Functions of smooth muscle tissue. Smooth muscle tissue: structure

Fabric - a collection of similar in structure cells, which are united by common functions. Virtually all multicellular organisms consist of different types of tissues.

Classification

In animals and humans, the following types of tissues are present in the body:

• Epithelial;
• Nervous;
• Connecting;
• Muscular.

These groups are united in several varieties. So, connective tissue is fatty, cartilaginous, bone. Also here are blood and lymph. Epithelial tissue exists multilayered and single-layered, depending on the structure of cells, it is also possible to isolate flat, cubic, cylindrical epithelium, etc. Nervous can only occur in one species. And we'll talk more about the muscle type of tissue in this article.

Types of muscle tissue

In the organism of all animals three types are distinguished:

• Smooth musculature;
• Striated muscles;
• Heart muscle tissue.

The functions of smooth muscle tissue differ from those of cross-striped and cardiac tissue , so the other has a structure. Let's take a closer look at the structure of each kind of musculature.

General characteristics of muscle tissue

Since all three species are of the same type, they have much in common.

The cells of the muscle tissue are called myocytes, or fibers. Depending on the variety of tissue, they can have a different structure.

The muscle tissue, the photo of which can be seen below, has practically no intercellular substance.

Another common feature of all muscle types is that they are able to contract, but in different species this process occurs individually.

Features of myocytes

Cells of smooth muscle tissue, as well as cross-striped and cardiac, have an elongated shape. In addition, they have special organoids, called myofibrils, or myofilaments. They contain contractile proteins (actin, myosin). They are necessary in order to ensure the movement of the muscle. An obligatory condition for the functioning of the muscle, in addition to the presence of contractile proteins, is also the presence of calcium ions in the cells. Therefore, inadequate or excessive consumption of foods with a high content of this element can lead to incorrect work of the musculature - both smooth and cross-striped.

In addition, another specific protein, myoglobin, is present in the cells. It is necessary in order to bind with oxygen and store it.

With regard to organelles, in addition to the presence of myofibrils, the content of a large number of mitochondria in the mitochondria cell - the biocomponent organoids responsible for cellular respiration - is special for muscle tissues . And this is not surprising, since the muscle fiber for reduction requires a large amount of energy produced by breathing mitochondria.

In some myocytes, more than one nucleus is also present. This is characteristic of the striated muscle, the cells of which can contain about twenty nuclei, and sometimes this figure reaches up to a hundred. This is due to the fact that the fiber of the striated muscle is formed from several cells, which are subsequently combined into one.

The structure of striated muscle

This type of tissue is also called skeletal musculature. The fibers of this type of muscles are long, collected in bundles. Their cells can reach several centimeters in length (up to 10-12). They contain many nuclei, mitochondria and myofibrils. The basic structural unit of each myofibril of transverse striated tissue is the sarcomere. It consists of a contractile protein.

The main feature of this musculature is that it can be controlled consciously, unlike the smooth and heart.

The fibers of this tissue are attached to the bones with the help of tendons. That is why such muscles are called skeletal muscles.

Structure of smooth muscle tissue

Smooth muscles lining some internal organs, such as the intestine, uterus, bladder, as well as blood vessels. In addition, sphincters and ligaments are formed from them.

The smooth muscle fiber is not as long as the striated muscle. But its thickness is greater than in the case of skeletal muscles. Cells of smooth muscle tissue have a spindle-like shape, and not threadlike, like myocytes transversely striated.

Structures that impair the contraction of smooth muscles are called protofibrils. Unlike myofibrils, they have a simpler structure. But the material from which they are built is the same contractile proteins actin and myosin.

The mitochondria in myocytes of smooth muscles are also smaller than in cells that are transversely striated and cardiac. In addition, they contain only one core.

Features of the heart muscle

Some researchers define it as a subspecies of striated muscle tissue. Their fibers are really similar in many respects. Heart cells - cardiomyocytes - also contain several nuclei, myofibrils and a large number of mitochondria. This tissue, like skeletal muscles, is able to contract much faster and stronger than smooth muscle.

However, the main feature that distinguishes the heart muscle from the striated muscle is that it can not be controlled consciously. Its reduction occurs only automatically, as in the case of smooth muscles.

In the heart tissue, in addition to typical cells, there are also secretory cardiomyocytes. They do not contain myofibrils and do not shrink. These cells are suspended for the production of the hormone atriopeptin, which is needed to regulate blood pressure and control the volume of circulating blood.

Functions of striated muscle

Their main task is to move the body in space. It is also the movement of parts of the body relative to each other.

Of the other functions of the striated muscles, one can note the maintenance of the pose, the depot of water and salts. In addition, they perform a protective role, which is especially true for abdominal muscles, which prevent mechanical damage to internal organs.

The regulation of temperature can also be included in the functions of the striated muscles, since with the active contraction of the muscles a significant amount of heat is released. That's why when the muscle freezes, the muscles begin to tremble involuntarily.

Functions of smooth muscle tissue

The musculature of this species performs the evacuation function. It is that the smooth muscles of the intestine push the stool to the place of their excretion from the body. This role also manifests itself in childbirth, when the smooth muscles of the uterus expel the fruit from the organ.

The functions of smooth muscle tissue are not limited to this. Also their sphincter role is important. From the tissue of this species, special circular muscles are formed, which can close and open. Sphincters are present in the urinary tract, in the intestine, between the stomach and esophagus, in the gall bladder, in the pupil.

Another important role played by smooth muscles is the formation of a ligamentous apparatus. It is necessary to maintain the correct position of the internal organs. With a decrease in the tone of these muscles, some organs can be omitted.

On this function, the smooth muscle tissue ends.

Purpose of the heart muscle

Here, in principle, there is nothing to talk about. The main and only function of this tissue is to ensure blood circulation in the body.

Conclusion: the differences between the three types of muscle tissue

For the disclosure of this issue, we present the table:

That's all the main characteristics of cross-striped, smooth and cardiac muscle tissue. Now you are familiar with their functions, structure and main differences and similarities.