Skin
Aside from the genitals, the fingertips possess the highest concentration of touch receptors and thermoreceptors among all areas of the human skin, making them extremely sensitive to temperature, pressure, vibration, texture and moisture. Recent studies suggest fingers can feel nano-scale wrinkles on a seemingly smooth surface, a level of sensitivity not previously recorded. This makes the fingers commonly used sensory probes to ascertain properties of objects encountered in the world, making them prone to injury. The pulp of a finger is the fleshy mass on the palmar aspect of the extremity of the finger. Fingertip wrinkling in water
Although a common phenomenon, the underlying functions and mechanism of fingertip wrinkling following immersion in water are relatively unexplored. Originally it was assumed that the wrinkles were simply the result of the skin swelling in water, but it is now understood that the furrows are caused by the blood vessels constricting due to signalling by the sympathetic nervous system in response to water exposure. One hypothesis for why this occurs, the “rain tread” hypothesis, posits that the wrinkles may help the fingers grip things when wet, possibly being an adaption from a time when humans dealt with rain and dew in forested primate habitats. A 2013 study supporting this hypothesis found that the wrinkled fingertips provided better handling of wet objects but gave no advantage for handling dry objects. However, a 2014 study attempting to reproduce these results was unable to demonstrate any improvement of handling wet objects with wrinkled fingertips.
Vasculitis is a group of disorders that destroy blood vessels by inflammation. Both arteries and veins are affected. Lymphangitis (inflammation of lymphatic vessels) is sometimes considered a type of vasculitis. Vasculitis is primarily caused by leukocyte migration and resultant damage. Although both occur in vasculitis, inflammation of veins (phlebitis) or arteries (arteritis) on their own are separate entities. Signs and symptoms
Possible signs and symptoms include:
General symptoms: Fever, unintentional weight loss
Skin: Palpable purpura, livedo reticularis
Muscles and joints: Muscle pain or inflammation, joint pain or joint swelling
Nervous system: Mononeuritis multiplex, headache, stroke, tinnitus, reduced visual acuity, acute visual loss
Heart and arteries: Heart attack, high blood pressure, gangrene
Respiratory tract: Nosebleeds, bloody cough, lung infiltrates
GI tract: Abdominal pain, bloody stool, perforations (hole in the GI tract)
Kidneys: Inflammation of the kidneys filtration units (glomeruli)

Cause
Classification
Vasculitis can be classified by the cause, the location, the type of vessel or the size of vessel. Underlying cause. For example, the cause of syphilitic aortitis is infectious (aortitis simply refers to inflammation of the aorta, which is an artery.) However, the causes of many forms of vasculitis are poorly understood. There is usually an immune component, but the trigger is often not identified. In these cases, the antibody found is sometimes used in classification, as in ANCA-associated vasculitides. Clinical studies with immunosuppressive drugs targeting specific cytokines and cells can also be used to understand the heterogeneous immunopathogenic mechanisms of vasculitis and support a mechanistic immunological classification. Location of the affected vessels.