The body of all animals, including humans, consists of four types of tissues: epithelial, nervous, connective and muscular. The latter will be discussed in this article.
Varieties of muscle tissue
It comes in three types:
- striped;
- smooth;
- hearty.
The functions of muscle tissues of different types are somewhat different. And the building too.
Where are muscle tissues in the human body?
Muscle tissues of different types occupy different locations in the body of animals and humans. So, from the heart muscles, as the name implies, the heart is built.
Skeletal muscles are formed from striated muscle tissue.
Smooth muscles line the inside of the cavities of organs that need to contract. This, for example, the intestines, bladder, uterus, stomach, etc.
The structure of muscle tissue varies from species to species. We'll talk about it in more detail later.
How is muscle tissue?
It consists of large cells - myocytes. They are also called fibres. Muscle tissue cells have several nuclei and a large number of mitochondria -organelles responsible for energy production.
In addition, the structure of human and animal muscle tissue provides for the presence of a small amount of intercellular substance containing collagen, which gives the muscles elasticity.
Let's look at the structure and function of muscle tissues of different types separately.
Structure and role of smooth muscle tissue
This tissue is controlled by the autonomic nervous system. Therefore, a person cannot consciously contract muscles built from smooth tissue.
It is formed from the mesenchyme. It is a type of embryonic connective tissue.
This tissue shrinks much less actively and quickly than striated.
Smooth tissue is built from spindle-shaped myocytes with pointed ends. The length of these cells can be from 100 to 500 micrometers, and the thickness is about 10 micrometers. The cells of this tissue are mononuclear. The nucleus is located in the center of the myocyte. In addition, such organelles as agranular EPS and mitochondria are well developed. Also in the cells of smooth muscle tissue there is a large number of inclusions from glycogen, which are nutrient reserves.
The element that provides the contraction of this type of muscle tissue are myofilaments. They can be built from two contractile proteins: actin and myosin. The diameter of myofilaments, which consist of myosin, is 17 nanometers, and those thatbuilt from actin - 7 nanometers. There are also intermediate myofilaments, the diameter of which is 10 nanometers. The orientation of myofibrils is longitudinal.
The composition of the muscle tissue of this type also includes an intercellular substance from collagen, which provides a connection between individual myocytes.
Functions of this type of muscle tissue:
- Sphincter. It consists in the fact that circular muscles are arranged from smooth tissues that regulate the transfer of contents from one organ to another or from one part of an organ to another.
- Evacuator. It lies in the fact that smooth muscles help the body remove unnecessary substances, and also take part in the process of childbirth.
- Creating the vessel lumen.
- Formation of the ligamentous apparatus. Thanks to him, many organs, such as the kidneys, for example, are held in place.
Now let's look at the following type of muscle tissue.
Striped
It is regulated by the somatic nervous system. Therefore, a person can consciously regulate the work of muscles of this type. Skeletal muscles are formed from striated tissue.
This fabric consists of fibers. These are cells that have many nuclei located closer to the plasma membrane. In addition, they contain a large number of glycogen inclusions. Organelles such as mitochondria are well developed. They are located near the contractile elements of the cell. All other organelles are localized near the nuclei and are poorly developed.
Structures due to which the cross-striated tissue is reduced, are myofibrils. Their diameter is from one to two micrometers. Myofibrils occupy most of the cell and are located in its center. The orientation of myofibrils is longitudinal. They consist of light and dark discs that alternate, which creates a transverse "striping" of the fabric.
Functions of this type of muscle tissue:
- Provides movement of the body in space.
- Responsible for the movement of body parts relative to each other.
- Able to maintain body posture.
- Participate in the process of temperature regulation: the more actively the muscles contract, the higher the temperature. When frozen, striated muscles may begin to contract involuntarily. This explains the trembling in the body.
- Perform a protective function. This is especially true of the abdominal muscles, which protect many internal organs from mechanical damage.
- Act as a depot of water and s alts.
Cardiac muscle tissue
This fabric is both striated and smooth at the same time. Like smooth, it is regulated by the autonomic nervous system. However, it is reduced as actively as the striated one.
It is made up of cells called cardiomyocytes.
Functions of this type of muscle tissue:
