Anatomical formations, which consist of muscle tissue, are the muscles of a person. Thanks to them, it is possible to move a person in space, the work of the heart and other internal organs. The content of muscle tissue in the female body is 28-32%. In men, this figure is slightly higher and reaches 45%.
There are three types of muscle tissue :
- skeletal,
- smooth
- heart.
Skeletal muscles are composed of striated fibers, bundled. Inside them are threads consisting of proteins, due to which the main function is realized - reduction.
Cardiac muscle tissue has a structure similar to striated fibers. They are intertwined in separate sections. Due to this feature, the heart muscle is capable of rapid contraction.
The smooth muscles of a person are present in the walls of all internal organs. The contraction of these muscle fibers is slow.
Human skeletal muscles have good innervation and blood supply. Nerves and blood vessels fit each muscle bundle. They have a shell, which is represented by connective tissue. Nerves that approach the muscles contain motor and sensory neurons. The first transmit impulses from the spinal cord, as a result of which the muscle fibers contract. Thus, the muscles in the body do this reflexively. Impulses emanating from the spinal cord are affected by the brain. Therefore, actions become arbitrary. When the muscles contract, various parts of the body are forced to move, which causes the body to move or a person to maintain a certain position. This effect is achieved due to the joint and coordinated work of the muscles of the extensors and flexors, which carry out opposite actions.
The human muscles perform mechanical work. They contract and thus act on the bone as a lever. Any movement requires a lot of energy. Its source is the decay and subsequent oxidation of organic substances (fats, carbohydrates, nucleic acids). Organic substances in muscle tissue undergo transformations, in which oxygen must necessarily participate.
With prolonged work, muscle performance gradually decreases. This condition is called fatigue. After resting, the ability of muscle tissue to work is fully restored.
The main muscles of a person perform their characteristic functions. These include:
- neck muscles. They provide a tilt and rotation of the head, its retention in a physiological position;
- trapezoidal. She brings the spine closer to the shoulder blades, raises the shoulder girdle;
- deltoid. The main function is the movement of the upper limb backward, forward, abduction to the side;
- biceps (biceps muscle of the shoulder). Responsible for bending the arm in the shoulder joint ;
-the three-headed muscle of the shoulder. Performs hand movements backward, pressing them to the body, extension of the arms;
- muscles of the forearm. They are divided into extensors and flexors, which respectively perform extension and flexion of the hands and fingers. There are also arch supports and pronators that carry out the movement of the radial bones;
- the pectoralis major muscle brings the hand to the body, lowers the raised shoulder, raises the ribs;
- oblique muscles of the abdomen rotate the body to the side, while contracting, pull the chest down, bend the spinal column, raise the pelvis with fixation of the chest;
- rectus abdominis muscle. By means of it, the spine is bent;
- latissimus dorsi muscle. At her expense, lowering the hand. Also pulls it back, rotates inward;
- buttock muscle. Performs a turn and extension of the thigh outwards. Fixes the body in a straightened position;
- back femoral muscles. The bending of the legs in the knee joint is impossible to imagine without the normal functioning of this muscle;
- The quadriceps muscle of the thigh. The legs are unbent in the knee joint only due to its work;
- tibial muscle. She participates in the extension of the foot, while raising its medial edge.
The human muscles are the most important organ of the human body, thanks to which not only all human movements are carried out, but also the coordinated work of all internal organs.