A muscle is a special structure in the human or animal body. It consists of tissue that has the ability to contract under the action of nerve impulses. Next, consider the structure and function of muscles in more detail. The article will provide a classification of muscles.
Anatomy
Muscles are presented as soft tissues, consisting of individual fibers. They can relax and contract. The muscle has bundles of striated (striated) structures. These fibers run parallel to each other. They are connected by connective tissue and form bundles of the first order. Several of them are also connected. They, in turn, form bundles of the 2nd order. 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: an overview
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 conduct "muscle feeling". Efferent nerves leadto the fibers of the impulse. In addition, sympathetic endings approach the muscles. Thanks to them, the fibers are in good shape - a state of slight contraction. 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 the same areas, along with the vessels, the muscles enter and then branch out and the nerves, respectively, to the bundles - across and along.
Fabric segments
In a muscle, it is customary to distinguish between the abdomen - the active part, the tendon - the passive element. With the help of the latter, the muscle is fixed to the bone. The tendon is presented in the form of a connective tissue, rather dense, having a light golden shiny color, which contrasts sharply with the reddish-brown tint 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 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 also contains various kinds of connective, nerve, smooth fibers and endothelium. However, striated tissue still predominates. Its property - contractility - 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, shape, position anddevelopment. Special attention deserves the features that the functions of human muscles have.
Muscle work
Practically everyone knows the function of muscles. 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 shorten and the two points of their attachment converge. Of these two sections, the mobile one is attracted to the static one. The result of this process is the movement of a given part of the body. By doing the described action, the muscle produces heaviness with a certain force. By moving a load, for example, the weight of a bone, the muscle performs mechanical work.
Features of the muscles
The number of fibers that make up a muscle determines its strength. The area of \u200b\u200bthe "physiological diameter" is also of no small importance. This is the size of the incision in the area through which all muscle fibers pass. The magnitude of the contraction itself depends on the length of the muscle. The bones that move in the joints under the influence of muscles are levers (in a mechanical sense). They can be called the simplest machines for moving weights.
Nuances of fiber attachment
The farther from the support site 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 according to Lesgaft, one should distinguish:
- Strong muscles. They are attached away fromsupport section.
- Nimble. These fibers are fixed near the support site.
Every muscle has a beginning and an attachment. The entire body is supported by the spine. It is located along 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). The fixation of the muscle coinciding with the mobile area is located further from the center. On the extremities, respectively, the place of attachment is located distally, remotely from the body. Movable and fixed areas can be interchanged. This happens when a fixed point is released. Also, a change of place is observed when strengthening the moving section. Consider standing as an example. In this position, their upper edge will become the moving part of the rectus abdominis muscles - the upper half of the body will be bent, and when hanging on the crossbar on the hands - the lower end.
Antagonists and synergists
Since the movement is carried out in two opposite directions - adduction-abduction, flexion-extension - to move around any one axis, at least two muscles are needed. They should be on opposite sides. Muscles that act in opposite directions are called antagonists. In the process of each flexion, not only the flexor is involved, but also the extensor. The latter gradually gives way to the former. The extensor holdsflexor from its excessive contraction. In this regard, muscle antagonism contributes to the proportionality and smoothness of movements. In contrast to the muscles described, the resultant of which lies in one direction, are called synergists. Depending on the nature of a particular 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. The change in the state of the muscles is determined by maintaining the position of the body and its individual zones, as well as constantly different dynamic and static load on the motor apparatus. So, muscle functions change in accordance with the position of the body (or its zone in which the action occurs) and the phase of the corresponding act of movement.
Classification of muscles
According to the functions performed, the muscles are divided into extensors, flexors, adductors, and abductors. There are also rotators. The muscles, during the contraction of which the limbs move away from the body, are called abductors. Muscles that approach the body are called adductors. Rotators provide rotation of a particular part of the body. The body has muscles of the head, limbs, torso. Let's take a closer look at them.
Torso
This part of the body contains the muscles of the abdomen, back and chest. Tothe latter include the internal and external intercostal muscles and the diaphragm. They are used for breathing. The functions of the abdominal muscles provide flexion of the spine to the side, forward, as well as its rotation around the axis. They form the abdominal press. Its contractions contribute to the excretion of urine and feces, deep exhalation, and childbirth. The superficial (latissimus dorsi and trapezius) muscles of the back provide movement and strengthening of the arms and shoulder girdle. Deep muscles fix the spine, bend and unbend it. With their help, the rotation of the head, respiratory movements also occur.
Upper limbs
There are two muscle groups here. Allocate muscle fibers of the shoulder girdle. These include the small thoracic, 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 to extend. Thanks to the musculature, a variety of hand movements are carried out.
Functions of the muscles of the head
The muscles of this part of the body are divided into two groups - mimic and chewing. The fibers of the latter start from the edge of the cheek bone and are fixed on the lower jaw. The functions of the muscles of the head of the masticatory group are to raise the upper jaw. This ensures the chewing of food. Mimic muscles are involved 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 mouth opening is the circular muscle of the mouth. Musculature is also present in the internal organs. Briefly describes the muscles and their functions table:
| Name | Task |
| Musculature of the heart | Contraction of the heart |
| Muscles of the vascular walls, intestines, skin, stomach, etc. | Movement of blood, contraction of walls in hollow organs, movement of food mass. |
