Tactile corpuscles or Meissner's corpuscles are a type of

mechanoreceptor A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure or distortion. Mechanoreceptors are innervated by sensory neurons that convert mechanical pressure into electrical signals that, in animals, ...

discovered by anatomist Georg Meissner (1829–1905) and

Rudolf Wagner Rudolf Friedrich Johann Heinrich Wagner (30 July 1805 – 13 May 1864) was a German anatomist and physiologist and the co-discoverer of the germinal vesicle. He made important investigations on ganglia, nerve-endings, and the sympathetic nerves ...

. This corpuscle is a type of

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

ending in the skin that is responsible for sensitivity to pressure. In particular, they have their highest sensitivity (lowest threshold) when sensing vibrations between 10 and 50 hertz. They are rapidly adaptive receptors. They are most concentrated in thick hairless skin, especially at the finger pads.

Structure

Tactile corpuscles are encapsulated myelinated

endings, surrounded by Schwann cells. The encapsulation consists of flattened supportive cells arranged as horizontal lamellae surrounded by a

connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...

capsule. The corpuscle is 30–140 μm in length and 40–60 μm in diameter. A single nerve fiber meanders between the lamellae and throughout the corpuscle.

Location

They are distributed on various areas of the skin, but concentrated in areas especially sensitive to light touch, such as the fingers, lips and male prepuce. More specifically, they are primarily located in glabrous skin just beneath the

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...

within the dermal papillae.

Comparison with other receptors

Feelings of deep pressure (from a poke, for instance) are generated from lamellar corpuscles (the only other type of phasic tactile mechanoreceptor), which are located deeper in the dermis, and some free nerve endings. Also, tactile corpuscles do not detect noxious stimuli; this is signaled exclusively by free nerve endings.

Development

The number of tactile corpuscles per square millimeter of human skin on the fingertips drops fourfold between the ages of 12 and 50. The rate at which they are lost correlates well with the age-related loss in touch sensitivity for small probes.

Function

Tactile corpuscles are rapidly adapting mechanoreceptors. They are sensitive to shape and textural changes in exploratory and discriminatory touch. Their acute sensitivity provides the neural basis for reading Braille text. Because of their superficial location in the

dermis The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided i ...

, these corpuscles are particularly sensitive to touch and vibrations, but for the same reasons, they are limited in their detection because they can only signal that something is touching the skin. Any physical deformation of the corpuscle will cause sodium ions to enter it, creating an action potential in the corpuscle's nerve fiber. Since they are rapidly adapting or phasic, the action potentials generated quickly decrease and eventually cease (this is the reason one stops "feeling" one's clothes). If the stimulus is removed, the corpuscle regains its shape and while doing so (i.e.: while physically reforming) causes another volley of action potentials to be generated.

Additional images

Skin.png, "Meissner's corpuscle" labeled at upper right Image:Gray940.png, Diagrammatic sectional view of the skin. Image:WVSOM Meissner's corpuslce.JPG, light micrograph

References

Sources

External links

* Donald L. Rubbelke D.A
Tissues of the Human Body: An Introduction. McGraw-Hill. 1999 Meissner's and Pacinian corpuscles
* Dawn A. Tamarkin, Ph.D

* - "Integument pigmented skin, Meissner's corpuscles " * - "Meissner's Tactile Corpuscle"

{{Authority control Sensory receptors