Pacinian Corpuscle

Lamellar corpuscles (or Pacinian corpuscles; discovered by Italian anatomist Filippo Pacini) are one of the four major types of mechanoreceptor cell in glabrous (hairless) mammalian skin. They are nerve endings in the skin responsible for sensitivity to vibration and pressure. They respond only to sudden disturbances and are especially sensitive to vibration. The vibrational role may be used to detect surface texture, e.g., rough vs. smooth. Lamellar corpuscles are also found in the pancreas, where they detect vibration and possibly very low frequency sounds. Lamellar corpuscles act as very rapidly adapting mechanoreceptors. Groups of corpuscles respond to pressure changes, e.g. on grasping or releasing an object.Diagrammatic sectional view of the skin (magnified)Schema (German)Light micrograph showing three corpuscles in the center of the fieldMicrograph of a Pacinian corpuscle Lamellar corpuscles (or Pacinian corpuscles; discovered by Italian anatomist Filippo Pacini) are one of the four major types of mechanoreceptor cell in glabrous (hairless) mammalian skin. They are nerve endings in the skin responsible for sensitivity to vibration and pressure. They respond only to sudden disturbances and are especially sensitive to vibration. The vibrational role may be used to detect surface texture, e.g., rough vs. smooth. Lamellar corpuscles are also found in the pancreas, where they detect vibration and possibly very low frequency sounds. Lamellar corpuscles act as very rapidly adapting mechanoreceptors. Groups of corpuscles respond to pressure changes, e.g. on grasping or releasing an object. Lamellar corpuscles are larger and fewer in number than Meissner's corpuscle, Merkel cells and Ruffini's corpuscles. The Lamellar corpuscle is approximately oval-cylindrical-shaped and 1 mm in length. The entire corpuscle is wrapped by a layer of connective tissue. Its capsule consists of 20 to 60 concentric lamellae including fibroblasts and fibrous connective tissue (mainly Type IV and Type II collagen network), separated by gelatinous material, more than 92% of which is water. Lamellar corpuscles are rapidly adapting (phasic) receptors that detect gross pressure changes and vibrations in the skin. Any deformation in the corpuscle causes action potentials to be generated by opening pressure-sensitive sodium ion channels in the axon membrane. This allows sodium ions to influx, creating a receptor potential. These corpuscles are especially susceptible to vibrations, which they can sense even centimeters away. Their optimal sensitivity is 250 Hz, and this is the frequency range generated upon fingertips by textures made of features smaller than 1 µm. Lamellar corpuscles cause action potentials when the skin is rapidly indented but not when the pressure is steady, due to the layers of connective tissue that cover the nerve ending. It is thought that they respond to high-velocity changes in joint position. Lamellar corpuscles have a large receptive field on the skin's surface with an especially sensitive center. Lamellar 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. When the lamellae are deformed, due to either pressure or release of pressure, a generator potential is created as it physically deforms the plasma membrane of the receptive area of the neuron, making it 'leak' Na+ ions. If this potential reaches a certain threshold, nerve impulses or action potentials are formed by pressure-sensitive sodium channels at the first node of Ranvier, the first node of the myelinated section of the neurite inside the capsule. This impulse is now transferred along the axon with the use of sodium channels and sodium/potassium pumps in the axon membrane.