Structure and function of muscles

Due to the muscles, rather, because of their ability to decrease the human body can perform a variety of movement, balance and a certain body position in space. Muscle, in contrast to the bones and joints, are the active element of the apparatus of motion.

In Fig. 90.
Human muscles (front view):
1 - frontal belly of the occipito-frontal muscle;
2 - temporalis muscle;
3 - the circular muscle of the eye;
4 - zygomaticus muscle;
5 - circular muscle of the mouth;
6 - masseter;
7 - muscle, lowered the angle of the mouth;
8 - mentalis;
9 - sternocleidomastoid muscle;
10 - sternohyoid muscle;
11 - trapezius muscle;
12 - ulnar extensor wrist;
13 - little finger extensor;
14 - extensor digitorum;
15 - elbow flexor wrist;
16 - anconeus;
17 - deltoid;
18 - pectoral muscle;
19 - serratus anterior;
20 - triceps brachii;
21 - the biceps;
22 - shoulder muscles;
23 - brachioradialis muscle;
24 - long radial extensor wrist;
25 - radial flexor wrist;
26 - short radial extensor wrist;
27 - long arm, thumb abductor;
28 - short extensor of the thumb brush;
29 - the rectus abdominis;
30 - external oblique muscle of abdomen;
31 - pyramidal muscle of abdomen;
32 - muscle, fascia stretched wide hips;
33 - ilio-psoas;
34 - comb muscle;
35 - long adductor;
36 - sartorius;
37 - the thin muscle;
38 - the longest straight thigh muscle;
39 - lateral thigh muscle broad;
40 - a broad medial thigh muscle;
41 - calf;
42 - soleus muscle;
43 - anterior tibial muscle;
44 - long extensor of fingers;
45 - the long flexor of fingers;
46 - the long tendon of extensor digitorum;
47 - a muscle that causes the big toe

Contractile ability of muscles is provided by the structural elements of muscle tissue (textus musculares), which are called myofibrils. Depends on the structure of myofibrils transverse striations of muscles - the alternation of light and dark bands, and the thickness of muscle fibers depends on the number and cross section of myofibrils. Myofibrils are composed of repeating units called sarcomeres, and are arranged parallel to the long axis of the muscle fiber. Skeletal muscles are formed of striated muscle tissue, the basic structural element of which is muscle fibers - myosymplasts. Fibers they are called because of the large difference between the cross section (0.05 to 0.11 mm) and length of the muscle cell (15 cm). The length of the fibers depends on the length and structure of most muscles.

Skeletal muscle, which is also called striated muscle (under the name of its constituent fibers) or arbitrary (in its contractile characteristics), is attached directly to bone or joint with tendon (tendo). Individual muscles on one end can be attached to the bones and the other - on the skin. The functioning of the muscles is to reduce them, in which the muscle shortens, so that the point at which the attached muscle, converge. The work of the skeletal muscle can be controlled: reduce or relax at any time necessary, to vary the speed and intensity of contractions.

The average muscle mass of an adult is approximately 30 kg in men, ie, 42-47% of total body weight, and 17 kg for women - 30-35% of total body weight. A total of 300 human body muscles, which are arranged in groups according to their functions.

Muscle fibers are arranged in parallel rows and connected to the beams that form the skeletal muscle itself. Small muscle bundles covered by a thin connective tissue - the endomysium (endomysium), large - perimiziem (perimysium), and the whole muscle as a whole covers a dense connective tissue - epimizy (epimysium). At the ends of the muscles go into the tendons, which are more flexible, elastic and durable than the muscle fibers, thus avoiding discontinuities of muscles and their separation from the bones with heavy internal load or a strong external impact.

The fibers are approximately 86-90% of the total muscle mass. The remaining percentage is divided between the blood vessels and nerves that provide trophic (livelihoods), the power and efficiency of the muscles.

In isolated muscle head (caput) - the initial part of the belly (venter) - the middle part and tail (cauda) - final part. The length of the muscle depends on the degree of scale that it can provide. Each muscle is the point of beginning (origo) and place attachment (insertio). The shape of the muscles varied and depends on the ratio of muscle fibers and tendons. Distinguish the following forms of muscle:

1) spindle-shaped muscle (m. fusiformis) - muscle, tapering to both ends of the tendons and ends;

2) biceps / triceps / quadriceps muscle (m. biceps / triceps / quadriceps)- a muscle that has the belly for one may be a few heads with different beginning and transitioning to different tendons;

3) The digastric (m. biventer / digastricus) - the muscle belly is divided into two intermediate tendon called the tendinous arch (arcus tendineus);

4) mnogobryushnaya muscle, such as the rectus (m. rectus) - the muscle fibers which course is interrupted by one or more jumpers tendon (intersectiones tendineae);

5) general muscle (m. latus) - the muscle, the muscle fibers which have the form of layers, passing into a broad tendon - aponeurosis (aponeurosis). These muscles are found mainly on the trunk;

6) semipenniform muscle (m. unipennatus) - the muscle in which muscle fibers are attached at an angle to one edge of the tendon;

7) dvuperistaya muscle (m. bipennatus) - the muscle fibers which are arranged on both sides of the tendon and at an angle.

In Fig. 91.
Forms of muscle
1 - spindle-shaped muscle:
a) the abdomen,
b) the tendon;
2 - biceps:
a) head,
b) the abdomen,
c) the tail;
3 - biventer:
a) the abdomen,
b) the tendinous arch;
4 - mnogobryushnaya muscle:
a) the abdomen,
b) the tendinous bridge;
5 - a broad muscle:
a) the abdomen,
b) the aponeurosis;
6 - semipenniform muscle;
7 - dvuperistaya muscle

 

At the place of attachment isolated articular muscle (m. articularis) - muscle attached to the joints. Annular muscles or close the cavity and in this case are called circular (m. orbicularis), or compress the output of the cavity body and called sphincter (m. sphincter). The size of the muscles are divided into long, forming the muscle groups of limbs, and short, are in the deep layers of the back.

In the body there are different anatomical education, facilitating the work of muscles. For example, a bursa (bursae synoviales) are located in areas of most intensive movement of muscles and tendons. They are slit-like cavities filled with fluid - synovitis, and help to reduce friction. Between the skin and subcutaneous projection of bone located bursa (bursae synoviales subcutaneae), and a tendon - podsuhozhilnye (bursae synoviales subtendineae). In the feet and hands, that is the most mobile areas of the upper and lower extremities, muscle tendon sheath are (vaginae tendinis). Within these fibrous or kostnofibroznyh channels are synovial sheaths (vaginae synoviales tendinum), which lists greased synovitis, tendon gliding provide free strictly in certain directions. In areas where bone is overlapped by the tendon to the bone are covered with cartilage hollow, which is called a block (trochlea). Blocks prevent the displacement of the tendon by changing their direction. In some ginglymoidal joints in thicker tendons are sesamoid bones (ossa sesamoidea), facilitating the free movement of joints. They can be found at the base of the first phalanx and the patella.

Individual muscles and muscle groups cover the fascia (fasciae), which function as a protective shell. They are formed by connective tissue and contain collagen and elastic fibers. Fascia define the direction of the blood and lymph vessels and nerves, and in some cases, are the site of the beginning or the attachment of muscles.

The deep fascia (fasciae propria) to form the muscles that surround them, the fibrous sheath with holes for blood vessels and nerves. In cases where the muscles are arranged in several layers deep fascia splits into separate plates, which are formed for each vaginal muscles. Fascia plate connected to each other by fibrous septa intermuscular that separate one group of muscles from each other and grow together with the periosteum of bone, forming kostnofibroznye vagina. Superficial fascia (fasciae superficialis) located directly beneath the subcutaneous fat covering the whole body, and following the course of the skin.





List of Abbreviations

a., aa. — arteria, arteriae (artery, the artery)

lig., ligg. — ligamentum, ligamenta (ligament, the ligaments)

m., mm. — musculus, musculi (muscle, the muscle)

n., nn. — nervus, nervi (nerve, the nerve)

r., rr. — ramus, rami (branch)

s. — seu (or)

v., vv. — vena, venae (vienna)