Connective (or support-trophic) tissue. Types of tissues in the human body Tissue cells have the greatest strength

There are four main types of tissues: epithelial, connective, muscle and nervous.

Epithelial tissue consists of cells that are very tightly adjacent to each other. The intercellular substance is poorly developed. Epithelial tissues cover the surface of the body from the outside (skin), and also line hollow organs from the inside (stomach, intestines, renal tubules, pulmonary vesicles). The epithelium is single-layered and multilayered. Epithelial tissues carry out protective, excretory and metabolic functions.

The protective function of the epithelium is to protect the body from damage and the penetration of pathogens into it. The epithelial tissues include the ciliated epithelium, the cells of which on the outer surface have cilia that can move. With the movement of cilia, the epithelium directs foreign particles outside the body. The ciliated epithelium lines the inner surface of the respiratory tract and removes dust particles that enter the lungs with air.

The excretory function is carried out by the glandular epithelium, the cells of which are able to form fluids - secrets: saliva, gastric and intestinal juices, sweat, tears, etc.

The metabolic function of epithelial tissues consists in the exchange of substances between the external and internal environment:

the release of carbon dioxide and the absorption of oxygen in the lungs, the absorption of nutrients from the intestines into the blood.

Most of the epithelial cells in the process of life die and slough off (in the skin, digestive tract), so their number must be restored all the time due to division.

Connective tissue. This name unites a group of tissues with a common origin and function, but with a different structure. The functions of connective tissue are to give strength to the body and organs, to maintain and interconnect all cells, tissues and organs of the body. Connective tissue consists of cells and the main, or intercellular, substance, which may be in the form of fibers or be continuous, homogeneous. Connective tissue fibers are built from collagen, elastin, etc. The following types of connective tissue are distinguished: dense, cartilaginous, bone, loose and blood. Dense connective tissue is found in the skin, tendons, ligaments. A large number of fibers in this fabric gives it strength. Cartilage tissue has a lot of dense and elastic intercellular substance, it is contained in the auricle, cartilage of the larynx, trachea, intervertebral discs. Bone tissue is the hardest due to the fact that its intercellular substance contains mineral salts. This tissue consists of bone plates connected to each other, and cells between them. All the bones of the skeleton are built from bone tissue. Loose connective tissue connects the skin to the muscles, fills the gaps between the organs. Its cells contain fat, so this tissue is often called Adipose. In the connective tissue, as in others, blood vessels and nerves pass. Blood is a fluid connective tissue made up of plasma and blood cells. Muscle tissue has the ability to contract and relax and performs a motor function. It is made up of fibers of various shapes and sizes. According to the structure of the fibers and their properties, striated and smooth muscles are distinguished. Microscopic examination of striated muscle fibers shows light and dark stripes running across the fiber. The fibers are cylindrical, very thin, but quite long (up to 10 cm). The striated muscles are attached to the bones of the skeleton and provide movement of the body and its parts. Smooth muscles consist of very small fibers (about 0.1 mm long), do not have striations and are located in the walls of hollow internal organs - the stomach, intestines, blood vessels. The heart is built from muscle fibers that have a transverse striation, but in terms of properties approaching smooth muscles.

Nervous tissue consists of neurons - cells that have a more or less rounded body with a diameter of 20-80 microns, short (dendrites) and long (axons) processes. Cells with one process are called unipolar, with two - bipolar and with several - multipolar (Fig. 35). Some of the axons are covered myelin sheath, containing myelin- fat-like white matter. Accumulations of such fibers form the white matter of the nervous system, accumulations of neuron bodies and short processes form gray matter. It is located in the central - the brain and spinal cord - and the peripheral nervous system - in the spinal nodes. In addition to the latter, the peripheral nervous system includes nerves, most of the fibers of which have a myelin sheath. The myelin sheath is covered by a thin Schwann sheath. This shell consists of cells of a kind of nervous tissue - glia in which all nerve cells are immersed. Glia plays an auxiliary role - it performs supporting, trophic and protective functions. Neurons are interconnected with the help of processes; junctions are called synapses.

The main properties of the nervous system are excitability and conductivity. Excitation is a process that occurs in the nervous system in response to irritation, and the ability of the nervous tissue to excite is called excitability. The ability to conduct excitation is called conductivity. Excitation propagates along nerve fibers at a speed of up to 120 m/s. The nervous system regulates all processes in the body, and also ensures the appropriate response of the body to the action of the external environment. These functions of the nervous system are performed reflexively. Reflex - the body's response to irritation, which occurs with the participation of the central nervous system. Reflexes are carried out due to the spread of the excitation process along the reflex arc. Reflex activity is, as a rule, the result of the interaction of two processes - excitation and inhibition. Inhibition in the central nervous system was discovered by the outstanding Russian physiologist I. M. Sechenov in 1863. Inhibition can reduce or completely stop the reflex response to irritation. For example, we withdraw our hand when we prick ourselves with a needle. But we do not withdraw our finger if they pierce it to take blood for analysis. In this case, we volitionally inhibit the reflex response to pain stimulation.

Excitation and inhibition are two opposite processes, the interaction of which ensures the coordinated activity of the nervous system and the coordinated work of the organs of our body. The nervous system through the processes of excitation and inhibition regulates the work of muscles and internal organs. In addition to the nervous system, there is also humoral regulation in the body, which is carried out by hormones and other physiologically active substances that are carried by the blood.

- Source-

Bogdanova, T.L. Handbook of biology / T.L. Bogdanova [and d.b.]. - K .: Naukova Dumka, 1985. - 585 p.

The structure and biological role of the tissues of the human body:

General instructions: Textile- a collection of cells that have a similar origin, structure and function.

Each tissue is characterized by development in ontogeny from a certain embryonic germ and its typical relationships with other tissues and position in the body (N.A. Shevchenko)

tissue fluid- an integral part of the internal environment of the body. It is a liquid with nutrients dissolved in it, end products of metabolism, oxygen and carbon dioxide. It is located in the spaces between the cells of tissues and organs in vertebrates. It acts as an intermediary between the circulatory system and the cells of the body. From the tissue fluid, carbon dioxide enters the circulatory system, and water and end products of metabolism are absorbed into the lymphatic capillaries. Its volume is 26.5% of body weight.

epithelial tissue:

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.

The epithelium separates the organism from the external environment, but at the same time serves as an intermediary in the interaction of the organism with the 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 (external and internal secretion glands), absorption (intestinal epithelium), gas exchange (lung epithelium).

The main feature of the epithelium is that it consists of a continuous layer of densely packed 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 clusters 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 elements of connective tissue, such an epithelium is called atypical.

Epithelial cells located in a layer can lie in many layers (stratified epithelium) or in one layer (single layer epithelium). According to the height of the cells, the epithelium is divided into flat, cubic, prismatic, cylindrical.

Connective tissue:

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

Generally, connective tissueconstitutes what is called the internal environment of the organism. It is very diverse and is represented by various types - from dense and loose forms to blood and lymph, the cells of which are in the liquid. The fundamental differences between the types of connective tissue are determined by the ratio of cellular components and the nature of the intercellular substance.

In dense fibrous connective tissue (tendons of muscles, ligaments of joints), fibrous structures predominate, it experiences significant mechanical loads.

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

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

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

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

nervous tissue:

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

Neuron- the main structural and functional unit of the nervous tissue. Its main feature is the ability to generate nerve impulses and transmit excitation to other neurons or muscle and glandular cells of the working organs. Neurons may 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 processes of two types: 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.

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. The motor fibers that go as part of the nerves transmit signals to the muscles and glands, the sensory fibers transmit information about the state of the organs to the central nervous system.

Muscle

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

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

Muscle has excitability and the ability to actively contract under the influence of the nervous system and certain substances. Microscopic differences make it possible to distinguish two types of this fabric – smooth(unstreaked) 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 that have merged, in addition to their nuclei, into one structure. It forms skeletal muscles. We can shorten them as we wish.

A variety of striated muscle tissue is the heart 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 a transverse striation. However, unlike skeletal muscle, there are special areas where the muscle fibers meet. Due to this structure, the contraction of one fiber is quickly transmitted to neighboring ones. This ensures the simultaneous contraction of large sections of the heart muscle.

Fabric types

Nervous tissue consists of nerve cells with their processes and the endings of these processes. It also includes formations that have a supporting and trophic value for the nervous tissue itself and are called neuroglia. /macro- and microglia/.

Each nerve cell contains a cytoplasm and a round nucleus.

processes of the cell, since, corresponding to each process, the body of the neuron forms a protrusion.

The nature of the origin of the processes makes it possible to differentiate neurons to unipolar(with one process, T-shapedly divided into two branches), bipolar(with two outgrowth

Rice. 9. The structure of the motor

neuron:

Pericaryon; 2 - axon and nerve fiber; 3 - nerve endings in the muscle; 4 - dendrites; 5 - pulpy shell; 6 - interceptions of Ranvier. The scheme compares light and electron microscopy (according to G.F. Ivanov and Kovalsky, modified)

or slightly oval. Mitochondria and the Golgi complex are well expressed in the cytoplasm. There are deposits of tigroid, which arose on the basis of modifications of the endoplasmic reticulum. Under an electron microscope, neurofilaments are determined - threads about 10 nm thick.

A nerve cell with its processes is called neuron(Fig. 9). It is a structural unit of the nervous tissue. Nerve cells, the processes of which go to organs (for example, muscles) and not

kami) and multipolar(multi-processed).

Some processes of nerve cells - short, protoplasmic, tree-like branching - dendrites; other-long neurites, or axons. The length of the processes of nerve cells can be very large (more than 1 m in some places). Along the neurites, irritations go from the cell body, while along the dendrites - to the cell body.

The processes continue in the composition of nerve fibers in the form axial cylinders, usually covered with glial membranes of a simpler or

Extract from the work program on the topic “Cage. Fabrics»

Lecture topic: "Cage. Tissue"

Cell is the smallest structural one that has all the features of a living thing.

Living characterizes a number of properties:

Ability to self-reproduce;

Variability;

Metabolism;

Irritability;

Adaptation.

The combination of these properties is first detected at the cell level.

Cell is an ordered structural system of biopolymers limited by an active membrane. It is a microscopic formation, different in size and shape.

Cells were discovered and described over 300 years ago. Robert Hooke observed plant cells with magnifying lenses. Cytology (the science of the cell) received its greatest development after T. Schwann (1838) formulated the cell theory, combining all the existing research results. Currently, the cell theory is based on the main provisions:

cell is the smallest unit of life;

cells of different organisms are similar in structure and function (homologous);

cell reproduction occurs by dividing the original cell.

cells are part of a multicellular organism, where they are combined into tissues and organs and are connected by intercellular, humoral and nervous forms of regulation.

According to the second principle of the theory, cells of various organisms, despite their diversity, have common principles of structure. Each cell consists of a plasma membrane (membrane), cytoplasm, and most cells are nuclei.

Consider the characteristics of the components of the cell.

plasmalemma is a membrane structure (a thin layer consisting of a double layer of lipids connected to proteins) and performs barrier-transport and receptor functions. It separates the cytoplasm of the cell from the external environment. The transport function of the plasmalemma is carried out by various mechanisms. Exist passive transfer molecules by diffusion (ions), osmosis (water molecules), active transfer - with the expenditure of ATP energy and with the help of enzymes - permease (transfer of AA, sodium, sugars). The transfer of larger molecules is called endocytosis. Its main varieties are phagocytosis – transport of solid particles and pinocytosis – transport in liquid media. The particles captured by the cell are immersed, surrounded by a section of the cytoplasm (phagosomes and pinosomes) and merge with lysosomes, which subject them to cleavage. The receptor function of the plasmolemma consists in the “recognition” by the cell of various chemical (hormones, proteins) and physical (light, sound) factors with the help of receptors located in the plasmolemma (polysaccharides, glycoproteins).

The plasmalemma can form a poison of special formations - microvilli, brush border, cilia and flagella, as well as a variety of intercellular contacts.

Microvilli - outgrowths of the cytoplasm, limited by the plasma membrane (many in the epithelial cells of the intestine, kidneys); increase the cell surface area.

Cilia and flagella - outgrowths of the cytoplasm, the origin of which is associated with centrioles, serve as an apparatus for cell movement.

Intercellular contacts - plasma membrane structures that provide connection and interaction of cells (transfer of ions, molecules).

Cytoplasm consists of hyaloplasm and organelles and inclusions located in it.

Hyaloplasm - the internal environment of the cell, structureless, translucent, semi-liquid formation, capable of changing its f.-x. condition. It consists of proteins and enzymes, transp. RNA, amino acids, polysaccharides, ATP, various ions. The main function is to ensure the chemical interaction of the structures located in it.

Organelles divided into membrane and non-membrane.

Membrane includes: endoplasmic reticulum

mitochondria

app. golgi

lysosomes

Non-membrane include: ribosomes

polysomes

microtubules

centrioles

EPS - a system of tubules, cisterns, vacuoles bounded by a single membrane. There are granular and agranular EPS. For granular, the presence of granules - ribosomes is characteristic.

The main function of EPS is in the synthesis of substances and their transportation to various parts of the cell and to the external environment. In the agranular ER, lipids and carbohydrates are synthesized, and in the granular ER, proteins are synthesized.

Mitochondria - structures of a rounded or rod-shaped form, formed by two membranes (outer and inner, which forms outgrowths inward - cristae, immersed in a matrix in which ribosomes, granules are located). ATP is formed on the cristae. The main function of mitochondria is to provide cellular respiration and ATP processing, the energy of which is used for cell movement, muscle contraction, the processes of synthesis and secretion of substances, and the passage of substances through membranes.

Golgi complex - multiple and single dictyosomes (membrane structures consisting of tanks with extensions, small transport vesicles, large secretory vesicles and granules). The Golgi complex is involved in the secretion process (proteins synthesized in the EPS ribosomes enter the Golgi complex), synthesizes polysaccharides, and forms lysosomes.

Lysosomes - these are small vesicles 0.2 - 0.4 µm in size, limited by a single membrane and containing more than 40 various enzymes that break down proteins, nucleic acids, lipids, carbohydrates. The function of lysosomes is to digest various substances coming from outside and destroy aging or defective structures in the cell itself.

Non-membrane organelles:

Ribosomes - protein synthesis organelle is formed in the nucleolus. They consist of two subunits - small and large, each of which is built from a twisted strand of ribonucleoprotein, where proteins and ribosomal RNA are equally represented. Young cells are characterized by the presence of free ribosomes that provide protein synthesis for the cell itself (growth). In differentiated cells, the number of ribosomes and polysomes associated with EPS and providing the synthesis of proteins "for export" (cell secret) increases.

Microtubules - hollow cylinders with a diameter of 24 nm, consisting of tubulin protein. They can constantly be formed in the hyaloplasm, participating in the formation of the cell cytoskeleton. They are part of the centroles, cilia, flagella, spindle division.

Centrioles - are paired, each consisting of microtubules. They are located perpendicular to each other and are surrounded by radially outgoing microtubules (centrosphere)

Microfilaments and microfibrils performs support-frame and contractile functions in the cell, which ensures the movement of the cell and the movement of organelles and inclusions in the hyaloplasm.

Core performs the most important functions in the cell - storage and transmission of genetic information and ensuring protein synthesis (formation of all types of RNA - inf., transsp., ribosomes, synthesis of ribosomal proteins). The structure and functions of a protein change during the cell cycle - the time of existence from division to division or from division to death.

The nucleus of an interphase cell (non-dividing) consists of the nuclear membrane, chromatin, nucleolus and karyoplasm (nucleoplasm)

nuclear envelope consists of two membranes - outer and inner. In the shell there are pores (complexes) that ensure the passage of macromolecules from the nucleus to the cytoplasm. One of the functions of the nuclear envelope is the fixation of chromosomes and ensuring their spatial position.

Chromosomes are constantly present in the nucleus and are clearly visible only during mitosis. In the interphase nucleus, the chromosomes are dispersed and not visible. Consists of DNA, protein, RNA.

nucleolus - a rounded body in which ribosomes are formed. The number of nucleoli in different cells varies. An increase in the number and size of nucleoli indicates a high intensity of RNA and protein synthesis.

Cell life cycle

The cell, being part of an integral multicellular organism, performs the functions characteristic of a living organism. Reproduction is one of them.

The main form of cell reproduction is mitosis (indirect division). Mitosis consists of 4 main phases: prophase, metaphase, anaphase, telophase.

- prophase chromosomes condense, they become visible, each chromosome consists of two sister chromosomes - chromatids, the nucleoli decrease and disappear, the nuclear membrane collapses, the number of ribosomes, gran decreases. ER breaks up into small vacuoles, the centrioles diverge, and the division spindle begins to form (microtubules extending from the centrioles);

- metaphase the spindle of division is completed and the chromosomes are located in the equatorial plane of the cell;

- anaphase halves of chromosomes lose their connection in the region. the centromere and diverge towards the poles of the cell, a diploid set of chromosomes departs to the pole (46 in humans);

- telophase there is a restoration of the structures of the interphase nucleus - despiralization of chromosomes, reconstruction of the shell of the nucleus, the appearance of nucleoli, division of the cell body into two parts.

The duration of mitosis and its individual phases varies in different cells from 30 minutes to 30 minutes. Up to 3 hours or more (interphase 10-30 hours, prophase 30-60 hours, metaphase 2-10 minutes, anaphase 2-3 minutes, telophase 20-30 minutes). The number of mitoses in tissues and organs is an indicator of the intensity of their growth and regeneration (physiological and reparative) in normal and pathological conditions.

A variation of mitosis is meiosis - the division of maturing germ cells, which leads to a 2-fold decrease in the number of chromosomes, i.e. the formation of the haploid number of chromosomes (23 in humans). Meiosis consists of two successive divisions with a short interphase - reduction (the number of chromosomes is reduced) and evation (mitosis).

In addition to the ability to reproduce, the cell has a number of properties that characterize the living:

Metabolism from the external environment (blood, lymph, tissue fluid) substances enter through the semipermeable membrane, which are used to build the cell, oxidative processes, and the waste products of the cell are excreted through the membrane.

Permeability cells depends on various factors, incl. from

salt concentration The intake of substances is possible by phagocytosis

and pinocytosis.

Secretion substances secreted by cells (hormones,

enzymes, biologically active substances).

Irritability the ability to respond with specific responses to

exposure to an external stimulus. Muscular, nervous, glandular cells have the highest degree of irritability -

excitability. As a particular type of irritability is the ability of cells to move - leukocytes, macrophages, fibroblasts, spermatozoa.

Fabrics. Species, their morphological and functional characteristics.

There are 4 types of tissues in the human body:

epithelial;

connecting;

muscular;

Epithelium covers the surface of the body, mucous membranes and serous membranes of internal organs and forms most of the glands.

Integumentary epithelium performs:

barrier function

exchange function

protective function

glandular epithelium performs a secretory function.

General characteristics of the integumentary epithelium.

Variety of morphological forms;

There is no intercellular substance;

Cells are arranged in the form of a layer;

They are located on the basement membrane;

There are no blood vessels;

High regeneration.

The structure and functions of the integumentary epithelium.

Morphological classification of the epithelium:

Single layer epithelium

Cubic

Prismatic

multi-row

Stratified epithelium

non-keratinizing

keratinizing

Transition

glandular epithelium.

Glands (gianduiae) perform a secretory function and are derivatives of the glandular epithelium.

Many glands are independent organs (pancreas, thyroid gland), other glands are part of an organ (gastric glands).

All glands are divided into:

Endocrine, producing their secret (hormones) into the blood.

Exocrine produce a secret into the external environment (on the skin and in the cavity of the organs).

By structure, the exocrine glands are divided into simple and complex with branching excretory ducts. According to the chemical composition of the secret, they are divided into protein (serous), mucous, protein-mucous.

Support-trophic tissues.

This group includes blood and lymph, as well as connective tissue. All of them have a similar structure: they contain a well-developed intercellular substance. All tissues of this group perform a trophic function (blood, lymph) and a supporting function (cartilaginous, bone).

Blood, lymph, loose connective tissue make up the internal environment of the body.

Connective tissue.

This group includes:

connective tissue proper(loose and dense)

with special properties(reticular, fatty, mucous, pigmented)

skeletal connective tissue(cartilaginous, bone tissue)

Connective tissue is characterized by a variety of cells and a well-developed intercellular substance consisting of fibers and a basic amorphous substance. The classification is based on the ratio of cells and intercellular substance, as well as the degree of orderliness of the arrangement of fibers.

tissue cells : fibroblasts, macrophages, plasmocytes, mast cells, adipocytes, pigmentocytes, adventitial cells, blood leukocytes.

intercellular substance : consists of collagen, reticular, elastic fibers and ground substance.

Loose fibrous connective tissue accompanies the blood and lymphatic vessels, forms the stroma of many organs.

Dense fibrous connective tissue contains a large number of densely arranged fibers and a small amount of cellular elements. This tissue underlies tendons, ligaments, fibrous membranes.

cartilage tissue consists of cells (chondrocytes) and a large amount of intercellular substance.

There are three types of cartilage:

hyaline (embryo skeleton, costosternal junction, laryngeal cartilages, articular surfaces)

elastic (at the base of the auricle)

fibrous (intervertebral discs, semi-movable joints)

Bone a specialized type of connective tissue with a high mineralization of the intercellular substance containing about 70% inorganic substances (calcium phosphates).

There are two types of bone tissue - reticulofibrous and lamellar.

Bone cells include: osteocytes, osteoblasts, osteoclasts.

lamellar bone tissue the most common bone tissue in the adult body. It consists of bone plates formed by bone cells and a mineralized ground substance with collagen fibers. In neighboring plates, the fibers have a different direction, which ensures greater strength of the bone tissue. The compact and spongy substance of the bones of the skeleton is built from this tissue.

Muscle.

Provides movement in space of the body as a whole and its parts. Muscle tissue has the ability to contract under the action of nerve impulses, which is accompanied by a change in membrane potentials. The contraction occurs due to the content of myofibrils in muscle cells, due to the interaction of actin and myosin proteins with the participation of Ca ions.

All muscle tissues are divided into two subgroups:

smooth muscle tissues (filaments of actin and myosin of myofibrils do not have transverse striation) are present on the walls of internal organs and have greater extensibility, less excitability than skeletal;

striated tissues (actin and myosin myofibrils create transverse striation) form cardiac muscle tissue and skeletal muscle tissue.

nervous tissue.

Nervous tissue regulates the activity of tissues and organs, their relationship and connection with the environment. Nervous tissue consists of neurons (nerve cells) and neuroglia, which carry out supporting, trophic, delimiting and protective functions.

Neurons conduct nerve impulses from the place of origin to the working organ. Each cell has branches axon(conducts an impulse from the cell body and ends on a neighboring neuron, muscle, gland) and dendrite(carries an impulse to the body, there may be several of them and they branch). According to the number of processes, neurons are divided into:

Unipolar (1 branch)

Bipolar (2 processes)

Multipolar (3 or more processes)

Bipolar cells also include pseudo-unipolar cells (the axon and dendrite of these cells begin with a common outgrowth). The processes of nerve cells, usually covered with sheaths, are called nerve fibres. All nerve fibers end in end apparatuses, which are called nerve endings, they are divided into three groups

Effector (motor and secretory)

Receptor (sensitive)

Terminal (interneuronal synapses).

epithelial tissue

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.

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 the 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 (external and internal secretion glands), absorption (intestinal epithelium), gas exchange (lung epithelium).

The main feature of the epithelium is that it consists of a continuous layer of densely packed 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 clusters 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 elements of connective tissue, such an epithelium is called atypical.

Epithelial cells located in a layer can lie in many layers (stratified epithelium) or in one layer (single layer epithelium). According to the height of the cells, the epithelium is divided into flat, cubic, prismatic, cylindrical.

Connective tissue

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

In contrast to epithelial tissue, in all types of connective tissue (except for adipose tissue), the intercellular substance predominates over cells in volume, i.e. 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 is represented by various types - from dense and loose forms to blood and lymph, the cells of which are in the liquid. The fundamental differences between the types of connective tissue are determined by the ratio of cellular components and the nature of the intercellular substance.

AT dense fibrous connective tissue (muscle tendons, ligaments of joints) is dominated by fibrous structures, it experiences significant mechanical stress.

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

Bone

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

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

cartilage tissue

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

There are three types of cartilage tissue: hyaline, which is part of the cartilage of the trachea, bronchi, ends of the ribs, 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, shaping 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 present mainly in a newborn child). 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

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

The classification of muscle tissues is carried out on the basis of the structure of the tissue (histologically): by the presence or absence of transverse striation, 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 make it possible to distinguish two types of this tissue - smooth (non-striated) 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, merged, in addition to their nuclei, into one structure. It forms skeletal muscles. We can shorten them as we wish.

A variety of striated muscle tissue is the heart 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 a transverse striation. However, unlike skeletal muscle, there are special areas where the muscle fibers meet. Due to this structure, the contraction of one fiber is quickly transmitted to neighboring ones.

This ensures the simultaneous contraction of large sections of the heart muscle.

nervous tissue

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

The neuron is the basic structural and functional unit of the nervous tissue. Its main feature is the ability to generate nerve impulses and transmit excitation to other neurons or muscle and glandular cells of the working organs. Neurons may 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 processes of two types: 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. The motor fibers that go as part of the nerves transmit signals to the muscles and glands, the sensory fibers transmit information about the state of the organs to the central nervous system.

human body tissues