Cartilage formation. Cartilage tissue: functions and structural features. Bone classification
Cartilage tissue (textus cartilaginus) forms articular cartilage, intervertebral discs, cartilage of the larynx, trachea, bronchi, external nose. Cartilage tissue consists of cartilage cells (chondroblasts and chondrocytes) and dense, elastic intercellular substance.
Cartilage 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 cartilage tissue: chondroblasts (from the Greek chondros - cartilage) and chondrocytes.
Chondroblasts are young, round or ovoid cells capable of mitotic division. 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 cells of cartilage tissue. 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) that occupy the cavity of the secondary lacuna. The walls of the lacuna consist of two layers: the outer one, formed by collagen fibers, and the inner one, consisting of proteoglycan aggregates that come into contact with the glycocalyx of cartilage cells.
The structural and functional unit of cartilage is a chondron formed by a cell or an isogenic group of cells, a pericellular matrix and a lacuna capsule.
Cartilage is nourished by diffusion of substances from the blood vessels of the perichondrium. In the tissue of the articular cartilage, nutrients penetrate from the synovial fluid or from the vessels of the adjacent bone. Nerve fibers are also localized in the perichondrium, from where individual branches of non-fleshy nerve fibers can penetrate into the cartilage tissue.
In accordance with the structural features of the cartilage tissue, three types of cartilage are distinguished: hyaline, fibrous and elastic cartilage.
Hyaline cartilage, from which the cartilage of the respiratory tract, the thoracic ends of the ribs and the articular surfaces of the bones are formed in humans. 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; Taken together, these zones form the cell territory, or chondrin ball. A complex of chondrocytes with a chondrin ball is usually taken as a functional unit of cartilaginous tissue - a chondron. The main substance between the chondrons is called interterritorial spaces.
Elastic cartilage (synonym: reticular, elastic) differs from hyaline in the presence of branching networks of elastic fibers in the main substance. The cartilage of the auricle, epiglottis, Vrisberg and Santorini cartilages of the larynx are built from it.
Fibrous cartilage (synonym for connective tissue) is located in the places of transition of dense fibrous connective tissue into hyaline cartilage and differs from the latter by the presence of real collagen fibers in the main substance.
7 Bone tissue - location, structure, function
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. Mineral substances make up 70% of bone tissue, organic - 30%.
Bone tissue functions:
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 cells with a large nucleus and a weakly expressed cytoplasm (nuclear-type cells). Cell bodies are localized in bone cavities (lacunae), and processes in bone tubules. Numerous bone tubules, anastomosed with each other, penetrate the bone tissue, communicating with the perivascular space, and 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.
Osteoblastscontained only in developing bone tissue. In the formed bone tissue, they are usually contained in an inactive form in the periosteum. In the developing bone tissue, osteoblasts cover 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 lamellar Golgi complex, and many mitochondria, which indicates a high synthetic activity of these cells. Osteoblasts synthesize collagen and glycosaminoglycans, which are then secreted into the intercellular space. Due to these components, an organic matrix of bone tissue is formed.
These cells provide the 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 largely reduced, synthetic and secretory activity decreases, and the functional activity inherent in osteocytes remains. Osteoblasts, localized in the cambial layer of the periosteum, are in an inactive state, the synthetic and transport organelles in them are poorly developed. When these cells are irritated (in the 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 occurs, the formation of an organic matrix (callus), and then the formation of definitive bone fabrics. In this way, due to the activity of osteoblasts in the periosteum, bone regeneration occurs when they are damaged.
Osteoclasts- bone-destroying cells, in the formed bone tissue are absent, 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 ontogenesis, osteoclasts are also 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 oval shape, but the part of the cell adjacent to the bone tissue is flat. 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. 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 are destroyed intracellularly. Resorption (destruction) of bone tissue occurs through these mechanisms, and therefore osteoclasts are usually localized in the depressions of the bone tissue. After the destruction of bone tissue due to the activity of osteoblasts, which are evicted from the connective tissue of the vessels, the construction of new bone tissue occurs.
Intercellular substancebone tissue consists of a basic (amorphous) substance and fibers, which contain calcium salts. Fibers consist of collagen and are folded into bundles that can be arranged in parallel (ordered) or irregularly, on the basis of which a histological classification of bone tissues is built. The main substance of bone tissue, like other types of connective tissue, consists of glycosamine and proteoglycans.
The bone tissue contains less chondroitinsulfuric acids, but more citric and others, which form complexes with calcium salts. In the process of development of bone tissue, an organic matrix is \u200b\u200bfirst formed - the main substance and collagen fibers, and then calcium salts are deposited in them. They form crystals - hydroxyapatites, which are deposited both in the amorphous substance and in the fibers. Providing strength to bones, calcium phosphate salts are also 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, the concepts of "bone tissue" and "bone" should also be clearly distinguished.
BoneIs an organ, the main structural component of which is bone tissue.
Bone classification
Cartilage is a special type of connective tissue. Along with bones, they form the human musculoskeletal system. Everything types of cartilage (hyaline, fibrous and elastic) line the surfaces of bones, which interact with other parts of the joints during movement, as well as in other places where flexible but strong connective tissue is required.
Basically, the body of cartilage consists of chondrocyte cells, around which an elastic intercellular substance is formed. In it, threads of collagen and elastin proteins develop.
Cartilage has distinctive feature - they have no blood vessels, and they are not innervated. Chondrocytes are nourished with the help of the perichondrium (perichondrium) and the synovial fluid contained in the joint capsule.
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 - a lot of elastin, and fibrous - a lot of collagen.
Hyaline cartilage... Hyaline cartilage contains about 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, 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 its size and mass several times.
Hyaline cartilage tissue it is used where the body needs its rigidity - joints, rib attachments, structures of the face and larynx, and other places. So, a nose is formed from it, partly a speech apparatus, trachea and bronchi. It consists of formations that attach the ribs to the spine and sternum, allowing them to move during breathing.
Elastic cartilage... Elastin protein predominates in elastic cartilage, although collagen is also present. The high concentration of elastin is due to the 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 consists of the auricles and, in part, the middle ear. As well as the epiglottis, some other cartilages of the larynx and speech apparatus.
Fibrous cartilage... The tissue of fibrous cartilage, in addition to chondrocytes and intercellular substance, has a significant amount of collagen fibers. This is due to her ability withstand colossal loadswhile staying elastic.
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, a repository spinal cord, and on the other hand, a key part of the musculoskeletal system, which carries the weight of half of the body on a daily basis. Other examples are the junction points of the ligaments and bones, fixed joints of bones (for example, the pelvic).
Formation and development of cartilage of the human skeleton
The skeletal rudiment in the embryo is formed from dense connective tissue. In the process of growth, it becomes stiffer, fibers penetrate it, and cartilage is obtained at the exit. After that, development is divided into 2 directions:
Perichondrium formation... A thin plate serving for nutrition, growth and regeneration of the cartilage tissue underneath. It is formed by two layers of different types of tissue: the outer layer (fibrous) is engaged in the production of collagen fibers, and the inner one contains immature chondrocytes. As they ripen, they pass into the body of the cartilage, contributing to its growth, and after the process is completed, it turns into the periosteum.
Epiphyseal plate formation, which lines the surface of the growing bones. It is primarily intended for the production of new bone tissue. During puberty, the cartilage cells of the pineal gland stop dividing, turning into bone.
The third method of cartilage formation stands apart. This is the so-called callus. It occurs with fractures, when the connective tissue around the damaged area thickens, gradually turning into cartilage. Then, the process of ossification takes place with it, new bone tissue is created at the site of the fracture.
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 differ in an ordered arrangement. It is found in the INTERVERTEBRATE DISCS and in the TENDONS attached to the ends of the long bones. The main constituent of fibrous cartilage is COLLAGEN fibrous protein.
Scientific and technical encyclopedic dictionary.
See what "FIBROUS cartilage" is in other dictionaries:
Hard skeletal connective tissue, consisting of chondroblasts and chondrocytes cartilage cells located in the main intercellular substance, formed by a looped collagen framework, the cells of which ... ... Medical terms
CARTILAGE - (cartilage) hard skeletal connective tissue, consisting of chondroblasts and chondrocytes cartilage cells located in the main intercellular substance formed by a looped collagen frame, cells ... ... Explanatory Dictionary of Medicine
A 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 embedded in the intercellular matrix. The matrix contains fibers of connective tissue proteins ... ... Collier's 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. Fibrous rings of intervertebral discs and 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 (support) function. It is found in all vertebrates and humans, as well as in some invertebrates (for example, cephalopods). In cartilaginous ... Big soviet encyclopedia
- (fibrocartilago) see Fibrous cartilaginous tissue ... Large Medical Dictionary
ELASTIC CARILY TISSUE.
Hyaline cartilage tissue.
Hyaline or vitreous cartilage, bluish-white in color, is found on the articular surfaces of the bones, at the junction of the ribs with the sternum, in the larynx, in the airways, the most common type of cartilage tissue.
Most of this cartilage is covered by the perichondrium (perichondroma), 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, there are young spindle-shaped chondrocytes, the long axis of which is directed along the surface of the cartilage.
In deeper layers, cartilage cells acquire an oval or round shape. Due to the weakening of their synthetic activity, they do not diverge far after division, but lie together, forming an isogenic group of 2-4 chondrocytes.
The areas immediately 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 the articular cartilage is the absence of the 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, horn-shaped and wedge-shaped 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 perichondrium.
Chondrocytes (young and specialized) are located in special capsules one by one or form isogenic groups.
In the intercellular substance of elastic cartilage, along with collagen fibers, there are elastic fibers that penetrate 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.
Elastic cartilage contains less lipids, glycogen, chondroitin sulfates.
Fibrous or collagenous-fibrous cartilage tissue is located in the intervertebral discs, semi-movable joints, in places where fibrous connective tissue (tendons, ligaments) transitions to hyaline cartilage, where limited movements are accompanied by strong tensions. The intercellular substance contains parallel directed collagen bundles, gradually turning into hyaline cartilage. Cartilage contains cavities with cartilaginous cells, which are located singly or form isogenic groups.
Towards the tendon, the fibrous cartilage becomes more tendon-like.
On the border of the cartilage and tendon between the collagen bundles there are columns of squeezed cartilaginous cells, which pass into the tendon cells of dense connective tissue.
The basis of the musculoskeletal system is cartilage. It is also part of the structures of the face, becoming the attachment point for muscles and ligaments. The histology of cartilage is represented by a small number of cellular structures, fibrous formations and nutrients. This ensures a sufficient damping function.
What is it?
Cartilage is a type of connective tissue. The structural features are in 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 a basic substance where fibers are located that provide elasticity to the cartilage. Cells within these structures form groups or are individually located. The location is usually near bones.
Varieties of cartilage
Depending on the characteristics of the structure and localization in the human body, there is such a classification of cartilaginous tissues:
- Hyaline cartilage contains chondrocytes, placed in the form of rosettes. The intercellular substance is more significant in volume than the fibrous one, and the threads 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 is less dense and transparent, having sufficient elasticity. This matter makes up the cartilage of the face, as well as the structures of the secondary 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
The histological specimen shows that the cells of the tacni are located loosely, being in an abundance of intercellular substance. All types of cartilage tissue are able to absorb and resist the compressive forces that arise during movement and stress. This ensures an even distribution of gravity and a decrease in the load on the bone, which stops its destruction. Skeletal areas, where friction processes constantly occur, are also covered with cartilage, which allows them to 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 in it loosely, 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, contains cells and the intercellular substance of cartilage. The peculiarity is 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 basis of the main substance of the cartilaginous tissue. In addition, the amount of moisture that is in it performs amortization functions, smoothly relieving bone tissue tension.
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 substance. In this regard, it is not able to withstand strong loads, since its tissues are destroyed from bone friction, however, it has a rather dense and solid structure. Therefore, it is characteristic that this type of cartilage consists of the bronchi, trachea and larynx. The skeletal and musculoskeletal structures are formed mainly by fibrous matter. Its variety includes the part of the ligaments connected to the hyaline cartilage. The elastic structure is intermediate between these two tissues.
Cellular composition
Chondrocytes do not have a clear and ordered structure, but more often they are located completely randomly. Sometimes their clusters resemble islets with large areas of lack of cellular elements. At the same time, a mature cell type and a young one, which are 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 the source of the 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;
- glucosaminoglycans;
- proteoglycans;
- hyaluronic acid.
During the embryonic period, most of the bones are hyaline tissues.
The structure of the intercellular substance
It consists of two parts - fibers and an amorphous substance. In this case, fibrillar structures are chaotically located in the tissue. The histology of cartilage is influenced by the production of chemicals by the cells responsible for the density, transparency and elasticity. Features of the structure of hyaline cartilage are in the presence of only collagen fibers in its composition. If an insufficient amount of hyaluronic acid is released, then this destroys the tissues due to degenerative-dystrophic processes in them.
Blood flow and nerves
Cartilage structures have no 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. On the surface of the perichondrium, there are few nerve fibers. The blood supply is poorly presented and the vessels do not penetrate deep into the cartilage. Therefore, nutrients enter the cells through the basic substance.
Struct functions
The auricle is formed from this tissue. Cartilage is the connecting part of the human musculoskeletal system, but it is sometimes found in other parts of the body. Cartilage histogenesis goes through several stages of development, thanks to which it is able to provide support, at the same time be completely elastic. They are also found in external formations of the body such as the cartilage of the nose and ears. Ligaments and tendons are attached to them.
Age-related changes and diseases
The structure of cartilage tissue changes with age. The reasons for this lie in an insufficient supply of nutrients to it, due to a violation of trophism, diseases arise that can destroy fibrous structures and cause cell degeneration. A young organism has a much larger supply of fluid, so the nutrition of these cells is sufficient. However, age-related changes cause drying out 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 is not able to perform its functions, since its nature changes.
Signs that tissue has been destroyed are visible during histological 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. A correct diet with a sufficient amount of protein is important, because it is a stimulant of the body's regeneration. It is shown to keep the body in good shape, because overweight and insufficient physical activity cause the destruction of structures.
