Skeletal muscles. Groups of skeletal muscles. Structure and function of skeletal muscles

Muscles - one of the main components of the body. They are based on a tissue, the fibers of which contract under the influence of nerve impulses, which allows the body to move and stay in the environment.

Muscles are located in every part of our body. And even if we do not know about their existence, they still exist. It is enough, for example, to go to the gym for the first time or exercise aerobics - the next day you will get sick even those muscles that you did not know exist.

They are responsible not only for the movement. At rest, the muscles also require energy to keep themselves toned. This is necessary in order that at any time a certain part of the body could respond to a nerve impulse with the appropriate movement, rather than wasting time preparing.

To understand how the muscles are arranged, we suggest remembering the basics, repeating the classification and looking into the cellular structure of the muscles. We also learn about the diseases that can worsen their work, and how to strengthen the skeletal muscles.

General concepts

By its filling and the reactions that occur, the muscle fibers are divided into:

• Cross-striped;
• Smooth.

Skeletal muscles are oblong tubular structures, the number of nuclei in one cell of which can reach several hundred. They consist of muscle tissue, which is attached to various parts of the skeleton. The contractions of the striated muscle contribute to the movement of the person.

Varieties of forms

What is the difference between the muscles? The photos presented in this article will help us to understand this.

Skeletal muscles are one of the main components of the musculoskeletal system. They allow you to move and maintain balance, and also involved in the process of breathing, voice formation and other functions.

In the human body, there are more than 60 muscles. In a percentage ratio, their total mass is 40% of the total body weight. Muscles are classified in shape and structure:

• Thick fusiform;
• Thin lamellar.

Classification simplifies the study

The division of skeletal muscles into groups is carried out depending on the location and their significance in the activity of various organs of the body. The main groups are:

Muscles of head and neck:

• Mimic - involved in smiling, communicating and creating various grimaces, while ensuring the movement of the constituent parts of the face;
• Chewing - help to change the position of the maxillofacial department;
• Arbitrary muscles of the internal organs of the head (soft palate, tongue, eyes, middle ear).

Groups of skeletal muscles of cervical department:

• Surface - contribute to the inclined and rotational movements of the head;
• Middle - create the lower wall of the oral cavity and facilitate the movement down the jaw, the hyoid bone and the laryngeal cartilage;
• Deep perform the slopes and turns of the head, create a lifting of the first and second ribs.

The muscles, the photos of which you see here, are responsible for the trunk and are divided into muscle beams of the following departments:

• Thoracic - activates the upper part of the torso and arm, and also helps to change the position of the ribs during breathing;
• Abdomen division - gives movement of blood through the veins, changes the position of the chest during breathing, affects the functioning of the intestinal tract, promotes bending of the trunk;
• Dorsal - creates a motor system of the upper limbs.

Muscles of the extremities:

• Upper - consist of muscular tissues of the shoulder girdle and free upper limb, help to move the arm in the shoulder joint bag and create movements of the wrist and fingers;
• Lower - play a major role in the movement of man in space, are divided into the muscles of the pelvic girdle and the free part.

Structure of skeletal muscle

In its structure, it has a huge number of muscle fibers of oblong form with a diameter of 10 to 100 microns, their length varies from 1 to 12 cm. Fibers (microfibrils) are thin - actinic, and thick - myosin.

The first consist of a protein that has a fibrillar structure. It's called actin. Thick fibers consist of different types of myosin. They differ in time, which is required for the decomposition of the ATP molecule, which causes different rates of contraction.

Myosin in smooth muscle cells is in a dispersed state, although there is a large amount of protein, which in turn is significant in prolonged tonic contraction.

The structure of the skeletal muscle is similar to a rope woven or a stranded wire. On top of it is a thin sheath of connective tissue called epimizium. From its inner surface, deeper branching of the connective tissue, creating septa, extends deeper into the muscle. In them, "wrapped" individual bundles of muscle tissue, which contain up to 100 fibrils in each. More narrow branches branch out from them even deeper.

Through all the layers in the skeletal muscles penetrate the blood and nervous systems. The arterial vein passes along the perimizium - this is a connective tissue covering the bundles of muscle fibers. Arterial and venous capillaries are located side by side.

Development process

Skeletal muscles develop from the mesoderm. On the side of the nerve groove, somites are formed. After the expiration of time, myotomes are allocated in them. Their cells, taking the form of a spindle, evolve into myoblasts, which divide. Some of them progress, while others remain unchanged and form myosatellite cells.

An insignificant part of myoblasts, thanks to the contact of the poles, creates contact between themselves, then in the contact zone of the plasmalemma disintegrate. Thanks to the fusion of cells, the symplasts are created. Undifferentiated young muscle cells that are in the same environment as the myosymplast of the basal membrane migrate to them.

Skeletal muscle functions

This musculature is the basis of the musculoskeletal system. If it is strong, the body is easier to maintain in the right position, and the likelihood of stoop or scoliosis is reduced to a minimum. Everyone knows about the advantages of sports, so let's look at the role that musculature plays in this.

The contractile tissue of skeletal muscles performs in the human body many different functions that are necessary for the correct arrangement of the body and the interaction of its individual parts with each other.

Muscles perform the following functions:

• Create mobility of the body;
• Protect the thermal energy created inside the body;
• Promote movement and vertical retention in space;
• Help reduce airways and help with swallowing;
• Form facial expressions;
• Contribute to the production of heat.

Ongoing support

When the muscle tissue is at rest, there is always a slight tension in it, called the muscle tone. It is formed because of the small pulse frequencies that enter the muscles from the spinal cord. Their action is caused by signals coming from the head to the spinal motoneurons. Muscle tone also depends on their general condition:

• Stretching;
• The level of filling of muscle cases;
• Enrichment with blood;
• Total water and salt balance.

Man has the ability to regulate the level of muscle load. As a result of long physical exercises or strong emotional and nervous overstrain, muscle tone is involuntarily increased.

Reductions of skeletal muscles and their variants

This function is basic. But even it, with apparent simplicity, can be divided into several types.

Types of contractile muscles:

• Isotonic - the ability of muscle tissue to shorten without changes in muscle fibers;
• Isometric - the fiber is shortened during the reaction, but its length remains the same;
• Auxotonic - the process of contraction of muscle tissue, where the length and tension of the muscles are subjected to changes.

Consider this process in more detail

First, the brain sends a pulse through the neuronal system, which reaches the motoneuron adjacent to the muscle bundle. Further, the efferent neuron is innervated from the synoptic vesicle, and the neurotransmitter is released. It combines with the receptors on the muscular fiber sarcolemma and opens the sodium channel, which leads to the depolarization of the membrane, which causes the action potential. With a sufficient number of neurotransmitter stimulates the production of calcium ions. Then it combines with troponin and stimulates its reduction. He, in turn, delays tropomezin, allowing actin to connect with myosin.

Then begins the process of sliding actin filaments relative to the myosin, resulting in the reduction of skeletal muscles. A schematic image will help to understand the process of compression of the striated muscle beams.

The principle of the functioning of skeletal muscles

The interaction of a large number of muscle beams promotes various movements of the trunk.

The work of skeletal muscles can occur in such ways:

• Muscles-synergists work in one direction;
• Muscle-antagonists contribute to the implementation of opposing movements to exercise tension.

The antagonistic action of muscles is one of the main factors in the activity of the musculoskeletal system. In the implementation of an action, not only the muscle fibers that perform it are involved, but also their antagonists. They contribute to counteraction and give the movement concrete and gracefulness.

Cross-striated skeletal muscle when exposed to the joint performs a difficult job. Its character is determined by the location of the axis of the joint and the relative position of the muscle.

Some functions of skeletal muscles are insufficiently lit, and are often not talked about. For example, some of the bundles act as a lever for the operation of the bones of the skeleton.

Muscle work at the cellular level

The action of skeletal muscles is carried out by two proteins: actin and myosin. These components have the ability to move relative to each other.

To realize the efficiency of muscle tissue, energy consumption is required, which is contained in the chemical bonds of organic compounds. Decay and oxidation of such substances occur in the muscles. There is necessarily air, and energy is allocated, 33% of all this is spent on the performance of muscle tissue, and 67% is transferred to other tissues and is spent on maintaining a constant body temperature.

Diseases of the musculature of the skeleton

In most cases, abnormalities in the functioning of muscles are due to the pathological state of the responsible parts of the nervous system.

The most common pathologies of skeletal muscles are:

• Muscle cramps - a violation of electrolyte balance in the extracellular fluid surrounding the muscle and nerve fibers, as well as changes in osmotic pressure in it, especially its increase.
• Hypocalcemic tetany - involuntary tetanic contractions of skeletal muscles, observed when the extracellular Ca2 + concentration falls to about 40% of the normal level.
• Muscular dystrophy is characterized by progressive degeneration of skeletal muscle fibers and myocardium, as well as muscular disability, which can lead to death due to respiratory or heart failure.
• Myasthenia gravis is a chronic autoimmune disease in which antibodies to the nicotinic ACh-receptor are formed in the body.

Relaxation and recovery of skeletal muscles

Proper nutrition, lifestyle and regular training will help you to become the owner of healthy and beautiful skeletal muscles. It is not necessary to engage in weightlifting and build muscle. Suffice regular cardio training and yoga.

Do not forget about the mandatory intake of essential vitamins and minerals, as well as regular visits to saunas and baths with brooms that can enrich the oxygen with muscle tissue and blood vessels.

Systematic relaxing massages increase the elasticity and reproductivity of muscle beams. Also, a positive impact on the structure and functioning of skeletal muscles is provided by a visit to cryosauna.