Tissue is a collection of cells similar in structure, which are united by common functions. Almost all multicellular organisms are composed of different types of tissues.
Classification
In animals and humans, the following tissue types are present in the body:
- epithelial;
- Nervous
- connecting;
- muscle
These groups combine several varieties. So, connective tissue is fatty, cartilage, bone. Also included are blood and lymph. Epithelial tissue exists multilayered and monolayer, depending on the structure of cells, it is also possible to distinguish flat, cubic, cylindrical epithelium, etc. Nervous can only be of one kind. And we’ll talk more about muscle type of tissue in this article.
Types of muscle tissue
In the body of all animals, three of its varieties are distinguished:
- smooth muscles;
- striated muscles;
- cardiac muscle tissue.
The functions of smooth muscle tissue differ from those of striated and cardiac, therefore, its structure is different. Let's take a closer look at the structure of each type of muscle.
General characteristics of muscle tissue
Since all three species are of the same type, they have a lot in common.
Muscle tissue cells are called myocytes, or fibers. Depending on the type of fabric, they can have a different structure.
Muscle tissue, the photo of which can be seen below, has practically no intercellular substance.
Another common sign of all types of muscles is that they are able to contract, but in different species, this process occurs individually.
Myocyte Features
Cells of smooth muscle tissue, like striated and cardiac, have an elongated shape. In addition, they have special organelles called myofibrils, or myofilaments. They contain contractile proteins (actin, myosin). They are necessary in order to provide muscle movement. A prerequisite for the functioning of the muscle, in addition to the presence of contractile proteins, is the presence of calcium ions in the cells. Therefore, insufficient or excessive consumption of foods with a high content of this element can lead to incorrect functioning of the muscles - both smooth and striated.
In addition, another specific protein is present in the cells - myoglobin. It is necessary in order to bind to oxygen and store it.
As for organoids, in addition to the presence of myofibrils, the content of a large amount of mitochondria in the cell - two-membrane organoids responsible for cellular respiration, is special for muscle tissues. And this is not surprising, since muscle fiber requires a large amount of energy produced by mitochondria breathing to contract.
Some myocytes also have more than one nucleus. This is characteristic of striated muscle, in the cells of which about twenty nuclei can be contained, and sometimes this figure reaches one hundred. This is due to the fact that the striated muscle fiber is formed from several cells, subsequently combined into one.
Striated muscle structure
This type of tissue is also called skeletal muscle. The fibers of this type of muscle are long, bundled. Their cells can reach several centimeters in length (up to 10-12). They contain many nuclei, mitochondria and myofibrils. The main structural unit of each myofibril of striated tissue is the sarcomere. It consists of contractile protein.
The main feature of this muscle is that it can be controlled consciously, as opposed to smooth and cardiac.
The fibers of this tissue are attached to the bones using tendons. That is why such muscles are called skeletal.
Smooth muscle structure
Smooth muscles line some internal organs such as the intestines, uterus, bladder, and blood vessels. In addition, sphincters and ligaments are formed from them.
Smooth muscle fiber is not as long as 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 striated myocytes.
Structures that cause smooth muscle contraction are called protofibrils. Unlike myofibrils, they have a simpler structure. But the material from which they are built is all the same contractile proteins actin and myosin.
Mitochondria in myocytes of smooth muscles are also less than in cells of 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 indeed very much alike. Heart cells - cardiomyocytes - also contain several nuclei, myofibrils and a large number of mitochondria. This tissue, like skeletal muscle, is able to contract much faster and stronger than smooth muscles.
However, the main feature that distinguishes the heart muscle from striated muscle is that it cannot be controlled consciously. Its reduction occurs only automatically, as in the case of smooth muscles.
In the composition of cardiac tissue, in addition to typical cells, secretory cardiomyocytes are also present. They do not contain myofibrils and do not contract. These cells are weighed for the production of the hormone atriopeptin, which is necessary for regulating blood pressure and controlling the volume of circulating blood.
Striated muscle function
Their main task is to move the body in space. It is also the movement of body parts relative to each other.
Of the other functions of the striated muscles, the maintenance of posture, depot of water and salts can be noted. In addition, they play a protective role, which is especially true for the abdominal muscles, which prevent mechanical damage to internal organs.
The functions of the striated muscles can also be attributed to temperature regulation, since with the active contraction of muscles, a significant amount of heat is released. That's why when freezing, the muscles begin to tremble involuntarily.
Smooth muscle function
The muscles of this type perform an evacuation function. It lies in the fact that the smooth muscles of the intestine push the feces to the place of their removal from the body. This role also manifests itself during childbirth, when the smooth muscles of the uterus push the fetus out of the organ.
The functions of smooth muscle tissue are not limited to this. Their sphincter role is also important. Special circular muscles are formed from this type of tissue, 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 that smooth muscles play is the formation of the ligamentous apparatus. It is necessary to maintain the correct position of the internal organs. With a decrease in the tone of these muscles, the omission of some organs may occur.
On this, the functions of smooth muscle tissue end.
The 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: differences between the three types of muscle tissue
To disclose this issue, we present the table:
| Smooth muscle | Striated muscle | Heart muscle tissue |
| Shrink automatically | Can be controlled consciously | Shrink automatically |
| Elongated, spindle-shaped cells | Long, filamentous cells | Elongated cells |
| Fibers do not bundle | Fibers bundled | Fibers bundled |
| One core in a cell | Several cores in a cell | Several cores in a cell |
| A relatively small number of mitochondria | A large number of mitochondria | |
| Myofibrils are absent | Myofibrils are present | There are myofibrils |
| Cells are able to share | Fibers Can't Share | Cells cannot share |
| Shrink slowly, weakly, rhythmically | Shrink fast, hard | Shrink quickly, violently, rhythmically |
| Lines the internal organs (intestines, uterus, bladder), form sphincters | Attached to the skeleton | Form a heart |
That's all the main characteristics of striated, smooth and cardiac muscle tissue. Now you are familiar with their functions, structure and main differences and similarities.