The muscle is an active element of the musculoskeletal system.
The classification of muscles is carried out according to various criteria: position in the human body, shape, direction of fibers, functions, attitude to joints, etc.
The main types of muscle
The classification of human and vertebral muscles suggests three different types: striated skeletal muscle, striated cardiac muscle (myocardium) and smooth muscles, which make up the walls of blood vessels and hollow internal organs.
The purpose of the striated muscles is to bring the bones into motion, to participate in the formation of the walls of the oral, chest, and abdominal cavities. They are part of the auxiliary parts of the organs of the eye, affect the auditory ossicles. The work of skeletal muscles ensures that the human body is in balance, moving in space, breathing and swallowing, facial expressions.
Skeletal muscle: structure
Almost 40% of the adult body mass is muscle tissue. The skeletal muscle in the body is more than 400.
The skeletal muscle units are the motor neuron and muscle fibers innervated by this neuromotor unit. With the help of impulses sent by a motor neuron, muscle fibers come into action.
Skeletal muscles are represented by a large number of muscle fibers. They have an elongated shape. The classification of human muscles suggests that their diameter is 10-100 microns, and the length varies from 2-3 to 10-12 cm.
A thin membrane surrounds the muscle cell - a sarcolemma containing sarcoplasm (protoplasm) and a large number of nuclei. The contractile part of the muscle fiber is represented by long muscle filaments - myofibrils, which consist mainly of a substance called actin.
Myosin contained in cells is in a dispersed state. It has a lot of protein, which plays an important role in maintaining tonic contraction. Even the relative rest of the skeletal muscle does not imply its complete relaxation. At this time, moderate stress, i.e. muscle tone.
Auxiliary muscle devices
The structure and classification of skeletal muscles determine their functionality. So, they are able to perform certain actions only with the help and with the participation of special anatomical formations that make up the auxiliary devices, which consist of fascia, vaginal tendons, synovial bags and blocks. Fascia is a cover made up of connective tissue, provides support to the muscle abdomen, when it contracts, interfere with the friction of the muscles from each other. In the case of pathology, the presence of fascia prevents the spread of pus and blood during hemorrhage.
Classification of skeletal muscle by dynamic and static properties
Skeletal muscles, based on the nature of the relationship between muscle bundles and intramuscular connective tissue formations, can vary greatly in structure, which determines their functional diversity. Muscle strength can be determined by the number of muscle bundles, since they determine the size of the physiological diameter. It is his attitude to the anatomical diameter that makes it possible to judge one or another force of dynamic and static characteristics.
The classification of skeletal muscles according to the differences in these ratios divides the skeletal muscles into dynamic, statodynamic and static.
The simplest structure is characteristic of dynamic muscles. In the presence of a gentle remix, their long fibers extend along the longitudinal axis of the muscle or at an angle to it, which leads to the coincidence of the anatomical diameter with the physiological one. These muscles perform a large dynamic load. They have a large amplitude, but they do not differ in strength. These muscles are considered fast, agile, but also quickly fatiguing.
The statodynamic muscles of the perimizium (internal and external) are more strongly developed than the dynamic ones, and the muscle fibers are shorter. They go in different directions, that is, they form, in contrast to dynamic ones, many physiological diameters. If there is one common anatomical diameter in the muscle, there may be 2, 3, or 10 physiological diameters. This suggests that statodynamic muscles are stronger than dynamic ones. Their role consists mainly in maintaining static function during support, holding unbent joints when standing. They are distinguished by great strength and considerable endurance.
Classification of muscles suggests the presence of a third type. These are static muscles. They can develop in the process of a large static load falling on them. The lower the location of the muscles on the body, the more static they differ in structure. A lot of static work when standing and supporting the limbs on the soil in motion, fixing the joints in a certain position is part of their direct tasks.
Classification of muscles in the direction of muscle fibers and their relation to tendons
Muscles whose fibers are parallel to the longitudinal axis are called spindle-shaped, or parallel. When the fibers are at an angle to the axis, this muscle is called the cirrus. In the limbs localized, mainly spindle-shaped and cirrus muscles.
Intramuscular tendon layers, or rather their number, and the directions of the muscle layers serve as criteria by which the cirrus muscles are divided into several types:
- single-ply, in which there are no tendon layers, the attachment of muscle fibers to the tendon is available on only one side;
- bifibrous; they have one tendon layer and bilateral attachment of muscle fibers to the tendon;
- multifibrous, in which two or more tendon layers, due to which the interweaving of muscle bundles occurs, they approach the tendon from several sides.
How do muscles divide in shape?
Classification of muscles in shape distinguishes several main types in their variety.
- Long. They are located mainly in the limbs. Their shape resembles a spindle. Each muscle is conditionally divided into three parts: the middle part is called the abdomen; the beginning of the muscle is called the head, the end opposite the beginning is the tail. Their tendons have a ribbon-like shape. There are such long muscles that have not one but several heads on different bones, which is necessary to strengthen their support. Such muscles are called multi-headed.
- Short. They are located where the range of movements is not too large. These are the junction of the individual vertebrae, the place between the vertebrae and ribs, etc.
- Flat wide. They are localized mainly on the trunk and belts of the upper and lower extremities. They have enlarged tendons called aponeuroses. The flat muscles perform not only the motor function, but also the supporting and protective.
- Muscles of other shapes: square, circular, deltoid, dentate, trapezoid, fusiform, etc.
The division of muscles into groups depending on the number of heads and location
The structure and classification of muscles are interconnected. So, one part of them has several heads. They are given a name according to the number of heads: biceps (biceps), triceps (triceps), etc.
Depending on the place that the muscles occupy in the body, they are superficial and deep, medial and lateral, external and internal.
Muscles according to joint effects
Classification of muscles in relation to joints implies the presence of single-joint (affect only one joint), double-joint (throws over two joints), and multi-joint muscles (affect three or more joints).
Classification of muscle by function
According to this criterion, synergistic muscles and antagonist muscles are distinguished. Synergists cause the joint to move in only one direction (flexors or extensors), and antagonists act on the joint in two opposite directions (flexors and extensors).
The classification of muscles by function includes other options. Muscles are also leading, abducting. They can perform rotational functions, compress, narrow, expand, raise, lower, strain, pull.