The structure and function of human muscles

A muscle is a special structure in the human or animal body. It consists of tissue with the ability to contract under the influence of nerve impulses. Next, we consider the structure and function of muscles in more detail. The article will provide 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 bind with the help of connective tissue and form bundles of the first order. Several of them are also connected. They, in turn, form bundles of 2 orders. As a result, all these groups are united by the muscular membrane, making up the "abdomen". Between the bundles there are connective tissue layers. Passing along the ends of the abdomen, they pass into the tendon zone of the muscle.

Processes Inside Fibers: General

Since the contraction is provoked by an impulse coming from the central nervous system, nerve endings depart from each muscle: afferent and efferent. The former are considered (according to Pavlov) motor analyzers. They have a "muscle feeling." Efferent nerves lead to fiber impulse. In addition, sympathetic endings are suitable for the muscles. Thanks to them, the fibers are in good shape - a state of slight reduction. Very active metabolic processes take place in the muscles. In this regard, the tissues have an extensive vascular network. Blood channels penetrate from the inside into the muscle in one or more areas. These places are called gates. In these same areas, along with the vessels, the muscles enter and then branch and the nerves, respectively, to the bundles - transversely and along.

Fabric segments

In the muscle, it is customary to distinguish the abdomen - the active part, the tendon - the passive element. Using the last muscle is fixed to the bone. The tendon is presented in the form of connective tissue, quite 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 moves directly from the bone or attaches to it with its abdomen. The supply of vessels to the tendon, in which there is less metabolism, is poorer. Skeletal muscle includes not only striated tissue. It contains various kinds of connective, nerve, smooth fibers and endothelium. However, still striated tissue prevails. Its property - contractility - and determines the functions of human muscles as organs of contraction. Each muscle is a separate organ, that is, a holistic formation. Each of them has its own structure, form, position and development. Particularly noteworthy are the features that have the functions of the muscles of a person.

Muscle work

Almost everyone knows what function the muscles perform. Of course, this is the provision of movement. The main property of muscle tissue is contractility. It is based on muscle activity. In the process of contraction, the fibers are shortened and the two points of their attachment come closer. Of these two sections, the movable is attracted to the static. The result of this process is the movement of a given part of the body. Performing the described action, the muscle produces heaviness with a certain force. Moving the load, for example, the severity of the bone, the muscle performs mechanical work.

Musculature Features

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

Fiber Attachment Nuances

The farther the muscles are fixed from the support site, the more profitable it will be. This is due to the fact that the larger the lever arm, the better the force is used. Carrying out the classification from that point of view according to Lesgaft, it is necessary to distinguish:

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

Every muscle has a beginning and an attachment. The whole body is supported by the spine. It is located on the middle axis of the body. 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 (proximal). Fixation of the muscle, which coincides with the moving area, is located further from the center. On the limbs, respectively, the attachment site is distal, remote from the body. Moving and fixed areas can change places. This happens when a fixed point is released. Also, a change of place is observed when strengthening the mobile site. You can consider an example of standing. In this position, the upper edge will become the movable section of the rectus abdominis muscles - the upper half of the body will be bent, and when hanging on the bar on the arms - the lower end.

Antagonists and synergists

Since the movement is carried out in two opposite directions - adduction-abduction, bending-unbending, at least two muscles must be involved to move around a single axis. They should be located on opposite sides. Muscles whose action occurs in opposite directions are called antagonists. In the process of each bending, not only the flexor is involved, but also the extensor. The latter is gradually inferior to the first. The extensor keeps the flexor from its excessive contraction. In this regard, muscle antagonism contributes to proportionality and smoothness of movements. In contrast to the described muscles, the resultant of which lies in one direction, are called synergists. Depending on the nature of a different movement and what functional combination of muscles takes part in it, the same structures can be both antagonists and agonists (synergists).

Change tasks

This process is noted in a living organism and is considered a variant of the norm. The elementary functions of muscles are determined by their anatomical relationship to the axis of rotation of a particular joint. A change in the state of the musculature is caused by maintaining the position of the trunk and its individual zones, as well as constantly varying dynamic and statistical load on the motor apparatus. So, muscle functions change in accordance with the position of the body (or its zone at which the action takes place) and the phase of the corresponding act of movement.

Muscle classification

In accordance with the functions performed, the muscles are divided into extensors, flexors, leading, abducting. There are also rotators. Muscles, during the contraction of which the limbs move from the body, are called abduction. Muscles that approach the body are called adductors. Rotators provide rotation of a particular part of the body. In the body there are muscles of the head, limbs, trunk. Let's 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 the diaphragm. With their help, breathing is carried out. The functions of the abdominal muscles provide the bending of the spine to the side, forward, as well as its rotation around the axis. They form the abdominals. Its contractions contribute to the excretion of urine and feces, deep exhalation, labor birth. Superficial (latitudinal and trapezoidal) muscles of the back provide movement and strengthening of the arms and shoulder girdle. Deep muscles fix the spine, bend-unbend it. With their help, there is also a rotation of the head, respiratory movements.

Upper limbs

There are two muscle groups. The muscle fibers of the shoulder girdle are isolated. These include small pectoral, large and deltoid structures. 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 are extension. Thanks to the muscles, various movements of the hands are carried out.

Muscle function of the head

The muscles of this part of the body are divided into two groups - facial and chewing. The fibers of the latter begin from the edge of the cheek bone 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. This ensures the chewing of food. Facial muscles are involved in the expression of emotions. The function of the circular muscle located near the orbit is to close the eyelids. There are frontal muscles on the forehead. A circular muscle of the mouth is located near the mouth opening. Musculature is present in the internal organs. Briefly describes the muscles and their functions table: