Structure and function of human muscles

The muscle is a special structure in the human or animal body. It consists of a tissue that has the ability to contract under the action of nerve impulses. Next, consider the structure and function of the muscles in more detail. The article will give a classification of muscles.

Anatomy

Muscles are presented in the form of soft tissues, consisting of individual fibers. They can relax and contract. In the muscle there are bundles of striated (striated) structures. These fibers run parallel to each other. They are connected by means of connective tissue and form first-order beams. Several of them are also connected. They, in turn, form bundles of 2 orders. As a result, all these groups unite the muscle shell, making up the "abdomen". Between the bundles there are connective tissue interlayers. Passing along the extremities of the abdomen, they pass into the tendon zone of the muscle.

Processes inside fibers: general information

Since the reduction is provoked by the impulse coming from the central nervous system, the nerves end from each muscle: afferent and efferent. The first are considered (according to Pavlov) motor analyzers. They carry out a "muscular feeling". Efferent nerves lead to fiber impulse. In addition, sympathetic terminations are suitable for muscles. Thanks to them, the fibers are in a tone - a state of slight reduction. In the muscles there are very active processes of metabolism. In this regard, the tissues have an extensive vascular network. Blood channels penetrate from the inside to the muscle in one or more areas. These places are called gates. In these same areas, along with the vessels, the nerves enter and then branch out and the nerves correspondingly to the bundles - across and along.

Fabric Segments

In the muscle, it is common to distinguish between the abdomen - the active part, the tendon - the passive element. With the help of the last muscle is fixed to the bone. The tendon is presented in the form of connective tissue, fairly dense, having a light-golden shiny color, which contrasts sharply with the red-brown tinge of the abdomen. As a rule, the tendon is located on both edges of the muscle. Sometimes it is very short. In such cases, it seems that the muscle departs directly from the bone or is attached to it by its abdomen. Vascular supply of the tendon, in which less metabolism, is poorer. The skeletal muscle includes not only the striated tissue. There are also various kinds of connective, nervous, smooth fibers and endothelium. However, the striated fabric is still predominant. Its property - contractility - and determines the functions of the muscles of the person as the organs of contraction. Each muscle is a separate organ, that is, an integral formation. Each of them has its own structure, form, position and development. Special attention should be paid to the features that the functions of the human muscles possess.

Musculature work

Practically everyone knows what function the muscles perform. Of course, this is the provision of traffic. The main property of musculature tissue is contractility. It is the basis of muscular activity. In the process of reduction, the fibers shorten and the two points of attachment become closer. From these two sites, the mobile is attracted to the static one. The result of this process is the movement of a given part of the body. By performing the described action, the muscle produces a heaviness with a certain force. Moving the load, for example, the heaviness of the bone, the muscle carries out mechanical work.

Musculature Features

The number of fibers that make up the muscle determines its strength. Also of no small importance is the area of the "physiological diameter". This is the size of the cut at the site through which all the muscle fibers pass . The magnitude of the contraction itself depends on the length of the muscle. Bones that move in joints under the influence of muscles are levers (in the mechanical sense). They can be called the simplest machines for moving weights.

Nuances of attaching fibers

The farther from the support area the muscles will be fixed, the more profitable it will be. This is due to the fact that the larger the lever arm, the better the use of force. Carrying out the classification from that point of view on Lesgaft, we should distinguish:

• Strong muscles. They are attached away from the support area.
• Artful. These fibers are fixed near the support section.

In every muscle there is a beginning and an attachment. The backbone of the whole body is the spine. It is located along the middle axis of the trunk. The beginning of the muscle, as a rule, coincides with a fixed point. It is located closer to the middle part, and on the limbs - to the body (proximally). The fixation of a muscle that coincides with the moving part is located farther from the center. On the limbs, respectively, the attachment site is distal, remote from the trunk. Movable and fixed areas can change places. This happens when a fixed point is freed. Also, the change of places is observed when the mobile section is strengthened. You can consider an example of standing. In this position, the movable portion of the rectus abdominal muscles will be their upper edge - the upper half of the trunk will be bent, and the lower end at the crossbar on the arms.

Antagonists and synergists

Since the movement is carried out in two opposite directions - reduction-retraction, flexion-extension, - at least two muscles must be involved in order to move around one axis. They should be located on opposite sides. Muscles, whose action occurs in opposite directions, are called antagonists. In the process of each flexion, not only the flexor, but also the extensor participates. The latter is gradually inferior to the former. Extensor retains the flexor from its excessive contraction. In this regard, the antagonism of muscles contributes to the proportionality and smoothness of movements. Unlike the described muscles, the resultant of which lies in one direction, are called synergists. Depending on the nature of any other movement and what functional combination of muscles it takes part in, the same structures may be both antagonists and agonists (synergists).

Changing tasks

This process is noted in the living body and is considered a variant of the norm. Elementary functions of muscles are determined by their anatomical relationship to the axis of rotation of a particular joint. The change in the state of the musculature is conditioned by the preservation of the position of the trunk and its separate zones, as well as by constantly different dynamic and statistical loads on the motor apparatus. Thus, the functions of the muscles change in accordance with the position of the body (or its zone, under which the action takes place) and the phases of the corresponding act of motion.

Classification of muscles

In accordance with the functions performed, the muscles are divided into extensors, flexors, leading, retractors. There are also rotators. Muscles, with the reduction of which limbs move from the body, are referred to as diversions. The muscles that approach the body are called reducers. Rotators provide rotation of this or that part of the body. In the body there are muscles of the head, limbs, trunk. Let us consider them in more detail.

Torso

In this part of the body there are muscles of the abdomen, back and chest. The latter include internal and external intercostal muscles and diaphragm. With their help, breathing is carried out. The functions of the abdominal muscles provide flexion of the spine to the side, forward, and also its rotation around the axis. They form the abdominal press. Its reduction contributes to the excretion of urine and feces, a deep exhalation, a generic act. Superficial (latissimus and trapezius) back muscles provide movement and strengthening of the arms and shoulder girdle. Deep muscles fix the spine, flex-unbend it. With their help, there is also a rotation of the head, respiratory movements.

Upper limbs

There are two groups of muscles. Muscular fibers of the shoulder girdle. These include a small thoracic, large and deltoid structure. They provide the necessary mobility. The functions of the muscles of the forearm are distributed depending on the location. On the front surface are the flexors of the fingers and hands. The functions of the muscles of the forearm of the posterior plane consist in extension. Thanks to the musculature, a variety of hand movements are carried out.

Functions of the muscles of the head

The musculature of this part of the body is divided into two groups - mimic and chewing. The fibers of the latter begin from the edge of the bone of the cheekbone and are fixed on the lower jaw. The functions of the muscles of the head of the chewing group consist in raising the upper jaw. Thus chewing food is provided. Mimic muscles participate in the expression of emotions. The function of the circular muscle, located near the orbit, is to close the eyelids. On the forehead are the frontal muscles. Near the oral opening there is a circular muscle of the mouth. Musculature is present in the internal organs. Briefly describes the muscles and their functions table: