The appearance and shape of the whole figure and its individual parts are largely determined by the muscles that lie beneath the skin, cover the bones and spread over the joints, connecting to each other the various bones of the skeleton.
Muscles are active organs of movement. While at rest, they retain their usual form of calm, familiar to the eye of the observer; while making movements, change this form and often so much that without a special study it is difficult to reproduce this altered form, especially from oneself and from memory. The plastic anatomy is studied by the plastic anatomy in the section "Teaching about muscles", and the plastic anatomy studies not only the mechanism and function of the muscles, but also the form that they form at rest and modify at work.
Any work of muscles, as well as the state of rest is regulated by the nervous system; nourishes the muscles of the circulatory system. When communication with these systems is broken, the muscles gradually die off (& quot; dry ").
Each muscle consists of a tendon and a muscle part - the abdomen. The muscular part has the ability to contract and relax. The tendon does not contract, but only transfers the action of the muscle. The shape of the muscles is very diverse. Muscles are short, wide and long. Short muscles, with the exception of facial muscles, connect the vertebrae and are hardly studied in plastic anatomy, the wide ones lie flat arrays on large areas of the trunk and often form the walls of the receptacles of internal organs (for example, abdominal muscles), the long muscles are located on the hands and feet. The function of muscles is related to their shape. Short and thick muscles produce strong movements, but limited in scope, long muscles produce large-scale movements, but less strong.
By contracting, the muscles change their shape; the abdomen, shortening, protrudes; with a sharp difference in the relief between the abdomen and the tendon.
In addition to this simple form, some muscles have a more complex form. The muscle can start from several sites on different bones and on the same bone (for example, the quadriceps muscle of the thigh).
These separate parts of the muscles, called heads, are connected to the common abdomen, which passes into the common tendon. Such muscles are called: two-headed, three-headed, four-headed. There are also biceps, for example on the neck; In such muscles, the abdomen is divided into two abdominals due to the intermediate tendon (Figure 26). Each muscle consists of bundles of muscle fibers, connected together by a translucent loose connective tissue and clad with an external, inextensible membrane - fascia. The fascia separates the muscle from the others, does not allow the muscle to shift to the side. Fascia also often wears a whole group of muscles, functionally connected, and sometimes an entire limb site. In these cases, the fascia becomes very dense and affects the formation of the external form of the musculature. For example, a wide fascia of the thigh (see below). Muscle fibers form a fleshy thicker part - the abdomen, which in long muscles is pointed at the ends. In muscles of different shapes, the structure of the ends is different: long muscles tend to pass into the tendon at both ends; there are muscles in which the tendon is present only at one end.
Fig. 26. The shape of the muscles:
/- spindle-shaped. 2 is a pinnate one. 3 - two-pinned. 4 - two-headed, 5 - wide. 6 - fan-shaped. 7 - two-abdominal. 8 - long with parallel fibers
Flat muscles (for example, the abdomen) have flattened tendons in the form of plates - they are called aponeuroses. Tendons are inextensible; their function is to transfer the force of the muscles to the site of the impact.
The structure of the muscles depends on the location of the fibers. Distinguish: longitudinally fibrous, feathery, fan-shaped and circular muscles (see Figures 26, 46).
The fibers in the longitudinally fibrous muscles run longitudinally, parallel to the longitudinal axis of the muscles; These muscles make large movements, but relatively less force; such muscles are spindle-shaped and ribbon-shaped. In pinnate muscles, the fibers are located at an angle to the longitudinal axis on both sides of the tendon that passes almost through the entire muscle; there are a lot of fibers, but they are short. Cutting, pinnate muscles produce movements of great strength. With relief muscles and strong tension, such a muscle, as if bifurcating, looks like two longitudinal muscles (for example, the straight muscle of the thigh) (see Figure 31, B). If the muscle fibers are located and attached to one side of the tendon, then such a muscle is called one-leaved, reminding itself of half of the feather; when the fibers are adjacent to the two sides of the tendon rod, the muscle is called bicircular.
In the fan-shaped muscles, the muscle fibers go fan-shaped. Starting from a wide area, the fibers converge fanwise to a narrow bridge of attachment: these muscles are very strong (for example, the gluteus gluteus muscle) (Figure 26).
Circular muscles are formed by a circle-going fibers, which are intertwined around the natural external openings (eyes, mouth), and close them with their contraction like the tightening of the pouch (see Figure 46).
Each muscle has its own name. The names were given on the basis of a variety of muscle properties. Part of the muscles was named according to their functions (flexor), some in shape (deltoid), others in position (supraspinatus); there are also names for the number of heads (double-headed) and for the place of origin and attachment (brachial).
As already mentioned above, the muscles are active organs of movement; they surround the joints from different sides, forming simple and more complex systems of muscles acting in opposite directions, producing flexion and extension, rotation and movement in different directions. The more complex the movements in the joint, the greater the number of muscles, is located around it, and, conversely, the easier the movement, the less the amount of muscles involved.
Muscles acting in the opposite direction are called antagonists, muscles that act in concert with others in one direction are called synergists.
It is necessary to make a reservation, the interaction of muscles and movement occurs not only in the joints; on the body, for example, constantly moving blades on the surface of the chest - there is a group of muscles working together (see below); often mimic muscles moving around soft tissues and facial skin.
As already mentioned above, the muscles, working, change shape - shortening and shortening with a contraction, they become thinner and longer when stretched. All this. accompanied by the movement of parts of the body, significantly changes its shape. Even in simple movements, several muscles are simultaneously involved: not only the muscles that make the movement work, but also their antagonists. Only the first work actively, while others are passive. For example, when flexing in any joint flexors are actively contracting, and extensors are also tensed and passively stretched - the motion is smooth and at any time can pause and go into extension, and extension in turn can also pause and again go into flexion. Such a possibility of an instant change in muscle movements is necessary because any, even seemingly simple movement, occurs not in one place, not in one joint, but in several, and a number of movements alternate, resulting in some kind of appearance simple, but in fact the total movement of the arm, leg, trunk, even a single finger.
Muscles shrink, not only producing an active movement. If, for example, two groups of opposing muscles contract simultaneously with the same strength - antagonists and synergists, then no movement occurs, but the object of their impact becomes immobile - it is fixed most often in order to serve as a support. For example, the scapula - to serve as a support for lifting the arm, the ankle joints, if necessary, firmly and motionlessly stand in place, etc.
Thus, the interaction of different muscle groups gives in total not only movement, but also supports the body or limbs in a stationary position. The interaction of the muscles strengthens the joints, fixes (with uniform mutual cutting) the parts of the skeleton in relation to each other, creating support parts: for example, lower limbs and pelvis when standing, pelvis and upper body with sitting, shoulder girdle and hands when arms are raised up and motionless, etc.
Active interaction of muscles serves as the basis for the movement of the whole body during walking, flexion and extension, lifting of gravity and other workers and sports movements of the body.
The movements of the body and its fixation, arising from the interaction of the muscles, would not be possible and would be accompanied by chaos of movement and loss of balance, if there was no coherence of interaction between different muscle groups - coordination of movements.
Coordination of movements appears in a person not immediately, but develops as the body grows and develops with the will of the will and under the control of the developing consciousness. For example, when walking, which is a very complex movement. The child does not start walking immediately, he learns it for a long time. First he falls, because his movements are not coordinated (not coordinated), but he wants to walk, the consciousness comes into force, and the child learns to control his movements, adjust them, coordinate the movements gradually acquire a habitual, automatic character, and the child hesitates, but nevertheless crosses without falling. Gradually, more and more complex and rapid movements are mastered, they are made freer and more confident. And now the child is already walking, at last, running and jumping. Coordination of movements is fully mastered.
With the mastering of all new complex movements, this happens not only with the child, but also with the adult - new movements in work, sports, dance, and art are not immediately mastered. But the mastered movements are habitually automatic: the person does not list mentally those muscles that should contract and relax, and small movements that need to be coordinated, but simply produce motion, which due to habit is automatic. However, this movement will be arbitrary, because it can be arbitrarily started, stopped or changed.Violation of the coordination of movements in diseases, poisoning, for example, in a drunk, leads to the fact that the gait becomes insecure, the legs and hands are "stumbling", the balance is lost, the person often falls.
Depending on the functions and location of the muscles, they are divided and described as the muscles of the trunk, pelvic muscles, lower limb muscles, shoulder girdle muscles, upper limb muscles, neck muscles and head muscles.
It is necessary to emphasize the following.
The term "trunk", "torso", by which is meant in the everyday life part of the figure consisting of the pelvis, abdomen and chest without arms and neck, which in everyday life is often regarded as a monolithic array, in plastic anatomy for a correct understanding of the form and movement should be treated differently.
Above it has already been said and shown that the pelvis and the thorax are mutually mobile, and the shoulder belt with respect to the thorax is also very mobile, therefore, the household term "trunk" consists of three moving parts:
1) the pelvis and its muscles going to the legs;
2) the actual trunk, which consists of the chest, spine, abdominal muscles and back, moving the mutually chest and pelvis, the muscles of the spine and intercostal muscles;
3) the bones and muscles that form and serve the shoulder girdle, which, as it were, are put on the upper part of the chest and are movably connected to it.
In accordance with this, instead of the everyday concept of "torso muscles" depending on the location and functions of the muscles, they are divided and described as three sections: 1) muscles of the trunk; 2) muscles of the pelvis; 3) muscles of the shoulder girdle.
Before proceeding with the description of the musculature, it is necessary to recall the following.
Although the study of individual muscles is absolutely necessary, this is not the main task of the student. The most important thing is to see how the body volumes are composed of individual muscles that cover the bones and joints, in conjunction with other muscles, bones and joints. Individual muscles, bones and joints are like letters, and large volumes- words and phrases. Like the way a word is composed of letters, the words are a phrase.
So, from the separate muscles, bones and joints, the three-dimensional forms of the whole body are composed.
It is in the knowledge of large arrays and in the ability to link them together, that is, to build a figure, and the most important goal of studying plastic anatomy is.
A well-constructed figure is easy to finish, detailed on the basis of knowledge of the form of individual anatomical details - the muscles of bones, joints. But if the figure is not built well, even if the individual details are correctly displayed, the figure will "collapse."
Thus, before the student there are two tasks:
1. The study of specific muscles: their functions, relief, connection with bones and joints, that is, the study of the anatomy of small forms or, as it may be called, small anatomy.
2. The study of large anatomical arrays and their interrelationships - the study of anatomy of large forms - large anatomy.
When describing the muscles, the terms & quot; start & quot; and & quot; attachment & quot ;. If the muscle lies on the trunk, then it is considered to be the beginning of its central end closest to the spine or to the midline; if the muscle lies on the limb, the beginning is the end of the muscle located on the less moving part of the skeleton.
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