Types of muscle tissue and their features

In the article we will consider the types of muscle tissue. This is a very important topic in biology, because everyone must know how our muscles function. They are a complex system, the study of which, we hope, will be interesting to you. And you can better imagine the types of muscle tissue pictures that you will find in this article. First of all, let's give a definition that is necessary when studying this topic.

Muscle tissue is a special group of human and animal tissues , the main function of which is to reduce it, causing the movement of the organism or its constituent parts in space. This function corresponds to the structure of the basic elements, of which different types of muscle tissues are composed. These elements have longitudinal and extended orientation of myofibrils, including in their composition contractile proteins - myosin and actin. Muscle tissue, like the epithelial tissue, is a prefabricated tissue group, since its main elements develop from embryonic primordia.

Reduction of muscle tissue

Her cells, as well as the nervous ones, can be excited by the action of electrical and chemical impulses. The ability to reduce (shorten) in response to the action of a stimulus is associated with the presence of myofibrils, special protein structures, each of which consists of microfilaments, short protein fibers. In turn, they are subdivided into myosin (thicker) and actin (thin) fibers. In response to nervous irritation, various types of muscle tissue are reduced. The contraction to the muscle is transmitted along the nervous process through the neurotransmitter, which is acetylcholine. Muscle cells in the body perform energy-saving functions, since the energy expended in contracting various muscles is then released as heat. That is why, when the body is subject to cooling, there is a shiver. This is nothing more than frequent muscle contractions.

The following types of muscle tissue can be distinguished, depending on the structure of the contractile apparatus: smooth and striated. They consist of histogenetic types that differ in their structure.

Muscular tissue striated

Myotoma cells, which are formed from the dorsal mesoderm, are the source of its development. This tissue consists of elongated muscle fibers, having the form of cylinders, the ends of which are pointed. 12 cm in length and 80 μm in diameter reach these formations. Simplasts (multinuclear formations) are contained in the center of muscle fibers. Outside, they are adjacent to cells called "myosatellites." The sarcolemma is limited to fibers. It is formed by the plasmolemma of the symplast and the basal membrane. Under the basal membrane of the fiber are located myosatellite cells - so that the plasmolemma of the symplast touches their plasmolemma. These cells are the cambial reserve of muscular skeletal tissue, and it is through this that regeneration of the fibers is carried out. Myosymplasts, in addition to the plasmolemma, also include sarcoplasm (cytoplasm) and numerous nuclei located along the periphery.

The value of striated muscle tissue

Describing the types of muscle tissue, it should be noted that the striated is the executive apparatus of the entire motor system. It forms skeletal muscles. In addition, this type of tissue is part of the structure of internal organs, such as the pharynx, tongue, heart, upper section of the esophagus, etc. The total weight of it in an adult is up to 40% of the body weight, and in the elderly, as well as newborns, its Share - 20-30%.

Features of striated muscle tissue

Reduction of this type of muscle tissue, as a rule, can be done with the participation of consciousness. It has a somewhat higher speed compared to the smooth one. As you can see, the types of muscle tissue are different (we'll talk about the smooth one very soon and note some other differences between them). In the striated muscle, the nerve endings perceive information about the current state of the muscle tissue, and then transmit it along the afferent fibers to the nerve centers responsible for the regulation of the motor systems. The signals controlling the muscle functions come from the regulators in the form of nerve impulses along the motor or vegetative efferent nerve fibers.

Smooth muscle tissue

Continuing to describe the types of muscle tissue of a person, we proceed to a smooth one. It is formed by spindle-shaped cells, whose length ranges from 15 to 500 μm, and the diameter is in the range of 2 to 10 μm. Unlike muscle fibers striated, these cells have one core. In addition, they do not have transverse striation.

The importance of smooth muscle tissue

From the contractile function of this type of muscle tissue depends on the functioning of all body systems, because it is part of the structure of each of them. So, for example, smooth muscle tissue is involved in controlling the diameter of the respiratory tract, blood vessels, in contraction of the uterus, bladder, in the realization of the motor functions of our digestive tract. It controls the diameter of the pupil of the eye, and also participates in many other functions of various body systems.

Muscular layers

Muscular layers form this kind of tissue in the walls of lymphatic and blood vessels, as well as all hollow organs. Usually it is two or three layers. Thick circular - the outer layer, the middle is not necessarily present, the thin longitudinal - the inner layer. Nutrient muscle tissue blood vessels, as well as nerves pass parallel to the axis of muscle cells between their beams. Smooth muscle cells can be divided into 2 types: unitary (combined, grouped) and autonomous myocytes.

Autonomous Myocytes

The autonomous function quite independently of each other, since each such cell is innervated by a nerve end. They were found in the muscle layers of large blood vessels, as well as in the ciliary muscle of the eye. Also to this type are the cells from which the muscles that lift the hair consist.

Unitary myocytes

Unitary muscle cells, on the other hand, are closely intertwined, so that their membranes can not simply adjoin tightly to each other, forming desmosomes, but also to merge, forming nexus (gap junctions). Beams are formed as a result of this association. Their diameter is about 100 μm, and the length reaches several mm. They form a network, and collagen fibers are woven into its cells . Fibers of vegetative neurons are innervated by bundles, and they become functional units of smooth muscle tissue. Depolarization upon excitation of a single cell of the beam propagates very rapidly to neighboring cells, since the resistance of the gap junctions is small. The tissue consisting of unitary cells is present in most organs. These include the ureters, the uterus, the digestive tract.

Reduction of myocytes

The reduction of myocytes is due to smooth tissue, as in the striated strand, by the interaction of myosin and actin filaments. In this are the different types of muscle tissue in man. These filaments are distributed within the myoplasm in a less orderly manner than in the striated muscle. This is associated with the absence of transverse striation in smooth muscle tissue. Intracellular calcium is the final executive link controlling the interaction of myosin and actin filaments (i.e., contraction of myocytes). The same applies to the striated muscle. However, the details of the control mechanism differ significantly from the latter.

Vegetative axons passing through the thickest muscular smooth tissue do not form synapses, which is characteristic of the striated tissue, but numerous thickening along the entire length, which play the role of synapses. Thickening produces a mediator that diffuses to the adjacent myocytes. Receptor molecules are on the surface of these myocytes. With them, the mediator interacts. It causes depolarization in the myocyte of the outer membrane.

Features of smooth muscle tissue

The nervous system, its vegetative department, is controlled without the involvement of consciousness by the work of smooth muscles. Muscles of the bladder are the only exception. Control signals are either directly realized, or indirectly through hormonal (chemical, humoral) effects.

The energy and mechanical properties of this type of muscle tissue ensure the maintenance of the tone of the (controlled) walls of hollow organs and vessels. This is due to the fact that smooth tissue functions efficiently, it does not require large expenditures of ATP. It has less speed than muscle stranded, but it can shorten for a longer time, in addition, it can develop significant stress and vary its length over a wide range.

So, we examined the types of muscle tissue and the features of their structural organization. Of course, this is just basic information. You can describe the types of muscle tissue for a long time. Drawings will help you visualize them.