Intercellular substance of cartilage tissue composition. Cartilage cells

27.09.2019

cartilage type	INTERCELLULAR SUBSTANCE		Localization
	fibers	Base substance
hyaline cartilage	collagen fibers (collagen II, VI, IX, X, XI types)	glycosaminoglycans and proteoglycans	trachea and bronchi, articular surfaces, larynx, connections of the ribs with the sternum
elastic cartilage	elastic and collagen fibers		auricle, horn-shaped and sphenoid cartilages of the larynx, cartilages of the nose
fibrocartilage	parallel bundles of collagen fibers; fiber content is greater than in other types of cartilage		places of transition of tendons and ligaments into hyaline cartilage, in intervertebral discs, semi-movable joints, symphysis
	in the intervertebral disc: the fibrous ring is located outside - it contains mainly fibers that have a circular course; and inside there is a gelatinous nucleus - it consists of glycosaminoglycans and proteoglycans and cartilage cells floating in them

cartilage tissue

It consists of cells - chondrocytes and chondroblasts and a large amount of intercellular hydrophilic substance, characterized by elasticity and density.

In fresh cartilage tissue contains:

70-80% water,

10-15% organic matter

4-7% salts.

50-70% of the dry matter of cartilage tissue is collagen.

The cartilage itself does not have blood vessels, and nutrients diffuse from the surrounding perichondrium.

Cartilage tissue cells are represented by chondroblastic differen:

1. Stem cell

2. Semi-stem cell (prechondroblasts)

3. Chondroblast

4. Chondrocyte

5. Chondroclast

Stem and semi-stem cell- poorly differentiated cambial cells, mainly localized around the vessels in the perichondrium. By differentiating, they turn into chondroblasts and chondrocytes, i.e. needed for regeneration.

Chondroblasts- young cells are located in the deep layers of the perichondrium singly, without forming isogenic groups. Under a light microscope, chondroblasts are flattened, slightly elongated cells with basophilic cytoplasm. Under an electron microscope, granular EPS, the Golgi complex, and mitochondria are well expressed in them; protein-synthesizing complex of organelles main function of chondroblasts- production of the organic part of the intercellular substance: collagen and elastin proteins, glycosaminoglycans (GAGs) and proteoglycans (PGs). In addition, chondroblasts are capable of reproduction and subsequently turn into chondrocytes. In general, chondroblasts provide appositional (superficial, neoplasms from the outside) cartilage growth from the side of the perichondrium.

Chondrocytes- the main cells of cartilage tissue are located in the deeper layers of cartilage in cavities - lacunae. Chondrocytes can divide by mitosis, while the daughter cells do not diverge, they remain together - the so-called isogenic groups are formed. Initially, they lie in one common gap, then an intercellular substance is formed between them, and each cell of this isogenic group has its own capsule. Chondrocytes are oval-round cells with basophilic cytoplasm. Under an electron microscope, granular ER, Golgi complex, mitochondria are well expressed; protein-synthesizing apparatus, tk. main function of chondrocytes- production of the organic part of the intercellular substance of cartilage tissue. Cartilage growth due to the division of chondrocytes and their production of intercellular substance provides interstitial (internal) cartilage growth.

There are three types of chondrocytes in isogenic groups:

1. Type I chondrocytes predominate in young, developing cartilage. They are characterized by a high nuclear-cytoplasmic ratio, the development of vacuolar elements of the lamellar complex, the presence of mitochondria and free ribosomes in the cytoplasm. In these cells, patterns of division are often observed, which allows us to consider them as a source of reproduction of isogenic groups of cells.

2. Type II chondrocytes are distinguished by a decrease in the nuclear-cytoplasmic ratio, a weakening of DNA synthesis, and the preservation of high level RNA, intensive development of the granular endoplasmic reticulum and all components of the Golgi apparatus, which provide the formation and secretion of glycosaminoglycans and proteoglycans into the intercellular substance.

3. Type III chondrocytes have the lowest nuclear-cytoplasmic ratio, strong development and ordered arrangement of the granular endoplasmic reticulum. These cells retain the ability to form and secrete protein, but the synthesis of glycosaminoglycans decreases in them.

In the cartilage tissue, in addition to the cells forming the intercellular substance, there are also their antagonists - the destroyers of the intercellular substance - these are chondroclasts(can be attributed to the macrophage system): rather large cells, there are many lysosomes and mitochondria in the cytoplasm. Function of chondroclasts- Destruction of damaged or worn parts of cartilage.

Intercellular substance of cartilage tissue contains collagen, elastic fibers and ground substance. The ground substance consists of tissue fluid and organic substances:

GAGs (chondroethin sulfates, keratosulfates, hyaluronic acid);

10% - PG (10-20% - protein + 80-90% GAG);

The intercellular substance has a high hydrophilicity, the water content reaches 75% of the mass of the cartilage, which leads to a high density and turgor of the cartilage. Cartilaginous tissues in the deep layers do not have blood vessels, nutrition is carried out diffusely due to the vessels of the perichondrium.

perichondrium is a layer of connective tissue that covers the surface of cartilage. In the perichondrium secrete external fibrous(from a dense unformed ST with large quantity blood vessels) layer and inner cell layer containing a large number of stem cells, semi-stem cells and chondroblasts.

Bone growth, cartilage, skeletal structure, limbs, pelvis. About 206 bones make up the adult human skeleton. Bones are hard, thick and durable outer layer and the soft core, or bone marrow. They are strong and strong, like concrete, and can withstand very big weight 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, there is a network of harder material, which results in concrete with "stones" (i.e. solid material), giving strength to the "cement" basis of fibrous tissue. The result is an extremely strong structure with a high degree of flexibility.

bone growth

When the bones begin to grow, they consist of a solid mass. Only at the secondary stage do they begin to form hollow spaces within themselves. The formation of voids inside the bone tube has very little effect on its strength, but greatly reduces its weight. This is the basic law of building technology, which nature made full use of when creating bones. The hollow spaces fill the bone marrow, in which the formation of blood cells occurs. It may seem surprising, but a newborn baby has more bones in his body than an adult.

At birth, about 350 bones form the backbone of a baby's skeleton; over the years, some of them coalesce into larger bones. Scull baby is good example this: during childbirth, it is squeezed to pass through a narrow channel. 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 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.

As the skeleton develops, its proportions change significantly. The head of a six-week-old fetus is the same length as its body; at birth, the head is still quite large compared to other parts of the body, but the median point has moved from the baby's chin to the navel. In an adult, the median line of the body passes through the pubic symphysis (pubic symphysis) or immediately above the genitals.

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 man's shoulders are broader, and rib cage 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

There are several different types of bones, each of which has a specific configuration depending on the function. The long tubular bones that form the limbs of the body are simply cylinders of hard bone with soft spongy marrow inside. Short tubular bones, such as the bones of the hand and ankle bones, are basically the same configuration as the long (tubular) bones, but they are shorter and thicker in order to make many different movements without losing strength, without getting tired.
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 greater strength (strength) and space to 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

Cartilage is a smooth, strong but flexible part skeletal system person. In an adult, they are found mainly in the joints and in covering the ends of bones, as well as in other important points skeleton where strength, smoothness and flexibility are required. The structure of cartilage is not the same everywhere in different parts skeleton. It depends on the specific function that this or that cartilage performs. All cartilage consists of a base, or matrix, in which cells and fibers are placed, consisting of proteins - collagen and elastin. The consistency of the fibers is different in different types of cartilage, but all cartilages are similar in that they do not contain blood vessels. Instead, they feed on nutrients that penetrate the covering (the perichondrium, or perichondrium) of the cartilage and are lubricated by the synovial fluid that is produced by the membranes that line the joints.
By their own physical qualities different types cartilage are known as hyaline cartilage, fibrous cartilage, and elastic cartilage.

hyaline cartilage

Hyaline cartilage (the first type of cartilage) is a bluish-white translucent tissue and of all three types of cartilage has the least number of cells and fibers. All the fibers present here are made up of collagen.
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, which 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

Fibrous cartilage (the second type of cartilage) consists of numerous bundles of a dense substance of collagen, which give the cartilage, on the one hand, elasticity, and on the other, the ability to withstand significant pressure. Both of these qualities are necessary in those areas where the most fibrous cartilage is located, namely, between the bones of the spinal column.
In the spine, each bone, or vertebrae, is separated from its neighbor by a disc of fibrocartilage. Intervertebral discs protect the spine from concussion 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 back wall 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

Each of the various bones of the skeleton is designed to perform certain actions. The skull protects the brain as well as the eyes and ears. Of the 29 bones of the skull, 14 form the main frame for the eyes, nose, cheekbones, upper and lower jaws. One look at the skull is enough to understand how vulnerable parts of the face are protected by these bones. Deep eye sockets with a forehead hanging over them protect complex and delicate eye mechanisms. Similarly, the odor-determining parts of the olfactory apparatus are hidden high behind the central nasal opening in the upper jaw.
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.

The spine is made up of a chain of small bones called vertebrae and forms the central axis of the skeleton. It has tremendous strength and strength and, since the rod is not solid, but consists of small individual sections, it is very flexible. This allows the person to bend over, touch the toes of the toes, and stay upright. The vertebrae also protect the delicate tissue of the spinal cord, which runs down the middle inside the spine. The lower end of the spine is called the coccyx. In some animals, such as the dog and the cat, the coccyx is much longer and forms a tail.

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 rib and the second 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.

Limbs and pelvis

The back of the pelvis is the sacrum. Massive iliac bones are attached to the sacrum on both sides, the rounded tops of which are well palpable on the body. The vertical sacroiliac joints between the sacrum and the ilium are packed with fibers and criss-crossed by a series of ligaments. In addition, the surface of the pelvic bones has small incisions, and the bones are stacked with each other like freely connected openwork saws, which gives additional stability to the entire structure. In front of the body, the two pubic bones are connected at the pubic symphysis (pubic articulation). Their connection cushions the cartilaginous or pubic disc. The joint envelops many ligaments; ligaments go to the ilium to give stability to the pelvis. In the lower part of the leg pass the tibia and thinner - fibula. The foot, like the hand, consists of a complex system of small bones. This enables a person to stand firmly and freely, as well as walk and run without falling.

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, cartilages 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. Therefore, the perichondrium, as component cartilage, performs following features: 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 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 comprises:

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.

Hello my friends!

In this article, we will explore what is cartilage of the knee. Consider what cartilage consists of and what function they have. As you understand, cartilage tissue is the same in all joints of our body, and everything described below applies to other joints.

The ends of our bones in the knee joint are covered with cartilage, between them lie two menisci - these are also cartilage, but only slightly different in composition. Read about menisci in the article "". I will only say that cartilage and menisci differ in the type of cartilage tissue: bone cartilage is hyaline cartilage, and the menisci fibrocartilage. This is what we will analyze now.

The thickness of the cartilage covering the ends of the bone is on average 5-6 mm, it consists of several layers. The cartilage is dense and smooth, which allows the bones to easily slide relative to each other during flexion and extension movements. With elasticity, cartilage acts as a shock absorber during movements.

In a healthy joint, depending on its size, fluid is from 0.1 to 4 ml, the distance between cartilage (articular space) is from 1.5 to 8 mm, acid-base balance is 7.2-7.4, water is 95% , protein 3%. The composition of cartilage is similar to blood serum: 200-400 leukocytes per 1 ml, of which 75% are lymphocytes.

Cartilage is a type of connective tissue in our body. The main difference between cartilage tissue and others is the absence of nerves and blood vessels that directly feed this tissue. The blood vessels would not withstand the loads and constant pressure, and the presence of nerves there would give off pain with each of our movements.

Cartilage is designed to reduce friction at the junctions of bones. Cover both heads of the bone and inside patella (patella). Constantly bathed in synovial fluid, they ideally reduce the processes of friction in the joints to zero.

Cartilage does not have access to blood vessels and nutrition, respectively, and if there is no nutrition, then there is no growth or repair. But cartilage is also made up of living cells, and they also need nutrition. They receive food due to the same synovial fluid.

The meniscus cartilage is riddled with fibers, which is why it is called fibrocartilage and is denser and harder than hyaline in structure, therefore it has greater tensile strength and can withstand pressure.

Cartilages differ in the ratio of fibers: . All this gives the cartilage not only hardness, but also elasticity. Working like a sponge under stress, cartilage and menisci are compressed, unclenched, flattened, stretched as you wish. They constantly absorb a new portion of the liquid and give the old one, make it constantly circulate; at the same time, the liquid is enriched with nutrients and again carries them to the cartilage. Pro synovial fluid we will talk later.

The main components of cartilage

articular cartilage is a complex fabric. Consider the main components of this fabric. make up almost half of the intercellular space in articular cartilage. Collagen in its structure consists of very large molecules intertwined in triple helixes. This structure of collagen fibers allows the cartilage to resist any kind of deformation. Collagen gives tissue elasticity. give elasticity, the ability to return to its original state.

The second important element of cartilage is water, which is found in large quantities in the intercellular space. Water is a unique natural element, it is not subject to any deformation, it cannot be stretched or compressed. This adds to the cartilage tissue stiffness and elasticity. Besides than more water, the better and more functional is the interarticular fluid. It spreads and circulates easily. With a lack of water, the joint fluid becomes more viscous, less fluid and, of course, does not perform its role in providing nutrition to the cartilage. !

Glycosamines- substances produced by the cartilaginous tissue of the joints are also part of the synovial fluid. Structurally, glucosamine is a polysaccharide that serves as an important constituent of cartilage.

Glucosamine is a precursor of glycosaminoglycans (the main component of articular cartilage), so it is believed that its additional use from the outside can help restore cartilage.

In our body, glucosamine binds cells and is part of cell membranes and proteins, making tissues stronger and more resistant to stretching. Thus, glucosamine supports and strengthens our joints and ligaments. With a decrease in the amount of glucosamines, the resistance of cartilage tissue to stress also decreases, the cartilage becomes more susceptible to damage.

The restoration of cartilage tissue and the production of the necessary compounds and substances are dealt with chondrocytes.

Chondrocytes, by their nature, do not differ from other cells in terms of development and regeneration, their metabolic rate is sufficiently high. But the problem is that there are very few of these same chondrocytes. In articular cartilage, the number of chondrocytes is only 2-3% of the mass of cartilage. Therefore, the restoration of cartilage tissue is so limited.

So, cartilage nutrition is difficult, cartilage tissue renewal is also a very long-term process, and recovery is even more problematic. What to do?

Considering all of the above, we come to the conclusion that in order for the cartilage of the knee joint to recover, it is necessary to achieve a high number and activity of chondrocyte cells. And our task is to provide them good nutrition, which they can only get through the synovial fluid. But, even if the nutrition is the richest, it will not reach its goal without the movement of the joint. That's why, move more - recovery is better!

With prolonged immobilization of the joint or the entire leg (gypsum, splints, etc.), not only muscles decrease and atrophy; it has been established that cartilage tissue also decreases, since it does not receive enough nutrition without movement. I will repeat myself for the hundredth time, but this is another proof of the need for constant movement. Man is created by nature in such a way that he must constantly run for food and run away from the mammoth, like other animals. Excuse me if I offend some of the "Crowns of the Creation of Nature" by this. to scale evolutionary development, we have gone too little way for the body to behave differently, it has not yet adapted to other conditions of existence. And if the body feels that something in its composition is not needed or does not work well, it gets rid of it. Why feed something that does not benefit? They stopped walking with their feet - the legs atrophy, the bodybuilder stopped swinging (use all his muscle mass) - immediately deflated. Well, I digress.

In other articles, we will, of course, touch on issues ( operating methods and conservative), their nutrition and movement. What I, with my cartilage injury, am trying to implement. I'll tell you too.

In the meantime, my instructions are: , COMPLETE VARIOUS FOOD,.

You can start this minute.

All the best, don't worry!

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. Cartilage histology is represented by a small number cell 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 connective tissue, which performs the functions of strong shock-absorbing elements and has a significant amount of fibers in its composition. 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 in it support function. Overall plan 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. As a result, he is unable 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 chemical table 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 tissue 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, thanks 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 to it, as a result of a violation of trophism, diseases arise that can destroy fibrous structures and cause cell degeneration. A young organism has much more stock 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 maintain the body in good shape, because overweight and insufficient exercise stress cause structural failure.