Tissue is a collection of structurally similar cells that are united by common functions. Almost all multicellular organisms are made up of different types of tissues.
Classification
In animals and humans, the following types of tissues are present in the body:
- epithelial;
- nervous;
- connective;
- muscular.
These groups combine several varieties. So, connective tissue is adipose, cartilage, bone. It also includes blood and lymph. Epithelial tissue is multi-layered and single-layered, depending on the structure of the cells, squamous, cubic, cylindrical epithelium, etc. can also be distinguished. There is only one type of nervous tissue. And we will talk about the muscle type of tissue in more detail in this article.
Types of muscle tissue
In the body of all animals, its three varieties are distinguished:
- smooth muscle;
- striated muscles;
- cardiac muscle tissue.
The functions of smooth muscle tissue are different from those of striated and cardiac tissue, so it has a different structure. Let's take a closer look at the structure of each type of muscle.
General characteristics of muscle tissues
Because all three species are of the same type, they have a lot in common.
The cells of muscle tissue are called myocytes, or fibers. Depending on the type of fabric, they may have a different structure.
Muscle tissue, the photo of which can be seen below, has practically no intercellular substance.
Another common feature of all types of muscles is that they are able to contract, but this process occurs individually in different types.
Features of myocytes
Cells of smooth muscle tissue, as well as 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 ensure the movement of the muscle. A prerequisite 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, insufficient or excessive consumption of foods high in this element can lead to incorrect functioning of the muscles - both smooth and striated.
In addition, there is another specific protein in cells - myoglobin. It is necessary in order to bind with oxygen and store it.
WhatAs for organelles, in addition to the presence of myofibrils, a special feature for muscle tissues is the content of a large number of mitochondria in the cell - two-membrane organelles responsible for cellular respiration. And this is not surprising, since the muscle fiber needs a large amount of energy generated during respiration by mitochondria to contract.
Some myocytes also have more than one nucleus. This is typical for striated muscles, the cells of which can contain about twenty nuclei, 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.
Structure of striated muscles
This type of tissue is also called skeletal muscle. The fibers of this type of muscle 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 main structural unit of each myofibril of striated tissue is the sarcomere. It is made up of a contractile protein.
The main feature of this musculature is that it can be controlled consciously, unlike smooth and cardiac.
The fibers of this tissue are attached to the bones with the help of tendons. That is why such muscles are called skeletal.
Structure of smooth muscle tissue
Smooth muscles line some of the internal organs such as the intestines, uterus, bladder, and blood vessels. Exceptmoreover, they form sphincters and ligaments.
Smooth muscle fiber is not as long as striated. But its thickness is greater than in the case of skeletal muscles. Smooth muscle tissue cells are spindle-shaped, rather than filamentous like striated myocytes.
The structures that provide smooth muscle contraction 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.
Mitochondria in smooth muscle myocytes are also less than in striated and cardiac cells. In addition, they contain only one core.
Features of the heart muscle
Some researchers define it as a subtype of striated muscle tissue. Their fibers are indeed very similar in many ways. 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 muscle.
However, the main feature that distinguishes the heart muscle from the striated muscle is that it cannot be controlled consciously. Its contraction occurs only automatically, as in the case of smooth muscles.
In addition to typical cells, there are also secretory cardiomyocytes in the heart tissue. They do not contain myofibrils and do not contract. These cellsweighed for the production of the hormone atriopeptin, which is necessary for the regulation of blood pressure and control of circulating blood volume.
Striated Muscle Functions
Their main task is to move the body in space. It is also the movement of body parts relative to each other.
Other functions of the striated muscles include the maintenance of posture, the depot of water and s alts. 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 striated muscles can also include temperature regulation, since with active muscle contraction, a significant amount of heat is released. This is why, when frozen, the muscles begin to tremble involuntarily.
Functions of smooth muscle tissue
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 excretion from the body. This role also manifests itself during childbirth, when the smooth muscles of the uterus push the fetus out of the organ.
Functions of smooth muscle tissue are not limited to this. Their sphincter role is also important. Special circular muscles are formed from the tissue of this type, which can close and open. Sphincters are present in the urinary tract, in the intestines, between the stomach and esophagus, in the gallbladder, in the pupil.
Another important role played by smooth muscles isformation 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, omission of some organs may occur.
This ends the function of smooth muscle tissue.
Purpose of the heart muscle
Here, in principle, there is nothing special 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 reveal this issue, we present the table:
| Smooth muscle | Striated muscles | Cardiac muscle tissue |
| Shorten automatically | Can be consciously controlled | Shorten automatically |
| Cells elongated, spindle-shaped | Cells are long, filamentous | Elongated cells |
| Fibers do not bundle together | The fibers are combined into bundles | The fibers are combined into bundles |
| One core per cell | Several cores in a cage | Several cores in a cage |
| Relatively few mitochondria | Lots of mitochondria | |
| Missing myofibrils | Myofibrils present | There are myofibrils |
| Cells are able to divide | Fibers cannot divide | Cells cannot divide |
| Contract slowly, weakly, rhythmically | Shrinking faststrongly | Cut quickly, strongly, rhythmically |
| Line internal organs (intestines, uterus, bladder), form sphincters | Attached to the skeleton | Shape the 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.
