Template:Short description Template:Infobox microanatomy The Pacinian corpuscle (also lamellar corpuscle, or Vater–Pacini corpuscle)<ref name="Germann">Template:Cite journal</ref> is a low-threshold mechanoreceptor responsive to vibration or pressure, found in the skin and other internal organs.<ref name="Cobo2021">Template:Cite journal</ref> In the skin it is one of the four main types of cutaneous receptors.
The corpuscles are present in skin notably on both surfaces of the hands and feet, arms, and neck.<ref name="Standring-2020">Template:Cite book</ref> Pacinian corpuscles are also found on bone periosteum, joint capsules, the pancreas and other internal organs, the breast, genitals,<ref name="OpenStax2024">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and lymph nodes.<ref name="f772">Template:Cite journal</ref>
Pacinian corpuscles are rapidly adapting mechanoreceptors. As phasic receptors they respond quickly but briefly to a stimulus with the response diminishing even when the stimulus is maintained.<ref name="Purves"/> They primarily respond to vibration, and deep pressure. They are especially sensitive to high-frequency vibrations. Groups of corpuscles sense pressure changes (such as on grasping or releasing an object). They are additionally crucially involved in proprioception.<ref name="Germann" /> The vibrational role may be used for detecting surface texture, such as rough and smooth.Template:Citation needed
StructureEdit
Pacinian corpuscles are larger and fewer in number than Meissner's corpuscles, Merkel cells and Ruffini's corpuscles.<ref name="Kandel2000">Template:Cite book</ref> They may measure up to 2 mm in length, and nearly 1 mm in diameter.<ref name="Bear-2016">Template:Cite book</ref> They are oval, spherical, or irregularly coiled in shape. Larger ones are visible to the naked eye.<ref name="Standring-2020" /> They have large receptive fields - as large as half of the palm.<ref name="Bear-2016" /> In the skin, the corpuscles are situated deep within the dermis.<ref name="Bear-2016" />
Axon terminalEdit
Each corpuscle is associated with a myelinated axon;<ref name="Standring-2020" /> these are some of the largest and fastest-conducting sensory axons arising from the skin.<ref name="Bear-2016" />
Towards the center of the corpuscle, the axon loses its sheaths, ending as with a slight bulge at the center of the corpuscle. This axon terminal issues brief projections of unknown functional significance into gaps between the surrounding innermost lamellae; large mitochondria and small vessels aggregate near these projections.<ref name="Standring-2020" />
CapsuleEdit
The capsule consists of 20-70 concentrically-arranged connective tissue lamellae around the axon terminal at its center, forming a structure much like an onion.<ref name="Bear-2016" /> The capsule consists of fibroblasts and fibrous connective tissue (mainly Type IV and Type II collagen network), separated by gelatinous material, more than 92% of which is water.<ref>Template:Cite journal</ref> It presents a whorled pattern on micrographs.Template:Citation needed
If the corpuscle's capsule is experimentally removed, the divested axon terminal becomes slowly adapting. The capsule is therefore responsible for the corpuscle's selectivity for high-frequency stimuli. This is a result of the slippery lamellae sliding past each other when the corpuscle is structurally deformed by external pressure so that effects of sustained pressure are soon dissipated by the lamellae, abolishing deformation of the central axon terminal itself.<ref name="Bear-2016" /> The capsule thus acts as a physiological high-pass filter.<ref name="Standring-2020" />
FunctionEdit
Template:Primary sources Pacinian corpuscles are rapidly adapting phasic receptors that detect gross pressure changes and vibrations in the skin.<ref name="Purves">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Pacinian corpuscles have a large receptive field on the skin's surface with an especially sensitive center.<ref name="Kandel2000" />
The corpuscles are especially sensitive to vibrations, which they can sense even centimeters away.<ref name="Kandel2000" /> Their optimal sensitivity is 250 Hz, and this is the frequency range generated upon fingertips by textures made of features smaller than 1 μm.<ref>Template:Cite journal</ref><ref>Skedung, Lisa, Martin Arvidsson, Jun Young Chung, Christopher M. Stafford, Birgitta Berglund, and Mark W. Rutland. 2013. "Feeling Small: Exploring the Tactile Perception Limits." Sci. Rep. 3 (September 12). {{#invoke:doi|main}}.</ref> Pacinian corpuscles respond when the skin is rapidly indented but not when the pressure is steady (due to the capsule).<ref name="Kandel2000" /> It is thought that they respond to high-velocity changes in joint position. They have also been implicated in detecting the location of touch sensations on handheld tools.<ref>Template:Cite news</ref>
Sensory transductionEdit
Pacinian corpuscles sense stimuli due to the deformation of their lamellae, which press on the membrane of the sensory neuron and causes it to bend or stretch.<ref>Template:Cite book</ref> When the lamellae are deformed, due to either application or release of pressure, a generator or receptor potential is created as it physically deforms the plasma membrane of axon terminal, making it "leak" different cations through mechanosensitive channels which initiates the receptor potential. This initial receptor potential is potentiated by voltage-activated ion channels present in the inner-coreof the corpuscle. Finally, the receptor potential is modulated to neural spikes or action potential with the help of opening of sodium ion channels present at the first Ranvier's Node of the axon.<ref name="PC_Mechanotransduction">Template:Cite journal</ref>
Due to generation of receptor potential in the receptive area of the neurite (especially near the heminode or half-node of the axon) the potential at the first Ranvier's node can reach certain threshold, triggering nerve impulses or action potentials at the first node of Ranvier. The first Ranvier's node of the myelinated section of the neurite is often found inside the capsule. This impulse is then transferred along the axon from node to node with the use of sodium channels and sodium/potassium pumps in the axon membrane.Template:Citation needed
Once the receptive area of the neurite is depolarized, it will depolarize the first node of Ranvier; however, as it is a rapidly adapting fibre, this does not carry on indefinitely, and the signal propagation ceases. This is a graded response, meaning that the greater the deformation, the greater the generator potential. This information is encoded in the frequency of impulses, since a bigger or faster deformation induces a higher impulse frequency. Action potentials are formed when the skin is rapidly distorted but not when pressure is continuous because of the mechanical filtering of the stimulus in the lamellar structure. The frequencies of the impulses decrease quickly and soon stop due to the relaxation of the inner layers of connective tissue that cover the nerve ending.Template:Citation needed
Surface vibrationsEdit
The Pacinian corpuscles in elephant feet have been suggested to enable seismic communication.<ref name="h511">Template:Cite journal</ref> The Pacinian corpuscles in mice can detect taps on a branch 2.5 meters away.<ref name="o544">Template:Cite journal</ref>
HistoryEdit
Pacinian corpuscles were the first cellular sensory receptor ever observed. They were first reported by German anatomist and botanist Abraham Vater and his student Johannes Gottlieb Lehmann in 1741, but ultimately named after Italian anatomist Filippo Pacini, who rediscovered them in 1835.<ref name="Bentivoglio-1995">Template:Cite journal</ref><ref>Template:Cite journal</ref> John Shekleton, a curator of the Royal College of Surgeons in Ireland, also discovered them before Pacini, but his results were published later.<ref name="Bentivoglio-1995" /> Similar to Pacinian corpuscles, Herbst corpuscles and Grandry corpuscles are found in bird species.Template:Citation needed
Additional imagesEdit
- Gray940.png
Diagrammatic sectional view of the skin (magnified)
- Vater Pacini Körperchen.png
Schema (German)
- WVSOM Pacinian Corpuscle.JPG
Light micrograph showing three corpuscles in the center of the field
- Histology of a Pacinian corpuscle.jpg
Micrograph of a Pacinian corpuscle
See alsoEdit
- Pallesthesia
- List of human anatomical parts named after people
- Pacinian neuroma – a very rare benign tumor of Pacinian corpuscles
- Rayleigh wave#Possible detection by animals