Vater-Pacini bodies and other mechanoreceptors

The receptor apparatus is formed as a result of evolution and is very widely represented in the human body.

Mechanoreception allows us to touch objects, to distinguish temperature, vibration characteristics, to imagine our location in space.

For this reason, they are called skin tactile receptors.

What are receptors?

Translated from the Latin language, the verb "recipere" means "to accept". This is the biological role of receptors - the reception, processing and transformation of the information received. From the point of view of evolution, this is a very important adaptation. Indeed, among the numerous stimuli, it is very difficult to isolate and process the necessary stimuli, having a finely organized nervous system capable of working only with action potentials.

Receptors are an important part of analyzer systems. For example, vision. The primary and perhaps the most important link in this system is the so-called rods and cones of the retina. By morphology, these are modified nerve cells. And by their biological and physiological essence, they are receptors. It is in them that the perception of irritation and the primary processing of the information received from the external environment take place.

According to the classification, receptors can process impulses from the surfaces of internal organs, the walls of their mucous membranes. These are internal receptors (mechanoreceptors of the lungs or, for example, the lamellar bodies of the pancreas).

Exteroreceptors are the next group of cells that encode information received from the outside. These include mechanoreceptors. Stimuli - pressure on receptor sites, their deformation or displacement.

Mechanoreceptor functions and their types

Both from the outside and from the inside, the human body is exposed to various kinds of stimuli. Mechanoreceptors are one of the most important groups of receptors that include heterogeneous cells. They transform mechanical factors into a unified nerve impulse with the formation of an action potential.

Mechanoreceptors are excited by the following factors:

• light;
• pressure;
• compression;
• temperature;
• sound waves;
• vibration.

Thus, the essence of the work of the described cellular structures of any analyzer is reduced to the following important processes:

1. Irritation of the receptor cell with various stimuli.
2. Conversion of impulse energy from the outside or from the inside into an action potential.
3. The so-called efferent regulation.

Among mechanoreceptors, primary sensing receptors are distinguished. All the processes described above proceed within the same morphological structure (cell). These include the cardiac muscles, endothelial cells of the vascular lining, receptors located in the epidermal layer of the skin. This is a very common group.

Secondary sensory receptors are also isolated. These include the mechanoreceptors of the auditory and vestibular analyzers. Irritation occurs in one cell structure, while the formation of an action potential is closed on another.

Below we will talk about cells of the first type, because the group of tactile mechanoreceptors is represented much wider.

Meissner Taurus

Another name for this histological structure is the tactile body. It perceives mechanical vibrations with a frequency range of 30,000-40,000 Hertz.

The morphology of this mechanoreceptor is simple. Outside the dermis, the tactile body is separated by a connective tissue capsule. Inside are located in the form of a zigzag myelin-free branches of the dendrites of nerve cells. They are located gliocytesnot covered with myelin. Glial cells are located at right angles to the Meissner body axis.

Meissner's bodies respond to vibration, pressure, precisely through gliocytes. These mechanical factors act on the latter, then the irritation is transmitted to the dendrites of the nerve cells. Through these processes, the action potential reaches the next neurons, ultimately forming a sensation of pressure (touch) and vibration.

Meissner's tactile bodies are found in the following organs and tissues of the human body:

• papillary dermis of the skin of the fingers, soles;
• skin of the eyelid area;
• areola of the nipples, as well as the nipples themselves;
• red border of the lips;
• the mucous membrane of the genitals (large congestion in the so-called G-spot).

The prevalence and density of Meissner's bodies are high. The location relative to the skin surface is perpendicular.

Taurus Merkel

These cellular structures are located somewhat more superficially than Meissner's bodies. Localization - basal, prickly layers of the epidermal cover of the skin. There are also a lot of them on the surface of the lining of hair follicles. There is evidence that Merkel cells in the epidermis of the hairless part of the skin are represented much more often, more. On the scalp, for example, there are not so many of them.

The cell contains branching outgrowths in the form of fingers, they are woven into the surrounding cellular and tissue structures. This feature allows you to perceive signals (light touch) from a large area of ​​the skin.

Otherwise, the described receptors are called Merkel disks (due to visual similarity). The collection of several bodies is the so-called tactile corpuscle. It contains up to 50 discoid structures.

The origin of Merkel cells is a moot point. Most often, morphologists and cytologists agree that these are derivatives of the neuroendocrine system (APUD). Their function is to participate in the formation of tactile sensations (to light static touch). In addition, given the origin, they stimulate the nutrition of the nerve fibers of the skin and its derivatives.

Taurus Ruffini

This type of mechanoreceptor allows us to perceive the sense of touch. Location - papillary dermis. In addition, they can be found in the superficial layers of subcutaneous fat and adipose tissue.

In morphology, Ruffini's little bodies resemble a flask. The core is filled with myelin-free fibers, which are arranged mainly in a spiral shape. Next comes the space of the capsule, delimited from the inner flask by a membrane. It contains cellular and fibrous structures characteristic of connective tissue. They perform a trophic function for the main elements of the core of Ruffini's little body.

The capsule space is filled with intercellular fluid. The next component is a connective tissue capsule. It has a layered structure, which is why this receptor is sometimes called Ruffini's bulb. The number of layers is about 4-5. They are composed of clearly oriented fibrocytes.

In addition to stretching, they allow receiving temperature pulses. This justifies their location in the lower layers of the epidermis, in the papillary dermis and subcutaneous fat. Through the work of Ruffini bulbs, there is a perception of touch, warmth.

Taurus Fatter-Pacini

Another name for this type of cellular structures is lamellar bodies. This is due to morphological features. It has been established that Vater-Pacini bodies are receptors that respond to vibration stimuli.

Outwardly, these structures resemble an onion. This is due to the layered arrangement of the connective tissue surrounding the myelin-free nerve endings. Between the layers there is a liquid that resembles cerebrospinal fluid in properties. The function of Pacini's little body is to respond to pressure and vibration.

The formation of a nerve impulse is the result of cell compression, which causes the layers of the body capsule to slide relative to each other. This irritation is captured by nerve endings and transmitted through afferent pathways to neurons of the 1st level.

Krause flasks

Unlike other tactile mechanoreceptors, they are spherical cells. In fact, these are the branches of the dendrites of the nerve cells of the skin, folded into a glomerular structure. They are surrounded by connective tissue.

A large number of these receptors are concentrated on the mucous membrane of the oral cavity and tongue. It is noticed that Krause's flasks are also found on the mucous membrane of the female genital organs.

In addition to tactile sensitivity, these receptors are responsible for cold sensations.

Mechanoreceptors allow you to respond to touch, tickle, vibration, and touch. They process incoming signals. As a result, we have an idea about our location, about the properties of surrounding objects and our own body.