Anatomical formations, which consist ofmuscle tissue - these are the muscles of a person. Thanks to them, it is possible to move a person in space, work the heart and other internal organs. The content of muscle tissue in the female body is 28-32%. In men, this indicator is slightly higher and reaches 45%.
There are three types of muscle tissue:
- Skeletal,
- smooth,
- heart.
Skeletal muscles consist of striated fibers collected in bundles. Inside of them pass the threads, consisting of proteins, thanks to which the basic function - reduction is realized.
Cardiac muscle tissue has a structure similar to striated fibers. They are intertwined in separate sections. Thanks to this feature, the heart muscle is capable of rapid contraction.
Human smooth muscles are present in the walls of all internal organs. The reduction in muscle fiber data is slow.
Human skeletal muscles have a good innervationand blood supply. For each muscle bundle, nerves, blood vessels are suitable. They have a sheath, which is represented by a connective tissue. The nerves that approach the muscles contain motor and sensitive neurons. The former transmit impulses from the spinal cord, as a result of which the muscle fibers contract. Thus, the muscles in the body make it reflexively. The impulses emanating from the spinal cord are affected by the brain. Therefore, the actions become arbitrary. With contraction, the muscles are forced to move different parts of the body, which causes the movement of the body or the preservation of a certain position by a person. This effect is achieved through the joint and concerted work of the extensor muscles and flexors, which carry out the 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 decomposition and subsequent oxidation of organic substances (fats, carbohydrates, nucleic acids). Organic substances in muscle tissue undergo transformations in which oxygen must necessarily participate.
With continued operation, the working capacity of muscles gradually decreases. This condition is called fatigue. After rest, the ability of muscle tissue to work is restored to the full.
The basic muscles of a person perform only functions that are characteristic of them. To such it is possible to carry:
- Neck muscles. They provide a tilt and turn of the head, its retention in a physiological position;
- trapezoidal. She brings the spine together with the shoulder blades, lifts the shoulder girdle;
- deltoid. The main function is the movement of the upper limb backwards, forward, and aside;
- biceps (biceps brachialis muscle). He is responsible for flexing the arm in the shoulder joint;
- triceps brachialis muscle. Performs movements of hands back, pressing them to the body, extension of hands;
- Forearm muscles.They are divided into extensors and flexors, which respectively perform extension and flexion of the hands and fingers. There are also supporters and pronators, which carry out the movement of the radius bones;
- the large pectoral muscle carries the arm to the trunk, lowers the raised shoulder, raises the ribs;
- oblique abdominal muscles turn the body to the side, with a simultaneous contraction pull the chest down, bend the vertebral column, raise the pelvis with the fixation of the chest;
- Straight abdominal muscle. By means of it the flexion of the spine is carried out;
- The widest back muscle. At her expense, the hand is lowered. Also pulls it back, rotates inside;
gluteus muscle. Performs turning and extension of the thigh to the outside. Fixes the trunk in the straightened position;
- hind femoral muscles. Bending of the legs in the knee joint can not be imagined without the normal operation of this muscle;
- quadriceps femoris muscle. Legs unbend at the knee joint only at the expense of its work;
- tibialis muscle. It participates in the extension of the foot, while lifting its medial edge.
The human muscles are the most important organ of the human body, thanks to which not only all human movements are realized, but also the coordinated work of all internal organs.
