Cartilage tissue is a skeletal connective tissue that performs supporting, protective and mechanical functions.
The structure of cartilage
Cartilaginous tissue consists of cells - chondrocytes, chondroblasts and a dense intercellular substance, consisting of amorphous and fibrous components.
Chondroblasts
Chondroblasts located singly along the periphery of the cartilaginous tissue. They are elongated flattened cells with basophilic cytoplasm containing a well-developed granular endoplasmic reticulum and the Golgi apparatus. These cells synthesize the components of the intercellular substance, release them into the intercellular environment and gradually differentiate into the definitive cells of the cartilage tissue - chondrocytes.
Chondrocytes
Chondrocytes by degree of maturity, according to morphology and function are divided into cells of type I, II and III. All varieties of chondrocytes are localized in the deeper layers of cartilage tissue in special cavities - gaps.
Young chondrocytes (type I) divide mitotically, but the daughter cells end up in the same gap and form a group of cells - an isogenic group. The isogenic group is a common structural and functional unit of cartilage tissue. The location of chondrocytes in isogenic groups in different cartilage tissues is not the same.
intercellular substance cartilage tissue consists of a fibrous component (collagen or elastic fibers) and an amorphous substance, which contains mainly sulfated glycosaminoglycans (primarily chondroitin sulfuric acids), as well as proteoglycans. Glycosaminoglycans bind a large amount of water and determine the density of the intercellular substance. In addition, the amorphous substance contains a significant amount of minerals that do not form crystals. Vessels in the cartilage tissue are normally absent.
Cartilage classification
Depending on the structure of the intercellular substance, cartilage tissues are divided into hyaline, elastic and fibrous cartilage tissue.
hyaline cartilage tissue
characterized by the presence of only collagen fibers in the intercellular substance. At the same time, the refractive index of the fibers and the amorphous substance is the same, and therefore the fibers in the intercellular substance are not visible on histological preparations. This also explains a certain transparency of cartilage, consisting of hyaline cartilage tissue. Chondrocytes in isogenic groups of hyaline cartilage tissue are arranged in the form of rosettes. In terms of physical properties, hyaline cartilage tissue is characterized by transparency, density and low elasticity. In the human body, hyaline cartilage tissue is widespread and is part of the large cartilage of the larynx. (thyroid and cricoid), trachea and large bronchi, makes up the cartilaginous parts of the ribs, covers the articular surfaces of the bones. In addition, almost all the bones of the body in the process of their development pass through the stage of hyaline cartilage.
Elastic cartilage tissue
characterized by the presence of both collagen and elastic fibers in the intercellular substance. In this case, the refractive index of elastic fibers differs from the refraction of an amorphous substance, and therefore elastic fibers are clearly visible in histological preparations. Chondrocytes in isogenic groups in elastic tissue are arranged in the form of columns or columns. In terms of physical properties, elastic cartilage is opaque, elastic, less dense, and less transparent than hyaline cartilage. She is part of elastic cartilage: auricle and cartilaginous part of the external auditory canal, cartilage of the external nose, small cartilages of the larynx and middle bronchi, and also forms the basis of the epiglottis.
Fibrous cartilage tissue
characterized by the content in the intercellular substance of powerful bundles of parallel collagen fibers. In this case, chondrocytes are located between the bundles of fibers in the form of chains. According to physical properties, it is characterized by high strength. It is found only in limited places in the body: it is part of the intervertebral discs (annulus fibrosus) and also localized in the places of attachment of ligaments and tendons to hyaline cartilage. In these cases, a gradual transition of connective tissue fibrocytes into cartilage chondrocytes is clearly seen.
There are the following two concepts that should not be confused - cartilage tissue and cartilage. cartilage tissue- This is a type of connective tissue, the structure of which is described above. Cartilage is an anatomical organ made up of cartilage and perichondrium.
perichondrium
The perichondrium covers the cartilaginous tissue from the outside (with the exception of the cartilaginous tissue of the articular surfaces) and consists of fibrous connective tissue.
There are two layers in the perichondrium:
external - fibrous;
internal - cellular or cambial (growth).
In the inner layer, poorly differentiated cells are localized - prechondroblasts and inactive chondroblasts, which, in the process of embryonic and regenerative histogenesis, first turn into chondroblasts, and then into chondrocytes. The fibrous layer contains a network of blood vessels. Consequently, the perichondrium, as an integral part of the cartilage, performs the following functions: provides trophic avascular cartilage tissue; protects cartilage; provides regeneration of cartilaginous tissue when it is damaged.
3. The structure of the bone
4. Osteohistogenesis
1. Skeletal connective tissues include cartilaginous and bone tissues that perform supporting, protective and mechanical functions, as well as taking part in the metabolism of minerals in the body.
cartilage tissue consists of cells - chondrocytes, chondroblasts and a dense intercellular substance, consisting of amorphous and fibrous components. Chondroblasts located singly along the periphery of the cartilaginous tissue. They are elongated flattened cells with basophilic cytoplasm containing a well-developed granular endoplasmic reticulum and the Golgi apparatus. These cells synthesize the components of the intercellular substance, release them into the intercellular environment and gradually differentiate into the definitive cells of the cartilage tissue - chondrocytes. Chondroblasts are capable of mitotic division. The perichondrium surrounding the cartilaginous tissue contains inactive, poorly differentiated forms of chondroblasts, which, under certain conditions, differentiate into chondroblasts that synthesize the intercellular substance, and then into chondrocytes.
Chondrocytes by degree of maturity, according to morphology and function are divided into cells of type I, II and III. All varieties of chondrocytes are localized in the deeper layers of cartilage tissue in special cavities - gaps. Young chondrocytes (type I) divide mitotically, but the daughter cells end up in the same gap and form a group of cells - an isogenic group. The isogenic group is a common structural and functional unit of cartilage tissue. The location of chondrocytes in isogenic groups in different cartilage tissues is not the same.
intercellular substance cartilage tissue consists of a fibrous component (collagen or elastic fibers) and an amorphous substance, which contains mainly sulfated glycosaminoglycans (primarily chondroitin sulfuric acids), as well as proteoglycans. Glycosaminoglycans bind a large amount of water and determine the density of the intercellular substance. In addition, the amorphous substance contains a significant amount of minerals that do not form crystals. Vessels in the cartilage tissue are normally absent.
Depending on the structure of the intercellular substance, cartilage tissues are divided into hyaline, elastic and fibrous cartilage tissue.
hyaline cartilage tissue characterized by the presence of only collagen fibers in the intercellular substance. At the same time, the refractive index of the fibers and the amorphous substance is the same, and therefore the fibers in the intercellular substance are not visible on histological preparations. This also explains a certain transparency of cartilage, consisting of hyaline cartilage tissue. Chondrocytes in isogenic groups of hyaline cartilage tissue are arranged in the form of rosettes. In terms of physical properties, hyaline cartilage tissue is characterized by transparency, density and low elasticity. In the human body, hyaline cartilage tissue is widespread and is part of the large cartilage of the larynx. (thyroid and cricoid), trachea and large bronchi, makes up the cartilaginous parts of the ribs, covers the articular surfaces of the bones. In addition, almost all the bones of the body in the process of their development pass through the stage of hyaline cartilage.
Elastic cartilage tissue characterized by the presence of both collagen and elastic fibers in the intercellular substance. In this case, the refractive index of elastic fibers differs from the refraction of an amorphous substance, and therefore elastic fibers are clearly visible in histological preparations. Chondrocytes in isogenic groups in elastic tissue are arranged in the form of columns or columns. In terms of physical properties, elastic cartilage is opaque, elastic, less dense, and less transparent than hyaline cartilage. She is part of elastic cartilage: auricle and cartilaginous part of the external auditory canal, cartilage of the external nose, small cartilages of the larynx and middle bronchi, and also forms the basis of the epiglottis.
Fibrous cartilage tissue characterized by the content in the intercellular substance of powerful bundles of parallel collagen fibers. In this case, chondrocytes are located between the bundles of fibers in the form of chains. According to physical properties, it is characterized by high strength. It is found only in limited places in the body: it is part of the intervertebral discs (annulus fibrosus) and also localized in the places of attachment of ligaments and tendons to hyaline cartilage. In these cases, a gradual transition of connective tissue fibrocytes into cartilage chondrocytes is clearly seen.
There are the following two concepts that should not be confused - cartilage tissue and cartilage. cartilage tissue- This is a type of connective tissue, the structure of which is described above. Cartilage is an anatomical organ made up of cartilage and perichondrium. The perichondrium covers the cartilaginous tissue from the outside (with the exception of the cartilaginous tissue of the articular surfaces) and consists of fibrous connective tissue.
There are two layers in the perichondrium:
external - fibrous;
internal - cellular or cambial (growth).
In the inner layer, poorly differentiated cells are localized - prechondroblasts and inactive chondroblasts, which, in the process of embryonic and regenerative histogenesis, first turn into chondroblasts, and then into chondrocytes. The fibrous layer contains a network of blood vessels. Consequently, the perichondrium, as an integral part of the cartilage, performs the following functions: provides trophic avascular cartilage tissue; protects cartilage; provides regeneration of cartilaginous tissue when it is damaged.
The trophism of the hyaline cartilage tissue of the articular surfaces is provided by the synovial fluid of the joints, as well as from the vessels of the bone tissue.
Development cartilage tissue and cartilage(chondrohistogenesis) is carried out from the mesenchyme. At first, mesenchymal cells in the places of cartilage tissue laying intensively proliferate, round and form focal accumulations of cells - chondrogenic islets. Then these rounded cells differentiate into chondroblasts, synthesize and secrete fibrillar proteins into the intercellular environment. Then chondroblasts differentiate into type I chondrocytes, which synthesize and secrete not only proteins, but also glycosaminoglycans and proteoglycans, that is, they form an intercellular substance. The next stage in the development of cartilage tissue is the stage of differentiation of chondrocytes, with the appearance of type II, III chondrocytes and the formation of lacunae. The perichondrium is formed from the mesenchyme surrounding the cartilaginous islands. In the process of cartilage development, two types of cartilage growth are noted: interstitial growth - due to the reproduction of chondrocytes and the release of intercellular substance by them; oppositional growth - due to the activity of chondroblasts of the perichondrium and the imposition of cartilaginous tissue along the periphery of the cartilage.
Age-related changes are more marked in hyaline cartilage tissue. In the elderly and senile age in the deep layers of hyaline cartilage, the deposition of calcium salts is noted. (shallowing of cartilage), sprouting into this area of the vessels, and then replacing the calcified cartilage tissue with bone tissue - ossification. Elastic cartilage tissue does not undergo calcification and ossification, however, the elasticity of cartilage also decreases in old age.
2. 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:
mechanical;
protective;
participation in the mineral metabolism of the body - the 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 weak cytoplasm (nuclear-type cells). Cell bodies are localized in bone cavities - lacunae, and processes - in bone tubules. Numerous bone tubules, anastomosing with each other, penetrate the entire bone tissue, communicating with the perivascular spaces, and form drainage system bone tissue. This drainage system contains tissue fluid, through which the exchange of substances is ensured not only between cells and tissue fluid, but also between the intercellular substance. The ultrastructural organization of osteocytes is characterized by the presence in the cytoplasm of a weakly expressed granular endoplasmic reticulum, a small number of mitochondria and lysosomes, and centrioles are absent. The nucleus is dominated by heterochromatin. All these data indicate that osteocytes have little functional activity, which is to maintain the metabolism between cells and intercellular substance. Osteocytes are definitive forms of cells and do not divide. They are formed from osteoblasts.
osteoblasts found only in developing bone tissue. They are absent in the formed bone tissue, but are usually contained in an inactive form in the periosteum. In developing bone tissue, they cover each bone plate along the periphery, tightly adhering to each other, forming a kind of epithelial layer. The shape of such actively functioning cells can be cubic, prismatic, angular. The cytoplasm of osteoblasts contains a well-developed granular endoplasmic reticulum and a lamellar Golgi complex, many mitochondria. This ultrastructural organization indicates that these cells are synthesizing and secreting. Indeed, osteoblasts synthesize collagen protein and glycosaminoglycans, which are then released into the intercellular space. Due to these components, an organic matrix of bone tissue is formed. Then these same cells provide the mineralization of the intercellular substance through the release of calcium salts. Gradually, releasing the intercellular substance, they seem to be immured 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. When these cells are irritated (in case of injuries, bone fractures, etc.), a granular endoplasmic reticulum 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 definitive bone tissue. In this way, due to the activity of periosteal osteoblasts, bones regenerate when they are damaged.
Oteoclasts- bone-destroying cells are absent in the formed bone tissue. But they are contained in the periosteum and in places of destruction and restructuring of bone tissue. Since local processes of bone tissue restructuring are continuously carried out in ontogenesis, osteoclasts are necessarily present in these places. In the process of embryonic osteogenesis, these cells play an important role and are found in large numbers. Osteoclasts have a characteristic morphology: firstly, these cells are multinucleated (3-5 or more nuclei), secondly, they are rather large cells (about 90 microns in diameter), thirdly, they have a characteristic shape - the cell has an oval shape , but the part of it adjacent to the bone tissue is flat. At the same time, two zones are distinguished in the flat part:
the central part - corrugated contains numerous folds and islands;
the peripheral (transparent) part is in close contact with the bone tissue.
In the cytoplasm of the cell, under the nuclei, there are numerous lysosomes and vacuoles of 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 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 ground substance and fibers, which contain calcium salts. The fibers consist of type I collagen and are folded into bundles that can be arranged in parallel (ordered) or disordered, on the basis of which the histological classification of bone tissues is built. The main substance of bone tissue, like other types of connective tissues, consists of glycosaminoglycans and proteoglycans, but the chemical composition of these substances is different. In particular, bone tissue contains less chondroitin sulfuric acids, but more citric and other acids that form complexes with calcium salts. In the process of development of bone tissue, an organic matrix, the main substance and collagen (ossein, type II collagen) fibers, are first formed, and then calcium salts (mainly phosphate) are deposited in them. Calcium salts form hydroxyapatite crystals, which are deposited both in the amorphous substance and in the fibers, but a small part of the salts is deposited amorphously. Providing bone strength, calcium phosphate salts are simultaneously a depot of calcium and phosphorus in the body. Therefore, bone tissue takes part in mineral metabolism.
Classification of bone tissue
There are two types of bone tissue:
reticulofibrous (coarse-fibrous);
lamellar (parallel fibrous).
AT reticulofibrous bone tissue bundles of collagen fibers are thick, tortuous and randomly arranged. In the mineralized intercellular substance, osteocytes are randomly located in the lacunae. lamellar bone tissue consists of bone plates in which collagen fibers or their bundles are arranged parallel in each plate, but at right angles to the course of the fibers in adjacent plates. Between the plates in the gaps are osteocytes, while their processes pass through the tubules through the plates.
In the human body, bone tissue is represented almost exclusively by a lamellar form. Reticulofibrous bone tissue occurs only as a stage in the development of some bones (parietal, frontal). In adults, they are located in the area of attachment of the tendons to the bones, as well as in place of the ossified sutures of the skull (sagittal suture of the scales of the frontal bone).
When studying bone tissue, it is necessary to differentiate the concepts of bone tissue and bone.
3. Bone is an anatomical organ, the main structural component of which is bone. Bone as an organ is made up of the following items:
bone;
periosteum;
bone marrow (red, yellow);
vessels and nerves.
Periosteum (periosteum) surrounds the bone tissue along the periphery (with the exception of the articular surfaces) and has a structure similar to the perichondrium. In the periosteum, the outer fibrous and inner cellular or cambial layers are isolated. The inner layer contains osteoblasts and osteoclasts. A pronounced vascular network is localized in the periosteum, from which small vessels penetrate into the bone tissue through perforating channels. Red bone marrow is considered as an independent organ and belongs to the organs of hematopoiesis and immunogenesis.
Bone in the formed bones it is represented only by a lamellar form, however, in different bones, in different parts of one bone, it has a different structure. In flat bones and epiphyses of tubular bones, bone plates form crossbars (trabeculae) that make up the spongy bone. In the diaphysis of tubular bones, the plates are adjacent to each other and form a compact substance. However, even in a compact substance, some plates form osteons, while other plates are common.
The structure of the diaphysis of the tubular bone
On the transverse section of the diaphysis of the tubular bone, next layers:
periosteum (periosteum);
the outer layer of common or general plates;
layer of osteons;
inner layer of common or general plates;
internal fibrous plate endost.
External common plates located under the periosteum in several layers, but without forming complete rings. Osteocytes are located between the plates in the gaps. Perforating channels pass through the outer plates, through which perforating fibers and vessels penetrate from the periosteum into the bone tissue. With the help of perforating vessels in the bone tissue, trophism is provided, and the perforating fibers connect the periosteum with the bone tissue.
Osteon layer consists of two components: osteons and insertion plates between them. Osteon- is a structural unit of the compact substance of the tubular bone. Each osteon consists of:
5-20 concentrically layered plates;
osteon canal, in which the vessels (arterioles, capillaries, venules) pass.
Between canals of neighboring osteons there are anastomoses. Osteons make up the bulk of the bone tissue of the diaphysis of the tubular bone. They are located longitudinally along the tubular bone, respectively, along the force and gravity lines and provide a support function. When the direction of the lines of force changes as a result of a fracture or curvature of the bones, non-load-bearing osteons are destroyed by osteoclasts. However, such osteons are not completely destroyed, and part of the bone plates of the osteon along its length is preserved, and such remaining parts of osteons are called osteons. insert plates. During postnatal ontogenesis, there is a constant restructuring of the bone tissue - some osteons are destroyed (resorbed), others are formed, and therefore there are always intercalated plates between the osteons, like the remains of previous osteons.
The inner layer shared records has a structure similar to the outer one, but it is less pronounced, and in the area of the transition of the diaphysis to the epiphyses, the common plates continue into trabeculae.
Endost - a thin connective tissue plate lining the cavity of the diaphysis canal. The layers in the endosteum are not clearly expressed, but among the cellular elements there are osteoblasts and osteoclasts.
Many human organs have cartilage tissue in their structure, which performs a number of important functions. This special type of connective tissue has a different structure depending on its localization in the body, and this explains its different purpose.
The structure and functions of cartilage tissue are closely interrelated, each of its types plays a specific role.
Cartilage tissue under the microscope
Like any tissue in the body, cartilage contains two main components. This is the main intercellular substance, or matrix, and the cells themselves. The structural features of human cartilage tissue are that the mass fraction of the matrix is much greater than the total cell weight. This means that during histological examination (examination of a tissue sample under a microscope), cartilage cells occupy an insignificant space, and the main area of the visual fields is the intercellular substance. In addition, despite the high density and hardness of the cartilage tissue, the matrix contains up to 80% water.
The structure of the intercellular substance of cartilage
The matrix has a heterogeneous structure and is divided into two components: the main, or amorphous, substance, with a mass fraction of 60%, and chondrin fibers, or fibrils, occupying 40% of the total weight of the matrix. These fibers are similar in structure to the collagen formations that make up, for example, human skin. But they differ from it in a diffuse, disordered arrangement of fibrils. Many cartilaginous formations have a kind of capsule called the perichondrium. It plays a leading role in the restoration (regeneration) of cartilage.
Cartilage Composition
Cartilage tissue in terms of chemical composition is represented by various protein compounds, mucopolysaccharides, glycosaminoglycans, hyaluronic acid complexes with proteins and glycosaminoglycans. These substances are the basis of cartilage tissue, the reason for its high density and strength. But at the same time, they ensure the penetration into it of various compounds and nutrients necessary for the implementation of metabolism and cartilage regeneration. With age, the production and content of hyaluronic acid and glycosaminoglycans decreases, as a result, degenerative-dystrophic changes begin in the cartilage tissue. To slow down the progression of this process, replacement therapy is needed, which ensures the normal functioning of the cartilage tissue.
Cellular composition of cartilage
The structure of human cartilage tissue is such that cartilage cells, or chondrocytes, do not have a clear and ordered structure. Their localization in the intercellular substance rather resembles single islands, consisting of one or more cell units. Chondrocytes can be of different ages, and are divided into young and undifferentiated cells (chondroblasts), and fully mature cells, called chondrocytes.
Chondroblasts are produced by the perichondrium and, gradually moving into the deep layers of cartilage, differentiate and mature. At the beginning of their development, they are located not in groups, but singly, have a round or oval shape and have a huge nucleus compared to the cytoplasm. Already at the initial stage of their existence in chondroblasts, the most active metabolism occurs, aimed at producing components of the intercellular substance. New proteins, glycosaminoglycans, proteoglycans are formed, which then diffusely penetrate into the matrix.
hyaline and elastic cartilage
The most important distinguishing feature of chondroblasts, localized immediately under the perichondrium, is their ability to divide, to form their own kind. This feature is actively studied by scientists, as it provides great opportunities for the introduction of the latest method of treating articular pathologies. By accelerating and adjusting the division of chondroblasts, it is possible to completely restore cartilage tissue damaged by disease or injury.
Adult differentiated cartilage cells, or chondrocytes, are localized in the deep layers of cartilage. They are arranged in groups of 2-8 cells and are called "isogenic groups". The structure of chondrocytes is different from that of chondroblasts, they have a small nucleus and a massive cytoplasm, and are no longer able to divide and form other chondrocytes. Much reduced and their metabolic activity. They are able only at a very moderate level to support metabolic processes in the cartilage matrix.
Location of elements in cartilage
Histological examination shows that the isogenic group is located in the cartilage gap and is surrounded by a capsule of intertwined collagen fibers. Chondrocytes in it are close to each other, separated only by protein molecules, and can have a variety of shapes: triangular, oval, round.
In diseases of cartilage, a new type of cell appears: chondroclasts. They are much larger than chondroblasts and chondrocytes, as they are multinucleated. These cells are not involved in either metabolism or cartilage regeneration. They are destroyers and "devourers" of normal cells and provide destruction and lysis of cartilage tissue during inflammatory or degenerative processes in it.
Cartilage types
The intercellular substance of cartilage can have a different structure, depending on the type and location of the fibers. Therefore, there are 3 types of cartilage:
- Hyaline, or vitreous.
- Elastic, or mesh.
- Fibrous, or connective tissue.
Cartilage types
Each type is characterized by a certain degree of density, hardness and elasticity, as well as localization in the body. Hyaline cartilage tissue lines the articular surfaces of bones, connects the ribs to the sternum, and is found in the trachea, bronchi, and larynx. Elastic cartilage is an integral part of the small and medium bronchi, larynx, and human auricles are also made of it. Connective cartilage, or fibrous, is so called because it connects the ligaments or tendons of the muscles with hyaline cartilage (for example, at the points of attachment of the tendons to the bodies or processes of the vertebrae).
Blood supply and innervation of cartilage tissue
The structure of the cartilage is very dense, even the smallest blood vessels (capillaries) do not penetrate it. All the nutrients and oxygen necessary for the life of the cartilage tissue enter it from the outside. In a diffuse way, they penetrate from nearby blood vessels, from the perichondrium or bone tissue, from the synovial fluid. The decay products are also removed diffusely, and are removed from the cartilage through the venous vessels.
Young and mature cartilage
Nerve fibers penetrate into the superficial layers of cartilage from the perichondrium with only separate single branches. This explains the fact that nerve impulses from the cartilage tissue do not arrive during its diseases, and the pain syndrome appears during the reaction of bone structures, when the cartilage is almost already destroyed.
Functions of cartilage
The main function of cartilage tissue is musculoskeletal, which consists in providing strong connections between various parts of the skeleton and a variety of movements. So, hyaline cartilage, which is the most important structural part of the joints and lining the bone surfaces, makes possible the whole range of human movements. Thanks to its physiological sliding, they occur smoothly, comfortably and painlessly, with the appropriate amplitude.
Cartilage of the knee joint
Other connections between the bones, which do not involve active movements in them, are also made by means of strong cartilaginous tissue, in particular, of the hyaline type. These may be inactive bone fusions that perform a supporting function. For example, in places where the ribs pass into the sternum.
The functions of the connective cartilage tissue are explained by its localization and consist in ensuring the mobility of various parts of the skeleton. It makes possible a strong and elastic connection of muscle tendons with bone surfaces covered with hyaline cartilage.
Other functions of human cartilage are also important, as they form the appearance, voice, and ensure normal breathing. First of all, this refers to the cartilaginous tissue that forms the basis of the auricles and the tip of the nose. The cartilage, which is part of the trachea and bronchi, makes them mobile and functional, and the cartilaginous structures of the larynx are involved in the formation of the individual timbre of the human voice.
Cartilages of the nose
Cartilage without pathological changes is of great importance for human health and normal quality of life.
Cartilage is a type of hard connective tissue. From the name it is clear that it consists of cartilage cells and intercellular substance. The main function of cartilage tissue is support.
Cartilage tissue has high elasticity and elasticity. For joints, cartilage is very important - it eliminates friction due to the release of fluid and lubrication of the joints. Due to this, the load on the joints is significantly reduced.
Unfortunately, with age, cartilage tissue loses its properties. Often, cartilage tissue is damaged at a young age. This is because cartilage is very prone to destruction. It is very important to take care of your health in time, since damaged cartilage tissue is one of the main causes of diseases of the musculoskeletal system.
Types of cartilage
- hyaline cartilage
- Elastic cartilage
- fibrocartilage
hyaline cartilage tissue found in the composition of the cartilage of the larynx, bronchi, bone temafises, in the area of attachment of the ribs to the sternum.
Made from elastic cartilage consist of auricles, bronchi, larynx.
Fibrous cartilage tissue is located in the area of transition of ligaments and tendons to hyaline cartilage tissue.
However, all three types of cartilage tissue are similar in composition - they consist of cells (chondrocytes) and intercellular substance. The latter has a high bypass, approximately 60-80 percent of water. In addition, the intercellular substance occupies more space than cells. The chemical composition is quite complex. The intercellular substance of the cartilaginous tissue is divided into an amorphous substance and a fibrillar component, which includes about forty percent of the dry matter - collagen. The production of the matrix (intercellular substance) is carried out by chondroblasts and young chondrocytes.
Chondroblasts and chondrocytes
Chondroblasts are round or ovoid cells. The main task: the production of components of the intercellular substance, such as collagen, elastin, glycoproteins, proteoglycans.
Chondrocytes take into account mature cells of cartilage tissue of large size. The shape can be round, oval, polygonal. Where are chondrocytes located? In lacunae. The intercellular substance surrounds chondrocytes. The walls of the lacunae are two layers - the outer one (made of collagen fibers) and the inner one (made of proteoglycan aggregates).
It combines not only collagen fibrils, but also elastic fibers, which consist of elastin protein. Its production is also the task of cartilage cells. Elastic cartilage tissue is characterized by increased flexibility.
The composition of fibrous cartilage tissue includes bundles of collagen fibers. Fibrous cartilage is very strong. Fibrous rings of intervertebral discs, intra-articular discs consist of fibrous cartilage tissue. In addition, fibrous cartilage covers the articular surfaces of the temporomandibular and sternoclavicular joints.
Bone growth, cartilage, skeletal structure, limbs, pelvis. About 206 bones make up the adult human skeleton. Bones have a hard, thick and durable outer layer and a soft core, or marrow. They are strong and strong, like concrete, and can support very large weights without bending, breaking, or collapsing. Connected together by joints and driven by muscles that are attached to them at both ends. bones form a protective frame for soft and vulnerable parts of the body, while providing the human body with greater flexibility of movement. In addition to this, the skeleton is a framework, or scaffolding, on which other parts of the body are attached and supported.
Like everything in the human body, bones are made up of cells. These are cells that create the framework of fibrous (fibrous) tissue, a relatively soft and plastic base. Within this framework is a network of harder material, resulting in a concrete-like "stone" (i.e., hard material) that gives strength to the "cement" fiber cloth backing. The result is an extremely strong structure with a high degree of flexibility.
bone growth
At birth, about 350 bones form the backbone of a baby's skeleton; over the years, some of them coalesce into larger bones. The skull of an infant is a good example of this: during childbirth, it is compressed to pass through a narrow canal. If the child's skull were all rigid, like the V of an adult, it would simply make it impossible for the child to pass through the pelvic opening of the mother's body. Fontanelles in different sections of the skull make it possible to give it the desired shape when passing through the birth tray. After the birth of the uti, the fontanelles gradually close.
The skeleton of a child consists not only of bones, but also of cartilage, which is much more flexible than the first. As the body grows, they gradually harden, turning into bones - this process is called ossification (ossification), which continues in the body of an adult. Body growth occurs due to an increase in the length of the bones of the arms, legs and back. The long (tubular) bones of the limbs have a growth plate at each end, where growth occurs. This growth plate is cartilage rather than bone and is therefore not visible on an x-ray. When the growth plate ossifies, the bone no longer grows in length. The growth plates in the various bones of the body form, as it were, a soft connection in a certain order. Around the age of 20, the human body acquires a fully developed skeleton.
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In general, the female skeleton is lighter and smaller than the male. The woman's pelvis is proportionately wider, which is necessary for the growing fetus during pregnancy. The shoulders of a man are wider and the chest is longer, but contrary to popular belief, men and women have the same number of ribs. An important and remarkable feature of bones is their ability to take on a certain shape in the process of growth. This is very important for the long bones that support the limbs. They are wider at the ends than in the middle, providing extra strength to the joint where it's most needed. This formation of form, known as modeling, is especially intense with bone growth; it continues for the rest of the time.
Various shapes and sizes
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Flat bones form, as it were, a sandwich of hard bones with a porous (spongy) layer between them. They are flat because they provide protection (like the skull, for example) or because they provide a particularly large surface to which certain muscles (like the shoulder blades) are attached. And finally, the last type of bone - mixed bones - has several configurations depending on the specific function. The bones of the spine, for example, are box-shaped to give more strength (strength) and space for the spinal cord inside them. And the bones of the face, which create the structure of the face, are hollow, with air cavities inside, to create an ultra-lightness of their weight.
cartilage
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Based on their physical properties, the different types of cartilage are known as hyaline cartilage, fibrous cartilage, and elastic cartilage.
hyaline cartilage
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This tyne of cartilage forms the skeleton of the embryo and is capable of great growth, which allows a child to grow 45 cm tall to an adult male 1.8 m tall. After growth is completed, hyaline cartilage remains as a very thin layer (1 - 2 mm) at the ends of the bones that they line, in the joints.
Hyaline cartilage is often found in the respiratory tract, where it forms the tip of the nose, as well as the rigid but flexible rings that surround the windpipe and the large tubes (bronchi) leading to the lungs. At the ends of the ribs, hyaline cartilage forms the connecting links (costal cartilages) between the ribs and the sternum that allow the chest to expand and contract during breathing.
In the larynx, or voice box, hyaline cartilage not only serves as a support, but also participates in the creation of voice. As they move, they control the volume of air passing through the larynx, and as a result, a sound of a certain pitch is produced.
fibrocartilage
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In the spine, each bone, or vertebrae, is separated from its neighbor by a disc of fibrocartilage. Intervertebral discs protect the spine from shock and allow the skeleton to stand upright.
Each disc has an outer covering of fibrocartilage that surrounds a thick, syrupy fluid. The cartilaginous part of the disc, which has a well-lubricated surface, prevents wear and tear of the bones during movement, and the fluid acts as a natural anti-shock mechanism.
Fibrous cartilage serves as a strong connecting material between bones and ligaments; in the pelvic girdle, they connect the two parts of the pelvis together at a joint known as the pubic symphysis. In women, this cartilage is especially important because it is softened by pregnancy hormones to allow the baby's head to come out during labor.
Elastic cartilage
Elastic cartilage (the third type of cartilage) got its name from the presence of elastin fibers in them, but they also contain collagen. Elastin fibers give elastic cartilage its distinctive yellow color. Strong, but resilient, elastic cartilage forms a flap of tissue called the epiglottis; it closes off the air when the beg is swallowed.
Elastic cartilage also forms the elastic part of the outer ear and supports the walls of the canal leading to the middle ear and the Eustachian tubes that connect each ear to the back of the throat. Together with hyaline cartilage, elastic cartilage is also involved in the formation of the supporting and voice-producing parts of the larynx.
Skeleton structure
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Striking in the skull is the size of the lower jaw. Suspended on hinges, it forms an ideal crushing tool at the moment of contact through the teeth with the upper jaw. Facial tissues - muscles, nerves and skin - cover the facial bones in such a way that it is imperceptible how skillfully the jaws are designed. Another example of first-class design is the face-to-skull ratio: the face around the eyes and nose is stronger, and this prevents the facial bones from being pressed into the skull or, conversely, too protruding.
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The thorax consists of the ribs on the sides, the vertebral column at the back and the sternum at the front. The ribs are attached to the spine by special joints that allow them to move during breathing. In front, they are attached to the sternum by costal cartilages. The two lower ribs (11th and 12th) are attached only at the back and are too short to connect to the sternum. They are called oscillating ribs and have little to do with breathing. The first and second ribs are closely connected to the collarbone and form the base of the neck, where several large nerves and blood vessels run to the arms. The ribcage is designed to protect the heart and lungs it contains, since damage to these organs can be life threatening.
