The formation of cartilage. Cartilaginous tissue: functions and structural features. Classification of bone tissue
Cartilaginous tissue (textus cartilaginus) forms articular cartilages, intervertebral discs, cartilages of the larynx, trachea, bronchi, external nose. Cartilage tissue consists of cartilage cells (chondroblasts and chondrocytes) and a dense, elastic intercellular substance.
Cartilaginous tissue contains about 70-80% water, 10-15% organic matter, 4-7% salts. About 50-70% of the dry matter of cartilage tissue is collagen. The intercellular substance (matrix) produced by cartilage cells consists of complex compounds, which include proteoglycans. hyaluronic acid, glycosaminoglycan molecules. There are two types of cells in the cartilaginous tissue: chondroblasts (from the Greek chondros - cartilage) and chondrocytes.
Chondroblasts are young, capable of mitotic division, rounded or ovoid cells. They produce components of the intercellular substance of cartilage: proteoglycans, glycoproteins, collagen, elastin. The cytolemma of chondroblasts forms many microvilli. The cytoplasm is rich in RNA, a well-developed endoplasmic reticulum (granular and non-granular), the Golgi complex, mitochondria, lysosomes, and glycogen granules. The chondroblast nucleus, rich in active chromatin, has 1-2 nucleoli.
Chondrocytes are mature large cartilage cells. They are round, oval or polygonal, with processes, developed organelles. Chondrocytes are located in cavities - lacunae, surrounded by intercellular substance. If there is one cell in the gap, then such a gap is called primary. Most often, the cells are located in the form of isogenic groups (2-3 cells) occupying the cavity of the secondary lacuna. The walls of the lacunae consist of two layers: the outer one, formed by collagen fibers, and the inner one, consisting of aggregates of proteoglycans that come into contact with the glycocalyx of cartilage cells.
The structural and functional unit of cartilage is the chondron, formed by a cell or an isogenic group of cells, a pericellular matrix, and a lacuna capsule.
Cartilage tissue is nourished by diffusion of substances from the blood vessels of the perichondrium. Nutrients enter the articular cartilage tissue from the synovial fluid or from the vessels of the adjacent bone. Nerve fibers are also localized in the perichondrium, from where separate branches of the amyopia nerve fibers can penetrate cartilage.
In accordance with the structural features of the cartilage tissue, there are three types of cartilage: hyaline, fibrous and elastic cartilage.
hyaline cartilage from which cartilage is formed in humans respiratory tract, thoracic ends of ribs and articular surfaces of bones. IN light microscope its main substance appears to be homogeneous. Cartilage cells or their isogenic groups are surrounded by an oxyphilic capsule. In differentiated areas of cartilage, a basophilic zone adjacent to the capsule and an oxyphilic zone located outside of it are distinguished; Together, these zones form a cellular territory, or chondrin ball. A complex of chondrocytes with a chondrin ball is usually taken as a functional unit of cartilage tissue - a chondron. The ground substance between chondrons is called interterritorial spaces.
Elastic cartilage(synonym: mesh, elastic) differs from hyaline by the presence of branching networks of elastic fibers in the main substance. The cartilage of the auricle, epiglottis, vrisberg and santorin cartilages of the larynx are built from it.
fibrocartilage(a synonym for connective tissue) is located at the transition points of dense fibrous connective tissue into hyaline cartilage and differs from the latter by the presence of real collagen fibers in the ground substance.
7. Bone tissue - location, structure, functions
Bone tissue is a type of connective tissue and consists of cells and intercellular substance, which contains a large amount of mineral salts, mainly calcium phosphate. Minerals make up 70% of bone tissue, organic - 30%.
Functions of bone tissue:
1) support;
2) mechanical;
3) protective (mechanical protection);
4) participation in the mineral metabolism of the body (depot of calcium and phosphorus).
Bone cells - osteoblasts, osteocytes, osteoclasts. The main cells in the formed bone tissue are osteocytes. These are process-shaped cells with a large nucleus and weakly expressed cytoplasm (nuclear-type cells). The cell bodies are localized in the bone cavities (lacunae), and the processes are located in the bone tubules. Numerous bone tubules, anastomosing with each other, penetrate the bone tissue, communicating with the perivascular space, form the drainage system of the bone tissue. In this drainage system contains tissue fluid, through which the exchange of substances is ensured not only between cells and tissue fluid, but also in the intercellular substance.
Osteocytes are definitive forms of cells and do not divide. They are formed from osteoblasts.
osteoblasts found only in developing bone tissue. In the formed bone tissue, they are usually contained in an inactive form in the periosteum. In developing bone tissue, osteoblasts surround each bone plate along the periphery, tightly adhering to each other.
The shape of these cells can be cubic, prismatic and angular. The cytoplasm of osteoblasts contains a well-developed endoplasmic reticulum, the Golgi lamellar complex, many mitochondria, which indicates a high synthetic activity of these cells. Osteoblasts synthesize collagen and glycosaminoglycans, which are then released into the extracellular space. Due to these components, an organic matrix of bone tissue is formed.
These cells provide mineralization of the intercellular substance through the release of calcium salts. Gradually releasing the intercellular substance, they seem to be walled up and turn into osteocytes. At the same time, 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 in them. When these cells are irritated (in case of injuries, bone fractures, etc.), a granular EPS and a lamellar complex rapidly develop in the cytoplasm, active synthesis and release of collagen and glycosaminoglycans, the formation of an organic matrix (bone callus), and then the formation of a definitive bone fabrics. In this way, due to the activity of osteoblasts of the periosteum, bones regenerate when they are damaged.
osteoclasts- bone-destroying cells are absent in the formed bone tissue, but 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 in ontogeny, osteoclasts are also necessarily present in these places. In the process of embryonic osteohistogenesis, these cells play a very important role and are present in large numbers. Osteoclasts have a characteristic morphology: these cells are multinucleated (3-5 or more nuclei), have a rather large size (about 90 microns) and a characteristic shape - oval, but the part of the cell adjacent to the bone tissue has a flat shape. In the flat part, two zones can be distinguished: the central (corrugated part, containing numerous folds and processes), and the peripheral part (transparent) in close contact with the bone tissue. In the cytoplasm of the cell, under the nuclei, there are numerous lysosomes and vacuoles of various 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 depressions of bone tissue. After the destruction of bone tissue due to the activity of osteoblasts, which are evicted from the connective tissue of the vessels, a new bone tissue is built.
intercellular substance bone tissue consists of the main (amorphous) substance and fibers, which contain calcium salts. The fibers consist of collagen and are folded into bundles, which can be arranged in parallel (orderly) or randomly, on the basis of which the histological classification of bone tissues is built. The main substance of bone tissue, as well as other types of connective tissues, consists of glycosamino- and proteoglycans.
The bone tissue contains less chondroitin sulfuric acids, but more citric and others, which form complexes with calcium salts. In the process of bone tissue development, an organic matrix is first formed - the main substance and collagen fibers, and then calcium salts are deposited in them. They form crystals - hydroxyapatites, which are deposited both in an amorphous substance and in fibers. Providing bone strength, calcium phosphate salts are also both a depot of calcium and phosphorus in the body. Thus, bone tissue takes part in the mineral metabolism of the body.
When studying bone tissue, one should also clearly separate the concepts of “bone tissue” and “bone”.
Bone is an organ whose main structural component is bone tissue.
Classification of bone tissue
Cartilage is a special type of connective tissue. Along with bones, they form the human musculoskeletal system. All types of cartilage (hyaline, fibrous and elastic) line the surfaces of bones, which, when moving, interact with other parts of the joints, as well as in other places where flexible but strong connective tissue is required.
Basically, the cartilage body consists of chondrocyte cells, around which an elastic intercellular substance is formed. It develops filaments of collagen and elastin proteins.
cartilage have distinguishing feature - they do not have blood vessels, and they are not innervated. The nutrition of chondrocytes is carried out with the help of the perichondrium (perchondrium) and the synovial fluid contained in the articular bag.
Types of cartilage (hyaline, fibrous, elastic)
There are 3 types of cartilage tissue: hyaline, elastic and fibrous. Belonging to any type is determined by the content and type of protein fibers. So, hyaline cartilage contain a small amount elastic- Lots of elastin fibrous- a lot of collagen.
hyaline cartilage. The composition of hyaline cartilage contains approximately 80% water, 15% organic matter and 5% mineral salts. The fabric is very strong, has a bluish translucent color and a small amount of fibers (mainly collagen). In the body of the joints they act as a shock absorber between the bones, while also ensuring their smooth running and fitting to each other. It is from them that the initial skeleton in the embryo is formed, the phenomenal ability to grow allows it (the embryo) to develop into an adult, increasing in size and mass several times.
hyaline cartilage tissue it is used where the body requires its rigidity - joints, fastenings of ribs, structures of the face and larynx, and other places. So, the nose is formed from it, partially - the speech apparatus, trachea and bronchi. It consists of formations that attach the ribs to the spine and sternum, allowing them to move in the process of breathing.
Elastic cartilage. Elastic cartilage is dominated by the protein elastin, although collagen is also present. A high concentration of elastin causes a yellowish translucent color. This fabric is strong, but less elastic, it easily takes the desired shape. Unlike hyaline, this species does not ossify over time..
It is from this cartilage tissue the auricles and, in part, the middle ear are composed. As well as the epiglottis, some other cartilages of the larynx and speech apparatus.
fibrocartilage. Fibrous cartilage tissue, in addition to chondrocytes and intercellular substance, has a significant amount of collagen fibers. This is the reason for her ability withstand enormous loads while remaining flexible.
It is used where these loads are present. The most striking example is the intervertebral discs. They have a very important role - the spine, on the one hand, is a very delicate organ, storage spinal cord, and on the other - a key part of the musculoskeletal system, which daily bears the weight of half the body. Other examples are the points of connection of ligaments and bones, the fixed joints of bones (for example, pelvic).
Formation and development of cartilage of the human skeleton
The rudiment of the skeleton in the embryo is formed from dense connective tissue. In the process of growth, it becomes stiffer, it is penetrated by fibers, and the output is cartilage. After that, development is divided into 2 directions:
The formation of the perichondrium. A thin plate that serves to nourish, grow and regenerate the cartilage tissue underneath. It is made up of two layers different types tissue: the outer layer (fibrous) is engaged in the production of collagen fibers, and the inner contains immature chondrocytes. As they mature, they pass into the body of the cartilage, contributing to its growth, and after the process is completed, it turns into the periosteum.
Formation of the epiphyseal plate, which lines the surface of bones growing in length. It is intended mainly for the production of new bone tissue. During puberty, the cartilaginous cells of the pineal gland stop dividing, turning into bone.
The third way of cartilage formation stands apart. This is the so-called bone marrow. It occurs during fractures, when the connective tissue around the damaged area thickens, gradually turning into cartilage. Then the process of ossification takes place with it, a new bone tissue is created at the fracture site.
FIBROUS CARTILAGE
FIBROUS CARTILAGE, is located mainly in those parts of the skeleton that experience great physical pressure or compression. Collagen fibers of cartilage are collected in bundles and are distinguished by an ordered arrangement. It is present in the INTERVERTEBRAL DISKS and parts of the TENDONS attached to the ends of the long bones. The main constituent of fibrous cartilage is the fibrous protein COLLAGEN.
Scientific and technical encyclopedic dictionary.
See what "Fibrous Cartilage" is in other dictionaries:
Solid skeletal connective tissue, consisting of cartilage cells of chondroblasts (chondroblasts) and chondrocytes (chondrocytes), located in the main intercellular substance formed by a looped collagen skeleton, the cells of which ... ... medical terms
CARTILAGE- (cartilage) solid skeletal connective tissue, consisting of cartilage cells of chondroblasts (chondroblasts) and chondrocytes (chondrocytes), located in the main intercellular substance formed by a looped collagen skeleton, cells ... ... Dictionary in medicine
Dense, but elastic supporting tissue of the body, one of the types of connective tissue. It consists of rounded cells (chondrocytes) that do not have processes and are immersed in the intercellular substance of the matrix. The matrix contains fibers of connective tissue proteins ... ... Collier Encyclopedia
Strong cartilage, the main substance of which contains a large number of dense bundles of collagen fibers that form the basis of its intercellular substance. The fibrous rings of the intervertebral discs and the pubic symphysis are built from fibrous cartilage ... medical terms
FIBROUS CARTILAGE- (fibrocartilage) strong cartilage, the main substance of which contains a large number of dense bundles of collagen fibers that form the basis of its intercellular substance. Fibrous rings of intervertebral discs are built from fibrous cartilage ... ... Explanatory Dictionary of Medicine
One of the types of connective tissue of the body of animals and humans, performing a mechanical (supporting) function. It is present in all vertebrates and humans, as well as in some invertebrates (for example, cephalopods). Cartilaginous... Big soviet encyclopedia
- (fibrocartilago) see Cartilage fibrous tissue ... Big Medical Dictionary
ELASTIC CARTILAGE TISSUE.
Hyaline cartilage.
Hyaline or vitreous cartilage, of a bluish-white color, is found on the articular surfaces of bones, at the junction of the ribs with the sternum, in the larynx, in the airways, the most common type of cartilage.
Most of this cartilage is covered by the perichondrium (perichondrome), in which two layers are distinguished: the outer, consisting of fibrous connective tissue with blood vessels, and the inner, cellular, containing chondroblasts and prechondroblasts.
Under the perichondrium in the surface layer of the cartilage are young fusiform chondrocytes, the long axis of which is directed along the surface of the cartilage.
In the deeper layers, cartilage cells acquire an oval or rounded shape. Due to the weakening of their synthetic activity, after division they do not diverge far, but lie together, forming an isogenic group of 2-4 chondrocytes.
The areas directly surrounding the cartilage cells are called the matrix. Type II collagen fibers are located here; they surround isogenic groups of cartilage cells, protecting them from mechanical pressure.
A feature of articular cartilage is the absence of perichondrium on the surface facing the joint cavity. Its nutrition is carried out mainly due to the synovial fluid.
Elastic cartilage tissue is found in those organs where the cartilage is prone to bending. These are the auricle, carob-shaped and sphenoid cartilages of the larynx, nose. This fabric is yellowish in color.
According to the general plan of the structure, elastic cartilage is similar to hyaline. Outside, it is covered with a perichondrium.
Chondrocytes (young and specialized) are located in special capsules singly or form isogenic groups.
In the intercellular substance of the elastic cartilage, along with collagen fibers, there are elastic fibers penetrating the intercellular substance in all directions. In the layers adjacent to the perichondrium, the elastic fibers pass without interruption into the elastic fibers of the perichondrium.
There are less lipids, glycogen, chondroitin sulfates in the elastic cartilage.
Fibrous or collagen-fibrous cartilage tissue is found in intervertebral discs, semi-movable joints, at the transition sites of fibrous connective tissue (tendons, ligaments) into hyaline cartilage, where limited movements are accompanied by strong tensions. The intercellular substance contains parallel directed collagen bundles, gradually turning into hyaline cartilage. In the cartilage there are cavities with cartilage cells, which are located singly or form isogenic groups.
In the direction of the tendon, the fibrocartilage becomes more like a tendon.
On the border of the cartilage and tendon between the collagen bundles, compressed cartilage cells lie in columns, which pass into the tendon cells of the dense connective tissue.
The basis of the musculoskeletal system are cartilage tissues. It is also part of the structures of the face, becoming the place of attachment of muscles and ligaments. The histology of cartilage is represented by a small number of cellular structures, fibrous formations and nutrients. This ensures sufficient damping function.
What does it represent?
Cartilage is a type of connective tissue. Structural features are increased elasticity and density, due to which it is able to perform a supporting and mechanical function. Articular cartilage consists of cells called chondrocytes and the main substance, where the fibers are located, providing the elasticity of the cartilage. Cells in the thickness of these structures form groups or are placed separately. The location is usually near the bones.
Cartilage varieties
Depending on the features of the structure and localization in the human body, there is such a classification of cartilage tissues:
- Hyaline cartilage contains chondrocytes, placed in the form of rosettes. The intercellular substance is larger in volume than the fibrous substance, and the filaments are represented only by collagen.
- Elastic cartilage contains two types of fibers - collagen and elastic, and the cells are arranged in columns or columns. This type of fabric has a lower density and transparency, having sufficient elasticity. This matter makes up the cartilages of the face, as well as the structures of the middle formations in the bronchi.
- Fibrous cartilage is a connective tissue that performs the functions of strong shock-absorbing elements and contains a significant amount of fibers. Localization of the fibrous substance is located throughout the musculoskeletal system.
Properties and structural features of cartilage tissue
On the histological preparation, it is seen that the tissue cells are located loosely, being in an abundance of intercellular substance. All types of cartilage are able to take on and resist the compressive forces that occur during movement and load. This ensures an even distribution of gravity and a reduction in the load on the bone, which stops its destruction. The skeletal zones, where friction processes constantly occur, are also covered with cartilage, which helps protect their surfaces from excessive wear. The histology of this type of tissue differs from other structures in a large amount of intercellular substance, and the cells are located loosely in it, form clusters or are located separately. The main substance of the cartilaginous structure is involved in the processes of carbohydrate metabolism in the body.
This type of material in the human body, like the rest, is composed of cells and intercellular substance of cartilage. A feature in a small number of cellular structures, due to which the properties of the tissue are provided. Mature cartilage refers to a loose structure. Elastic and collagen fibers perform a supporting function in it. The general plan of the structure includes only 20% of the cells, and everything else is fibers and amorphous matter. This is due to the fact that due to the dynamic load, the vascular bed of the tissue is poorly expressed and therefore it is forced to feed on the main substance of the cartilage tissue. In addition, the amount of moisture that is in it performs shock-absorbing functions, smoothly relieving tension in bone tissues.
What are they made of?
The trachea and bronchi are composed of hyaline cartilage. Each type of cartilage has unique properties due to the difference in location. The structure of hyaline cartilage differs from the rest in a smaller number of fibers and a large filling with amorphous matter. In this regard, it is not able to withstand heavy loads, since its tissues are destroyed by bone friction, however, it has a rather dense and solid structure. Therefore, it is characteristic that the bronchi, trachea and larynx consist of this type of cartilage. Skeletal and musculoskeletal structures are formed mainly by fibrous matter. Its variety includes a part of the ligaments connected to hyaline cartilage. The elastic structure occupies an intermediate location relative to these two tissues.
Cellular composition
Chondrocytes do not have a clear and ordered structure, but are more often located completely randomly. Sometimes their clusters resemble islets with large areas of absence of cellular elements. At the same time, a mature cell type and a young one, which is called chondroblasts, are located together. They are formed by the perichondrium and have interstitial growth, and in the process of their development they produce various substances.
Chondrocytes are a source of components of the intercellular space, it is thanks to them that there is such a chemical table of elements in the composition of an amorphous substance:
Hyaluronic acid is contained in an amorphous substance. - proteins;
- glycosaminoglycans;
- proteoglycans;
- hyaluronic acid.
In the embryonic period, most bones are hyaline tissues.
The structure of the intercellular substance
It consists of two parts - these are fibers and an amorphous substance. At the same time, fibrillar structures are randomly located in the tissue. The histology of cartilage is affected by its production by cells chemical substances, responsible for the density of transparency and elasticity. The structural features of hyaline cartilage are the presence of only collagen fibers in its composition. If an insufficient amount of hyaluronic acid is released, then this destroys tissues due to degenerative-dystrophic processes in them.
Blood flow and nerves
Cartilage structures do not have nerve endings. Pain reactions in them are presented only with the help of bone elements, while the cartilage will already be destroyed. This causes a large number of untreated diseases of this tissue. Few nerve fibers are present on the surface of the perichondrium. The blood supply is poorly represented and the vessels do not penetrate deep into the cartilage. Therefore, nutrients enter the cells through the main substance.
Struct functions
The auricle is formed from this tissue. Cartilage is the connecting part of the human musculoskeletal system, but is sometimes found in other parts of the body. The histogenesis of cartilage tissue goes through several stages of development, due to which it is able to provide support, at the same time being fully elastic. They are also part of the external formations of the body such as the cartilages of the nose and auricles. They are attached to the bone ligaments and tendons.
Age-related changes and diseases
The structure of cartilage tissue changes with age. The reasons for this lie in the insufficient supply of nutrients, as a result of violation of trophism, diseases arise that can destroy fibrous structures and cause cell degeneration. A young body has a much larger supply of fluid, so the nutrition of these cells is sufficient. However, age-related changes cause "drying" and ossification. Inflammation due to bacterial or viral agents can cause cartilage degeneration. Such changes are called "chondrosis". At the same time, it becomes less smooth and unable to perform its functions, as its nature changes.
Signs that the tissue has been destroyed are visible during histology analysis.
How to eliminate inflammatory and age-related changes?
To cure cartilage, drugs are used that can restore the independent development of cartilage tissue. These include chondroprotectors, vitamins and products that contain hyaluronic acid. Important proper diet with a sufficient amount of protein, because it is a stimulator of body regeneration. It is shown to keep the body in good shape, because excess body weight and insufficient physical activity cause the destruction of structures.
