The structure of cartilage tissue. Types of cartilage tissue and its structure. Joint diseases: how they manifest themselves

23.09.2019

Tissue is a collection of cells and intercellular substance that have the same structure, function and origin.

In the body of mammals, animals and humans, there are 4 types of tissues: epithelial, connective, in which bone, cartilage and adipose tissue can be distinguished; muscular and nervous.

Tissue - location in the body, types, functions, structure

Tissues are a system of cells and intercellular substances that have the same structure, origin and functions.

Intercellular substance is a product of cell activity. It provides communication between cells and creates a favorable environment for them. It can be liquid, such as blood plasma; amorphous - cartilage; structured - muscle fibers; hard - bone tissue (in the form of salt).

Tissue cells have different shapes, which determine their function. Fabrics are divided into four types:

epithelial - border tissues: skin, mucous membrane;
connective - the internal environment of our body;
muscle tissue;
nerve tissue.

Epithelial tissue

Epithelial (border) tissues - line the surface of the body, the mucous membranes of all internal organs and body cavities, serous membranes, and also form the glands of external and internal secretion. The epithelium lining the mucous membrane is located on the basement membrane, and its inner surface directly faces the external environment. Its nutrition is accomplished by the diffusion of substances and oxygen from blood vessels through the basement membrane.

Features: there are many cells, there is little intercellular substance and it is represented by a basement membrane.

Epithelial tissues perform the following functions:

protective;
excretory;
suction

Classification of epithelia. Based on the number of layers, a distinction is made between single-layer and multi-layer. They are classified according to shape: flat, cubic, cylindrical.

If all epithelial cells reach the basement membrane, it is a single-layer epithelium, and if only cells of one row are connected to the basement membrane, while others are free, it is multilayered. Single-layer epithelium can be single-row or multi-row, which depends on the level of location of the nuclei. Sometimes mononuclear or multinuclear epithelium has ciliated cilia facing the external environment.

Stratified epithelium Epithelial (integumentary) tissue, or epithelium, is a boundary layer of cells that lines the integument of the body, the mucous membranes of all internal organs and cavities, and also forms the basis of many glands.

Glandular epithelium The epithelium separates the organism (internal environment) from the external environment, but at the same time serves as an intermediary in the interaction of the organism with environment. Epithelial cells are tightly connected to each other and form a mechanical barrier that prevents the penetration of microorganisms and foreign substances into the body. Epithelial tissue cells live for a short time and are quickly replaced by new ones (this process is called regeneration).

Epithelial tissue is also involved in many other functions: secretion (exocrine and endocrine glands), absorption (intestinal epithelium), gas exchange (lung epithelium).

The main feature of the epithelium is that it consists of a continuous layer of tightly adjacent cells. The epithelium can be in the form of a layer of cells lining all surfaces of the body, and in the form of large accumulations of cells - glands: liver, pancreas, thyroid, salivary glands, etc. In the first case, it lies on the basement membrane, which separates the epithelium from the underlying connective tissue . However, there are exceptions: epithelial cells in the lymphatic tissue alternate with connective tissue elements; such epithelium is called atypical.

Epithelial cells, arranged in a layer, can lie in many layers (stratified epithelium) or in one layer (single-layer epithelium). Based on the height of the cells, epithelia are divided into flat, cubic, prismatic, and cylindrical.

Single-layer squamous epithelium - lines the surface of the serous membranes: pleura, lungs, peritoneum, pericardium of the heart.

Single-layer cubic epithelium - forms the walls of the kidney tubules and the excretory ducts of the glands.

Single-layer columnar epithelium - forms the gastric mucosa.

Bordered epithelium - a single-layer cylindrical epithelium, on the outer surface of the cells of which there is a border formed by microvilli that ensures the absorption of nutrients - lines the mucous membrane of the small intestine.

Ciliated epithelium (ciliated epithelium) is a pseudostratified epithelium consisting of cylindrical cells, the inner edge of which, i.e. facing the cavity or canal, is equipped with constantly oscillating hair-like formations (cilia) - the cilia ensure the movement of the egg in the tubes; removes germs and dust from the respiratory tract.

Stratified epithelium is located at the border between the body and the external environment. If keratinization processes occur in the epithelium, i.e., the upper layers of cells turn into horny scales, then such a multilayered epithelium is called keratinization (skin surface). Multilayer epithelium lines the mucous membrane of the mouth, food cavity, and cornea of the eye.

Transitional epithelium lines the walls of the bladder, renal pelvis, and ureter. When these organs are filled, the transitional epithelium stretches, and cells can move from one row to another.

Glandular epithelium - forms glands and performs a secretory function (releases substances - secretions that are either released into the external environment or enter the blood and lymph (hormones)). The ability of cells to produce and secrete substances necessary for the functioning of the body is called secretion. In this regard, such an epithelium was also called secretory epithelium.

Connective tissue

Connective tissue Consists of cells, intercellular substance and connective tissue fibers. It consists of bones, cartilage, tendons, ligaments, blood, fat, it is present in all organs (loose connective tissue) in the form of the so-called stroma (framework) of organs.

In contrast to epithelial tissue, in all types of connective tissue (except adipose tissue), the intercellular substance predominates over the cells in volume, i.e., the intercellular substance is very well expressed. The chemical composition and physical properties of the intercellular substance are very diverse in different types of connective tissue. For example, blood - the cells in it “float” and move freely, since the intercellular substance is well developed.

In general, connective tissue makes up what is called the internal environment of the body. It is very diverse and represented various types- from dense and loose forms to blood and lymph, the cells of which are in liquid. The fundamental differences in the types of connective tissue are determined by the ratios of cellular components and the nature of the intercellular substance.

Dense fibrous connective tissue (muscle tendons, joint ligaments) is dominated by fibrous structures and experiences significant mechanical stress.

Loose fibrous connective tissue is extremely common in the body. It is very rich, on the contrary, in cellular forms different types. Some of them are involved in the formation of tissue fibers (fibroblasts), others, which is especially important, provide primarily protective and regulatory processes, including through immune mechanisms (macrophages, lymphocytes, tissue basophils, plasma cells).

Bone tissue

Bone tissue Bone tissue, which forms the bones of the skeleton, is very durable. It maintains body shape (constitution) and protects organs located in the skull, chest and pelvic cavities, and participates in mineral metabolism. The tissue consists of cells (osteocytes) and intercellular substance in which nutrient channels with blood vessels are located. The intercellular substance contains up to 70% mineral salts (calcium, phosphorus and magnesium).

In its development, bone tissue passes through fibrous and lamellar stages. In various parts of the bone it is organized in the form of compact or spongy bone substance.

Cartilage tissue

Cartilage tissue consists of cells (chondrocytes) and intercellular substance (cartilage matrix), characterized by increased elasticity. It performs a supporting function, as it forms the bulk of cartilage.

There are three types of cartilage tissue: hyaline, which is part of the cartilage of the trachea, bronchi, ends of the ribs, and articular surfaces of bones; elastic, forming the auricle and epiglottis; fibrous, located in the intervertebral discs and joints of the pubic bones.

Adipose tissue

Adipose tissue is similar to loose connective tissue. The cells are large and filled with fat. Adipose tissue performs nutritional, shape-forming and thermoregulatory functions. Adipose tissue is divided into two types: white and brown. In humans, white adipose tissue predominates, part of it surrounds the organs, maintaining their position in the human body and other functions. The amount of brown adipose tissue in humans is small (it is found mainly in newborns). The main function of brown adipose tissue is heat production. Brown adipose tissue maintains the body temperature of animals during hibernation and the temperature of newborns.

Muscle tissue

Muscle cells are called muscle fibers because they are constantly stretched in one direction.

Classification of muscle tissue is carried out on the basis of the structure of the tissue (histologically): by the presence or absence of transverse striations, and on the basis of the mechanism of contraction - voluntary (as in skeletal muscle) or involuntary (smooth or cardiac muscle).

Muscle tissue has excitability and the ability to actively contract under the influence of the nervous system and certain substances. Microscopic differences allow us to distinguish two types of this tissue - smooth (unstriated) and striated (striated).

Smooth muscle tissue has a cellular structure. It forms the muscular membranes of the walls of internal organs (intestines, uterus, bladder, etc.), blood and lymphatic vessels; its contraction occurs involuntarily.

Striated muscle tissue consists of muscle fibers, each of which is represented by many thousands of cells, fused, in addition to their nuclei, into one structure. It forms skeletal muscles. We can shorten them at will.

A type of striated muscle tissue is cardiac muscle, which has unique abilities. During life (about 70 years), the heart muscle contracts more than 2.5 million times. No other fabric has such strength potential. Cardiac muscle tissue has transverse striations. However, unlike skeletal muscle, there are special areas where the muscle fibers meet. Thanks to this structure, the contraction of one fiber is quickly transmitted to neighboring ones. This ensures simultaneous contraction of large areas of the heart muscle.

Also, the structural features of muscle tissue are that its cells contain bundles of myofibrils formed by two proteins - actin and myosin.

Nervous tissue

Nervous tissue consists of two types of cells: nerve (neurons) and glial. Glial cells are closely adjacent to the neuron, performing supporting, nutritional, secretory and protective functions.

Neuron is the basic structural and functional unit of nervous tissue. Its main feature is the ability to generate nerve impulses and transmit excitation to other neurons or muscle and glandular cells of working organs. Neurons can consist of a body and processes. Nerve cells are designed to conduct nerve impulses. Having received information on one part of the surface, the neuron very quickly transmits it to another part of its surface. Since the processes of a neuron are very long, information is transmitted over long distances. Most neurons have two types of processes: short, thick, branching near the body - dendrites, and long (up to 1.5 m), thin and branching only at the very end - axons. Axons form nerve fibers.

A nerve impulse is an electrical wave traveling at high speed along a nerve fiber.

Depending on the functions performed and structural features, all nerve cells are divided into three types: sensory, motor (executive) and intercalary. Motor fibers running as part of the nerves transmit signals to muscles and glands, sensory fibers transmit information about the state of organs to the central nervous system.

Now we can combine all the information received into a table.

Types of fabrics (table)

Fabric group	Types of fabrics	Tissue structure	Location
Epithelium	Flat	The surface of the cells is smooth. Cells are tightly adjacent to each other	Skin surface, oral cavity, esophagus, alveoli, nephron capsules	Integumentary, protective, excretory (gas exchange, urine excretion)
	Glandular	Glandular cells produce secretions	Skin glands, stomach, intestines, endocrine glands, salivary glands	Excretory (secretion of sweat, tears), secretory (formation of saliva, gastric and intestinal juice, hormones)
	Ciliated (ciliated)	Consists of cells with numerous hairs (cilia)	Airways	Protective (cilia trap and remove dust particles)
Connective	Dense fibrous	Groups of fibrous, tightly packed cells without intercellular substance	The skin itself, tendons, ligaments, membranes of blood vessels, cornea of the eye	Integumentary, protective, motor
	Loose fibrous	Loosely arranged fibrous cells intertwined with each other. The intercellular substance is structureless	Subcutaneous fatty tissue, pericardial sac, nervous system pathways	Connects skin to muscles, supports organs in the body, fills gaps between organs. Provides thermoregulation of the body
	Cartilaginous	Living round or oval cells lying in capsules, the intercellular substance is dense, elastic, transparent	Intervertebral discs, laryngeal cartilage, trachea, auricle, joint surface	Smoothing the rubbing surfaces of bones. Protection against deformation of the respiratory tract and ears
	Bone	Living cells with long processes connected to each other, intercellular substance - inorganic salts and ossein protein	Skeleton bones	Supportive, motor, protective
	Blood and lymph	Liquid connective tissue consists of formed elements (cells) and plasma (liquid with organic and mineral substances dissolved in it - serum and fibrinogen protein)	Circulatory system of the whole body	Carries O2 and nutrients throughout the body. Collects CO 2 and dissimilation products. Ensures the constancy of the internal environment, chemical and gas composition of the body. Protective (immunity). Regulatory (humoral)
Muscular	Cross-striped	Multinucleate cylindrical cells up to 10 cm in length, striated with transverse stripes	Skeletal muscles, cardiac muscle	Voluntary movements of the body and its parts, facial expressions, speech. Involuntary contractions (automatic) of the heart muscle to push blood through the chambers of the heart. Has excitability and contractility properties
Muscular	Smooth	Mononuclear cells up to 0.5 mm long with pointed ends	Walls of the digestive tract, blood and lymph vessels, skin muscles	Involuntary contractions of the walls of internal hollow organs. Raising hair on the skin
Nervous	Nerve cells (neurons)	Nerve cell bodies, varied in shape and size, up to 0.1 mm in diameter	Form gray matter brain and spinal cord	Higher nervous activity. The body's connection with external environment. Centers of conditioned and unconditioned reflexes. Nervous tissue has the properties of excitability and conductivity
		Short processes of neurons - tree-branching dendrites	Connect with processes of neighboring cells	They transmit the excitation of one neuron to another, establishing a connection between all organs of the body
		Nerve fibers - axons (neurites) - long processes of neurons up to 1.5 m in length. Organs end with branched nerve endings	Nerves of the peripheral nervous system that innervate all organs of the body	Pathways of the nervous system. They transmit excitation from the nerve cell to the periphery via centrifugal neurons; from receptors (innervated organs) - to nerve cell by centripetal neurons. Interneurons transmit excitation from centripetal (sensitive) neurons to centrifugal (motor) neurons

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Cartilage tissue is a type of connective tissue consisting of cartilage cells (chondrocytes) and large quantity dense intercellular substance. Serves as a support. Chondrocytes have a variety of shapes and lie singly or in groups within cartilaginous cavities. The intercellular substance contains chondrinic fibers, similar in composition to collagen fibers, and the ground substance, rich in chondromucoid.

Depending on the structure of the fibrous component of the intercellular substance, three types of cartilage are distinguished: hyaline (vitreous), elastic (mesh) and fibrous (connective tissue).

Pathology of cartilage tissue - see Chondritis, Chondrodystrophy.

Cartilaginous tissue (tela cartilaginea) is a type of connective tissue characterized by the presence of a dense intercellular substance. In the latter, a basic amorphous substance is distinguished, which contains compounds of chondroitinsulfuric acid with proteins (chondromucoids) and chondrinum fibers, similar in composition to collagen fibers. Fibrils of cartilage tissue belong to the type of primary fibers and have a thickness of 100-150 Å. Electron microscopy in the fibers of cartilage tissue, in contrast to the collagen fibers themselves, reveals only a vague alternation of light and dark areas without a clear periodicity. Cartilage cells (chondrocytes) are located in the cavities of the ground substance individually or in small groups (isogenic groups).

The free surface of the cartilage is covered with dense fibrous connective tissue - perichondrium, in the inner layer of which poorly differentiated cells - chondroblasts - are located. The cartilaginous tissue covering the articular surfaces of the bones does not have perichondrium. The growth of cartilage tissue is carried out due to the proliferation of chondroblasts, which produce the ground substance and subsequently turn into chondrocytes (appositional growth) and due to the development of a new ground substance around the chondrocytes (interstitial, intussusceptive growth). During regeneration, the development of cartilage tissue can also occur by homogenizing the ground substance of fibrous connective tissue and converting its fibroblasts into cartilage cells.

Nutrition of cartilage tissue occurs through the diffusion of substances from the blood vessels of the perichondrium. Nutrients penetrate into the tissue of articular cartilage from the synovial fluid or from the vessels of the adjacent bone. Nerve fibers are also localized in the perichondrium, from where individual branches of the soft nerve fibers can penetrate into the cartilage tissue.

In embryogenesis, cartilaginous tissue develops from mesenchyme (see), between the contiguous elements of which layers of the main substance appear (Fig. 1). In such a skeletogenic rudiment, hyaline cartilage is first formed, temporarily representing all the main parts of the human skeleton. Subsequently, this cartilage can be replaced by bone tissue or differentiate into other types of cartilage tissue.

The following types of cartilage tissue are known.

Hyaline cartilage(Fig. 2), from which in humans the cartilages of the respiratory tract, thoracic ends of the ribs and articular surfaces of bones are formed. In a light microscope, its main substance appears homogeneous. Cartilage cells or isogenic groups of them are surrounded by an oxyphilic capsule. In differentiated areas of cartilage, a basophilic zone adjacent to the capsule and an oxyphilic zone located outside it are distinguished; Collectively, these zones form the cellular territory, or chondrin ball. The complex of chondrocytes with the chondrinic ball is usually taken to be the functional unit of cartilage tissue - the chondrone. The main substance between chondrons is called interterritorial spaces (Fig. 3).

Elastic cartilage(synonym: reticular, elastic) differs from hyaline in the presence of branching networks of elastic fibers in the ground substance (Fig. 4). The cartilage of the auricle, epiglottis, Wrisberg and Santorini cartilages of the larynx are built from it.

Fibrous cartilage(synonym for connective tissue) is located in the places of transition of dense fibrous connective tissue into hyaline cartilage and differs from the latter in the presence of real collagen fibers in the ground substance (Fig. 5).

Pathology of cartilage tissue - see Chondritis, Chondrodystrophy, Chondroma.

Rice. 1-5. The structure of cartilage tissue.
Rice. 1. Histogenesis of cartilage:
1 - mesenchymal syncytium;
2 - young cartilage cells;
3 - layers of the main substance.
Rice. 2. Hyaline cartilage (low magnification):
1 - perichondrium;
2 - cartilage cells;
3 - main substance.
Rice. 3. Hyaline cartilage (high magnification):
1 - isogenic group of cells;
2 - cartilaginous capsule;
3 - basophilic zone of the chondrin ball;
4 - oxyphilic zone of the chondrin ball;
5 - interterritorial space.
Rice. 4. Elastic cartilage:
1 - elastic fibers.
Rice. 5. Fibrous cartilage.

The bone marrow that fills the bone marrow cavities contains mainly fats (up to 98% of the dry yellow marrow) and smaller amounts of choline phosphatides, cholesterol, proteins and minerals. The composition of fats is dominated by palmitic, oleic, and stearic acids.
In accordance with the characteristics of the chemical composition, bone is used for the production of semi-finished products, jellies, brawn, bone fat, gelatin, glue, and bone meal.
Cartilage tissue. Cartilage tissue performs supporting and mechanical functions. It consists of a dense ground substance in which round-shaped cells, collagen and elastin fibers are located (Fig. 5.14). Depending on the composition of the intercellular substance, hyaline, fibrous and elastic cartilages are distinguished. Hyaline cartilage covers the articular surfaces of bones, and the costal cartilages and trachea are built from it. Calcium salts are deposited in the intercellular substance of such cartilage with age. Hyaline cartilage is translucent and has a bluish tint.

Fibrous cartilage makes up the ligaments between the vertebrae, as well as the tendons and ligaments at their attachment to the bones. Fibrous cartilage contains many collagen fibers and a small amount of amorphous substance. It has the appearance of a translucent mass.
Elastic cartilage is cream-colored, the intercellular substance of which is dominated by elastin fibers. Lime is never deposited in elastic cartilage.

Cartilage tissue

It is part of the auricle and larynx.
Average chemical composition cartilage tissue includes: 40-70% water, 19-20% proteins, 3.5% fats, 2-10% minerals, about 1% glycogen.
Cartilage tissue is characterized by a high content of mucoprotein - chondromucoid and mucogylisaccharide - chondroitinsulfuric acid in the main intercellular substance. An important property of this acid is its ability to form salt-like compounds with various proteins: collagen, albumin, etc. This apparently explains the “cementing” role of mucopolysaccharides in cartilage tissue.
Cartilage tissue is used for food purposes, and gelatin and glue are also produced from it. However, the quality of gelatin and glue is often not high enough, since mucopolysaccharides and glucoproteins pass into solution from the tissue along with gelatin, reducing the viscosity and strength of the jelly.

Cartilaginous tissue is a type of supporting tissue characterized by the strength and elasticity of the matrix. This is due to their position in the body: in the joints, in the intervertebral discs, in the wall of the respiratory tract (larynx, trachea, bronchi).

Cartilaginous

○ Hyaline

○ Elastic

○ Fibrous

However, the general plan of their structure is similar.

1. Presence of cells (chondrocytes and chondroblasts).

2. Formation of isogenic groups of cells.

3. The presence of a large amount of intercellular substance (amorphous, fibers), which provides strength and elasticity - that is, the ability to undergo reversible deformation.

4. Lack of blood vessels - nutrients diffuse from the perichondrium, due to the high water content (up to 70–80%) in the matrix.

5. Characterized by a relatively low level of metabolism.

Cartilage tissue

They have the ability to continuously grow.

During the development of cartilage tissue, a differentiation of cartilage cells is formed from the mesenchyme. This includes:

1. Stem cells - characterized by a round shape, a high value of nuclear-cytoplasmic ratios, a diffuse arrangement of chromatin and a small nucleolus. The organelles of the cytoplasm are poorly developed.

2. Semi-stem cells (prechondroblasts) – the number of free ribsomes increases in them, grEPS appears, the cells become elongated, and the nuclear-cytoplasmic ratio decreases. Like stem cells, they exhibit low

proliferative activity.

3. Chondroblasts are young cells located on the periphery of cartilage. They are small flattened cells capable of proliferation and synthesis of components of the intercellular substance. In the basophilic cytoplasm, grEPS is well developed and

agrEPS, Golgi apparatus. During development they turn into chondrocytes.

4. Chondrocytes are the main (definitive) type of cartilage tissue cells. They come in oval, round or polygonal shapes. Located in special cavities

– lacunae – intercellular substance, singly or in groups. These groups are called isogenic cell groups.

Isogenic groups of cells - (from the Greek isos - equal, genesis - development) - groups of cells (chondrocytes) formed by the division of one cell. They lie in a common cavity (lacuna) and are surrounded by a capsule formed by the intercellular substance of cartilaginous tissue.

The main amorphous substance (cartilage matrix) contains:

1. Water – 70–80%

2. Inorganic compounds – 4–7%.

3. Organic matter – 10–15%

– Glycosaminoglycans:

Ø chondroitin sulfates (chondroitin-6-sulfate, chondroitin-4-sulfate,

Ø hyaluronic acid;

– Proteoglycans.

– Chondronectin – this glycoprotein connects cells to each other and to various substrates (cell connection with type I collagen).

There are many fibers in the intercellular substance:

1. Collagen (types I, II, VI)

2. And in elastic cartilage - elastic.

Ways of cartilage growth.

Interstitial growth of cartilage is an increase in the volume of cartilage tissue (cartilage) due to an increase in the number of dividing chondrocytes and the accumulation of intercellular substance components secreted by these cells.

Appositional growth of cartilage is an increase in the volume of cartilaginous tissue (cartilage) due to the replenishment of cells located on the periphery (mesenchymal cells - during embryonic chondrogenesis, perichondrium chondroblasts - during the postembryonic period of ontogenesis).

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The structure of individual human tissues, types of cartilage

Tendons and ligaments. Strength (muscle pulling or external forces) acts on tendons and ligaments in one direction. Therefore, the fibrous plates of tendons, consisting of fibroblasts (fibrocytes), ground substance and collagen fibers, are located parallel to each other. Bundles (from 10 to 1000) of fibrous plates are separated from each other by layers of unformed connective tissue. Small bundles are combined into larger ones, etc. The entire tendon is covered by a thicker layer of unformed tissue called the peritendon. It carries vessels and nerves to the tendon, ligament; There are also germ cells there.

Fascia, muscle aponeuroses, capsules of joints and organs, etc. The forces acting on them are directed in different directions. The bundles of fibrous plates are located at an angle to each other, so the fascia and capsules are difficult to stretch and separate into separate layers.

Cartilage tissue. It can be permanent (for example, cartilage of the ribs, trachea, intervertebral discs, menisci, etc.) and temporary (for example, in bone growth zones - metaphyses). Temporary cartilage is subsequently replaced by bone tissue. Cartilage tissue does not have connective tissue layers, vessels or nerves. Its trophism is provided only from the side of the perichondrium (a layer of fibrous connective tissue covering the cartilage) or from the side of the bone. The growth layer of cartilage is located in the lower layer of the perichondrium. When damaged, cartilage does not recover well.

There are three types of cartilage:

1. Hyaline cartilage. Covers the articular surfaces of bones, forms the cartilaginous ends of the ribs, rings of the trachea and bronchi. The elastic ground substance (chondromucoid) of the cartilaginous plates contains individual collagen fibers.

2. Elastic cartilage.

Structure and functions of human cartilage tissue

Forms the auricle, wings of the nose, epiglottis, and cartilage of the larynx. The main substance of the cartilaginous plates contains predominantly elastic fibers.

3. Fibrous cartilage. Forms intervertebral and articular discs, menisci, articular lips. The cartilaginous plates are penetrated by a large number of collagen fibers.

Bone tissue forms individual bones - the skeleton. Makes up about 17% of a person's total weight. Bones have strength with low mass. The strength and hardness of bone is provided by collagen fibers, a special basic substance (ossein) impregnated with minerals (mainly hydroxyapatite-phosphoric lime) and the orderly arrangement of bone plates. Bone plates form the outer layer of any bone and the inner layer of the medullary cavity; The middle layer of the tubular bone is made up of special, so-called osteon systems - multi-row, concentrically located plates around a canal in which vessels, nerves, and loose connective tissue are located. The spaces between the osteons (tubes) are filled with intercalated bone plates. Osteons are located along the length of the bone or in accordance with the load. Very thin tubules extend to the sides from the osteon canal, connecting the separated osteocytes.

There are two types of bone - cortical(compact or dense), up to 80% and trabecular(spongy or porous), constituting up to 20% of the total bone mass. If osteons and intercalary plates lie tightly, a compact substance is formed. It forms the diaphyses of long bones, the top layer of flat bones and covers the spongy part of the bone. At the ends of the bones, where a large volume is needed for joint articulation while maintaining lightness and strength, a spongy substance is formed. It consists of crossbars, beams (trabeculae), forming bone cells (like a sponge). Trabeculae are composed of osteons and intercalated bone plates, which are positioned in accordance with the pressure on the bone and the pull of the muscles.

On the outside, the bone, with the exception of the articular surfaces, is covered with periosteum (a layer of connective tissue, dense on top and loose closer to the bone). The latter contains many vessels, nerves, and contains bone-like cells - osteoblasts, which contribute to the growth of bones in width and the healing of fractures.

The rate of renewal of cortical and trabecular bone in an adult is from 2.5 to 16% per year.

Location of cartilage in the body n Cartilage tissues perform a formative function in the fetus and a supporting function in the adult body. Cartilaginous tissue can be found: n in the area of the joints (covering the articular surface with a relatively narrow layer), n in the metaphyses (i.e., between the epiphysis and diaphysis) of tubular bones, n in the intervertebral discs, in the anterior sections of the ribs, in the wall of the respiratory organs (larynx , trachea, bronchi), etc.

Development n Like all other tissues of the internal environment of the body, skeletal tissues develop n from mesenchyme (the cells of which, in turn, are evicted from somites and splanchnotomes

Features n The special nature of the intercellular substance gives two important properties: n elasticity and n strength. n intercellular substance of these tissues. n In many cases, cartilage is covered with perichondrium, a fibrous connective tissue that is involved in the growth and nutrition of cartilage.

An important feature of cartilage tissue is the absence of blood vessels. Therefore, nutrients enter the cartilage by diffusion from the vessels of the perichondrium. In some cases, there is no perichondrium - for example, in articular cartilage, since their surface should be smooth. Here nutrition is provided from the side of the synovial fluid and from the side of the underlying bone.

Cellular composition n Chondroblasts are young cells, located in the deep layers of the perichondrium singly and located closer to the surface of the cartilage n - small flattened cells capable of - proliferation and - synthesis of components of the intercellular substance of cartilage. n the granular ER, Golgi complex, and mitochondria are well expressed in them n Chondroblasts, releasing the components of the intercellular substance, “wall up” themselves in it and turn into chondrocytes.

Functions n The main function of chondroblasts is the production of the organic part of the intercellular substance: proteins collagen and elastin, glycosaminoglycans (GAG) and proteoglycans (PG). n chondroblasts provide appositional (superficial) growth of cartilage from the perichondrium.

Chondrocytes n a) Chondrocytes are the main cell type of cartilage. n - lie in special cavities of the intercellular substance (lacunae) and n - can divide by mitosis, while the daughter cells do not diverge, they remain together - isogenic groups (of 2-6 cells) are formed, originating from one cell. n b) They have an n-larger (compared to chondroblasts) size and an oval shape. n Well developed granular ER and Golgi complex

Functions n Chondrocytes that have stopped dividing actively synthesize components of the intercellular substance. n Due to the activity of chondrocytes, the mass of cartilage increases from the inside - interstitial growth.

Chondroclasts n In cartilage tissue, in addition to the cells that form the intercellular substance, there are also their antagonists - destroyers of the intercellular substance - these are chondroclasts (can be classified as a macrophage system): rather large cells, in the cytoplasm there are many lysosomes and mitochondria. Function - destruction of damaged or worn areas of cartilage.

Intercellular substance n The intercellular substance of cartilage tissue contains fibers and ground substance. n there are many fibrous structures: n - collagen fibers, n and in elastic cartilage - elastic fibers.

n The intercellular substance is highly hydrophilic, the water content reaches 75% of the cartilage mass, this determines the high density and turgor of the cartilage. Cartilaginous tissues in the deep layers do not have blood vessels,

n The main amorphous substance contains: n -water (70-80%), -minerals (4-7%), -organic component (10-15%), represented by n-proteoglycans and -glycoproteins.

Proteoglycans n A proteoglycan aggregate contains 4 components. n The aggregate is based on a long thread of hyaluronic acid (1). n With the help of globular binding proteins (2), n linear (fibrillar) peptide chains of the so-called n linear (fibrillar) peptide chains are connected to this thread. core (core) protein (3). n In turn, oligosaccharide branches depart from the latter (4).

These n complexes are highly hydrophilic; therefore, they bind a large amount of water and ensure high elasticity of the cartilage. n At the same time, they remain permeable to low molecular weight metabolites.

n The perichondrium is a layer of connective tissue covering the surface of the cartilage. In the perichondrium, there is an outer fibrous layer (from a dense, unformed CT with a large number of blood vessels) and an inner cellular layer containing a large number of stem and semi-stem cells.

Hyaline cartilage n Externally, this tissue is bluish-white in color and looks like glass (Greek hyalos - glass). Hyaline cartilage - covers all articular surfaces of bones, is found in the sternal ends of the ribs, in the airways.

Distinctive features n 1. the intercellular substance of hyaline cartilage in preparations stained with hematoxylin-eosin appears homogeneous and does not contain fibers. n 2. around isogenic groups there is a clearly defined basophilic zone - the so-called territorial matrix. This is due to the fact that chondrocytes secrete a large amount of GAG with an acidic reaction, so this area is stained with basic dyes, i.e. basophilic. The weakly oxygenic areas between the territorial matrices are called the interterritorial matrix. n

n Large number of proteoglycan aggregates. n Glycosaminoglycans. High elasticity depends on the content of GAGs n Chondroitin sulfates (chondroitin-6-sulfate, chondroitin-4-sulfate) n Keratan sulfates n contains type II collagen, which is more hydrophilic (due to more high content hydroxy groups) and n forms only fibrils (not united into fibers). n Collagen IX, VI and X n Protein chondronectin

Cellular composition n a) Immediately under the perichondrium there are n young chondrocytes (3) - n somewhat larger in size and more oval in shape. n b) Deeper are n mature chondrocytes, n large oval cells with light cytoplasm, n forming isogenic groups (4) of 2-6 cells.

n 1) Articular surfaces of bones. n 2) Airways. n 3) The junction of the ribs with the sternum.

Elastic cartilage n In the auricle, epiglottis, cartilages of the larynx. In addition to collagen fibers, the intercellular substance contains a large number of randomly arranged elastic fibers, which gives elasticity to cartilage. In elastic cartilage less content lipids, chondroitin sulfates and glycogen.

n b) in the thickness of the cartilaginous plate - isogenic groups of chondrocytes, n large, oval and n have light cytoplasm. n Groups of chondrocytes usually have n type of chains (of 2, less often more cells) are oriented perpendicular to the surface.

Age-related changes n Due to the relatively low content of collagen fibrils and the absence of collagen X, deposition of calcium salts (calcification) does not occur in elastic cartilage due to malnutrition.

Fibrous cartilage n Fibrous cartilage is located at the sites of attachment of tendons to bones and cartilage, intervertebral discs. In structure it occupies an intermediate position between densely formed connective and cartilaginous tissue. n

n In the intercellular substance there are much more collagen fibers, arranged oriented - they form thick bundles, clearly visible under a microscope. Chondrocytes often lie alone along the fibers, without forming isogenic groups. They have an elongated shape, a rod-shaped nucleus and a narrow rim of cytoplasm.

n At the periphery, the fibrous cartilage gradually transforms n into a dense, formed connective collagen fibers of which acquire orientation and go from one vertebra to another. tissue, oblique n b) In the central part of the disc, fibrous cartilage passes into the nucleus pulposus, which contains hyaline cartilage, type II collagen (in the form of fibrils)

Cartilage regeneration n Hyaline – insignificant. The perichondrium is mainly involved n Elastic - less susceptible to degeneration and does not calcify n Fibrous - weak regeneration, capable of calcification

Composition n Bone tissue consists of cells and intercellular substance. n The differentiation of bone tissue includes n 1. stem and semi-stem (osteogenic) cells, n osteoblasts, n osteocytes n 2. osteoclasts.

Osteoblasts n Osteoblasts are the most functionally active cellular elements of the differential during osteohistogenesis. In the adult body, the source of cells that support the population of osteoblasts are the cells of the dispersed cambium in the osteogenic layer of the periosteum. Osteoblasts have a cubic or prismatic shape. The core is located eccentrically. Osteoblasts are typical actively synthesizing and secreting cells; secretion occurs over the entire cell surface. The cell has a well-developed granular endoplasmic reticulum, filling almost the entire cytoplasm, many free ribosomes and polysomes,

Functions n secrete type I collagen, alkaline phosphatase, osteocalcin, osteopontin, transforming growth factors, osteonectin, collagenase, etc. n Highly differentiated osteoblasts are characterized by a gradual decrease in the activity of alkaline phosphatase, osteocalcin, osteopontin and the absence of proliferative activity.

n Role in the mineralization of the organic basis of the bone matrix. The process of bone matrix mineralization begins with the deposition of amorphous calcium phosphate. Calcium cations enter the extracellular matrix from the bloodstream, where they are bound to proteins. n In the presence of alkaline phosphatase, synthesized by osteoblasts, glycerophosphates located in the intercellular substance are broken down to form phosphate anion. An excess of the latter leads to a local increase in Ca and P to a level at which calcium phosphate precipitates. The overwhelming fraction of bone mineral is in the form of hydroxyapatite crystals. The crystals form on the collagen fibers of the bone matrix. The latter have structural features that facilitate this process. The fact is that the molecules of the collagen precursor - tropocollagen - are packed into the fiber in such a way that between the end of one and the beginning of the other there remains a gap called the hole zone. It is in this zone that bone mineral is initially deposited. Subsequently, the crystals begin to grow in both directions, and the process covers the entire fiber

n Matrix vesicles play a significant role in the mineralization of the synthesized organic bone matrix. Such vesicles are derivatives of the Golgi complex of osteoblasts, have a membrane structure and contain various enzymes necessary for mineralization reactions or their inhibition, as well as amorphous calcium phosphates. Matrix vesicles exit the cells into the extracellular space and release the products contained in them. The latter initiate mineralization processes.

Osteocytes n According to their quantitative composition, they are the most numerous cells of bone tissue. These are process cells that lie in bone cavities - lacunae. The cell diameter reaches up to 50 microns. The cytoplasm is weakly basophilic. Organelles are poorly developed (granular ER, PC and mitochondria). They don't share. n Function: take part in the physiological regeneration of bone tissue, produce the organic part of the intercellular substance. n The thyroid hormone calcitonin has a stimulating effect on osteoblasts and osteocytes - the synthesis of the organic part of the intercellular substance increases and the deposition of calcium increases, while the concentration of calcium in the blood decreases.

Osteoclasts n n n Specialized macrophages. Their diameter reaches up to 100 microns. Different osteoclast compartments are specialized to perform specific functions. the basal zone, in which the genetic apparatus of the cell is concentrated as part of numerous (5 - 20) nuclei. light zone in direct contact with the bone matrix. Thanks to it, the osteoclast tightly adheres to the bone along its entire perimeter, creating an isolated space between itself and the surface of the mineralized matrix. Osteoclast adhesion is ensured by a number of receptors to matrix components, the main of which are vitronectin receptors. The selective permeability of this barrier makes it possible to create a specific microenvironment in the cell adhesion zone. the vesicular zone contains lysosomes. Enzymes and acidic substances are transported through the membrane of the corrugated rim, and carbonic acid H 2 CO 3 is formed; carbonic acid dissolves calcium salts, dissolved calcium is washed into the blood. carrying out demineralization and disorganization of the bone matrix, which leads to the formation of a resorption (erosion) Howship lacuna.

Osteoclasts n osteoclasts have many nuclei and a large volume of cytoplasm; the zone of cytoplasm adjacent to the bone surface is called a corrugated border, there are many cytoplasmic processes and lysosomes functions - destruction of fibers and amorphous bone substance

n Thick collagen fibers, devoid of cementitious substance, create the appearance of a “brush border.” Lysosomal enzymes carry out proteolysis of collagen and other matrix proteins. Proteolysis products are removed from osteoclastic lacunae by transcellular transport. In general, the process of reducing river. H in the lacuna is carried out by two mechanisms: by exocytosis of the acidic contents of the vacuoles into the lacuna and due to the action of proton pumps - H+-ATPases, localized in the membrane of the corrugated border. The source of hydrogen ions is water and carbon dioxide, which are the result of mitochondrial oxidation reactions.

Intercellular substance n 1. Inorganic part of the matrix Contains calcium (35%) and phosphorus (50%) (calcium phosphates and carbonates) mainly in the form of hydroxyapatite crystals (Ca 10(PO 4)6(OH)2 (3 · Ca(OH)2), n and a little - in an amorphous state, a small amount of magnesium phosphate - make up 70% of the intercellular substance. In the plasma, inorganic phosphorus is contained in the form of anions HPO 4 -2 and H 2 PO 4 -2. The ratio of the organic and inorganic part of the intercellular substance depends on age: in children the organic part is slightly more than 30%, and the inorganic part is less than 70%, so their bones are less strong, but more flexible (not brittle; in old age, on the contrary); the inorganic part increases, and the organic part decreases, so the bones become harder, but more brittle - blood vessels are present:

Organic part of the bone matrix The organic part of the intercellular substance is represented by n collagen (collagen types I, X, V) and very few glycosaminoglycans and proteoglycans. n - glycoproteins (alkaline phosphatase, osteonectin); n - proteoglycans (acidic polysaccharides and glycosaminoglycans - chondroitin-4 - and chondroitin-6 sulfates, dermatan sulfate and keratan sulfate.); n - growth factors (fibroblast growth factor, transforming growth factors, bone morphogenetic proteins) - cytokines secreted by bone and blood cells that carry out local regulation of osteogenesis.

proteins that mediate cell adhesion n Osteonectin is a glycoprotein of bone and dentin, has a high affinity for type I collagen and hydroxyapatite, and contains Ca-binding domains. Maintains the concentration of Ca and P in the presence of collagen. It is assumed that the protein is involved in the interaction between the cell and the matrix. n Osteopontin is the main component of the protein composition of the matrix, in particular the interfaces, where it accumulates in the form of a dense cover called cementation lines (lamina limitans). Due to its physicochemical properties, it regulates matrix calcification and specifically participates in the adhesion of cells to the matrix or matrix to the matrix. Osteopontin production is one of the earliest manifestations of osteoblast activity. n Osteocalcin (OC) is a small protein (5800 Da, 49 amino acids) in the mineralized bone matrix, involved in the process of calcification,

Classification n There are tubular, flat and mixed bones. The diaphysis of tubular bones and the cortical plates of flat and mixed bones are built from lamellar bone tissue covered with periosteum or periosteum. In the periosteum, it is customary to distinguish two layers: the outer layer is fibrous, consisting mainly of fibrous connective tissue; internal, adjacent to the surface of the bone - osteogenic, or cambial.

Types of bone tissue coarse-fibrous (reticulofibrous) lamellar (fine-fibrous) Main feature Collagen fibers form a) Bone substance is thick bundles running in different (organized into plates). directions. b) Moreover, within one plate the fibers have the same direction, but within adjacent plates they have different directions. Localization 1. Flat bones of the embryo. 2. Bone tubercles; places of overgrown cranial sutures. Almost all the bones of an adult: flat (scapula, pelvic bones, skull bones), spongy (ribs, sternum, vertebrae) and tubular.

Lamellar bone tissue can have a spongy and compact organization. Spongy bone substance Compact bone substance Localization Spongy bone substance consists of: the epiphyses of tubular bones, the inner layer (adjacent to the medullary canal) of the diaphyses of tubular bones, spongy bones, the inner part of flat bones. Most of the diaphysis of tubular bones and the surface layer of flat bones have a compact structure. Distinctive feature The spongy substance is built from avascular bone crossbars (beams), between which there are spaces - bone cells. There are practically no gaps in the compact bone substance: due to the growth of bone tissue deep into the cells, only narrow spaces remain for blood vessels - the so-called. central canals of osteons Bone marrow The cells of the spongy substance contain vessels that nourish the bone and red bone marrow - a hematopoietic organ. The medullary cavity of the diaphysis of long bones in adults contains yellow bone marrow - adipose tissue.

Structure Consist of bone plates a) In this case, the plates of the spongy substance are usually oriented along the direction of the bone beams, and not around the vessels, as in the osteons of the compact substance. b) osteons can occur in sufficiently thick beams. The unit of structure is the bone plate. They consist of bone plates. In the compact substance there are plates of 3 types: general (general) - surround the entire bone, osteon - lie in concentric layers around the vessel, forming the so-called. osteons; intercalary - located between osteons. osteons.

The structure of an osteon, the main structural unit of bone. In the center of each osteon there is a blood vessel (1), around the latter there are several concentric layers of bone plates (2), called osteons. Osteons are delimited by a resorption (commissural) line (3). Between the osteons lie intercalated bone plates (4), which are remnants of previous generations of osteons. bone plates include cells (osteocytes), collagen fibers and a ground substance rich in mineral compounds. the fibers in the intercellular substance are indistinguishable, and the intercellular substance itself has a solid consistency.

Development of BONE FROM MESENCHYME (direct osteohistogenesis). Immature (coarse-fiber) bone is formed from mesenchyme, which is subsequently replaced by lamellar bone. There are 4 stages of development: n 1. formation of an osteogenic island - in the area of bone formation, mesenchymal cells turn into osteoblasts n

2. formation of intercellular substance n osteoblasts begin to form the intercellular substance of bone, while some of the osteoblasts find themselves inside the intercellular substance, these osteoblasts turn into osteocytes; the other part of the osteoblasts appears on the surface of the intercellular substance,

3. calcification of the n intercellular substance of the bone; the intercellular substance is impregnated with calcium salts. n a) At the third stage, the so-called. matrix vesicles similar to lysosomes. They accumulate calcium and (due to alkaline phosphatase) inorganic phosphate. n b) When the vesicles rupture, mineralization of the intercellular substance occurs, i.e., deposition of hydroxyapatite crystals on the fibers and in the amorphous substance. As a result, bone trabeculae (beams) are formed - mineralized areas of tissue containing all 3 types of bone cells - n n n on the surface - osteoblasts and osteoclasts, and in the depths - osteocytes.

4. Formation of osteons n Subsequently, in the inner part of the flat bone, n the primary spongy tissue is replaced by a secondary one, n which is built from bone plates oriented along the course of the beams.

The development of lamellar bone tissue is closely related to 1. the process of destruction of individual sections of bone and the ingrowth of blood vessels into the thickness of reticulofibrous bone. Osteoclasts take part in this process both during embryonic osteogenesis and after birth. 2. vessels growing to the trabeculae. In particular, around the vessels, the bone substance is formed in the form of concentric bone plates that make up the primary osteons.

DEVELOPMENT OF BONE AT THE PLACE OF CARTILAGE (indirect osteogenesis) n Mature (lamellar) bone is immediately formed in place of cartilage n 4 stages are distinguished in development: n 1. formation of cartilage - hyaline cartilage is formed in place of the future bone

2. perichondral ossification takes place only in the area of the diaphysis; in the area of the diaphysis, the perichondrium turns into periosteum, in which osteogenic cells appear, then osteoblasts, due to the osteogenic cells of the periosteum on the surface of the cartilage, bone formation begins in the form of common plates that have a circular course, like the annual rings of a tree

3. endochondral ossification n Occurs both in the region of the diaphysis and in the region of the epiphysis; Blood vessels grow inside the cartilage, where there are osteogenic cells - osteoblasts, due to which bone is formed around the vessels in the form of osteons, and osteoclasts. n Simultaneously with the formation of bone, cartilage is destroyed

zone of vesicular cartilage (4). At the border of the still preserved cartilage, the cartilage cells are in a swollen, vacuolated state, i.e., the zone of columnar cartilage has a bubble shape (5). In the adjacent region of the epiphysis, cartilage continues to grow and the proliferating cells are arranged in columns along the long axis of the bone.

n a) Subsequently, ossification of the epiphysis itself (with the exception of the articular surface) will occur - by the enchondral route. n b) That is, mineralization will also occur here, n vessels will grow here, the substance of the cartilage will be destroyed and first coarse fibrous, n and then lamellar bone tissue will be formed.

n 4. reconstruction and growth of bone - old sections of bone are gradually destroyed and new ones are formed in their place; due to the periosteum, common bone plates are formed, due to osteogenic cells located in the adventitia of bone vessels, osteons are formed. A layer of cartilaginous tissue is preserved between the diaphysis and the epiphysis, due to which the growth of bone in length continues until the end of the period of growth of the body in length, i.e. until 20-21 years.

Bone growth Sources of growth Until the age of 20, tubular bones grow: in width - through appositional growth from the side of the perichondrium, in length - due to the activity of the metaepiphyseal cartilaginous plate. Metaepiphyseal cartilage a) Metaepiphyseal plate - part of the epiphysis adjacent to the diaphysis and preserving (unlike the rest of the epiphysis) a cartilaginous structure. b) It has 3 zones (in the direction from the pineal gland to the diaphysis): the border zone - contains oval chondrocytes, the zone of columnar cells - it ensures the growth of cartilage in length due to the proliferation of chondrocytes, the zone of vesicular cartilage - borders the diaphysis and undergoes ossification . c) Thus, 2 processes occur simultaneously: the growth of cartilage (in the columnar zone) and its replacement by bone (in the vesicular zone).

Regeneration n Regeneration and growth of bone thickness is carried out due to the periosteum and endosteum. All long bones, as well as most flat bones, are histologically fine-fiber bone.

n In bone tissue, two oppositely directed processes constantly occur - resorption and new formation. The ratio of these processes depends on several factors, including age. Restructuring of bone tissue is carried out in accordance with the loads acting on the bone. n The process of bone tissue remodeling occurs in several phases, in each of which the leading role is played by certain cells. Initially, the area of bone tissue that is subject to resorption is “marked” by osteocytes using specific cytokines (activation). The protective layer on the bone matrix is destroyed. Precursors of osteoclasts migrate to the bare surface of the bone and merge into a multinuclear structure - symplast - mature osteoclast. At the next stage, the osteoclast demineralizes the bone matrix (resorption), gives way to macrophages, which complete the destruction of the organic matrix of the intercellular substance of the bone and prepare the surface for the adhesion of osteoblasts (reversion). At the last stage, precursors arrive at the destruction zone and differentiate into osteoblasts; they synthesize and mineralize the matrix in accordance with the new conditions of static and dynamic load on the bone (formation).

Hello my friends!

In this article we will look at what it is cartilage knee joint . Let's look at what cartilage is made of and what its function is. As you understand, in all joints of our body the cartilage tissue is the same, and everything described below also 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 cartilages, but only slightly different in composition. Read about menisci in the article "". I will only say that cartilages and menisci differ in the type of cartilage tissue: bone cartilage is hyaline cartilage, and the menisci – fibrocartilage. This is what we will look at now.

The thickness of the cartilage covering the ends of the bone is on average 5-6 mm, it consists of several layers. Cartilage is dense and smooth, which allows bones to easily slide against each other during flexion and extension movements. Possessing 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 cartilages (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: leukocytes 200-400 per ml, of which 75% are lymphocytes.

Cartilage is one of the types 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 be able to withstand the stress and constant pressure, and the presence of nerves there would cause pain with every movement.

Cartilage is designed to reduce friction where bones connect. Cover both heads of the bone and inner side patella (patella). Constantly washed by synovial fluid, they ideally reduce 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 also consists of living cells and they also need nutrition. They receive nutrition from the same synovial fluid.

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

Cartilage differs in its fiber ratio: . All this gives the cartilage not so much hardness as elasticity. Working like a sponge under load, cartilage and menisci are compressed, unclenched, flattened, stretched as you wish. They constantly absorb a new portion of liquid and give away the old one, forcing it to constantly circulate; at the same time, the liquid is enriched with nutrients and again carries them to the cartilage. We'll talk about synovial fluid later.

Main components of cartilage

Articular cartilage - This is a complex fabric in its structure. Let's look at 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 helices. This structure of collagen fibers allows cartilage to resist any type of deformation. Collagen gives tissue elasticity. give elasticity, the ability to return to its original state.

The second element of cartilage that is of great importance 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 can neither be stretched nor compressed. This adds rigidity and elasticity to the cartilage tissue. In addition, the more water, the better and more functional the interarticular fluid. It spreads and circulates easily. With a lack of water, the joint fluid becomes more viscous, less fluid and, of course, performs its role in providing nutrition to the cartilage worse. !

Glycosamines– substances produced by the cartilage tissue of the joints are also part of the synovial fluid. By its structure, glucosamine is a polysaccharide and serves as an important component of cartilage.

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

In our body, glucosamine binds cells and is part of cell membranes and proteins, making tissue 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, and the cartilage becomes more sensitive to damage.

The issues of restoration of cartilage tissue and the production of 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 quite 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 the cartilage. Therefore, the restoration of cartilage tissue is so limited.

So, nutrition of cartilage is difficult, renewal of cartilage tissue is also a very long-term process, and restoration 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 with adequate nutrition, which they can only receive through synovial fluid. But, even if the nutrition is the richest, it will not achieve its goal without moving the joint. That's why, If you move more, your recovery will be better!

With prolonged immobilization of a joint or the entire leg (plaster, splints, etc.), not only the 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 yet 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 Nature” by this. On the scale of evolutionary development, we have come too far for the organism 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 is not beneficial? They stopped walking with their legs - their legs atrophied, the bodybuilder stopped pumping (using all his muscle mass) - he immediately deflated. Well, I got distracted.

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

In the meantime, my instructions: , COMPLETE VARIED NUTRITION,.

You can start right now.

All the best, don't get sick!

In the human body, cartilage tissue serves as a support and connection between skeletal structures. There are several types of cartilaginous structures, each of which has its own location and performs its own tasks. Skeletal tissue undergoes pathological changes due to intense physical activity, congenital pathologies, age and other factors. To protect yourself from injuries and diseases, you need to take vitamins, calcium supplements and not get injured.

The importance of cartilaginous structures

Articular cartilage holds skeletal bones, ligaments, muscles and tendons together into a single musculoskeletal system. It is this type of connective tissue that provides shock absorption during movement, protecting the spine from damage, preventing fractures and bruises. The function of cartilage is to make the skeleton elastic, elastic and flexible. In addition, cartilage forms a supporting frame for many organs, protecting them from mechanical damage.

Features of the structure of cartilage tissue

The specific gravity of the matrix exceeds the total mass of all cells. General plan The structure of cartilage consists of 2 key elements: intercellular substance and cells. During histological examination of a sample under a microscope lens, cells are located in a relatively smaller percentage of the space. The intercellular substance contains about 80% water in the composition. The structure of hyaline cartilage provides it main role in the growth and movement of joints.

Intercellular substance

The strength of cartilage is determined by its structure.

The matrix, as an organ of cartilage tissue, is heterogeneous and contains up to 60% amorphous mass and 40% chondrin fibers. Fibrils are histologically reminiscent of human skin collagen, but differ in a more chaotic arrangement. The main substance of cartilage consists of protein complexes, glycosaminoglycans, hyaluronan compounds and mucopolysaccharides. These components provide the strong properties of cartilage tissue, keeping it permeable to essential nutrients. There is a capsule, its name is perichondrium, this is the source of elements for cartilage regeneration.

Cellular composition

Chondrocytes are located in the intercellular substance rather chaotically. The classification divides cells into undifferentiated chondroblasts and mature chondrocytes. Precursors are formed by the perichondrium, and as they move into the deeper tissue balls, the cells differentiate. Chondroblasts produce matrix ingredients, which include proteins, proteoglycans and glycosaminoglycans. Young cells, by dividing, provide interstitial growth of cartilage.

Chondrocytes, located in the deep balls of tissue, are grouped in groups of 3-9 cells, known as “isogenic groups”. This mature cell type has a small nucleus. They do not divide, and their metabolic rate is greatly reduced. The isogenic group is covered by interwoven collagen fibers. The cells in this capsule are separated by protein molecules and have a variety of shapes.

During degenerative-dystrophic processes, multinucleated chondroclast cells appear, which destroy and absorb tissue.

The table presents the main differences in the structure of the types of cartilage tissue:

View	Peculiarities
Hyaline	Thin collagen fibers
Hyaline	Has basophilic and oxyphilic zones
Elastic	Consists of elastin
	Very flexible
	Has a cellular structure
Fibrous	Formed from a large number of collagen fibrils
	Chondrocytes are comparatively larger in size
	Lasting
	Able to withstand high pressure and compression

Blood supply and nerves

The tissue is not supplied with blood from its own vessels, but receives it by diffusion from nearby ones.

Due to its very dense structure, cartilage does not have blood vessels of even the smallest diameter. Oxygen and all nutrients necessary for life and functioning are supplied by diffusion from nearby arteries, perichondrium or bone, and are also extracted from synovial fluid. Decomposition products are also excreted diffusely.

In the superior balls of the perichondrium there are only a small number of individual branches of nerve fibers. Thus, the nerve impulse is not formed and does not spread in pathologies. The localization of the pain syndrome is determined only when the disease destroys the bone, and the structures of the cartilage tissue in the joints are almost completely destroyed.

Types and functions

Depending on the type and relative position of fibrils, histology distinguishes the following types of cartilage tissue:

hyaline;
elastic;
fibrous.

Each type is characterized by a certain level of elasticity, stability and density. The location of the cartilage determines its tasks. The main function of cartilage is to ensure the strength and stability of the joints of skeletal parts. The smooth hyaline cartilage found in joints makes bone movements possible. Due to its appearance it is called glassy. The physiological conformity of the surfaces guarantees smooth gliding. The structural features of hyaline cartilage and its thickness make it an integral part of the ribs and rings of the upper respiratory tract.

The shape of the nose is formed by an elastic type of cartilage tissue.

Elastic cartilage forms the appearance, voice, hearing and breathing. This applies to structures that are located in the framework of the small and medium-caliber bronchi, the ears and the tip of the nose. Elements of the larynx are involved in the formation of a personal and unique timbre of the voice. Fibrous cartilage connects skeletal muscles, tendons, and ligaments to vitreous cartilage. Intervertebral and intraarticular discs and menisci are built from fibrous structures; they cover the temporomandibular and sternoclavicular joints.