Location of connective tissue. Connective tissues.
Types, structure, functions Concept of fabric. Epithelial tissue. Types, structure, functions. Glandular epithelium.
Fabrics is a system of cells and intercellular substance that have the same structure, origin and functions. Tissue cells have
different shape, which determines their function. Tissues are divided into four types: epithelial, connective, muscle tissue, and nervous 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
inner surface
directly facing 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.
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.
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 ensure the absorption of nutrients - lines the mucous membrane of the small intestine.
Ciliated epithelium (ciliated epithelium) is a pseudostratified epithelium, equipped with cilia. Stratified epithelium is located at the border between the body and the external environment. Lines the mucous membrane of the mouth, food cavity, and cornea of the eye. Transitional epithelium lines the walls of the bladder,
renal pelvis , ureter. Glandular epithelium - forms glands and performs a secretory function (releases substances - secretions, which are either excreted into
external environment
, or enter the blood and lymph (hormones)). varied in structure. Connective tissue includes blood and hematopoietic tissue, lymphatic tissue, bone tissue, cartilage tissue, and fibrous connective tissue. Features: few cells, a lot of intercellular substance.
Connective tissues perform four main functions: musculoskeletal, trophic, protective, and reparative.
1. Skeletal connective tissue
1.1 Bone Has special mechanical properties. It consists of osteocyte cells, which are of two types: osteoblasts - destroyer cells, destroy bone tissue and prepare a place for calcium and nutrients; osteoclasts - bring calcium and nutrients. The intercellular substance consists of ossein fibers and mineral salts (calcium phosphate - Ca 3 (PO 4) 2 - is the main building material for bones and teeth of vertebrates.) Function bone tissue- support, protection, protein and mineral metabolism.
1.2 Cartilaginous. Consists of chondrocyte cells. There are three types of cartilage tissue: 1. healine (vitreous) cartilage - forms the cartilage of the larynx and the surface of the joints of bones; 2. elastic cartilage - forms the auricle; 3. fibrocartilage - forms intervertebral discs. The function of cartilage tissue is musculoskeletal
Connective tissues are diverse in their structure, as they perform supporting, trophic and protective functions. They consist of cells and intercellular substance, which is more numerous than cells. These tissues have a high regenerative ability, plasticity, and adaptation to changing living conditions. Their growth and development occurs due to the reproduction and transformation of poorly differentiated young cells.
Connective tissues originate from mesenchyme, i.e. embryonic connective tissue, which was formed from the middle germ layer - mesoderm.
There are several types of connective tissue:
· Blood and lymph;
· Loose fibrous unformed fabric;
· Dense fibrous (shaped and unshaped) fabric;
· Reticular tissue;
· Fat;
· Cartilaginous;
· Bone;
Of these types, dense fibrous, cartilaginous and bone perform a supporting function, while the remaining tissues perform a protective and trophic function.
1 - collagen fibers, 2 - elastic fibers, 3 - macrophages, 4 - fibroblasts, 5 - plasma cells
This tissue consists of various cellular elements and intercellular substance. It is part of all organs, in many of them it forms the stroma of the organ. She accompanies blood vessels, through it there is an exchange of substances between the blood and the cells of the organs and, in particular, the transfer of nutrients from the blood to the tissues.
The intercellular substance includes three types of fibers: collagen, elastic and reticular. Collagen fibers are located in different directions in the form of straight or wavy curved strands with a thickness of 1-3 microns or more. Elastic fibers are thinner than collagen fibers, anastomose with each other and form a more or less broadly woven network. The reticular fibers are thin and form a delicate mesh.
The ground substance is a gelatinous, structureless mass that fills the space between the cells and fibers of the connective tissue.
The cellular elements of loose fibrous tissue include the following cells: fibroblasts, macrophages, plasma cells, mast cells, adipose cells, pigment cells and adventitial cells.
Fibroblasts- these are the most numerous flat cells, having a spindle-shaped shape on a section, often with processes. They are capable of reproduction. They take part in the formation of the main substance, in particular they form connective tissue fibers.
Macrophages- cells capable of absorbing and digesting microbial bodies. There are macrophages that are in a quiet state - histocytes and wandering ones - free macrophages. They can be round, elongated and irregular shape. Capable of amoeboid movements, destroy microorganisms, neutralize toxins, and participate in the formation of immunity.
Plasma cells found in loose connective tissue of the intestine, lymph nodes, and bone marrow. They are small, round or oval in shape. They play an important role in the body’s defense reactions, for example, they take part in the synthesis of antibodies. They produce blood globulins.
Mast cells- their cytoplasm contains granularity (granules). They are found in all organs where there is a layer of loose, unformed connective tissue. The form is varied; granules contain heparin, histamine, hyaluronic acid. The importance of cells lies in the secretion of these substances and the regulation of microcirculation.
Fat cells- these are cells capable of depositing reserve fat in the form of droplets in the cytoplasm. They can crowd out other cells and form fatty tissue. The cells are spherical in shape.
Adventitial cells located along the blood capillaries. They have an elongated shape with a core in the center. Capable of multiplying and transforming into other cellular forms of connective tissue. When a number of connective tissue cells die, they are replenished from these cells.
Dense fibrous connective tissue
This fabric is divided into dense, shaped and unshaped.
Thick, unshaped fabric consists of, relatively, large quantity densely located connective tissue fibers and a small number of cellular elements between the fibers.
Thick decorated fabric characterized by a certain arrangement of connective tissue fibers. Tendons, ligaments and some other formations are built from this tissue. Tendons are composed of densely arranged parallel bundles of collagen fibers. Between them there is a thin elastic network and small spaces are filled with the main substance. Of the cellular forms in tendons, only fibrocytes are present.
A type of dense connective tissue is elastic fibrous connective tissue. Some cords are built from it, for example, vocal cords. In these ligaments, thick rounded or flattened elastic fibers are located parallel to each other, but often branch. The space between them is filled with loose, unformed connective tissue. Elastic tissue forms the membrane of round vessels and is part of the walls of the trachea and bronchi.
Cartilage tissue
This tissue consists of cells, a large amount of intercellular substance and performs a mechanical function.
There are two types of cartilage cells:
· Chondrocytes- These are oval cells with a nucleus. They are located in special capsules surrounded by intercellular substance. Cells are located alone or in groups of 2-4 cells or more; they are called isogenic groups.
· Chondroblasts- these are young, flattened cells located along the periphery of the cartilage.
There are three types of cartilage: glionic, elastic and collagen.
Glian cartilage. It is found in many organs: in the ribs, on the articular surfaces of bones, along the airways. Its intercellular substance is homogeneous and translucent.
Elastic cartilage. Its intercellular substance contains well-developed elastic fibers. The epiglottis, cartilages of the larynx are built from this tissue, and it is part of the wall of the external auditory canals.
Collagen cartilage. Its intermediate substance consists of dense fibrous connective tissue, i.e. includes parallel bundles of collagen fibers. Intervertebral discs are built from this tissue and are found in the sternoclavicular and mandibular joints.
All types of cartilage are covered with dense fibrous tissue, in which collagen and elastic fibers are found, as well as cells similar to fibroblasts. This tissue is called perichondrium; richly supplied with blood vessels and nerves. The growth of cartilage occurs due to the perichondrium through the transformation of its cellular elements into cartilage cells. There are no vessels in the intercellular substance of mature cartilage and its nutrition occurs through the diffusion of substances from the vessels of the perichondrium.
Bone
This tissue consists of cells and dense intercellular substance. It differs in that its intercellular substance is calcified. This gives the bone the hardness necessary to perform its supporting function. The bones of the skeleton are made from this tissue.
The cellular elements of bone tissue include bone cells, or osteocytes, osteoblasts and osteoclasts.
Osteocytes- have a branched shape and a compact, dark-colored core. The cells lie in bone cavities that follow the contours of osteocytes. Osteocytes are not capable of reproduction.
1 - process; 2 - intercellular substance
Osteoblasts- cells that create bone tissue. They are round in shape, sometimes contain several nuclei, and are located in the periosteum.
Osteoclasts– cells that take an active part in the destruction of calcified cartilage and bone. These are multinucleate, rather large cells. Throughout life, the destruction of structural parts of bone tissue occurs and at the same time the formation of new ones, both at the site of destruction and from the periosteum. Osteoclasts and osteoblasts take part in this process.
Intercellular substance bone tissue consists of an amorphous ground substance in which ossein fibers are located. A distinction is made between coarse fibrous tissue, which is present in embryos, and lamellar bone tissue, which is present in adults and children.
The structural unit of bone tissue is bone plate. It is formed by bone cells lying in capsules and a fine-fibrous intercellular substance impregnated with calcium salts. The ossein fibers of these plates lie parallel to each other in a certain direction. In adjacent plates, the fibers usually have a direction perpendicular to them, which provides greater strength to the bone tissue. Bone plates in different bones are arranged in a certain order. Almost all flat, tubular and mixed bones of the skeleton are built from them.
In the diaphysis of the tubular bone, the plates form complex systems in which three layers are distinguished:
1) external, in which the plates do not form complete rings and overlap on the surface with the next layer of plates; 2) the middle layer is formed by osteons. In an osteon, the bony plates are arranged concentrically around the blood vessels; 3) inner layer The plates delimit the medullary space where the bone marrow is located.
Diagram of the structure of an osteon: the left half shows bone cavities and tubules, the right half shows the direction of fibers in individual plates
Bone grows and repairs itself through the periosteum, which covers outer surface bone and consists of fine fibrous connective tissue and osteoblasts.
Loose fibrous connective. tissue - an image of mesenchyme. it accompanies the blood vessels and lymph. vessels, forms the stroma of many organs, is located under the epithelia - image. the lamina propria of the mucous membranes, the submucosa, is located between the muscle cells. and fibers. Consists of many cells, little intercellular substance (few fibers and amorphous substance). Unformed - bundles of fibers are multidirectional. F: relationship between tissues, support of homeostasis, protective, plastic, trophic, barrier, support. Very reactive tissue (response to irritation). There is a class. 8 types. Highlight sedentary ()- optional
Interstitial material - amorphous + fibers. Fibers: 1. collagen - made from collagen protein, strong, do not stretch 2. elastic - protein - elastin; They stretch well and then return to their original shape. 3. reticular - a type of collagen.
Loose fibrous connective tissue. tissue image from mesenchyme. it accompanies the blood and lymph. vessels, forms the stroma of many organs, is located under the epithelia - image. the lamina propria of the mucous membranes, the submucosa, is located between the muscle cells. and fibers. Consists of a lot of cells, little intercellular substance (few fibers and amorphous substance). Unformed - bundles of fibers are multidirectional.
There is a class. 8 types. Highlight sedentary ( constantly synthesized in tissue )- fibroblasts, fibrocytes, hytocytes, adventitia, adipose, reticular and optional (immigrants emerging from the blood system) - T and B lymphocytes, monocytes, mast cells, pigment cells.
Naib. numerous - cl. fibroblast series. Fibroblasts- cells synthesizing components of intercells. substances: proteins (collagen, elastin) (wound healing), proteoglycans, glycoproteins. They are distinguished: poorly differentiated, activated, differentiated, mature.
Low-differential
fibroblasts - have a round nucleus with a small nucleolus, basophilic cytoplasm, few organelles, characterized by: low protein synthesis, high mitotic index
Activated - large wing-shaped cells, a light nucleus, 1-2 nucleoli, protein-synthesizing organelles.
Differentiated - 2 rubles larger. Light nuclei with chromatin, 1-2 nucleoli, weakly basophilic cytoplasm, there is a network of microfilaments - they move!
Active synthesis, and destroyed with the help of (collagenase). - regulation of secretion. Mature ones are fibrocytes. long-lived. Cl. elongated or process-shaped, organelles are partially reduced. Not active synthesis. Myofibroblasts
- class, capable of collagen synthesis, but also contractile proteins. Functional. similar to smooth myocytes, but no BM + well-developed EPS. Appear during regeneration - healing wounds, and the endometrium of the uterus during pregnancy. Fibroclasts
- class with high phagocytic and hydrolytic activity - as there are many vacuoles, they participate in the “resorption” of intercl. things Etc: in the uterus at the end of pregnancy. Macrophages
(histiocytes) - are formed from a blood stem cell. F F:: protective + transmit information to immunocompetent lymphocytes. Cl. have clear boundaries. The number increases with pathology. Resting cells are elongated, rounded with a hyperchromic nucleus. Active-processed, light nucleus. vacuoles + phagosomes (!).
Plasmocytes– round in shape, small, nucleus with radial clumps of chromatin. The characteristically pronounced development of granular EPS is basophilic cytoplasm. neutralization of antigens regulate local connective tissue homeostasis is reduced by coagulation. blood, increasing the permeability of the blood-tissue barrier, participation in the processes of inflammation and immunogenesis. They originate from hematopoietic stem cells of the red bone marrow.
Adipocytes(fat cells) - large. class vesicle-shaped, flattened core near the plasma membrane. The main part of the cytoplasm is the fatty droplet Rasolag. there is blood around vessels. F: energetic exchange, water metabolism.
Pigment cells(pigmentocytes, melanocytes). Cl. with short processes granulated with melanin pigment. F: prevent the penetration of ultraviolet radiation. There are moles in the skin and retina.
Adventitial cells-. low-specialized cells accompanying blood vessels. Flattened or spindle-shaped with slightly basophilic cytoplasm, an oval nucleus and a small number of organelles. They can transform into fibroblasts, myofibroblasts, and lipocytes.
Pericytes– derivatives of advetnitia, flattened in shape, associated with the BM of the blood. capillaries. Capable of turning into smooth myocytes.
1) Trophic function.
Superficial connective tissue covers all blood vessels, so the exchange of substances between blood and any other tissue occurs with the obligatory participation of connective tissue. Essentially, loose connective tissue regulates the exchange of substances between blood and other tissues.
2) Support function.
There are two types of support function: stromal and shape-forming
— Stromal function.
Loose connective tissue forms the stroma - the framework of the internal organs.
- Shape-forming.
Dense connective tissue forms the organ capsule, which forms the shape of the organ.
3) Protective function.
Connective tissue mainly performs the functions of immune protection rather than mechanical protection. Immune defense is performed by macrophages, mast cells, and antibodies produced by connective tissue. Although dense connective tissue can serve as mechanical protection.
4) Mechanical function is the function of organizing movement.
Dense connective tissue forms tendons and ligaments that participate in the organization of the musculoskeletal system.
5) Plastic function.
Participation of loose connective tissue in the organization of regeneration. If, during the process of vital activity, any defect or wounds form in an organ, they are filled with loose connective tissue. As a result, the shape of the organ is restored.
The regulation of connective tissue functions is carried out at all levels of organization - at the level of a cell, an organ, an organism. At the cellular level, intercellular contacts are important through an effector substance closely associated with the cell membrane and mediators released into the intercellular space: lymphokines, monokines, fibrokines, labrokines (respectively, mediators of lymphocytes, monocytes, fibroblasts, tissue basophils). In addition to specific mediators, for which there are corresponding receptors on cell membranes, there are also nonspecific ones - prostaglandins, muramidase, fibronectin, proteases.
The relationship between the elements of connective tissue is carried out according to the principle of feedback, which under normal conditions ensures the adequacy of responses, and in pathology, high adaptability and reliability. Autoregulation “down”, based on cooperative interactions between cells, is complemented by endocrine and nervous regulation, built on a hierarchical “top-down” principle.
In this regard, an important role belongs to the hormone of the anterior pituitary gland - somatotropin. It stimulates the proliferation of connective tissue cells and synthetic processes in them. At the same time, corticotropin and glycocorticoids inhibit proliferation and cause premature differentiation and maturation of fibroblasts, which is accompanied by impaired collagenogenesis. The role of insulin in regulating the structure and function of connective tissue is that it accelerates the exchange of hyaluronic acid and chondroitin sulfate. Apparently, this explains serious disorders of connective tissue in general and the vascular wall, in particular, in diabetes mellitus (diabetic angiopathy).
Dysregulation of the connective tissue system can also occur at any level. Within the connective tissue, the established autoregulatory relationships and its connections with parenchyma cells may be disrupted. The disorder may manifest itself predominantly in one or another organ (joints in rheumatism, skin in systemic lupus erythematosus). Finally, dysregulation of connective tissue can manifest itself in all organs and in the body as a whole (bone overgrowth with acromegaly, dwarfism and mucous edema with hypothyroidism).
The condition of connective tissue plays an important role during aging. At one time, A. A. Bogomolets noted that “aging begins precisely with connective tissue.” He saw the reason for aging in the fact that physical and chemical changes in its macromolecular components occur - “the maturation of cellular colloids and micelloids, their transformation into precipitates and flocculates, forming biologically inert inclusions that inhibit the vital activity of cells.”
Modern research has shown that with age, changes actually occur in connective tissue that disrupt its trophic, protective and other functions. In the skin, tendons, cartilage tissue, and aorta, the number of cells, their size, and the size of the nuclei decreases. The reproduction of fibroblasts, for example, during inflammation in old people is slowed down. In fibrous structures, age-related changes are expressed by an increase in the number of cross-links between collagen fibers. Collagen with an excess amount of macromolecular “crosslinks” acquires new properties. It becomes more resistant to temperature influences, its solubility and ability to bind water decreases. Normally metabolically stable, collagen becomes increasingly inert. Its self-renewal slows down, which inevitably leads to the accumulation of new errors in the molecules. The amount of hyaluronic acid in the main substance decreases, which probably reduces the body's ability to bind water with age. At the same time, the amount of chondroitin sulfate in the vascular wall increases. The latter promotes vascular calcification, since sulfated glycosaminoglycans have an affinity for calcium ions.
The protective function of connective tissue is expressed by the fact that by participating in the structure of the skin, mucous membrane, fibrous capsules, as well as in the structures of specialized barriers (glia in the blood-brain barrier), it contributes to the creation of mechanical barriers. Connective tissue cells determine such a form of protection as phagocytosis (macrophagocytes), as well as the ability to delimit damaged tissue from normal tissue (granulation shaft). Finally, connective tissue cells, interacting with lymphocytes, participate in the immune response.
A. A. Bogomolets was the first to fully appreciate the protective role of connective tissue. He and his students showed that low reactivity of connective tissue, as a rule, is combined with a more severe course of disease: wounds heal more slowly, fractures heal less well.
All this allowed us to assume that by influencing connective tissue it is possible to worsen or improve the course of the disease, making it less severe. It was only necessary to find a way to stimulate its functions. Certain results could be achieved by methods such as physical therapy, massage, insolation, diet, but A. A. Bogomolets had in mind specific selective stimulation of all elements of connective tissue, wherever they are located in the body. As a result, this was achieved immunologically, i.e. injection into people of serum obtained as a result of immunization of animals (horses) with organs rich in connective tissue (bone marrow, spleen). This serum received the abbreviated name ACS (antireticular cytotoxic serum) and was studied in detail by A. A. Bogomolets and his students, and then used in the clinic.
It was found that the effect of antireticular cytotoxic serum depends on its dose. Large doses of serum had a cytotoxic effect, i.e. destroys connective tissue cells, small - stimulating. This was expressed by an increase in metabolism in macrophagocytic tissue elements and activation of phagocytosis, an increase in the titer of antimicrobial antibodies, and normalization of water-electrolyte and fat metabolism. Activation of enzymatic processes allows the connective tissue to free itself from ballast substances that accumulate in it during various metabolic diseases, as well as during aging. In this case, substances can be formed that have a nonspecific effect on the cells of the body, constituting a general stimulating effect.
Mechanical functions of the skeleton 1. Support function is that the bones support those attached to them soft fabrics
(muscles, fascia and other organs) participate in the formation of the walls of cavities in which internal organs are located. 2. Spring function
due to the presence in the skeleton of formations that soften shocks and shocks (cartilaginous pads, articular cartilage between connecting bones, etc.) 3. Protective function
is that the skeleton forms containers for vital organs and protects them from external influences. 4. Motor function
possible due to the structure of bones in the form of long and short levers connected by movable joints and driven by muscles controlled by the nervous system. 5. Anti-gravity function
In addition, bones determine the direction of the course of blood vessels, nerves and muscles, as well as the shape of the body and its size.
Biological functions of the skeleton
1. Metabolic functions- the skeleton is involved in metabolism (especially in mineral metabolism), being a depot of mineral salts - phosphorus, calcium, iron, etc.
2. Hematopoietic function due to the fact that inside the bones there is red bone marrow - the central hematopoietic organ - the organic part of the bone.
3. Immunological function is also associated with red bone marrow: the latter contains a self-sustaining population of hematopoietic stem cells, from which immune system cells or lymphocytes are also formed.
Bone as an organ
Each tubular bone has the following parts:
1. Diaphysis(bone body) is a bone tube that contains yellow bone marrow in adults and performs the function of support and protection, respectively.
2. Metaphyses(ends of the diaphysis), adjacent to the metaepiphyseal cartilage, develop together with the diaphysis, but participate in the growth of bones in length and consist of spongy substance.
3. Epiphyses(articular ends of each tubular bone) are located on the other side of the metaepiphyseal cartilage.
4. Apophyses(bony protrusions located near the epiphysis).
Classification of bones
The number of individual bones that make up the adult human skeleton is more than 200 (206 bones). Bones vary in size and shape and occupy specific positions in the body. Based on their external shape, bones are distinguished between long, short, wide and mixed.
However, it is more correct to distinguish bones based on three principles on which any anatomical classification is based - form (structure), function and development. From this point of view, the following groups of bones are distinguished:
BONES
Tubular Spongy Flat Mixed Airborne
Long Long Short Skull Bones
Short Sesamoid Bone Belts
Connection of bones
There are three types of bone connections:
1) Continuous connections (synarthrosis), when there is a layer of connective tissue or cartilage between the bones. There is no gap or cavity between the connecting bones.
2) Intermittent connections or joints (diarthrosis, or synovial joints) - when there is a cavity between the bones and a synovial membrane lining the inside of the joint capsule.
3) Half-joints or symphyses (hemiarthrosis), when there is a small gap in the cartilaginous or connective tissue layer between the connecting bones.
1. Continuous connections - synarthrosis. Depending on the structure of the tissue connecting the bones, the following groups of these connections are distinguished:
— fibrous (syndesmoses) or connective tissue;
— cartilaginous (synchondrosis);
- bone connections (synostoses);
- elastic;
- muscle connections.
Fibrous joints (syndesmoses) These are strong connections through dense fibrous connective tissue. These include:
A) membranes or interosseous membranes.
b) ligaments
V) seams:
- serrated (for example, the connection of the frontal and parietal bones);
- scaly (for example, the connection of the temporal bone with the parietal);
- smooth (for example, connections between the bones of the facial skull)/
G) hammering
Cartilage joints (synchondrosis) They are connections between bones and cartilage. According to the duration of their existence, synchondrosis is:
A) temporary– exist until a certain age, after which they are replaced by synostoses (for example, between the bones of the pelvic girdle).
b) permanent– exist until a certain age, after which they are replaced by synostoses (for example, between the pyramid of the temporal bone and the adjacent bones of the pelvic girdle);
Elastic connections do not have the strength that connective tissue or fibrous compounds have.
Bone joints (synostoses): in the space between the bones, the connective tissue turns into bone or first into cartilage, and then into bone.
Muscular connections They are movable and variable in length connections of two or more bones with the help of striated muscles.
2. Discontinuous joints or joints (diarthrosis) are the most perfect views bone connections.
In each joint the following are distinguished: essential elements:
- articular surfaces covered with cartilage;
- joint capsule or bursa;
- articular cavity with no big amount synovial fluid.
Some joints also have auxiliary formations in the form of articular discs, menisci and articular labrum.
Articular surfaces most often correspond to each other in articulating bones.
They are covered with articular cartilage, which facilitates the sliding of articular surfaces and softens shocks.
Joint capsule grows to the articulating bones along the edge of their articular surfaces or slightly retreating from them and hermetically surrounds the articular cavity.
The capsule has 2 layers: outer fibrous and inner synovial.
Fibrous layer in places it forms ligaments - thickenings that strengthen the capsule and also act as passive brakes, limiting movement in the joint.
Synovial layer thin. It lines the fibrous layer from the inside and continues on the surface of the bone, not covered with articular cartilage.
Articular cavity It is a hermetically sealed slit-like space limited by articular surfaces and a synovial membrane. The joint cavity contains a small amount of synovial fluid.
3. Half-joints or symphyses (hemiarthrosis) - transition connections from continuous to discontinuous or vice versa. These are cartilaginous or fibrous compounds, in the thickness of which there is a small cavity in the form of a gap.
Classification of joints
In joints, depending on the structure of the articulating surfaces (shape, curvature, size), movements can occur around different axes. In the biomechanics of joints, the following axes of rotation are distinguished: 1) frontal, 2) sagittal and 3) vertical. In addition, circular motion is distinguished.
Joints are classified according to the following criteria:
- by the number of articular surfaces;
- according to the shape of the articular surfaces;
- by function.
I. Based on the number of articular surfaces, they are distinguished:
A) simple joint– has 2 articular surfaces (e.g. humerus, interphalangeal)
b) complex joint– has more than 2 articular surfaces (eg, elbow, knee). A complex joint consists of several simple joints in which movements can be performed separately.
V) complex joint– contains intra-articular cartilage inside the joint capsule, which divides the joint into two chambers (eg, temporomandibular joint, knee).
G) combined joint– represents a combination of several joints isolated from each other, joints located separately from each other, but functioning together (for example, both temporomandibular joints, proximal and distal radioulnar joints, etc.)
II. According to form and function, the classification is carried out as follows: the function of a joint is determined by the number of axes around which movements are made. The number of these axes depends on the shape of the articular surfaces of the joint. Based on this, joints are distinguished:
1. Uniaxial joints(cylindrical or rotary and block-shaped):
2. Biaxial joints (ellipsoid, saddle, condylar):
3. Triaxial or multiaxial joints(spherical, nut-shaped, flat):
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The bulk of the body mass of animals is formed by connective tissue. They consist of cartilage, bones, tendons, and ligaments.
The structure of connective tissues in different animals and in different parts one organism is different. Wherein general feature their structure is that the cells seem to be scattered in a mass of intercellular substance. There are several types of connective tissues that perform different functions.
Fibrous connective tissue is found everywhere in the animal body. It connects the skin with the muscles, holding it in the desired position, and connects the organs. The cells of this type of tissue are surrounded by a dense network of fibers that form the intercellular substance.
Bone tissue forms the bones of the skeleton - the internal support of vertebrates. Bone tissue consists of mineral substances, which give it strength, and organic substances, which provide elasticity.
This combination helps bone tissue perform a supporting function.
Bone cells remain alive and secrete intercellular substance throughout the life of the animal. The cells are connected to each other by numerous processes lying in the interosseous substance.
Bone tissue forms bones. The growth and nutrition of bones formed by bone tissue is ensured by the periosteum covering them.
Cartilage tissue covers the heads of bones and is found at the joints, which gives the skeleton flexibility.
Cells of cartilage tissue, singly or in groups, are immersed in an elastic intercellular substance. The skeletons of sharks and rays do not have bone tissue, they are entirely built from cartilage. In humans, cartilage can be felt in the auricle and at the tip of the nose.
Blood is a special connective tissue. It contains a liquid intercellular substance - plasma. Plasma contains blood cells: erythrocytes (red blood cells), leukocytes (white blood cells) and platelets (round, oval cells or platelets).
When blood moves through the smallest vessels - capillaries, nutrients in a dissolved state penetrate into the intercellular space. As a result, tissue fluid is formed. Lymph arises from it (gr. limpha - moisture, pure water), which collects in the lymphatic vessels and from them again enters the blood.
Blood, lymph and tissue fluid create the internal environment of the body.
Adipose tissue is also a connective tissue. It consists of a large number of fat cells. This tissue is mainly located in the subcutaneous fat layer. It stores fats that can be used by the body in case of insufficient nutrition. In addition, adipose tissue helps animals retain heat and protects them from external shocks.
Consists of cells and a large amount of intercellular substance. The intercellular substance contains fibers and ground substance. Fibers provide strength and elasticity.
Fibers are divided into:
û collagen
û reticular
û elastic
Collagen fibers contain the protein collagen and are highly durable.
Reticular fibers are part of the red bone marrow, lymph nodes and spleen. They are thin and can form a fine network.
Elastic fibers contain the protein elastin, they are less durable than collagen and can stretch easily.
The main substance that belongs to the intercellular fills the space between cells and fibers.
The function is varied:
Connective tissue includes connective tissue itself, which includes loose fibrous and dense fibrous; skeletal connective tissues (cartilage and bone), as well as connective tissue with special properties (adipose tissue, blood, lymph and hematopoietic tissues).
Loose fibrous connective tissue (FCT).
PBST fills the space between organs.
The PBST includes the following cells:
Fibroblasts are flat, spindle-shaped cells.
Participate in wound healing and scar tissue formation.
ü Macrophages are cells that capture and digest foreign particles.
ü Mast cells produce heparin, which prevents blood clotting.
ü Plasma - participate in the synthesis of antibodies.
Antibodies are proteins that protect against infection.
ü Fat cells - capable of accumulating reserve fat.
ü Pigment cells - contain grains of the pigment melanin.
Dense fibrous connective tissue (DFCT).
In this fabric, the fibers are arranged tightly. There is little intercellular substance. PVST is part of ligaments, tendons, fascia, and membranes.
Fascia is a thin connective tissue sheath in which a muscle is placed.
Contains a lot of collagen fibers.
Cartilage tissue consists of chondrocyte cells and dense intercellular substance.
Various fibers are found in the intercellular substance:
- hyaline
ñ elastic
ñ fibrous
Hyaline cartilage is part of the ribs. Located at the junction of the rib and sternum.
Elastic cartilage is part of the auricle and cartilage of the larynx. Calcium is never deposited in elastic cartilage.
Fibrous cartilage forms the intervertebral discs and covers the lower jaw joint.
Bone.
Consists of cells and intercellular substance.
The intercellular substance contains the ground substance, which contains a lot inorganic salts(calcium, magnesium).
Organic substances - fats, proteins, carbohydrates containing carbon.
Inorganic substances - mineral salts.
Thanks to this, bones are strong. Bone contains a lot of calcium salts. If there is not enough calcium salts, it develops osteoporosis . The bone becomes brittle and fractures are possible.
Among the organic salts in bone, the most oseina, which gives bones flexibility.
The process of destruction and formation of new cells constantly occurs in the bone.
There are 3 types of bone cells:
There are 2 types of bone tissue:
Ø coarse fiber
Ø plate
Coarse fibrous tissue is found at the sutures of the skull. Consists of collagen fibers and osteocytes.
Lamellar tissue is denser than coarse fibrous tissue and all bones are built from it. It also includes a large number of collagen fibers and cells in the form of plates.
The functional unit of bone is osteon.
Adipose tissue
This is connective tissue, in which the bulk is occupied by fat cells - adipocytes. There are 2 types: white adipose tissue (forms superficial and deep accumulations), brown adipose tissue (located between the shoulder blades, in the armpits, in the area of large vessels of the neck).
Blood and lymph
They consist of a liquid part and formed elements.
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Connective tissues- this is a complex of mesenchymal derivatives, consisting of cellular differons and a large amount of intercellular substance (fibrous structures and amorphous substance), involved in maintaining the homeostasis of the internal environment and differing from other tissues by a lesser need for aerobic oxidative processes.
Connective tissue makes up more than 50% of the human body weight. It participates in the formation of the stroma of organs, the layers between other tissues, the dermis of the skin, and the skeleton.
The concept of connective tissues (tissues of the internal environment, supporting-trophic tissues) combines tissues that are different in morphology and functions, but have some common properties and develop from a single source - mesenchyme.
Structural and functional features of connective tissues:
internal location in the body;
predominance of intercellular substance over cells;
variety of cell forms;
the common source of origin is mesenchyme.
Functions of connective tissues:
mechanical;
supporting and form-building;
protective (mechanical, nonspecific and specific immunological);
reparative (plastic).
trophic (metabolic);
morphogenetic (structure-forming).
Fibrous connective tissues:
Loose fibrous unformed connective tissue
Unformed
Dense fibrous connective tissue:
Unformed
Decorated
Connective tissues with special properties:
Reticular tissue
Adipose tissue:
Mucous
Pigmented
Peculiarities:
many cells, little intercellular substance (fibers and amorphous substance)
Localization:
forms the stroma of many organs, the adventitia of the vessels, located under the epithelia - forms its own lamina of mucous membranes, submucosa, located between muscle cells and fibers
Functions:
1. Trophic function: located around the vessels, it regulates the exchange of substances between the blood and the tissues of the organ.
2. The protective function is due to the presence of macrophages, plasma cells and leukocytes in the pvst. Antigens that break through the I - epithelial barrier of the body, meet with the II barrier - cells of nonspecific (macrophages, neutrophil granulocytes) and immunological defense (lymphocytes, macrophages, eosinophils).
3. Support-mechanical function.
4. Plastic function - participates in the regeneration of organs after damage.
1. Fibroblasts
Fibroblastic differon cells: stem and semi-stem cell, low-specialized fibroblast, differentiated fibroblast, fibrocyte, myofibroblast, fibroclast.
Stem and semi-stem cells- these are small cambial reserve cells that rarely divide.
Unspecialized fibroblast- small, weakly branched cells with basophilic cytoplasm (due to the large number of free ribosomes), organelles are poorly expressed; actively divides by mitosis, does not take a significant part in the synthesis of intercellular substance; as a result of further differentiation, it turns into differentiated fibroblasts.
Differentiated fibroblasts- the most functionally active cells of this series: they synthesize fiber proteins (proelastin, procollagen) and organic components of the main substance (glycosaminoglycans, proteoglycans). In accordance with their function, these cells have all the morphological characteristics of a protein-synthesizing cell - in the nucleus: clearly defined nucleoli, often several; euchromatin predominates; in the cytoplasm: the protein synthesizing apparatus is well expressed (granular EPS, lamellar complex, mitochondria).
At the light-optical level - weakly branched cells with unclear boundaries, with basophilic cytoplasm; the nucleus is light, with nucleoli.
There are 2 populations of fibroblasts: Short-lived (several weeks) Function:
protective. Short-lived (several weeks) Long-lived (several months)
musculoskeletal. Fibrocyte - mature and aging cell of this series; spindle-shaped, weakly branched cells with slightly basophilic cytoplasm.
They have everything
morphological characteristics and functions of differentiated fibroblasts, but less pronounced. Cells of the fibroblastic series are the most numerous pvst cells (up to 75% of all cells) and produce most of the intercellular substance. The antagonist is, Golgi apparatus, relatively large but few mitochondria), as well as lysosomes with their characteristic hydrolytic enzymes.
Myofibroblast- a cell containing contractile actomyosin proteins in the cytoplasm, therefore capable of contracting. Cells that are morphologically similar to fibroblasts, combining the ability to synthesize not only collagen, but also contractile proteins in significant quantities.
It has been established that fibroblasts can transform into myofibroblasts, which are functionally similar to smooth muscle cells, but unlike the latter they have a well-developed endoplasmic reticulum. Such cells are observed in granulation tissue during wound healing and in the uterus during pregnancy. They take part in wound healing, bringing the edges of the wound closer together during contraction.
2. Macrophages
Functions: The next pvst cells in number are tissue macrophages (synonym: histiocytes), making up 15-20% of pvst cells. They are formed from blood monocytes and belong to the macrophage system of the body. Large cells with a polymorphic (round or bean-shaped) nucleus and a large amount of cytoplasm. Of the organelles, lysosomes and mitochondria are well defined. Uneven contour of the cytomembrane, capable of active movement.
protective function through phagocytosis and digestion of foreign particles, microorganisms, tissue breakdown products; participation in cellular cooperation in humoral immunity; production of the antimicrobial protein lysozyme and the antiviral protein interferon, a factor stimulating the immigration of granulocytes.
3. Mast cells (synonyms: tissue basophil, mast cell, mast cell) They make up 10% of all pvst cells. They are usually located around blood vessels. A round-oval, large, sometimes branched cell with a diameter of up to 20 microns; there are a lot of basophilic granules in the cytoplasm. The granules contain heparin and histamine, serotonin, chymase, tryptase. When stained, mast cell granules have the property metachromasia
Functions: Heparin reduces the permeability of intercellular substances and blood clotting, and has an anti-inflammatory effect. Histamine acts as its antagonist. The number of tissue basophils varies depending on the physiological conditions of the body: it increases in the uterus and mammary glands during pregnancy, and in the stomach, intestines, and liver at the height of digestion. In general, mast cells regulate local homeostasis.
4. Plasmocytes
Formed from B lymphocytes. In morphology they are similar to lymphocytes, although they have their own characteristics. The nucleus is round and eccentrically located; heterochromatin is located in the form of pyramids with a sharp apex facing the center, delimited from each other by radial stripes of euchromatin - therefore, the plasmacyte nucleus is torn off like a “wheel with spokes”. The cytoplasm is basophilic, with a light “yard” near the nucleus. Under an electron microscope, the protein synthesizing apparatus is clearly visible: granular EPS, lamellar complex (in the area of the light “yard”) and mitochondria. Cell diameter is 7-10 microns. Short-lived (several weeks) are effector cells of humoral immunity - they produce specific antibodies (gamma globulins)
5. Leukocytes
Leukocytes released from the vessels are always present in the RVST.
6. Lipocytes (synonyms: adipocyte, fat cell).
1). White lipocytes- round cells with a narrow strip of cytoplasm around one large droplet of fat in the center. There are few organelles in the cytoplasm. The small core is located eccentrically. When preparing histological preparations in the usual way, a drop of fat is dissolved in alcohol and washed away, so the remaining narrow ring-shaped strip of cytoplasm with an eccentrically located nucleus resembles a ring.
Short-lived (several weeks) white lipocytes store fat as a reserve (high-calorie energy material and water).
2). Brown lipocytes- round cells with a central location of the nucleus. Fatty inclusions in the cytoplasm are detected in the form of numerous small droplets. The cytoplasm contains many mitochondria with high activity of the iron-containing (brown color) oxidative enzyme cytochrome oxidase. Short-lived (several weeks) brown lipocytes do not accumulate fat, but, on the contrary, “burn” it in the mitochondria, and the heat released in this case is used to warm the blood in the capillaries, i.e. participation in thermoregulation.
7. Adventitial cells
These are poorly specialized cells that accompany blood vessels. They have a flattened or spindle-shaped shape with slightly basophilic cytoplasm, an oval nucleus and a small number of organelles. During the process of differentiation, these cells can, apparently, turn into fibroblasts, myofibroblasts and adipocytes.
8. Pericytes
Located in the thickness of the basement membrane of the capillaries; participate in the regulation of the lumen of hemocapillaries, thereby regulating the blood supply to surrounding tissues.
9. Vascular endothelial cells
They are formed from poorly differentiated mesenchymal cells and cover all blood and lymphatic vessels from the inside; produce a lot of biologically active substances.
10. Melanocytes (pigment cells, pigmentocytes)
Processed cells with inclusions of melanin pigment in the cytoplasm. Origin: from cells migrating from the neural crest. Short-lived (several weeks) UV protection.
