Vater-Pacini Corpuscles: Structure, Function & Diseases

Vater-Pacini corpuscles are among the mechanoreceptors in the skin that are particularly useful for detecting vibration. A thickening at the medullary ends of the otherwise medullary nerves serves as the sensor and can reach a diameter of up to 2 millimeters. The thickening consists of 40 to 60 concentrically superimposed layers of lamellae, which is enclosed externally by a connective tissue capsule.

What is the Vater-Pacini corpuscle?

Vater-Pacini corpuscles are named after the 18th-century German anatomist Abraham Vater and the 19th-century Italian anatomist Philippo Pacini. Together with 4 other types of mechanoreceptors, they belong to the tactile sensors, each type optimized for the detection of specific stimuli. The Vater-Pacini corpuscles are the only tactile sensors located in the subcutis because they can cover a relatively wide field according to their specialization. They are fast adapting, which means that they are specialized for fast stimulus changes. Their main task is the sensory detection of vibrations. Due to their extremely fast adaptation, they are optimized for vibrations in the frequency range of 300 Hz (vibrations per second), a frequency that is already perceived as a low tone by the human ear. The sensory head of Vater-Pacini corpuscles consists of a thickening at the medullary nerve endings of afferent neurons, which are surrounded by a medullary sheath in the remaining course. Vater-Pacini corpuscles are found clustered in the palms and soles of the feet and at the fingertips. Other clusters are found in the periosteum, pancreas, other organs of the lower abdomen, urinary bladder, and vaginal area.

Anatomy and structure

Vater-Pacini corpuscles mark the unmarked terminal portion of sensory nerves, which are surrounded by a medullary sheath throughout the rest of their course. The Vater-Pacini corpuscles consist of a thickening of nerve endings that arise from a concentric – onionskin-like – superimposition of up to 60 lamellae. The lamellae are composed of oblate Schwann cells that normally encase marbless neurons. The individual lamellae are each separated by an extremely thin film of interstitial body fluid. Inside the sensing heads is a fluid-filled space in which the free end of the nerve can move. On the outside, the sensory corpuscles are enclosed by a connective tissue capsule. The anatomical structure of the Vater-Pacini corpuscles makes them the very fast adapting tactile sensors. A deformation of only a few micrometers already causes an influx of sodium ions that trigger an action potential. The sensors hardly react at all to slow deformations that last longer. They are specialized for fast-changing pressure deformations such as those typically caused by vibrations.

Function and tasks

Vater-Pacini corpuscles, together with Merkel cell receptors, Krause corpuscles, Meissner corpuscles, and Ruffini corpuscles, form a composite of skin sensors called the sense of touch. To provide a more complete picture to the brain areas responsible for it, the sense of touch is supplemented by temperature and pain sensors. Not only is the brain able to create a picture of the situation from the millions of sensor messages, but the received and processed messages can also be translated into conscious or unconscious instructions for action. For example, high temperature messages lead to an unconscious opening of the skin’s sweat pores to increase evaporative cooling for a cooling effect. Vater-Pacini corpuscles are specialized for rapid pressure changes and directional changes in pressure inputs, so they are very good at sensing vibrations. They can detect even faint vibrations up to several hundred vibrations, vibrations that are already detected well within the audible range, which starts at about 200 Hz. Vater-Pacini corpuscles respond not only to vibrations that act on the skin from the outside, but also to changes in pressure on the skin when the hands glide over a rough surface. This means that they not only serve as part of a warning device against potentially imminent injury, but are also part of the sense of touch for better haptic detection of a surface.At the same time, they complement the fine sensory detection of lightweights such as spiders and insects that crawl across the skin and can be potentially dangerous.

Diseases

As with all sensory outputs, which are detected by the formation of neural action potentials and transmitted in the form of electrical impulses via ganglia and other “clearing sites” such as the thalamus, dysfunction can occur in the Vater-Pacini bodies. Reduced performance of the tactile corpuscles can be due to mechanical injuries in the affected skin areas or to infections or tumors that lead to serious physiological changes. Far more frequently, however, the transmission pathways of the nervous impulses, i.e. the neurons themselves or the conversions of the nervous impulses at the synapses, are affected. Only rarely are disorders in surface sensitivity limited to Vater-Pacini bodies. Usually, such disorders extend to all skin sensors in a given area. In this case, the perceptual sensation may refer not only to an attenuation (hypesthesia) but also to an increase (hyperesthesia) of sensations. Attenuations of surface sensibility are frequently observed, which in many cases can be attributed to circulatory disturbances (ischemia) and thus to a lack of supply to the afferent sensory nerves. Often, ischemias in this area are indicators of serious metabolic disorders such as diabetes. In addition to metabolic disorders, hypesthesia, up to and including complete loss of sensation (numbness), can also be caused by mechanical pressure exerted on the nerves. The mechanical pressure can typically occur at constrictions that serve to pass nerves and blood vessels at joints, such as the carpal tunnel at the wrist.