Fingertips increase touch sensitivity due to mechanoreceptors underneath the surface of the skin

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Human fingertips are probably the most sensitive skin areas in the animal world; they can feel the difference between a smooth surface and one with a pattern embedded just 13 nm deep. This is due to epidermal ridges on the surface of the fingertip, which allow humans to differentiate between a wide range of textures, materials, temperatures, and pressures. While each person has a unique pattern of ridges (i.e. fingerprints), the pattern is not crucial to the function. Just underneath the ridges are mechanoreceptors, a type of sensory receptor that responds to tactile stimulus. Friction caused by movement of the fingertip along a surface or material stimulates the mechanoreceptors, which then transmit the tactile information to the brain.

There are four major types of mechanoreceptors on smooth (non-hairy) parts of mammalian skin: lamellar corpuscles, tactile corpuscles, Merkel nerve endings, and bulbous corpuscles. Lamellar corpuscles respond to changes in vibration and pressure, while tactile corpuscles are particularly sensitive to light touch. Merkel nerve endings respond to general changes in pressure and location, as well as deep static touch, such as edges and overall shape. Bulbous corpuscles are sensitive to skin stretching and slippage of an object against the skin, allowing for improved grip.

This strategy was contributed by Safi Marroun and Teresa McNulty.

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References

Journal article
Feeling small: exploring the tactile perception limitsScientific reports. 3(2617): 1-6.Skedung L, Arvidsson M, Chung JY, Stafford CM, Berglund B, Rutland MW.

“Four major types of encapsulated mechanoreceptors are specialized to provide information to the central nervous system about touch, pressure, vibration, and cutaneous tension: Meissner’s corpuscles, Pacinian corpuscles, Merkel’s disks, and Ruffini’s corpuscles. These receptors are referred to collectively as low-threshold (or high-sensitivity) mechanoreceptors because even weak mechanical stimulation of the skin induces them to produce action potentials. All low-threshold mechanoreceptors are innervated by relatively large myelinated axons, ensuring the rapid central transmission of tactile information.” (Purves et al. 2001).

Book
Mechanoreceptors Specialized to Receive Tactile InformationSunderland (MA): Sinauer Associates. Chapter 9, Neuroscience, 2nd editionPurves D, Augustine GJ, Fitzpatrick D, et al.

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Living System/s

Organism
HumanHomo sapiensSpecies

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