Features of the structure of human muscle tissue briefly. Muscle tissues, their structure and significance. Smooth structural features

Muscle tissues are tissues that differ both in their structure and origin. However, what they have in common is that they are capable of pronounced contractions. Muscle tissue is based on elongated cells, which receive impulses from the central nervous system, and the reaction to this is their reduction. Thanks to muscle tissue, the body and internal organs and systems (heart, lungs, intestines, etc.) of which it consists are able to move, changing their position in space. Cells of other tissues also have the ability to change shape and contract. However, in muscle tissue this function is basic.

Features of the structure of muscle tissue

The most important features of the main components of muscle tissue are their elongated shape, the presence of elongated and appropriately arranged myofilaments and myofibrils (which ensure muscle contractility), as well as the presence of mitochondria, lipids, glycogen and myoglobin. Inside the contractile organelles, myosin and actin interact (with the simultaneous participation of Ca ions in the reaction), resulting in muscle contraction. The source of energy for contractile processes is mitochondria, lipids and glycogen. Oxygen is bound and stored through a protein called myoglobin, which occurs when muscle contraction and simultaneous compression of blood vessels.

Classification of muscle fibers

Taking into account the nature of the contraction, tonic and phasic muscle fibers are distinguished. In particular, the first type of fibers is designed to provide tone (or static muscle tension), which is especially important for maintaining a particular body position relative to spatial coordinates. Phasic fibers are designed to ensure the ability to perform rapid contractions, but are not able to maintain the shortening of the muscle fiber at a certain level for a long time. Taking into account the biochemical characteristics, as well as color, white and red fibers are distinguished. The color of muscle tissue is determined by the concentration of myoglobin in it (the so-called degree of vascularization). One of the features of red muscle fiber is the presence in its composition of chains of mitochondria surrounded by myofibrils. Slightly lower number of mitochondria in white muscle fiber. They are usually evenly distributed in the sarcoplasm.

Depending on the characteristics of oxidative metabolism, muscle fibers can be glycolytic, oxidative and intermediate. Fibers are distinguished based on information about the degree of activity of the SDH enzyme, which is a marker for the so-called Krebs cycle and mitochondria. The intensity of energy metabolism can be determined by the degree of activity of this enzyme. Glycolytic fibers(or A-type fibers) are characterized by low activity of the above enzyme, and oxidative (or C-type fibers), on the contrary, have increased succinate dehydrogenase activity. B-type fibers are fibers that occupy intermediate position. The process of transition from type A fibers to type C fibers is a transition to oxygen-dependent metabolism from anaerobic glycolysis. An example would be a situation where sports training in combination with nutrition are aimed at the rapid development and formation of glycolytic muscle fibers, which contain glycogen in large quantities, and energy production is carried out anaerobically. This type of training is usually reserved for bodybuilders or sprinters. At the same time, for those sports that require endurance, it is necessary to develop oxidative muscle fibers, which have more blood vessels and mitochondria that provide aerobic glycolysis.

Muscle tissue can be of several types, if we consider their sources of development. That is, depending on the type of embryonic rudiments, they can be mesenchymal (desmal rudiment), epidermal (prechordal plate or cutaneous ectoderm), coelomic (myoepicardial plate of the so-called visceral section of the splanchnotome), neural (neural tube) or somatic/myotome.

Types of muscle tissue

There are smooth and striated (skeletal and cardiac) muscle tissue. Included smooth fabric predominantly myocytes (mononuclear cells) are present, having the shape of a spindle. The cytoplasm of such myocytes is homogeneous and does not have transverse stripes. Smooth muscle tissue has special properties. First of all, it relaxes and contracts extremely slowly. In addition, she is uncontrollable by humans and usually all her reactions are involuntary. The walls of the vessels of the lymphatic and circulatory systems, urinary tract, stomach and intestines are composed of smooth muscle tissue. Striated skeletal tissue contains very long multinucleated (one hundred or more nuclei) myocytes. If you examine the cytoplasm under a microscope, it will look like alternating light and dark stripes. Striated skeletal muscle tissue is characterized by a fairly high rate of contraction and relaxation. The activity of this type of tissue can be controlled by a person, and it itself is present in the skeletal muscles, in the upper esophagus, in the tongue, as well as in the muscles responsible for the movements of the eyeball.

The composition of striated cardiac muscle tissue includes cardiomyocytes with one or two nuclei, as well as cytoplasm, striated along the periphery of the cytolemma with transverse stripes. Cardiomyocytes are quite highly branched and form intercalated discs with cytoplasm integrated into them at the junctions. Cells also contact through cytolemmas, resulting in the formation of anastomoses. Striated cardiac muscle tissue is found in the myocardium. The most important feature of this tissue is its ability, in the case of cellular excitation, to rhythmic contractions and subsequent relaxations. Striated cardiac muscle tissue belongs to involuntary tissues (so-called atypical cardiomycytes). There is also a third type of cardiomycyte - these are secretory cardiomycytes, which lack fibrils.

The most important functions of muscle tissue

The main functional features of muscle tissue include its abilities such as conductivity, excitability, and contractility. Muscle tissue provides the functions of heat exchange, movement and protection. In addition to the above, one more functional feature of muscle tissue can be identified - facial (or, as it is also called, social). In particular, a person’s facial muscles control his facial expressions, thereby transmitting a certain information message to other people around him.

Blood supply to muscle tissue

Blood enters muscle tissue due to its work. This provides the muscle with the necessary amount of oxygen. If a muscle is at rest, then it, as a rule, requires much less oxygen (usually this figure is five hundred times less than the figure reflecting the oxygen requirement of an actively working muscle). Thus, during active muscle contractions, the volume of blood entering the muscle increases many times over. This is approximately 300 to 500 capillaries per cubic millimeter, or approximately twenty times more than the amount of blood required by a muscle at rest.

Muscle tissue: types, structural features, location in the body

Muscle tissue (textus musculares)– these are specialized tissues that provide movement (movement in space) of the body as a whole, as well as its parts and internal organs. Contraction of muscle cells or fibers is carried out with the help of myofilaments and special organelles - myofibrils and is the result of the interaction of contractile protein molecules.

According to the morphological classification, muscle tissue is divided into two groups:

I - striated (striated) muscle tissue - constantly contains complexes of actin and myosin myofilaments - myofibrils and has transverse striations;

II - smooth (unstriated) muscle tissue - consists of cells that constantly contain only actin myofilaments and do not have transverse striations.

Striated muscle tissue

Striated muscle tissue is divided into skeletal and cardiac. Both of these varieties develop from mesoderm.

Striated skeletal muscle tissue. This tissue forms skeletal muscles, muscles of the mouth, pharynx, partly the esophagus, muscles of the perineum, etc. It has its own characteristics in different sections. Has a high contraction speed and fatigue. This type of contractile activity is called tetanic. Striated skeletal muscle tissue cuts arbitrarily in response to impulses coming from the cerebral cortex. However, some muscles (intercostal muscles, diaphragm, etc.) not only contract voluntarily, but also contract without the participation of consciousness under the influence of impulses from the respiratory center, and the muscles of the pharynx and esophagus contract involuntarily.

The structural unit is the striated muscle fiber- simplast, cylindrical in shape with rounded or pointed ends, with which the fibers are adjacent to each other or woven into the connective tissue of tendons and fascia.

Their contractile apparatus is striated myofibrils., which form a bundle of fibers. These are protein threads located along the fiber. Their length coincides with the length of the muscle fiber. Myofibrils consist of dark and light areas - disks. Since the dark and light discs of all myofibrils of one muscle fiber are located at the same level, transverse striations are formed; therefore, the muscle fiber is called striated. Dark discs in polarized light are birefringent and are called anisotropic, or A-discs; light discs are not birefringent and are called isotropic, or I-discs.

The different light refractive ability of the disks is due to their different structure. Light (I) wheels homogeneous in composition: formed only by parallel thin threads – actin myofilaments consisting predominantly of protein actin, and troponin And tropomyosin. Dark (A) wheels heterogeneous: formed as thick myosin myofilaments consisting of protein myosin, and partially penetrating between them with thin actin myofilaments.

In the middle of each I-disc there is a dark line called Z-line, or telophragm. One end of the actin filaments is attached to it. The area of myofibril between two telophragms is called sarcomere. Sarcomere is a structural and functional unit of myofibril. In the center of the A-disk you can identify a light stripe, or zone H, containing only thick threads. In the middle there is a thin dark line M, or mesophragm. Thus, each sarcomere contains one A-band and two halves of an I-band.

Striated cardiac muscle tissue. Forms the myocardium of the heart. Contains, like the skeletal one, myofibrils, consisting of dark and light disks. Consists of cells - cardiomyocytes, interconnected by insertion disks. In this case, chains of cardiomyocytes are formed - functional muscle fibers, which anastomose with each other (transition into one another), forming a network. This system of connections ensures contraction of the myocardium as a whole. Reduction heart muscle involuntary, is regulated by the autonomic nervous system.

Among cardiomyocytes there are:

· contractile (working) cardiomyocytes - contain fewer myofibrils than skeletal muscle fibers, but a lot of mitochondria, therefore they contract with less force, but do not get tired for a long time; with the help of intercalary disks, mechanical and electrical communication of cardiomyocytes is carried out;

· atypical (conductive) cardiomyocytes – form the conduction system of the heart for the formation and conduction of impulses to contractile cardiomyocytes;

secretory cardiomyocytes – located in the atria, capable of producing a hormone-like peptide – sodium uretic factor, lowering blood pressure.

Smooth muscle tissue

It develops from mesenchyme and is located in the wall of tubular organs (intestine, ureter, bladder, blood vessels), as well as the iris and ciliary body of the eye and the muscles that raise hair in the skin.

Smooth muscle tissue has cellular structure (smooth myocyte) and has contractile apparatus in the form of smooth myofibrils. It contracts slowly and is able to remain in a state of contraction for a long time, consuming a relatively small amount of energy and without getting tired. This type of contractile activity is called tonic. Autonomic nerves approach smooth muscle tissue, and unlike skeletal muscle tissue, it is not subject to consciousness, although it is under the control of the cerebral cortex.

The smooth muscle cell has a spindle-shaped shape and pointed ends. It has a nucleus, cytoplasm (sarcoplasm), organelles and a membrane (sarcolemma). Contractile myofibrils are located along the cell periphery along its axis. These cells are closely adjacent to each other. The supporting apparatus in smooth muscle tissue is thin collagen and elastic fibers located around the cells and connecting them to each other.

Related information.

Tissue is a collection of cells of similar structure that are united by common functions. Almost all consist of different types of fabrics.

Classification

In animals and humans, the following types of tissues are present in the body:

epithelial;
nervous;
connecting;
muscular.

These groups combine several varieties. Thus, connective tissue can be fatty, cartilaginous, or bone. This also includes blood and lymph. Epithelial tissue is multilayered and single-layered; depending on the structure of the cells, one can also distinguish flat, cubic, columnar epithelium, etc. Nervous tissue is of only one type. And we will talk about it in more detail in this article.

Types of muscle tissue

In the body of all animals there are three types of it:

striated muscles;
cardiac muscle tissue.

The functions of smooth muscle tissue differ from those of striated and cardiac tissue, therefore its structure is different. Let's take a closer look at the structure of each type of muscle.

General characteristics of muscle tissue

Since all three species belong to the same type, they have a lot in common.

Muscle tissue cells are called myocytes, or fibers. Depending on the type of fabric, they may have a different structure.

Another common feature of all types of muscles is that they are able to contract, but in different types this process occurs individually.

Features of myocytes

Smooth muscle cells, like striated and cardiac tissue, have an elongated shape. In addition, they have special organelles called myofibrils, or myofilaments. They contain (actin, myosin). They are necessary to ensure muscle movement. A prerequisite for muscle functioning, in addition to the presence of contractile proteins, is also the presence of calcium ions in the cells. Therefore, insufficient or excessive consumption of foods high in this element can lead to incorrect muscle function - both smooth and striated.

In addition, another specific protein is present in the cells - myoglobin. It is necessary to bind with oxygen and store it.

As for organelles, in addition to the presence of myofibrils, what is special for muscle tissue is the content of a large number of mitochondria in the cell - double-membrane organelles responsible for cellular respiration. And this is not surprising, since muscle fiber needs a large amount of energy to contract, which is produced during respiration by mitochondria.

Some myocytes also have more than one nucleus. This is typical for striated muscles, the cells of which can contain about twenty nuclei, and sometimes this figure reaches one hundred. This is due to the fact that the striated muscle fiber is formed from several cells, subsequently combined into one.

The structure of striated muscles

This type of tissue is also called skeletal muscle. The fibers of this type of muscle are long, collected in bundles. Their cells can reach several centimeters in length (up to 10-12). They contain many nuclei, mitochondria and myofibrils. The basic structural unit of each myofibril of striated tissue is the sarcomere. It consists of contractile protein.

The main feature of this muscle is that it can be controlled consciously, unlike smooth and cardiac muscles.

The fibers of this tissue are attached to the bones using tendons. That is why such muscles are called skeletal.

Structure of smooth muscle tissue

Smooth muscles line some internal organs, such as the intestines, uterus, bladder, and blood vessels. In addition, sphincters and ligaments are formed from them.

Smooth muscle fiber is not as long as striated muscle fiber. But its thickness is greater than in the case of skeletal muscles. Smooth muscle cells have a spindle-like shape, rather than a thread-like shape like striated myocytes.

The structures that mediate smooth muscle contraction are called protofibrils. Unlike myofibrils, they have a simpler structure. But the material from which they are built is the same contractile proteins actin and myosin.

There are also fewer mitochondria in smooth muscle myocytes than in striated and cardiac cells. In addition, they contain only one core.

Features of the heart muscle

Some researchers define it as a subtype of striated muscle tissue. Their fibers are indeed similar in many ways. Heart cells - cardiomyocytes - also contain several nuclei, myofibrils and a large number of mitochondria. This tissue, likewise, is capable of contracting much faster and stronger than smooth muscle.

However, the main feature that distinguishes cardiac muscle from striated muscle is that it cannot be controlled consciously. Its contraction occurs only automatically, as in the case of smooth muscles.

In addition to typical cells, the cardiac tissue also contains secretory cardiomyocytes. They do not contain myofibrils and do not contract. These cells are responsible for producing the hormone atriopeptin, which is necessary for regulating blood pressure and controlling blood volume.

Functions of striated muscles

Their main task is to move the body in space. It is also the movement of body parts relative to each other.

Other functions of the striated muscles include maintaining posture and storing water and salts. In addition, they play a protective role, especially for muscles abdominals, preventing mechanical damage to internal organs.

The functions of striated muscles can also include temperature regulation, since during active muscle contraction a significant amount of heat is released. This is why, when freezing, the muscles begin to tremble involuntarily.

Functions of smooth muscle tissue

This type of muscle performs an evacuation function. It lies in the fact that the smooth muscles of the intestines push feces to the place where they are excreted from the body. This role also manifests itself during childbirth, when the smooth muscles of the uterus push the fetus out of the organ.

The functions of smooth muscle tissue are not limited to this. Their sphincteric role is also important. Special circular muscles are formed from this type of tissue, which can close and open. Sphincters are present in the urinary tract, in the intestines, between the stomach and esophagus, in the gallbladder, and in the pupil.

Another important role played by smooth muscles is the formation of the ligamentous apparatus. It is necessary to maintain the correct position of internal organs. When the tone of these muscles decreases, prolapse of some organs may occur.

This is where the functions of smooth muscle tissue end.

Purpose of the heart muscle

Here, in principle, there is nothing special to talk about. The main and only function of this tissue is to ensure blood circulation in the body.

Conclusion: differences between the three types of muscle tissue

To clarify this issue, we present a table:

Smooth muscle	Striated muscles	Cardiac muscle tissue
Shrinks automatically	Can be controlled consciously	Shrinks automatically
Cells are elongated, spindle-shaped	Cells are long, filamentous	Elongated cells
Fibers are not bundled	Fibers are combined into bundles	Fibers are combined into bundles
One nucleus per cell	Several nuclei in a cell	Several nuclei in a cell
Relatively small number of mitochondria	Large number of mitochondria
No myofibrils	Myofibrils present	There are myofibrils
Cells are capable of dividing	Fibers cannot divide	Cells cannot divide
Contracts slowly, weakly, rhythmically	Contracts quickly and strongly	Contracts quickly, strongly, rhythmically
Line internal organs (intestines, uterus, bladder), form sphincters	Attached to the skeleton	Shape the heart

That's all the main characteristics of striated, smooth and cardiac muscle tissue. Now you are familiar with their functions, structure and main differences and similarities.

Muscle tissue (lat. textus muscularis - “muscle tissue”) - tissues that are different in structure and origin, but similar in their ability to undergo pronounced contractions. They consist of elongated cells that receive irritation from the nervous system and respond to it with contraction. They ensure movement in space of the body as a whole, its movement of organs within the body (heart, tongue, intestines, etc.) and consist of muscle fibers. Cells of many tissues have the ability to change shape, but in muscle tissue this ability becomes the main function.

The main morphological characteristics of muscle tissue elements: elongated shape, the presence of longitudinally located myofibrils and myofilaments - special organelles that ensure contractility, the location of mitochondria next to the contractile elements, the presence of inclusions of glycogen, lipids and myoglobin.

Special contractile organelles - myofilaments or myofibrils - provide contraction, which occurs when two main fibrillar proteins interact in them - actin and myosin - with the obligatory participation of calcium ions. Mitochondria provide energy for these processes. The reserve of energy sources is formed by glycogen and lipids. Myoglobin is a protein that ensures the binding of oxygen and the creation of its reserve at the time of muscle contraction, when the blood vessels are compressed (the oxygen supply drops sharply).

In origin and structure, muscle tissue differs significantly from each other, but they are united by the ability to contract, which ensures the motor function of organs and the body as a whole. The muscle elements are elongated and connected either with other muscle elements or with supporting structures.

Types of muscle tissue

There are smooth, striated muscle tissue and cardiac muscle tissue.

Smooth muscle tissue.

This tissue is formed from mesenchyme. The structural unit of this tissue is the smooth muscle cell. It has an elongated spindle-shaped shape and is covered with a cell membrane. These cells adhere tightly to each other, forming layers and groups separated from each other by loose, unformed connective tissue.

The cell nucleus has an elongated shape and is located in the center. Myofibrils are located in the cytoplasm; they run along the periphery of the cell along its axis. They consist of thin threads and are the contractile element of the muscle.

The cells are located in the walls of blood vessels and most internal hollow organs (stomach, intestines, uterus, bladder). The activity of smooth muscles is regulated by the autonomic nervous system. Muscle contractions are not subject to human will and therefore smooth muscle tissue is called involuntary muscles.

Striated muscle tissue.

This tissue is formed from myotomes, derivatives of the mesoderm. The structural unit of this tissue is striated muscle fiber. This cylindrical body is a symplast. It is covered with a membrane - sarcolemma, and the cytoplasm is called sarcoplasm, which contains numerous nuclei and myofibrils. Myofibrils form a bundle of continuous fibers running from one end of the fiber to the other parallel to its axis. Each myofibril consists of discs that have a different chemical composition and appear dark and light under a microscope. The homogeneous disks of all myofibrils coincide, and therefore the muscle fiber appears striated. Myofibrils are the contractile apparatus of muscle fiber.

All skeletal muscles are built from striated muscle tissue. Musculature is voluntary, because its contraction may occur under the influence of neurons in the motor zone of the cerebral cortex.

Muscle tissue of the heart.

The myocardium, the middle layer of the heart, is made up of striated muscle cells (cardiomyocytes). There are two types of cells: typical contractile cells and atypical cardiac myocytes that make up the conduction system of the heart.

Typical muscle cells perform a contractile function; they are rectangular in shape, there are 1-2 nuclei in the center, myofibrils are located along the periphery. There are intercalary discs between adjacent myocytes. With their help, myocytes are collected into muscle fibers, separated from each other by fine fibrous connective tissue. Connective fibers pass between adjacent muscle fibers, which ensure contraction of the myocardium as a whole.

The conduction system of the heart is formed by muscle fibers consisting of atypical muscle cells. They are larger than contractile ones, richer in sarcoplasm, but poorer in myofibrils, which often intersect. The nuclei are larger and are not always in the center. The fibers of the conduction system are surrounded by a dense plexus of nerve fibers.

6. Muscle tissue: functions, types

Muscle tissue. Motor processes in the human and animal body are caused by contraction of muscle tissue that has contractile structures. Muscle tissue includes unstriated (smooth) And striated (cross-striped) muscle tissue, including skeletal And cardiac.

The contractile elements are muscle fibrils - myofibrils(muscle threads). Muscle cells - myocytes. Muscle tissues have excitability and contractility.

Muscle(Sterki P., 1984).

a - longitudinal section of skeletal muscle; b - cardiac striated muscle tissue; c - unstriated (smooth) muscle tissue; 1 - sarcolemma; 2 - transverse striation; 3 - cores; 4 — insert disks; 5 - smooth muscle cells

Three types of muscle tissue:

Smooth muscle tissue- consists of spindle-shaped cells with longitudinal striations.

Features: long-term contraction; remains in a contracted state for a long time; contracts involuntarily.

Forms the walls of blood vessels and intestines.

Smooth muscle fibers.

1 - protoplasm; 2 - core

Striated musculoskeletal tissue- cylindrical cells with striations.

Features: shrink quickly; remain in a contracted state for a long time; not much energy is spent on reduction; it is not reduced arbitrarily, but according to our desire.

Forms skeletal muscles, muscles of the tongue, pharynx and parts of the esophagus.

Striated cardiac muscle tissue.

Features: similar to striated musculoskeletal, but there are intercalary discs and anastomoses; contracts arbitrarily, regardless of our consciousness; there are atypical cells that form the conducting system.

Forms the muscles of the heart.

Striated muscle fibers. Nuclei and transverse striations are visible.

The left fiber is torn; the sarcolemma is visible in the mess of the rupture

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Muscle tissue: types, structural features, location in the body

According to the morphological classification, muscle tissue is divided into two groups:

I - striated (striated) muscle tissue - constantly contains complexes of actin and myosin myofilaments - myofibrils and has transverse striations;

II - smooth (unstriated) muscle tissue - consists of cells that constantly contain only actin myofilaments and do not have transverse striations.

Striated muscle tissue

Striated muscle tissue is divided into skeletal and cardiac.

Both of these varieties develop from mesoderm.

Striated skeletal muscle tissue. This tissue forms skeletal muscles, muscles of the mouth, pharynx, partly the esophagus, muscles of the perineum, etc.

It has its own characteristics in different departments. Has a high contraction speed and fatigue. This type of contractile activity is called tetanic. Striated skeletal muscle tissue cuts arbitrarily in response to impulses coming from the cerebral cortex. However, some muscles (intercostal muscles, diaphragm, etc.) not only contract voluntarily, but also contract without the participation of consciousness under the influence of impulses from the respiratory center, and the muscles of the pharynx and esophagus contract involuntarily.

Their contractile apparatus is striated myofibrils., which form a bundle of fibers.

These are protein threads located along the fiber. Their length coincides with the length of the muscle fiber. Myofibrils consist of dark and light areas - disks. Since the dark and light discs of all myofibrils of one muscle fiber are located at the same level, transverse striations are formed; therefore, the muscle fiber is called striated. Dark discs in polarized light are birefringent and are called anisotropic, or A-discs; light discs are not birefringent and are called isotropic, or I-discs.

The different light refractive ability of the disks is due to their different structure.

Light (I) wheels homogeneous in composition: formed only by parallel thin threads – actin myofilaments consisting predominantly of protein actin, and troponin And tropomyosin. Dark (A) wheels heterogeneous: formed as thick myosin myofilaments consisting of protein myosin, and partially penetrating between them with thin actin myofilaments.

In the middle of each I-disc there is a dark line called Z-line, or telophragm.

One end of the actin filaments is attached to it. The area of myofibril between two telophragms is calledsarcomere. Sarcomere is a structural and functional unit of myofibril. In the center of the A-disk you can identify a light stripe, or zone H, containing only thick threads. In the middle there is a thin dark line M, or mesophragm. Thus, each sarcomere contains one A-band and two halves of an I-band.

Striated cardiac muscle tissue. Forms the myocardium of the heart.

Contains, like the skeletal one, myofibrils, consisting of dark and light disks. Consists of cells - cardiomyocytes, interconnected by insertion disks.

In this case, chains of cardiomyocytes are formed - functional muscle fibers, which anastomose with each other (transition into one another), forming a network. This system of connections ensures contraction of the myocardium as a whole. Reduction heart muscle involuntary, is regulated by the autonomic nervous system.

Among cardiomyocytes there are:

contractile (working) cardiomyocytes - contain fewer myofibrils than skeletal muscle fibers, but a lot of mitochondria, therefore they contract with less force, but do not get tired for a long time; with the help of intercalary disks, mechanical and electrical communication of cardiomyocytes is carried out;
atypical (conductive) cardiomyocytes – form the conduction system of the heart for the formation and conduction of impulses to contractile cardiomyocytes;
secretory cardiomyocytes – located in the atria, capable of producing a hormone-like peptide – sodium uretic factor, lowering blood pressure.

Smooth muscle tissue

Smooth muscle tissue has cellular structure (smooth myocyte) and has contractile apparatus in the form of smooth myofibrils.

It contracts slowly and is able to remain in a state of contraction for a long time, consuming a relatively small amount of energy and without getting tired. This type of contractile activity is called tonic. Autonomic nerves approach smooth muscle tissue, and unlike skeletal muscle tissue, it is not subject to consciousness, although it is under the control of the cerebral cortex.

The smooth muscle cell has a spindle-shaped shape and pointed ends.

It has a nucleus, cytoplasm (sarcoplasm), organelles and a membrane (sarcolemma). Contractile myofibrils are located along the periphery of cells along its axis. These cells are closely adjacent to each other. The supporting apparatus in smooth muscle tissue is thin collagen and elastic fibers located around the cells and connecting them to each other.

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Functions of muscle tissue, types and structure

The body of all animals, including humans, consists of four types of tissue: epithelial, nervous, connective and muscle. The latter will be discussed in this article.

Types of muscle tissue

It comes in three types:

striated;
smooth;
cardiac.

The functions of muscle tissue of different types are somewhat different.

And the building too.

Where are muscle tissues located in the human body?

Muscle tissues of different types occupy different locations in the body of animals and humans.

So, as the name implies, the heart is built from cardiac muscles.

Skeletal muscles are formed from striated muscle tissue.

Smooth muscles line the inside of the cavities of organs that need to contract. These are, for example, the intestines, bladder, uterus, stomach, etc.

The structure of muscle tissue varies between species. Let's talk about it in more detail later.

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How is muscle tissue structured?

It consists of large cells - myocytes.

They are also called fibers. Muscle tissue cells have several nuclei and a large number of mitochondria - organelles responsible for energy production.

In addition, the structure of muscle tissue in humans and animals provides for the presence of a small amount of intercellular substance containing collagen, which gives the muscles elasticity.

Let's look at the structure and functions of muscle tissue of different types separately.

Structure and role of smooth muscle tissue

This tissue is controlled by the autonomic nervous system.

Therefore, a person cannot consciously contract muscles made of smooth tissue.

It is formed from mesenchyme. This is a type of embryonic connective tissue.

This tissue contracts much less actively and quickly than striated tissue.

Smooth tissue is built from spindle-shaped myocytes with pointed ends.

The length of these cells can range from 100 to 500 micrometers, and the thickness is about 10 micrometers. The cells of this tissue are mononuclear. The nucleus is located in the center of the myocyte. In addition, organelles such as the agranular ER and mitochondria are well developed. Also in the cells of smooth muscle tissue there are a large number of inclusions from glycogen, which represent reserves of nutrients.

The element that ensures the contraction of this type of muscle tissue is myofilaments.

They can be built from two contractile proteins: actin and myosin. The diameter of myofilaments that are composed of myosin is 17 nanometers, and those that are built of actin are 7 nanometers. There are also intermediate myofilaments, the diameter of which is 10 nanometers. The orientation of myofibrils is longitudinal.

The composition of muscle tissue of this type also includes an intercellular substance made of collagen, which provides communication between individual myocytes.

Functions of muscle tissue of this type:

Sphincteric.
It consists in the fact that smooth tissues are made of circular muscles that regulate the transition of contents from one organ to another or from one part of an organ to another.
Tow truck. The point is that smooth muscles help the body remove unnecessary substances and also take part in the birth process.
Creation of vascular lumen.
Formation of the ligamentous apparatus. Thanks to it, many organs, such as the kidneys, are held in place.

Now let's take a look next view muscle tissue.

Cross-striped

It is regulated by the somatic nervous system.

Therefore, a person can consciously regulate the work of muscles of this type. Skeletal muscles are formed from striated tissue.

This fabric consists of fibers. These are cells that have many nuclei located closer to the plasma membrane. In addition, they contain a large number of glycogen inclusions. Organelles such as mitochondria are well developed.

They are located near the contractile elements of the cell. All other organelles are localized near the nuclei and are poorly developed.

The structures through which striated tissue contracts are myofibrils.

Their diameter ranges from one to two micrometers. Myofibrils occupy most of the cell and are located in its center. The orientation of myofibrils is longitudinal. They consist of light and dark discs that alternate, which creates the transverse “striation” of the tissue.

Functions of muscle tissue of this type:

Provide movement of the body in space.
Responsible for the movement of body parts relative to each other.
Capable of maintaining body posture.
They participate in the process of temperature regulation: the more actively the muscles contract, the higher the temperature.
When frozen, striated muscles may begin to contract involuntarily. This explains the trembling in the body.
Perform a protective function. This is especially true for the abdominal muscles, which protect many internal organs from mechanical damage.
Act as a depot of water and salts.

Cardiac muscle tissue

This fabric looks like both cross-striped and smooth. Like smooth, it is regulated by the autonomic nervous system.

However, it contracts just as actively as the striated one.

It consists of cells called cardiomyocytes.

Functions of this type of muscle tissue:

There is only one thing: ensuring the movement of blood throughout the body.

Muscle tissue (lat. textus muscularis) - tissues that are different in structure and origin, but similar in their ability to undergo pronounced contractions. They consist of elongated cells that receive irritation from the nervous system and respond to it with contraction. They ensure movement in space of the body as a whole, its movement of organs within the body (heart, tongue, intestines, etc.) and consist of muscle fibers. Cells of many tissues have the ability to change shape, but in muscle tissue this ability becomes the main function.

Special contractile organelles - myofilaments or myofibrils - provide contraction, which occurs when two main fibrillar proteins interact in them - actin and myosin - with the obligatory participation of calcium ions. Mitochondria provide these processes with energy. The supply of energy sources is formed by glycogen and lipids. Myoglobin is a protein that ensures the binding of oxygen and the creation of its reserve at the time of muscle contraction, when the blood vessels are compressed (the oxygen supply drops sharply).

Consists of mononuclear cells - spindle-shaped myocytes with a length of 20-500 microns. Their cytoplasm in a light microscope looks uniform, without transverse striations. This tissue has special properties: it contracts and relaxes slowly, is automatic, and is involuntary (that is, its activity is not controlled by the will of a person). It is part of the walls of internal organs: blood and lymphatic vessels, urinary tract, digestive tract (contraction of the walls of the stomach and intestines).

Consists of myocytes that are long (up to several centimeters) and have a diameter of 50-100 microns; these cells are multinucleated, containing up to 100 or more nuclei; in a light microscope, the cytoplasm appears as alternating dark and light stripes. The properties of this muscle tissue are high speed contractions, relaxations and voluntariness (that is, its activities are controlled by the will of a person). This muscle tissue is part of the skeletal muscles, as well as the wall of the pharynx, the upper part of the esophagus, it forms the tongue, and the extraocular muscles. The fibers are 10 to 12 cm long.

Consists of 1 or 2 nuclear cardiomyocytes with transverse striations of the cytoplasm (along the periphery of the cytolemma). Cardiomyocytes are branched and form connections with each other - intercalary discs, in which their cytoplasm is united. There is also another intercellular contact - anostamosis (invagination of the cytolemma of one cell into the cytolemma of another) This type of muscle tissue forms the myocardium of the heart. Develops from the myoepicardial plate (visceral layer of the splanchnotome of the fetal neck). A special property of this tissue is automaticity - the ability to rhythmically contract and relax under the influence of excitation that occurs in the cells themselves (typical cardiomyocytes). This tissue is involuntary (atypical cardiomyocytes). There is a 3rd type of cardiomyocytes - secretory cardiomyocytes (they do not have fibrils). They synthesize the hormone troponin, which lowers blood pressure and dilates the walls of blood vessels.