Muscle tissue is made up of cells that can contract.
The structural and functional unit of muscle tissue is a muscle cell – myocyte.
There are three types of muscle tissue:
- striated skeletal (skeletal muscle contraction);
- striated heart (contraction of the heart muscle);
- smooth (change in the lumen of blood vessels, contraction of internal organs such as the stomach, bladder, etc.).
The structure of these tissues depends on the characteristics of the location and the functions performed.
Thus, the more intensive work of the heart and skeletal muscles determined the structural features of the striated tissue, in contrast to the smooth one.
Striated muscle tissue consists of developed multinucleated muscle fibers with transverse striation. She is capable of rapid contraction.
In the heart muscle, fibers are intertwined in some places so that the entire heart muscle can quickly contract.
Smooth tissue is formed by short, mononuclear muscle fibers that contract very slowly.
The striated skeletal musculature is responsible for body movement and facial expressions. Its reduction is arbitrary, that is, it depends on the will of the person.
Smooth muscles carry out an involuntary contraction of internal organs, constriction and expansion of blood vessels, regardless of the will of a person.
The work of the heart is regulated by the autonomic nervous system.
The common properties of all types of muscle tissue are excitability and contractility.
Nerve tissue is represented by nerve cells – neurons and satellite cells – neuroglia.
Neurons provide the basic functions of nerve tissue, glial cells provide nutrition for neurons.
The main properties of the nervous tissue are excitability and conductivity.
Nervous tissue provides the transmission of excitation from nerve endings (receptors) to the central nervous system, and from it to the organ.
This is possible due to the special structure of neurons.
A neuron has a body, a long process (axon), and short processes (dendrites). Neurons are connected to each other using special contacts – synapses.
Nerve tissue is located in the brain and spinal cord, nerve nodes, nerve fibers.