According to the Mayo Clinic, the nails are composed of laminated layers of a protein called keratin. This same protein is also found in the hair and skin. The nails are made up of several parts, including the nail beds, folds, cuticles and lunula. The nails can indicate a possible deficiency in the body or other condition. Yellow and discolored nails can represent a respiratory condition such as chronic bronchitis. In addition, many defects on the nails can appear like vertical ridges, but may actually be spots, streaks or cracks.
Many nail blemishes produce the appearance of vertical ridges on the nails; however true vertical ridges on the nails are harmless. According to the Mayo Clinic, vertical ridges may result from injury to the nail bed or plate and can become more apparent with age, as can white spots and lines.
Melanoma (a form of cancer) can in some cases be indicated by dark spots or streaks that can appear similar to ridges on the nails. When this occurs and is not the result of an injury, the American Academy of Dermatology (AAD) recommends seeing a dermatologist.
A splinter hemorrhage, according to the AAD, may appear as a red to reddish-brown faint vertical line resembling a splinter underneath the nail. This is the result of damaged blood vessels in the nail that is commonly caused by injury to the nail. Other causes of a splinter hemorrhage include medications and conditions such as psoriasis.
According to the AAD, approximately 80 percent of those with psoriatic arthritis and 10 to 50 people of those with psoriasis experience nail problems (specifically with the fingernails). Other problems that may occur include, separation from the nail bed, crumbling and splitting of the nails.