Everyone knows that due to the presence of muscle tissue it is possible to move the human body and its individual parts in space. But in our body there are also contracting organs. All of them perform functions indispensable for normal life.
What are organs
For starters, let's figure out what an organ is. This is a part of the body that occupies a certain position, has a characteristic structure and performs one or a number of functions. A very important feature of any organ is that it includes several tissues at once.
There are four of them in the human body: epithelial, connective, muscular and nervous. All of them are formed by cells similar in structure and function.
Contracting human organs
Contracting organs necessarily include muscle tissue or cells similar in properties to it. For example, collagen fibers are located in the skin. Due to this structure, it is capable of stretching and does not interfere with the implementation of various movements. All contracting organs can change their volume and length, afterwhich return to the standard state again.
Features of the structure of muscle tissue
Muscle tissue is made up of individual contractile fibers called myofibrils. The latter are formed by filaments of special proteins - actin and myosin. They are connected to each other by cross bridges. Nerve impulses excite muscle fibers, and they begin to contract. The essence of this process is that the actin filaments are pulled between the myozone with the help of transverse bridges. At the same time, the length of the muscle fiber decreases.
Striated muscle tissue
There are several types of muscle tissue. What contracting organs does the striated or striated tissue form? These are mimic and skeletal muscles, diaphragm, larynx, tongue, upper part of the esophagus. The fibers of this tissue type are long and multinucleated. Under a microscope, they look like alternating dark and light stripes.
Striated muscle tissue is characterized by a high speed of contraction and relaxation, which are carried out consciously. After all, the person himself controls the movement of the limbs and changes the facial expression.
Cardiac muscle tissue
The heart is a special organ. It is constantly at work, because a person’s life depends on the frequency of its contractions. Therefore, this organ is also formed by a special type of striated tissue, which is called the heart tissue. It has special areas in which individual fibers are joined together. This structure ensures the simultaneous contraction of the entire organ. Conductivity is a very important property of the heart muscle. It consists in the spread of excitation that has arisen in one area throughout the organ. In special cells of the heart, impulses periodically arise that spread throughout the heart muscle and regulate the rhythm of its contractions. This property is called automatism.
Unstriated muscle tissue
Internal contracting organs are mostly composed of smooth or unstriated tissue. These are the gastrointestinal tract, bladder, bronchi and lungs, walls of blood and lymphatic vessels. Fusiform cells of smooth tissue are mononuclear and look homogeneous under a light microscope. Their characteristic feature is rather slow contraction and relaxation. Their activity is involuntary and does not depend on the will of man. For example, we cannot stop the contractions of the stomach or intestines.
So, contracting human organs have in their structure one of the varieties of muscle tissue. The coordinated automatic work of the heart is provided by a special kind of striated fibers. Smooth muscle tissue contracts slowly and involuntarily, forming the walls of internal organs. The movement of the body and its individual parts is provided by striated fibers. They contract quickly and are controlled by the person.
