors. The X-ray method of research has established that the presence of periosteal and intraosseous vessels is common to all bones, regardless of their shape and type, and the periosteal vessels feed mainly the bone tissue, and the intraosseous vessels feed the bone marrow. Both vascular systems of bones are connected by a huge number of anastomoses through numerous channels of the compact and spongy substance. The vessels of the periosteum and bone marrow are anastomosed through Volkmann's perforating canals.

The inflexibility of the walls of the Volkmann canals limits the diameter of the vessels lying in them, which can cause thrombosis in some diseases. In addition, through the vessels of these channels, the inflammatory process spreads from the periosteum to the bone marrow and vice versa.

The periosteal vascular network, due to the many anastomoses, has a finely looped structure, sometimes in the form of a very beautiful lacy pattern. The networks of these vessels with their branches are connected to the large highways of the bone and to the vessels of the subcutaneous tissue.

Intraosseous vessels of the bones of the limb are divided into three main types. The first type of vessels supplying the epiphyses and metaphyses fluctuates, especially due to additional branches, while the diaphysis always has one access to all short bones, which have several supply vessels entering the bone through all attachment surfaces, free from articulations. The second type is vessels located in long tubular bones, in which three vascular regions clearly protrude: vessels of the epiphyses, metaphyses and diaphysis. The number is a rather large vessel penetrating the bone. The third type of vessels includes a peculiar construction of the arterial system of the coffin bone.

Lymphatic circulation in bone tissue
The anatomy of the lymphatic system of the bones and, in particular, the anatomy of the lymphatic vessels of the periosteum of the bones and their compact and spongy bone, as well as the bone marrow, as rightly pointed out by prof. D. A. Zhdanov, "belongs to the most difficult sections of the doctrine of the deep lymphatic system." Literature data on the anatomy of the lymphatic system of bones in animals, unfortunately, are very small and, moreover, contradictory; they are based primarily on individual, far from complete and not always irreproachable experiments. Meanwhile, the relevance of studying this problem is undeniable. Sometimes the issues of etiology and pathogenesis in the pathology and therapy of bone tissue, it seems to us, could find their explanation in resolving this problem.

The observations of some authors have established that the bone cavities with their processes (tubules) penetrating through the bone plates are connected to the perivascular lymphatic spaces of the Haversian canals, which in turn pass into the periosteal lymphatic networks.

Baum (1912) injected a contrast liquid with an injection into the thickness | bones of the efferent lymphatic vessels of the bones of large domestic animals and established two groups of efferent lymphatic vessels of the bones: 1) entering places with blood vessels from nutrient openings, mainly tubular bones, and 2) originating from the subperiosteal lymphatic network.

G. M. Iosifov (1927), with an injection into the periosteum of the tibia, injected Gerota's mass into the outlet lymphatic vessels leading to the deep collateral lymphatic trunk accompanying the peroneal artery. Through an injection into the periosteum of the lateral malleolus, he injected the indicated mass into the lymphatic vessels flowing into the superficial lymphatic collectors of the limb.

[V. P. Gukov (1937) injected carcass suspensions into the bone marrow of the thigh of a living dog and stated that this carcass spread through the Haversian canals, as well as its absorption by bone cells and their processes that fill the bone tubules.
|D. A. Zhdanov (1940) injected a contrast fluid into the periosteal lymphatic vessels of the tibia and observed that the initial periosteal lymphatic network opens with great difficulty only at the edges of the injection spot. Clearer filled vessels in the upper layers of the periosteum on the medial and lateral surfaces of the bone. According to him, the lymphatic vessels go in three directions: one at the anterior ridge and the medial edge of the bone passes, perforating the fascia, into the medial group of subcutaneous collectors of the lower leg; others are sent, crossing the lateral surface of the bone, to the anterior tibial artery and enter the accompanying path of deep lymphatic collectors; the third at the medial edge of the bone go under the fascia and go to the posterior tibial artery and with it towards the popliteal fossa.
From the above literature review, it can be seen that in the issue of perivascularization of the lymphatic spaces of the compact bone.

There are no conflicting opinions. However, the relationship between the perivascular spaces and the real, formalized lymphatic vessels remained unclear. Some authors deny the existence of slit-like spaces around osteocytes in the bone cavities, and it is also doubtful that there are juice gaps around the islands of bone cells in the tubules penetrating the bone plates. There is no clarity in the anatomy of the efferent lymphatic vessels of the bones in animals in general and in the horse in particular. The question of the presence or absence of lymphatic vessels in the bone marrow has not been resolved.
The role and significance of the bone lymphatic system in the pathology and therapy of bone tissue has not been completely elucidated. All these questions require their immediate resolution through experimental and clinical studies.

The composition of the fresh bone of an adult includes water - 50%, fat - 16%, other organic substances - 12%, inorganic substances - 22%.

Defatted and dried bones contain approximately 2/3 inorganic and 1/3 organic matter. In addition, bones contain vitamins A, D and C.

Organic bone tissue ossein- gives them elasticity. It dissolves when boiled in water, forming bone glue. The inorganic content of bones is represented mainly by calcium salts, which, with a small admixture of other mineral substances, form hydroxyapatite crystals.

The combination of organic and inorganic substances determine the strength and lightness of bone tissue. Thus, at a low specific gravity of 1.87, i.e. twice the specific gravity of water, the strength of bone exceeds the strength of granite. The femur, for example, when compressed along the longitudinal axis, can withstand loads of more than 1500 kg. If the bone is fired, then the organic matter burns out, while the inorganic matter remains and retains the shape of the bone and its hardness, but such a bone becomes very brittle and crumbles when pressed. On the contrary, after soaking in a solution of acids, as a result of which mineral salts dissolve, and organic matter remains, the bone also retains its shape, but becomes so elastic that it can be tied into a knot. Consequently, the elasticity of the bone depends on ossein, and its hardness depends on mineral substances.

The chemical composition of bones is associated with age, functional load, and the general condition of the body. The greater the load on the bone, the more inorganic substances. For example, the femur and lumbar vertebrae contain the largest amount of calcium carbonate. With increasing age, the amount of organic in-in decreases, and inorganic increases. In small children, there is relatively more ossein, respectively, the bones are very flexible and therefore rarely break. On the contrary, in old age the ratio of organic and inorganic substances changes in favor of the latter. Bones become less elastic and more fragile, as a result of which bone fractures are most often observed in the elderly.

Bone classification

According to the shape, function and development of the bones are divided into three parts: tubular, spongy, mixed.

tubular bones are part of the skeleton of the limbs, playing the role of levers in those parts of the body where movements on a large scale predominate. Tubular bones are divided into long- humerus, forearm bones, femur, lower leg bones and short- bones of the metacarpus, metatarsus and phalanges of the fingers. Tubular bones are characterized by the presence of a middle part - diaphysis, containing a cavity (bone marrow cavity), and two expanded ends - epiphyses. One of the epiphyses is located closer to the body - proximal, the other is further away from it - distal. The segment of the tubular bone located between the diaphysis and the epiphysis is called metaphysis. The processes of bone that serve to attach muscles are called apophyses.

spongy bones are located in those parts of the skeleton where it is necessary to provide sufficient strength and support with a small range of motion. Among spongy bones, there are long(ribs, sternum) short(vertebrae, bones of the wrist, tarsus) and flat(bones of the skull, bones of the belts). Cancellous bones include sesamoid bones (patella, pisiform bone, sesamoid bones of fingers and toes). They are located near the joints, are not directly connected with the bones of the skeleton and develop in the thickness of the tendons of the muscles. The presence of these bones contributes to an increase in the arm of the muscle and, consequently, to an increase in its torque.

mixed dice- this includes bones that merge from several parts that have a different function, structure and development (bones of the base of the skull).

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