Formed fibrous connective tissue. Functions of fibrous connective tissues

Loose fibrous unformed connective tissue is the most common, located next to epithelial tissues, accompanies blood and lymphatic vessels in more or less quantity; is part of the skin and mucous membranes of organs. As layers of membranes containing an abundance of vessels, loose fibrous tissue is found in all tissues and organs (Fig. 30).

The intercellular substance is represented by two components: the main (amorphous) substance - a structureless matrix with a gelatinous consistency; fibers - collagen and elastic, located relatively loose and randomly, therefore the tissue is called unformed. Loose fibrous unformed connective tissue, due to the presence of intercellular substance, performs a support-trophic function, cells participate in immune reactions and regenerative processes in tissue damage. As part of the connective tissue, cells of various shapes are differentiated: adventitial, fibroblasts, fibrocytes, histiocytes, mast cells (tissue basophils), plasma cells and fat cells. adventitial(from lat. adventicus- alien, wandering) cells are the least differentiated, located along the outer surface of the capillaries, being cambial, actively dividing by mitosis and differentiating into fibroblasts, myofibroblasts and lipocytes. fibroblasts(from lat. fibrin- protein; blastos- sprout, overgrowth -

Rice. thirty

7 - macrophage; 2 - amorphous intercellular substance; 3 - plasma cell;
4 - fat cell; 5 - endothelium; 6 - adventitial cell; 7 - pericyte;
8 - endothelial cell; 9 - fibroblast; 10 - elastic fiber; 11 - mast cell; 12 - collagen fiber current) - protein producers, are permanent and most numerous cells. In mobile cell forms, the peripheral part of the cell contains contractile filaments, cells with a large number of contractile filaments - myofibroblasts - contribute to wound healing. Part of the fibroblasts is enclosed between densely spaced fibers, such cells are called fibrocytes, they lose the ability to divide, take an elongated shape and have strongly flattened nuclei. Macrophages (histiocytes) cells that have the ability to phagocytosis and accumulation of suspended colloidal substances in the cytoplasm are involved in general and local protective reactions of the immune system. The nucleus has well-defined contours. Possessing the ability to directed movement - chemotaxis, macrophages migrate to the focus of inflammation, where they become dominant cells. Macrophages are involved in the recognition, processing and presentation of antigen to lymphocytes. During inflammation, cells become irritated, increase in size, become mobile, and transform into structures called polyblasts. Macrophages cleanse the focus of foreign particles and destroyed cells, but also stimulate the functional activity of fibroblasts. Tissue basophils (labrocytes, mast cells) have an irregularly oval or rounded shape, numerous granules (grains) are located in the cytoplasm. The cells contain histamine, which dilates blood vessels, and secrete heparin, which prevents blood from clotting. Plasma cells (plasma cells) synthesize and secrete the bulk of immunoglobulins - antibodies (proteins formed in response to the action of an antigen). These cells are found in their own layer of the intestinal mucosa, the omentum, in the connective tissue between the lobules of the salivary, mammary glands, in the lymph nodes, and in the bone marrow. pigment cells have processes, in the cytoplasm there are many dark brown or black grains of pigment from the melanin group. The connective tissue of the skin of lower vertebrates - reptiles, amphibians, fish - contains a significant amount of pigment cells - chromatophores, which determine one or another color of the outer cover and perform a protective function. Pigment cells in mammals are concentrated mainly in the sclera, choroid and iris, and the ciliary body. Fat cells (lipocytes) are formed from adventitial cells of loose connective tissue, which are usually located in groups along blood vessels.

The drug "Loose fibrous unformed connective tissue of the subcutaneous tissue of the rat"(stained with hematoxylin). The drug is a small area of fixed subcutaneous tissue, stretched in the form of a thin film on a coverslip. At a low magnification (x10), the intercellular substance is revealed: a structureless amorphous matrix and two types of fibers - rather wide collagen fibers having a ribbon-like shape, and thin filamentous elastic fibers. With a high magnification of the microscope (x40), cells of various shapes differentiate in the connective tissue: adventitial cells - elongated cells with long processes; fibroblasts - have a spindle shape, since the central part is significantly thickened. The nucleus is large, weakly stained, one or two nucleoli are clearly visible. Ectoplasm is very light, endoplasm, on the contrary, is intensely stained due to the presence of a large amount of granular endoplasmic reticulum, which is due to the participation in the synthesis of high-molecular substances necessary both for building fibers and for the formation of an amorphous substance. Macrophages in the cytoplasm contain many vacuoles, which indicates an active participation in metabolism, the contours of the cytoplasm are clear, processes in the form of pseudopodia, so the cell is similar to an amoeba. Tissue basophils (labrocytes, mast cells) have an irregularly oval or round shape, sometimes with wide short processes; numerous basophilic granules (grains) are located in the cytoplasm. Plasmocytes (plasma cells) may be round or oval; the cytoplasm is sharply basophilic, with the exception of only a small rim of the cytoplasm near the nucleus - the perinuclear zone, along the periphery of the cytoplasm there are numerous small vacuoles.

The preparation "Adipose tissue of the omentum". The omentum is a film penetrated by blood vessels. When stained with Sudan III, accumulations of yellow rounded fat cells are visible. When stained with hematoxylin and eosin, the cricoid fat cells are not stained, the violet core is pushed to the periphery of the cytoplasm (Fig. 31).

In many parts of the animal body, significant accumulations of fat cells are formed, called adipose tissue. In connection with the peculiarities of the natural coloration, the specifics of the structure and function, as well as the location in mammals, there are two types of fat cells and, accordingly, two types of adipose tissue: white and brown.

White adipose tissue a significant amount is contained in the so-called fat depots: subcutaneous adipose tissue, especially developed in pigs, adipose tissue around the kidneys in the mesentery (perinephric tissue), in some breeds of sheep at the root of the tail (fat tail). The structural unit of white adipose tissue is spherical fat cells, up to 120 microns in diameter. With the development of cells, fatty

Rice. 31

A- total preparation of the omentum (Sudan III and hematoxylin); b- preparation of subcutaneous adipose tissue (hematoxylin and eosin): 7 - lipocyte; 2 - blood vessel;

3 - a piece of adipose tissue; 4 - fibers and cells of loose connective tissue

The values in the cytoplasm appear first in the form of small scattered drops, later merging into one large drop. The total amount of white adipose tissue in the body of animals of various species, breeds, sex, age, fatness ranges from 1 to 30% of live weight. Reserve fats are the most high-calorie substances, during the oxidation of which a large amount of energy is released in the body (1 g of fat \u003d 39 kJ). In cattle of meat and meat and dairy breeds, groups of fat cells are located in layers of loose fibrous connective tissue of skeletal muscles. The meat obtained from such animals has the best taste and is called "marble". Subcutaneous adipose tissue is of great importance for protecting the body from mechanical damage, from heat loss. Adipose tissue along the neurovascular bundles provides relative isolation, protection and limitation of mobility. Accumulations of fat cells combined with bundles of collagen fibers in the skin of the soles and paws create good cushioning properties. The role of adipose tissue as a depot of water is significant; the formation of water is an important feature of the metabolism of fats in animals living in arid regions (camels). During starvation, the body primarily uses spare fats from fat depot cells, in which fatty inclusions decrease and disappear. Adipose tissue of the eye orbit, epicardium, paws is preserved even with severe exhaustion. The color of adipose tissue depends on the type, breed and type of feeding of animals. Most animals, with the exception of pigs and goats, contain a pigment in their fat. carotene, giving yellow color to adipose tissue. In cattle, the adipose tissue of the pericardium contains many collagen fibers. kidney fat called the fatty tissue surrounding the ureters. In the back area, adipose tissue of pigs contains muscle tissue, as well as often hair follicles (bristle) and even hair bags. In the area of the peritoneum there is an accumulation of adipose tissue, the so-called mesenteric or mesenteric fat, which contains a large number of lymph nodes that accelerate oxidative processes and spoilage of fat. Blood vessels are often found in mesenteric fat, for example pigs have more arteries and cattle have more veins. Internal fat is a fatty tissue located under the peritoneum, contains a large number of fibers located in oblique and perpendicular directions. Sometimes pigment grains are found in the adipose tissue of pigs, in such cases brown or black spots are detected.

brown adipose tissue it is present in significant quantities in rodents and hibernating animals, as well as in newborn animals of other species. Location mainly under the skin between the shoulder blades, in the cervical region, mediastinum and along the aorta. Brown adipose tissue consists of relatively small cells that are very tightly adjacent to each other, resembling glandular tissue in appearance. Numerous nerve fibers approach the cells, braided with a dense network of blood capillaries. Brown adipose tissue cells are characterized by centrally located nuclei and the presence of small fat droplets in the cytoplasm, which do not merge into a larger drop. In the cytoplasm, between the fat drops, there are glycogen granules and numerous mitochondria, stained proteins of the transport electron system - cytochromes give the brown color to this tissue. In the cells of brown adipose tissue, oxidative processes are intense, accompanied by the release of a significant amount of energy. However, most of the generated energy is spent not on the synthesis of ATP molecules, but on heat generation. This property of brown tissue lipocytes is important for temperature regulation in newborn animals and for warming animals after waking up from hibernation.

Control questions

1. Describe the embryonic connective tissue - mesenchyme.
2. What is the structure of mesenchymal cells?
3. Give a structural and functional characteristic of the cells of the reticular connective tissue.
4. What is the structure of reticular fibers and how can they be detected on histological preparations?
5. Describe the cells of loose fibrous connective tissue.
6. What is the structure of the intercellular substance?
7. What is the function of the structureless matrix - the main substance?
8. What is the structure and function of loose fibrous connective tissue fibers?
9. What dye can be used to detect fat inclusions?

It is characterized by a predominance of densely arranged fibers and a low content of cellular elements, as well as the main amorphous substance. Depending on the nature of the location of the fibrous structures, it is divided into dense formed and dense unformed connective tissue (see table).

Dense loose connective tissue characterized by a disordered arrangement of fibers. It forms capsules, perichondrium, periosteum, reticular layer of the dermis of the skin.

Densely formed connective tissue contains strictly ordered fibers, the thickness of which corresponds to the mechanical loads in which the organ functions. Formed connective tissue is found, for example, in tendons, which consist of thick, parallel bundles of collagen fibers. In this case, each bundle, delimited from the neighboring layer of fibrocytes, is called bundleI-th order. Several bundles of the first order, separated by layers of loose fibrous connective tissue, are called bundleII-th order. Layers of loose fibrous connective tissue are called endotenonium. Beams of the second order are combined into thicker bundlesIII-th order, surrounded by thicker layers of loose fibrous connective tissue called perithenonium. The bundles of the III order can be a tendon, and in larger tendons they can be combined into bundlesIV-th order, which are also surrounded by perithenonium. The endothenonium and perithenonium contain the tendon-feeding blood vessels, nerves, and proprioceptive nerve endings.

Connective tissues with special properties

Connective tissues with special properties include reticular, adipose, pigmented and mucous. These tissues are characterized by the predominance of homogeneous cells.

Reticular tissue

Consists of process reticular cells and reticular fibers. Most reticular cells are associated with reticular fibers and are in contact with each other by processes, forming a three-dimensional network. This tissue forms the stroma of hematopoietic organs and the microenvironment for the blood cells developing in them, carries out phagocytosis of antigens.

Adipose tissue

It consists of accumulations of fat cells and is divided into two types: white and brown adipose tissue.

White adipose tissue is widely distributed in the body and performs the following functions: 1) a depot of energy and water; 2) depot of fat-soluble vitamins; 3) mechanical protection of organs. Fat cells are quite close to each other, have a rounded shape due to the content of a large accumulation of fat in the cytoplasm, which pushes the nucleus and a few organelles to the cell periphery (Fig. 4-a).

Brown adipose tissue is found only in newborns (behind the sternum, in the area of the shoulder blades, on the neck). The main function of brown adipose tissue is to generate heat. The cytoplasm of brown fat cells contains a large number of small liposomes that do not merge with each other. The nucleus is located in the center of the cell (Fig. 4-b). The cytoplasm also contains a large number of mitochondria containing cytochromes, which give it a brown color. Oxidative processes in brown fat cells are 20 times more intense than in white ones.

Rice. 4. Scheme of the structure of adipose tissue: a - ultramicroscopic structure of white adipose tissue, b - ultramicroscopic structure of brown adipose tissue. 1 - adipocyte nucleus, 2 - lipid inclusions, 3 - blood capillaries (according to Yu.I. Afanasiev)

The material is taken from the site www.hystology.ru

This type of connective tissue is characterized by a quantitative predominance of fibers over the main substance and cells. Depending on the relative position of the fibers and the bundles and networks formed from them, two main types of dense connective tissue are distinguished: unformed and formed.

In dense irregular connective tissue fibers form a complex system of intersecting bundles and networks. This arrangement of them reflects the versatility of mechanical influences on a given area of tissue, according to which these fibers are located, ensuring the strength of the entire tissue system. Dense unformed tissue is found in large quantities in the composition of the skin of animals, where it performs a supporting function. Along with intertwining collagen fibers, it contains a network of elastic fibers, which determines the ability of the tissue system to stretch and return to its original state after the termination of the external mechanical factor. Varieties of dense unformed tissue are part of the perichondrium and periosteum, membranes and capsules of many organs.

Rice. 112. Dense formed connective tissue of the tendon in the longitudinal section:

1 - collagen fibers - bundles of the first order; 2 - tendon bundle II order; 3 - nuclei of fibrocytes; 4 - layers of loose connective tissue.

Densely formed connective tissue characterized by ordered fibers, which corresponds to the action of the mechanical tension of the fabric in one direction. In accordance with the type of predominant fibers, collagen and elastic densely shaped tissues are distinguished. Dense, well-formed collagen tissue is most typically found in tendons. It consists of tightly lying collagen fibers oriented parallel along the tendon and bundles formed from them (Fig. 112). Each collagen fiber, consisting of numerous fibrils, is designated as a bundle of the first order. Between the fibers (beams of the first order), clamped by them, there are also longitudinally oriented fibrocytes. A set of bundles of the first order form bundles of the second order, surrounded by a thin layer of loose connective tissue - endotenonium. Several bundles of the II order form a bundle of the III order, surrounded by a thicker layer of loose connective tissue - perithenonium. In large tendons, there may also be bundles of the IV order. Peritenonium and endotenonium contain blood vessels that feed the tendon, nerve endings and fibers that send signals to the central nervous system about the state of tissue tension.

Dense formed elastic tissue in animals is found in ligaments (for example, in the vulva). It is formed by a network of thick longitudinally elongated elastic fibers. Fibrocytes and thin intertwining collagen fibrils are located in narrow slit-like spaces between elastic fibers. In some places there are wider layers of loose connective tissue through which blood vessels pass. This tissue, represented by a system of circularly located membranes and elastic networks, is present in large arterial vessels.

Distinctive characteristic of dense fibrous connective tissue:

a very high content of fibers that form thick bundles that occupy the bulk of the tissue volume;

a small amount of the main substance;

the predominance of fibrocytes.

The main property is high mechanical strength.

Irregular dense connective tissue- this type of tissue is characterized by a disordered arrangement of collagen bundles forming a three-dimensional network. The gaps between the fiber bundles contain the main amorphous substance that combines the tissue into a single framework, cells - fibrocytes (mainly) and fibroblasts, blood vessels, nerve elements. Unformed dense connective tissue forms a mesh layer of the dermis and capsules of various organs. Performs a mechanical and protective function.

Dense connective tissue differs in that the collagen bundles in it lie parallel to each other (in the direction of the load). Forms tendons, ligaments, fascia and aponeuroses (in the form of plates). Between the fibers are fibroblasts and fibrocytes. In addition to collagen, there are elastic ligaments (voice, yellow, connecting the vertebrae) formed by bundles of elastic fibers.

INFLAMMATION

Inflammation is a protective and adaptive reaction to local damage, developed in the course of evolution. Factors causing inflammation can be exogenous (infection, trauma, burns, hypoxia) or endogenous (necrosis, salt deposition). The biological meaning of this protective reaction is the elimination or restriction of the damaged tissue from healthy tissue, and tissue regeneration. Although this is a protective reaction, but in some cases, manifestations of this reaction, especially chronic inflammation, can cause severe tissue damage.

Phases of inflammation:

I. alteration phase- tissue damage and excretion inflammatory mediators, a complex of bioactive substances responsible for the occurrence and maintenance of inflammatory phenomena.

Inflammatory mediators:

humoral(from blood plasma) - kinins, coagulation factors, etc.;

cellular mediators released by cells in response to damage; produced by monocytes, macrophages, mast cells, granulocytes, lymphocytes, platelets. These mediators: bioamines (histamine, serotonin), eicosanoids (derivatives of arachids O new acid: prostaglandins, leukotrie e us), and others.

II. exudation phase includes:

Changes in microcirculation I torn bed: spasm of arterioles, then expansion of arterioles, capillaries and venules - hyperemia occurs And I - redness and fever.

Formation of liquid (cell-free) exudate - due to increased vascular permeability, changes in osmotic pressure in the focus of inflammation (due to damage) and hydrostatic pressure in the vessels. Violation of the outflow leads to the occurrence edema.

Formation of cellular exudate (migration of leukocytes through the endothelium).

Cellular composition inflammation phases:

1 phase : at the initial stages, the most actively evicted neutrophilic granulocytes, which perform phagocytic and microbicidal functions; as a result of their activity, decay products are formed, which attract monocytes evicted from the blood to the focus of inflammation;

2 phase : monocytes in connective tissue are converted into macrophages. Macrophages phagocytize dead neutrophils, cell debris, microorganisms and can initiate an immune response.

IN focus of chronic inflammation microphages and lymphocytes predominate, which form clusters - granulomas. Merging, macrophages form giant multinucleated cells.

III. phase of proliferation (repair) – Macrophages, lymphocytes and other cells cause: chemotaxis, proliferation and stimulation of synthetic activity fibroblasts; activation of the formation and growth of blood vessels. Young granulation tissue is formed, collagen is deposited, a scar is formed.

CONNECTIVE TISSUES WITH SPECIAL PROPERTIES

ADIPOSE TISSUE

Adipose tissue is a special type of connective tissue, in which the main volume is occupied by fat cells - adipocytes. Adipose tissue is ubiquitous in the body, accounting for 15-20% of body weight in men and 20-25% in women (i.e. 10-20 kg in a healthy person). With obesity (and in developed countries it is about 50% of the adult population), the mass of adipose tissue increases to 40-100 kg. Anomalies in the content and distribution of adipose tissue are associated with a number of genetic disorders and endocrine disorders.

Mammals, including humans, have two types of adipose tissue - white And brown, which differ in color, distribution in the body, metabolic activity, the structure of the cells (adipocytes) that form them, and the degree of blood supply.

White adipose tissue - the predominant type of adipose tissue. It forms superficial (hypoderm - a layer of subcutaneous fatty tissue) and deep - visceral - accumulations, forms soft elastic layers between internal organs.

During embryogenesis, adipose tissue develops from mesenchyme. The precursors of adipocytes are poorly differentiated fibroblasts (lipoblasts) that lie along the course of small blood vessels. During differentiation, small lipid droplets are first formed in the cytoplasm, the droplets merge with each other, forming one large droplet (95-98% of the cell volume), and the cytoplasm and nucleus are displaced to the periphery. These fat cells are called single droplet adipocytes. Cells lose their processes, acquire a spherical shape, during development their size increases by 7-10 times (up to 120 microns in diameter). The cytoplasm is characterized by a developed agranular EPS, a small Golgi complex, and a small number of mitochondria.

White adipose tissue consists of lobules (compact accumulations of adipocytes) separated by thin layers of loose fibrous connective tissue that carry blood and lymphatic vessels and nerves. In the lobules, the cells take the form of polyhedra.

Functions of white adipose tissue:

· energy (trophic): adipocytes have a high metabolic activity: lipogenesis (fat deposition) - lipolysis (fat mobilization) - providing the body with reserve sources;

· supporting, protective, plastic- completely or partially surrounds various organs (kidneys, eyeball, etc.). Sudden weight loss can lead to displacement of the kidneys;

· heat-insulating;

· regulatory– in the process of myeloid hematopoiesis, adipocytes are part of the stromal component of the red brain, which creates a microenvironment for proliferating and differentiating blood cells;

· depositing ( vitamins, steroid hormones, water )

· endocrine- synthesizes estrogens (the main source in men and

older women) and a hormone that regulates food intake - leptin. Leptin inhibits the secretion of a special neuropeptide NPY by the hypothalamus, which increases food intake. When fasting, leptin secretion decreases, when saturated, it increases. Insufficient production of leptin (or lack of leptin receptors in the hypothalamus) leads to obesity.

Obesity

In 80%, an increase in the mass of adipose tissue occurs due to an increase in the volume (hypertrophy) of adipocytes. In 20% (with the most severe forms of obesity developing at a young age) - an increase in the number of adipocytes (hyperplasia): the number of adipocytes can increase by 3-4 times.

Starvation

A decrease in body weight as a result of therapeutic or forced fasting is accompanied by a decrease in the mass of adipose tissue - increased lipolysis and inhibition of lipogenesis - a sharp decrease in the volume of adipocytes with maintaining their total number. When normal nutrition is resumed, cells quickly accumulate lipids, cells increase in size, and turn into typical adipocytes, resulting in a rapid recovery of body weight after diet is discontinued. Adipose tissue on the palms, soles and retroorbital areas is very resistant to lipolysis processes. A decrease in the mass of adipose tissue by more than a third of the norm causes dysfunction of the hypothalamus-pituitary-ovaries system - suppression of the menstrual cycle and infertility. Anorexia nervosa is a type of eating disorder in which the body fat is reduced to 3% of the normal level of adipose tissue mass, often resulting in death.

brown adipose tissue

In an adult, brown adipose tissue is present in a small amount, only in a few clearly defined areas (between the shoulder blades, on the back of the neck, at the gates of the kidneys). In newborns, it is up to 5% of body weight. Its content changes little with insufficient or excessive nutrition. Brown adipose tissue is most strongly developed in hibernating animals.

It is characterized by a strong development of fibrous structures, giving it greater density and strength. There are unformed and formed dense connective tissue.

The first includes the mesh layer of the skin, the connective tissue of the membranes covering the joints and some internal organs. Collagen fibers in unformed dense connective tissue are closely adjacent to each other and form a thick felt with a disordered arrangement of fibrillar structures. There is little amorphous substance in this tissue, the variety of cells is not great (almost exclusively fibroblasts and fibrocytes). The cells are usually strongly flattened by the surrounding fibers. These tissues perform mainly a mechanical function.

The formed dense connective tissue differs from the unformed one in that the fibers of its intercellular substance are regularly oriented relative to each other, that is, they are arranged in a strictly ordered manner. Formed fibrous connective tissue is found in tendons and ligaments, in fibrous membranes.

The fibrous connective tissue of the tendons is an inextensible cord that attaches the muscle to the bones. This tissue is characterized by a parallel arrangement of collagen fibers, very closely adjacent to each other. Each of the fibers has the same structure as in loose connective tissue. Between the collagen fibers are cells - fibrocytes and tendon cells. On longitudinal sections of the tendon, the cells have the shape of parallelograms, rhombuses, or trapeziums and are arranged in rows between collagen fibers. On transverse sections, fibrocytes have a stellate shape. Short processes, tapering towards the ends, cover collagen fibers that are multifaceted or irregularly round in cross section. Lamellar processes surround fibers built from collagen fibrils.

The tendon as a whole has a rather complex organization. Collagen fibers arranged parallel to each other are called bundles of the first order. They are separated by tendon cells. Groups of bundles of the first order (50-100 fibers each) are combined into more powerful bundles, covered with a connective tissue sheath, equipped with vessels and nerve branches. These are bundles of the second order. Layers of loose fibrous connective tissue that separate the bundles of the second order are called endotenonium. Groups of such bundles are again covered by a common, thicker connective tissue membrane and form bundles of the third order, separated by thicker layers of loose connective tissue (peritenonium). In large tendons, there may be bundles of the fourth and even fifth orders. In the perithenonium and endotenonium, there are blood vessels that feed the tendon, nerves and nerve endings that send signals to the central nervous system about the state of tension in the tendon tissue.

Tendon cells are highly differentiated, incapable of mitotic division. However, if the tendon is damaged, regenerative processes develop in it. The source is poorly differentiated cells located along the course of the vessels in the endothenium and perithenonium.

The nuchal ligament also belongs to the dense, formed fibrous connective tissue, only its bundles are formed by elastic fibers and are indistinctly subdivided.

fibrous membranes . This type of dense fibrous connective tissue includes tendon centers of the diaphragm, capsules of some organs, dura mater, sclera, perichondrium, periosteum, etc. Fibrous membranes are difficult to stretch due to the fact that bundles of collagen fibers and fibroblasts and fibrocytes lying between them are located in a certain order in multiple layers on top of each other. Separate bundles of fibers located at different levels pass from one layer to another, linking them together. In addition to bundles of collagen fibers, fibrous membranes contain elastic fibers.

PRACTICE!

Connective tissues

1. Actually connective tissues
2. Characterization of cell types
3. Intercellular substance of connective tissue
4. Connective tissues with special properties

1. The concept of connective tissues (tissues of the internal environment, supporting-trophic tissues) combines tissues that are not the same 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;

The predominance of intercellular substance over cells;

Variety of cellular forms;

The common source of origin is mesenchyme.\

Functions of connective tissues:

Trophic (metabolic);

reference;

Protective (mechanical, non-specific and specific immunological);
reparative (plastic).

Connective tissue classification:

Blood and lymph;

II. connective tissues proper - fibrous: loose and dense

(formed and unformed); special: reticular, fatty, mucous, pigmented;

III. skeletal tissues - cartilaginous: hyaline, elastic, fibrous-fibrous; bone: lamellar, reticulo-fibrous.

Despite the similarities in the structure and development of various subgroups of connective tissue, they differ significantly from each other and, above all, in the structure of the intercellular substance: from liquid - blood and lymph, to dense - cartilage tissue, and even mineralized - bone tissue. These structural features determine their functional differences that will be noted when characterizing each tissue subgroup.

The most common in the body are fibrous connective tissues and especially loose fibrous connective tissue, which is part of almost all organs, forming stroma, layers and layers, accompanying blood vessels.