Tactile corpuscles (or Meissner's corpuscles; discovered by anatomist Georg Meissner (1829-1905) and Rudolf Wagner) are a type of mechanoreceptor. They are a type of nerve ending in the skin that is responsible for sensitivity to light touch. 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.
Video Tactile corpuscle
Location
They are distributed on various areas of the skin, but concentrated in areas especially sensitive to light touch, such as the fingers and lips. More specifically, they are primarily located in glabrous skin just beneath the epidermis within the dermal papillae.
Maps Tactile corpuscle
Structure
Tactile corpuscles are encapsulated unmyelinated nerve endings, which consist of flattened supportive cells arranged as horizontal lamellae surrounded by a connective tissue capsule. The corpuscle is 30-140 ?m in length and 40-60 ?m in diameter.
A single nerve fiber meanders between the lamellae and throughout the corpuscle.
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, 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 in the corpuscle will cause an action potential in the nerve. 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.
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 signalled exclusively by free nerve endings.
Additional images
References
Sources
- Gilman S (2002). "Joint position sense and vibration sense: anatomical organisation and assessment". Journal of Neurology, Neurosurgery, and Psychiatry. 73 (5): 473-477. doi:10.1136/jnnp.73.5.473.
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
- Histology image: 08105loa - Histology Learning System at Boston University - "Integument pigmented skin, Meissner's corpuscles "
- Anatomy Atlases - Microscopic Anatomy, plate 06.123 - "Meissner's Tactile Corpuscle"
- Histology at rutgers.edu
Source of article : Wikipedia
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