Properties of smooth muscles, mechanism of smooth muscle contraction. Muscle system. Smooth muscles. Musculoskeletal system Where can you find smooth and striated muscles

It describes the basic principles of the structure of muscle tissue. The following topics are considered.

The structure of striated muscles (muscle fibers, connective tissue fascia, blood supply and muscle innervation).
receptors in muscle tissue.
The structure of the muscle-tendon junction, the histological structure of the tendons and their attachment to the bone (bone-tendon junction).
Description of different types of muscles and muscle fibers.
The functional significance of striated muscles.
Anatomy of the most important muscles: origin, attachment, innervation, function and significance in various sports.

Muscles allow the human body to perform various movements. In the cytoplasm of muscle fibers (muscle tissue cells) there are a large number of special proteins (actomyosin), due to which muscle contraction is possible. In the human body, three types of muscle tissue are distinguished, differing in their morphological and physiological properties.

Striated, or skeletal, muscle tissue - consists of muscle fibers of a cylindrical shape and is innervated by the somatic nervous system (voluntary muscles).
Smooth muscle tissue - consists mainly of spindle-shaped cells. Smooth muscle tissue is found in the walls of internal organs and blood vessels, as well as in hair roots, exocrine glands, and the eyeball (Tillmann, 1998). Smooth muscle tissue receives innervation from the autonomic nervous system (involuntary muscles) (Silbernagl and Despopoulos, 1983). Some smooth muscle fibers receive autonomous innervation from pacemaker cells through gap junctions (nexuses).
Striated cardiac muscle tissue - consists of transversely striated cardiomyocytes arranged parallel to each other and connected by the so-called intercalated discs. Cardiac muscle tissue receives impulses from autonomous cells - pacemakers," the autonomic nervous system also exerts a regulatory influence on it (Mauer, 2006).

The human body has 430 muscles, which make up 40-50% of its mass and are thus the most abundant human tissue (Cabri, 1999). Skeletal muscles are attached to the bones of the skeleton with the help of tendons, and muscle attachment can be direct or indirect. Muscle tissue together with auxiliary structures (connective tissue membranes - fascia, blood vessels, nerves, synovial bags, tendon sheaths, neuromuscular spindles and tendon receptors) form an effective system that harmoniously transfers force to the musculoskeletal system. Due to its structure, the skeletal muscles, on the one hand, provide movement, and on the other hand, are involved in maintaining the posture. At the same time, the muscular system also performs a protective function when exposed to external forces.

Muscle fiber is not a cell. It consists of myosymplast and myosatellitocytes (companion cells) covered by a common basement membrane. Myosymplast is a collection of fused cells, it has a large number of nuclei located along the periphery of the muscle fiber. Muscle fiber is the structural unit of muscle tissue.
Actomyosin consists of actin and myosin proteins, which form an actomyosin complex with ATPase activity, i.e. the ability to break down ATP, while freeing up the energy necessary to ensure muscle contractions.

Smooth muscles

contractile tissue, which, in contrast to striated muscles (See striated muscles), is made up of cells (not symplasts) and does not have a transverse striation. In invertebrates (except for all arthropods and individual representatives of other groups), G. m. form the entire musculature of the body; in vertebrates, they are part of the membranes of internal organs: intestines, blood vessels, respiratory tract, excretory and genital organs, as well as many glands. G.'s cells of the m at invertebrates are various in a form and a structure; in vertebrates, in most cases, fusiform, strongly elongated, with a rod-shaped nucleus, dl. 50-250 micron, in the uterus of pregnant animals - up to 500 micron; surrounded by connective tissue fibers forming a dense case. The contractile material - protofibrils - is usually located in the cytoplasm in isolation; only in some animals they are collected in bundles - myofibrils. All three types of contractile protein are found in G. m. - Actin, Myosin and tropomyosin. Predominantly there are protofibrils of the same type (with a diameter of about 100 Å). There are fewer cellular organelles (mitochondria, the Golgi complex, elements of the endoplasmic reticulum) in the G. than in the striated muscles. They are located mainly at the poles of the nucleus in the cytoplasm, devoid of contractile elements. The cell membrane often forms pockets in the form of pinocytic (see Pinocytosis) vesicles, which indicates resorption and absorption of substances by the cell surface. Soviet scientists A. A. Zavarzin, N. G. Khlopin, and others established that tissue mastication is a group of tissues of different origins, united by a single functional feature—the ability to contract. Thus, in invertebrates, G. m. develop from mesodermal sheets and coelomic epithelium. In vertebrates, the GM of the salivary, sweat, and mammary glands originate from the ectoderm; the GM of the internal organs originates from the mesenchyme, and so on. Neighboring G.'s cells of m contact with each other shoots so that membranes of two cells adjoin. In mouse gut muscles, contact zones occupy 5% of the cell membrane surface. Here, probably, there is a transfer of excitation from one cell to another (see. Synapses).

Unlike striated muscles, slow contraction is characteristic of m. G., the ability to be in a state of contraction for a long time, spending relatively little energy and not being fatigued. The motor innervation of the brain is carried out by the processes of the cells of the autonomic nervous system, and the sensory innervation is by the processes of the cells of the spinal ganglia. Not every G.'s cell of m has a specialized nerve ending.

Lit.: Zavarzin A. A., Izbr. works, vol. 1-4, M. - L., 1950-53; Polikar A. and Bo Sh. A., Submicroscopic structures of cells and tissues in health and disease, trans. from French, Leningrad. 1962; Electron microscopic anatomy, trans. from English, M., 1967.

E. S. Kirpichnikova.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what "Smooth Muscle" is in other dictionaries:

- (involuntary muscles), one of the three types of muscles in vertebrates. Unlike SKELETAL MUSCLES, they are not subject to conscious control by the brain, but are stimulated by the AUTONOMIC NERVOUS SYSTEM and HORMONES in the blood. Remember my smooth ... ... Scientific and technical encyclopedic dictionary

Contractile (muscle) tissue, consisting of spindle-shaped mononuclear cells. Unlike striated muscles, they do not have transverse striation. In most invertebrates, they make up the entire musculature of the body; Vertebrates are part of... Big Encyclopedic Dictionary

Smooth muscle tissue, hematoxylin, eosin. Smooth muscles are contractile tissue, which, unlike striated muscles, consists of cells (and not syncytium) and does not have ... Wikipedia

SMOOTH MUSCLES- muscles of internal organs that form the muscular layer of the stomach, intestines, blood vessels, etc. Unlike striated muscles, G.'s contraction of m is slower and longer; they can be in a reduced state for a long time ... Psychomotor: Dictionary Reference

SMOOTH MUSCLES (musculi glaberi), contractile tissue, consisting of otd. cells and not having transverse striation. In invertebrates (except for arthropods and some representatives of other groups, for example, pteropods), G. m. form the entire ... ...

Contractile (muscle) tissue, consisting of spindle-shaped mononuclear cells. Unlike striated muscles, they do not have transverse striations. In most invertebrates, they make up the entire musculature of the body; Vertebrates are part of... Natural science. encyclopedic Dictionary

MUSCLES- MUSCLES. I. Histology. In general morphologically, the tissue of the contractile substance is characterized by the presence of specific differentiation in the protoplasm of its elements. fibrillar structure; the latter are spatially oriented in the direction of their contraction and ... ...

Muscles (musculi), organs of the body of animals and humans, consisting of muscle tissue that can contract under the influence of nerve impulses. Carry out the movement of the body in space, the displacement of some of its parts relative to others (dynamic function) ... Biological encyclopedic dictionary

HUMAN MUSCLES- “80 No. Name Latin and Russian. Synonyms. Forsh, and position Beginning and attachment Innervation and relation to the nets Thyreo epiglotticus (shield-like supraglottic M.). Syn.: thyreo epiglotticus inferior, s. major, thyreo membranosus ... Big Medical Encyclopedia

Muscle tissue is recognized as the dominant tissue of the human body, the share of which in the total weight of a person is up to 45% in men and up to 30% in the fair sex. Musculature includes a variety of muscles. There are more than six hundred types of muscles.

The importance of muscles in the body

Muscles play an extremely important role in any living organism. With their help, the musculoskeletal system is set in motion. Thanks to the work of muscles, a person, like other living organisms, can not only walk, stand, run, make any movement, but also breathe, chew and process food, and even the most important organ - the heart - also consists of muscle tissue.

How are muscles worked?

The functioning of muscles occurs due to the following properties:

Excitability is an activation process manifested as a response to a stimulus (usually an external factor). The property manifests itself in the form of a change in the metabolism in the muscle and its membrane.
Conductivity is a property that means the ability of muscle tissue to transmit a nerve impulse formed as a result of exposure to an irritant from a muscle organ to the spinal cord and brain, as well as in the opposite direction.
Contractility - the final action of the muscles in response to a stimulating factor, manifests itself in the form of shortening of the muscle fiber, the tone of the muscles also changes, that is, the degree of their tension. At the same time, the rate of contraction and the maximum tension of the muscles can be different as a result of the different influence of the stimulus.

It should be noted that muscle work is possible due to the alternation of the above properties, most often in the following order: excitability-conductivity-contractility. If we are talking about voluntary work of the muscles and the impulse comes from the central nervous system, then the algorithm will look like conduction-excitability-contractility.

Muscle structure

Any human muscle consists of a set of oblong cells acting in the same direction, called a muscle bundle. The bundles, in turn, contain muscle cells up to 20 cm long, also called fibers. The shape of the cells of the striated muscles is oblong, smooth - spindle-shaped.

A muscle fiber is an elongated cell bounded by an outer shell. Under the shell, parallel to each other, protein fibers capable of contracting are located: actin (light and thin) and myosin (dark, thick). In the peripheral part of the cell (near the striated muscles) there are several nuclei. Smooth muscles have only one nucleus, it is located in the center of the cell.

Classification of muscles according to various criteria

The presence of various characteristics that are different for certain muscles allows them to be conditionally grouped according to a unifying feature. To date, anatomy does not have a single classification by which human muscles could be grouped. Muscle types, however, can be classified according to various criteria, namely:

In shape and length.
According to the functions performed.
In relation to the joints.
By localization in the body.
By belonging to certain parts of the body.
According to the location of the muscle bundles.

Along with the types of muscles, three main muscle groups are distinguished depending on the physiological features of the structure:

Striated skeletal muscles.
Smooth muscles that make up the structure of internal organs and blood vessels.
heart fibres.

The same muscle can simultaneously belong to several groups and types listed above, since it can contain several cross-signs at once: shape, functions, relation to a body part, etc.

Shape and size of muscle bundles

Despite the relatively similar structure of all muscle fibers, they can be of different sizes and shapes. Thus, the classification of muscles according to this feature distinguishes:

Short muscles move small parts of the human musculoskeletal system and, as a rule, are located in the deep layers of the muscles. An example is the intervertebral spinal muscles.
Long ones, on the contrary, are localized on those parts of the body that make large amplitudes of movements, for example, limbs (arms, legs).
Wide ones cover mainly the torso (on the stomach, back, sternum). They can have different directions of muscle fibers, thereby providing a variety of contractile movements.

Various forms of muscles are also found in the human body: round (sphincters), straight, square, rhomboid, spindle-shaped, trapezoid, deltoid, serrated, one- and two-pinnate and muscle fibers of other shapes.

Varieties of muscles according to their functions

Human skeletal muscles can perform various functions: flexion, extension, adduction, abduction, rotation. Based on this feature, the muscles can be conditionally grouped as follows:

Extensors.
Flexors.
Leading.
Discharging.
Rotational.

The first two groups are always on the same part of the body, but on opposite sides in such a way that when the first contract, the second relax, and vice versa. The flexor and extensor muscles move the limbs and are antagonist muscles. For example, the biceps brachii muscle flexes the arm, while the triceps extends it. If, as a result of the work of the muscles, a part of the body or an organ moves towards the body, these muscles are adductors, if in the opposite direction, they are abducting. The rotators provide circular movements of the neck, lower back, head, while the rotators are divided into two subspecies: pronators, which move inward, and arch supports, which provide movement to the outside.

In relation to the joints

The musculature is attached with the help of tendons to the joints, setting them in motion. Depending on the attachment option and the number of joints that the muscles act on, they are: single-joint and multi-joint. Thus, if the musculature is attached to only one joint, then it is a single-joint muscle, if to two, it is bi-articular, and if there are more joints, it is multi-joint (flexors / extensors of the fingers).

As a rule, single-articular muscle bundles are longer than multi-articular ones. They provide a fuller range of motion of the joint relative to its axis, since they spend their contractility on only one joint, while polyarticular muscles distribute their contractility over two joints. The latter types of muscles are shorter and can provide much less mobility while simultaneously moving the joints to which they are attached. Another property of multi-joint muscles is called passive insufficiency. It can be observed when, under the influence of external factors, the muscle is completely stretched, after which it does not continue to move, but, on the contrary, slows down.

Localization of muscles

Muscle bundles can be located in the subcutaneous layer, forming superficial muscle groups, and maybe in deeper layers - these include deep muscle fibers. For example, the musculature of the neck consists of superficial and deep fibers, some of which are responsible for the movements of the cervical region, while others pull the skin of the neck, the adjacent area of the skin of the chest, and also participate in turning and tipping the head. Depending on the location in relation to a particular organ, there can be internal and external muscles (external and internal muscles of the neck, abdomen).

Types of muscles by body parts

In relation to parts of the body, the muscles are divided into the following types:

The muscles of the head are divided into two groups: chewing, responsible for the mechanical grinding of food, and facial muscles - types of muscles, through which a person expresses his emotions, mood.
The muscles of the body are divided into anatomical sections: cervical, pectoral (large sternal, trapezius, sternoclavicular), dorsal (rhomboid, latissimus dorsalis, large round), abdominal (internal and external abdominal, including the press and diaphragm).
Muscles of the upper and lower extremities: shoulder (deltoid, triceps, biceps brachialis), elbow flexors and extensors, gastrocnemius (soleus), tibia, foot muscles.

Varieties of muscles according to the location of muscle bundles

Muscle anatomy in different species may differ in the location of muscle bundles. In this regard, muscle fibers such as:

Cirrus resemble the structure of a bird's feather, in which the muscle bundles are attached to the tendons on only one side, and the other diverge. The pinnate form of the arrangement of muscle bundles is characteristic of the so-called strong muscles. The place of their attachment to the periosteum is quite extensive. As a rule, they are short and can develop great strength and endurance, while muscle tone will not be very large.
Muscles with parallel arrangement of bundles are also called dexterous. Compared to feathery, they are longer, while less hardy, but they can perform more delicate work. When reduced, the voltage in them increases significantly, which significantly reduces their endurance.

Muscle groups by structural features

Accumulations of muscle fibers form whole tissues, the structural features of which determine their conditional division into three groups:

Where are muscles located in vertebrates?

What are the functions of muscles in the animal body?

Muscles in vertebrates are differentiated and represented by many diversely located muscles; mammals are characterized by the presence of a diaphragm, and subcutaneous muscles are developed, mimic on the face.

An important feature of animals is their ability to move. The movement of most animals is the result of muscle contractions. Muscles are made up of muscle tissue. Distinguish between smooth and striated muscle tissue. Their main property is excitability and contractility.

2. Where can you find smooth muscles, and where are striated ones?

Smooth muscles form the walls of blood vessels, respiratory tract, stomach, and intestines. Skeletal muscles include the striated muscles of the head, trunk and limbs, as well as the heart.

3. What common property do all muscles have and what are the conditions for their work?

The main property of muscle tissue is contractility. Muscle work is based on this property. In an excited state, the muscle shortens and thickens - it contracts, then relaxes and takes on its previous size. When the muscles contract, they do work to move the body, limbs or hold the load. For the normal functioning of the muscles, nutrients and oxygen supplied with the blood are necessary, since the energy of muscle contraction is associated with the biological oxidation of the organic substances of the muscle fiber. The decay products formed during the work of the muscles are carried away by the blood. That is why the deterioration of blood supply disrupts muscle activity and often causes pain.

4. How do facial muscles differ from masticatory muscles?

Chewing muscles move the lower jaw, provide chewing of food and are involved in the formation of speech sounds. Mimic muscles change facial expression. With the help of these muscles, a person's face can express feelings of joy and grief, kindness and anger, friendliness and discontent.

5. Why are many of the muscles that move the shoulder and hip located on the trunk? Why are the muscles that compress and unclench the fingers of the hand located on the forearm?

The amplitude - the range of motion - depends on the length of the muscle fibers, and the strength - on the cross-sectional area of \u200b\u200bthe muscle bundle. To bend the hand into a fist, the muscles must be long enough. That is why the muscles that flex and extend the fingers are on the forearm, the muscles that lower and raise the shoulder are on the torso.

6. What human muscles provide a vertical position of the body? Name the muscles involved in breathing.

The muscles of the legs hold the body, ensure the preservation of its vertical position, and among the muscles of the body, the muscles of the chest, back and abdomen are distinguished. They perform the function of breathing and support the body in an upright position.

They do not have transverse striation (hence their name). Secondly, smooth muscles receive innervation not from the somatic, but from the autonomic part of the nervous system, therefore, they are deprived of direct voluntary regulation.

Just as in skeletal muscle, in smooth muscle, force is generated due to the fact that transverse bridges perform their rotational movements between actin and myosin filaments, the activity of which is regulated by Ca2 + ions. However, the organization of contractile filaments and the process of electromechanical coupling for these two types of muscles are different. The mechanism of electromechanical coupling in different smooth muscles varies significantly.

The concentration of myosin in smooth muscle is only about a third of that in striated muscle, while the content of actin can be twice as high. Despite these differences, the maximum stress per unit cross-sectional area developed by smooth muscle is similar to that developed by skeletal muscle.

The relationship between isometric tension and length for smooth muscle cells is quantitatively the same as for skeletal muscle fibers. With the optimal length of the smooth muscle, the maximum tension develops, and with its shifts in both directions from the optimal value, it decreases. However, compared to skeletal muscle, smooth muscle is able to develop tension over a wider range of lengths. This is an important adaptive property, given that most of them are part of the walls of hollow organs, with a change in the volume of which the length of smooth muscle cells also changes. Even with a relatively large increase in volume, as, for example, when filling the bladder, smooth muscle cells in its walls retain to a certain extent the ability to develop tension; in striated fibers, such stretching could lead to the separation of thick and thin filaments beyond the zone of their overlap.