Plant and animal organisms differ not only externally, but also, of course, internally. However, the most important distinguishing feature of the lifestyle is that animals are able to actively move in space. This is ensured due to the presence in them of special tissues - muscle. We will consider them in more detail further.
Animal fabrics
In the body of mammals and humans, there are 4 types of tissues lining all organs and systems, forming blood and performing vital functions.
- Epithelial. Forms integuments of organs, outer walls of blood vessels, lines mucous membranes, forms serous membranes.
- Nervous. It forms all the organs of the system of the same name, has the most important features - excitability and conductivity.
- Connective. It exists in various manifestations, including in liquid form - blood. Forms tendons, ligaments, fat layers, fills bones.
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Muscular tissue, the structure and functions of which allow animals and humans to carry out a wide variety of movements, and many internal structures to contract and expand (vessels and so on).
muscle tissue structure and function
The total combination of all the listed species ensures the normal structure and functioning of living beings.
Muscle tissue: classification
A specialized structure plays a special role in the active life of humans and animals. Its name is muscle tissue. Its structure and functions are very peculiar and interesting.
In general, this fabric is heterogeneous and has its own classification. It should be considered in more detail. There are such types of muscle tissue as:
- smooth;
- striped;
- hearty.
Each of them has its place of localization in the body and performs strictly defined functions.
Structure of muscle cells
All three types of muscle tissue have their own structural features. However, it is possible to identify the general patterns of the structure of a cell of such a structure.
Firstly, it is elongated (sometimes up to 14 cm), that is, it stretches along the entire muscular organ. Secondly, it is multinuclear, since it is in these cells that the processes of protein synthesis, the formation and breakdown of ATP molecules proceed most intensively.
Also, the structural features of muscle tissue is that its cells contain bundles of myofibrils formed by two proteins - actin and myosin. They provide the main property of this structure - contractility. Each filamentous fibril includes bands that are visible under the microscope as lighter and darker. They are protein molecules that form something like strands. actinforms light, and myosin - dark.
Features of muscle tissue of any type is that their cells (myocytes) form whole clusters - bundles of fibers, or symplasts. Each of them is lined from the inside with whole accumulations of fibrils, while the smallest structure itself consists of the proteins named above. If we consider figuratively this structural mechanism, then it turns out, like a nesting doll, - less in more, and so on to the very bundles of fibers, united by loose connective tissue into a common structure - a certain type of muscle tissue.
The internal environment of the cell, that is, the protoplast, contains all the same structural components as any other in the body. The difference is in the number of nuclei and their orientation not in the center of the fiber, but in the peripheral part. Also in the fact that division does not occur due to the genetic material of the nucleus, but due to special cells called satellites. They are part of the myocyte membrane and actively perform the function of regeneration - restoration of tissue integrity.
Properties of muscle tissue
Like any other structures, these types of fabrics have their own characteristics not only in structure, but also in their functions. The main properties of muscle tissues, thanks to which they can do this:
- abbreviation;
- excitability;
- conductivity;
- lability.
Due to the large number of nerve fibers, blood vessels and capillaries that feed the muscles, they can quickly perceive signal impulses. This propertycalled excitability.
Also, the peculiarities of the structure of muscle tissue allow it to quickly respond to any irritation, sending a response impulse to the cerebral cortex and spinal cord. This is how the property of conductivity manifests itself. This is very important, since the ability to respond in time to threatening effects (chemical, mechanical, physical) is an important condition for the normal safe life of any organism.
Muscular tissue, structure and functions it performs - all this as a whole comes down to the main property, contractility. It implies a voluntary (controlled) or involuntary (without conscious control) decrease or increase in the length of the myocyte. This happens due to the work of protein myofibrils (actin and myosin filaments). They can stretch and thin almost to invisibility, and then quickly restore their structure again.
This is the peculiarity of any type of muscle tissue. This is how the work of the heart of man and animals, their vessels, eye muscles that rotate the apple is built. It is this property that provides the ability for active movement, movement in space. What would a person be able to do if his muscles could not contract? Nothing. Raise and lower your arm, jump, crouch, dance and run, perform various physical exercises - only muscles help to do all this. Namely, myofibrils of actin and myosin nature, which form tissue myocytes.
The last property to mention islability. It implies the ability of the tissue to quickly recover after excitation, to come to absolute performance. Better than myocytes, only axons, nerve cells, can do this.
The structure of muscle tissues, the possession of the listed properties, distinctive features are the main reasons for their performance of a number of important functions in animals and humans.
Smooth
One of the varieties of muscle. It is of mesenchymal origin. Set up differently than others. Myocytes are small, slightly elongated, resembling fibers thickened in the center. The average cell size is about 0.5 mm in length and 10 µm in diameter.
Protoplast is distinguished by the absence of a sarcolemma. There is one nucleus, but many mitochondria. The localization of the genetic material separated from the cytoplasm by the karyolemma is in the center of the cell. The plasma membrane is arranged quite simply, complex proteins and lipids are not observed. Near the mitochondria and throughout the cytoplasm, myofibril rings are scattered, containing actin and myosin in small amounts, but sufficient to contract the tissue. The endoplasmic reticulum and the Golgi complex are somewhat simplified and reduced compared to other cells.
Smooth muscle tissue is formed by bundles of myocytes (fusiform cells) of the described structure, innervated by efferent and afferent fibers. Submits to the control of the autonomic nervous system, that is, it contracts, is excited without conscious control of the body.
In some organs, smooth muscles are formed due to individualsingle cells with special innervation. Although this phenomenon is quite rare. In general, there are two main types of smooth muscle cells:
- secretory myocytes, or synthetic;
- smooth.
The first group of cells is poorly differentiated, contains many mitochondria, a well-defined Golgi apparatus. Bundles of contractile myofibrils and microfilaments are clearly visible in the cytoplasm.
The second group of myocytes specializes in the synthesis of polysaccharides and complex combinative high-molecular substances, from which collagen and elastin are subsequently built. They also produce a significant part of the intercellular substance.
Locations in the body
Smooth muscle tissue, its structure and functions allow it to be concentrated in different organs in different amounts. Since the innervation is not subject to control by the directed activity of a person (his consciousness), then the places of localization will be appropriate. Such as:
- walls of blood vessels and veins;
- most internal organs;
- leather;
- eyeball and other structures.
In this regard, the nature of the activity of smooth muscle tissue is fast-acting low.
Performed functions
The structure of muscle tissues leaves a direct imprint on their functions. So, smooth muscle is needed for the following operations:
- exercise contraction and relaxationorgans;
- narrowing and expansion of the lumen of blood and lymphatic vessels;
- eye movement in different directions;
- control over the tone of the bladder and other hollow organs;
- ensure response to hormones and other chemicals;
- high plasticity and connection of excitation and contraction processes.
The gallbladder, the places where the stomach flows into the intestine, the bladder, lymphatic and arterial vessels, veins and many other organs - all of them are able to function normally only thanks to the properties of smooth muscles. Management, once again, is strictly autonomous.
Striated muscle tissue
The types of muscle tissue discussed above are not controlled by the human consciousness and are not responsible for its movement. This is the prerogative of the next type of fiber - striated.
First, let's figure out why they were given such a name. When viewed through a microscope, one can see that these structures have a clearly defined striation across certain strands - actin and myosin protein filaments that form myofibrils. This was the reason for this name of the fabric.
Cross-muscular tissue has myocytes that contain many nuclei and are the result of the fusion of several cellular structures. Such a phenomenon is denoted by the terms "symplast" or "syncytium". The appearance of the fibers is represented by long, elongated cylindrical cells, tightly interconnected.common intercellular substance. By the way, there is a certain tissue that forms this environment for the articulation of all myocytes. It also has smooth muscle. Connective tissue is the basis of the intercellular substance, which can be either dense or loose. It also forms a series of tendons, with the help of which the striated skeletal muscles are attached to the bones.
Myocytes of the tissue in question, in addition to their significant size, have several other features:
- sarcoplasm of cells contains a large number of well-defined microfilaments and myofibrils (actin and myosin at the base);
- these structures are combined into large groups - muscle fibers, which, in turn, directly form the skeletal muscles of different groups;
- there are many nuclei, a well-defined reticulum and the Golgi apparatus;
- well-developed numerous mitochondria;
- innervation is carried out under the control of the somatic nervous system, that is, consciously;
- fatigue of the fibers is high, but so is performance;
- Above average lability, fast recovery from refraction.
In the body of animals and humans, striated muscles are red. This is due to the presence of myoglobin, a specialized protein, in the fibers. Each myocyte is covered on the outside with an almost invisible transparent membrane - the sarcolemma.
At a young age in animals and humans, skeletal muscles contain more dense connective tissue betweenmyocytes. Over time and aging, it is replaced by loose and fatty, so the muscles become flabby and weak. In general, skeletal muscles take up to 75% of the total mass. It is she who makes up the meat of animals, birds, fish, which a person eats. The nutritional value is very high due to the high content of various protein compounds.
A variety of striated muscles, in addition to skeletal, is cardiac. Features of its structure are expressed in the presence of two types of cells: ordinary myocytes and cardiomyocytes. Ordinary ones have the same structure as skeletal ones. Responsible for the autonomic contraction of the heart and its vessels. But cardiomyocytes are special elements. They contain a small amount of myofibrils, which means actin and myosin. This indicates a low ability to contract. But that is not their task. The main role is to perform the function of conducting excitability through the heart, the implementation of rhythmic automation.
Cardiac muscle tissue is formed by multiple branching of its constituent myocytes and subsequent merging into a common structure of these branches. Another difference from striated skeletal muscle is that heart cells contain nuclei in their central part. Myofibrillar areas are localized along the periphery.
What organs does it form?
All skeletal muscle in the body is striated muscle tissue. A table reflecting the localization of this tissue in the body is given below.
| Striated skeletal muscle tissue | Cardiac muscle tissue |
| 1. Musculoskeletal system | The main organ of the cardiovascular system is the heart. |
| 2. Muscles of the larynx and esophagus | |
| 3. Throat | |
| 4. Language |
Value for the body
The role played by the striated muscles is difficult to overestimate. After all, it is she who is responsible for the most important distinctive property of plants and animals - the ability to actively move. A person can perform a lot of the most complex and simple manipulations, and all of them will depend on the work of skeletal muscles. Many people engage in thorough training of their muscles, achieve great success in this due to the properties of muscle tissue.
Let's consider what other functions the striated muscles perform in the body of humans and animals.
- Responsible for complex facial expressions, expression of emotions, external manifestations of complex feelings.
- Maintains body position in space.
- Performs the function of protecting the abdominal organs (against mechanical stress).
- The cardiac muscles provide the rhythmic contractions of the heart.
- Skeletal muscles are involved in the acts of swallowing, form the vocal cords.
- Regulate tongue movements.
Thus, we can draw the following conclusion: muscle tissues are important structural elements of any animal organism, endowing it with certain unique abilities. properties andthe structure of different types of muscles provide vital functions. The basis of the structure of any muscle is the myocyte - a fiber formed from the protein filaments of actin and myosin.
