Tactile corpuscle

Template:Short description Template:Infobox microanatomy Tactile corpuscles or Meissner's corpuscles are a type of mechanoreceptor discovered by anatomist Georg Meissner (1829–1905) and Rudolf Wagner.<ref name="Whonamedit">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref> This corpuscle is a type of nerve 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 nerve endings,<ref name=":1">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> surrounded by Schwann cells.<ref name=":1" /> The encapsulation consists of flattened supportive cells arranged as horizontal lamellae surrounded by a connective tissue 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.Template:Citation needed

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.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite book</ref><ref>Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref> More specifically, they are primarily located in glabrous skin just beneath the epidermis within the dermal papillae.<ref>Template:Cite journal</ref>

Comparison with other receptors

{{ safesubst:#invoke:Unsubst||date=__DATE__ |$B= {{ safesubst:#invoke:Unsubst||date=__DATE__ |$B= Template:Ambox }} }}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 fourfoldTemplate:Clarify 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.<ref>Template:Cite journal</ref>Template:Clarify

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, 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.<ref name=":0">Template:Cite book</ref> They also contribute to two-point discrimination, allowing the skin to detect stimuli at closely spaced points.<ref>Template:Cite book</ref>

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).<ref name=":0" />

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.Template:Citation needed

Additional images

• Skin.png

  "Meissner's corpuscle" labeled at upper right

• Gray940.png

  Diagrammatic sectional view of the skin.

• WVSOM Meissner's corpuslce.JPG

  light micrograph

Sources

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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. Anatomy and Physiology Unit 15 Vision and Somatic Senses: Touch and Pressure
• Template:BUHistology - "Integument pigmented skin, Meissner's corpuscles "
• Template:AnatomyAtlasesMicroscopic - "Meissner's Tactile Corpuscle"
• Histology at rutgers.edu