Definition: Human Nails
Fingernails and toenails are made of a tough protective protein called keratin. This protein is also found in the hooves and horns of different animals. The nail consists of the nail plate, the nail matrix and the nail bed below it, and the grooves surrounding it.
Information and facts on fingernails and toenails including nail fungus and nail color health indicators.
Fingernails and toenails are made of a tough protein called keratin and include:
- Nail fold - A fold of hard skin overlapping the base and sides of a fingernail or toenail.
- Nail bed - The adherent connective tissue that underlies the nail, often referred to as the "quick."
- Nail plate - The hard and translucent portion, composed of keratin.
- Hyponychium - The attachment between the skin of the finger or toe and the distal end of the nail.
- Lunula - The crescent shaped whitish area of the nail bed (when visible)
- Free edge - The part of the nail that extends past the finger, beyond the nail plate.
- Eponychium or cuticle - The fold of skin at the proximal end of the nail.
- Paronychium - The fold of skin on the sides of the nail.
Major illness can cause a deep transverse groove to form across the nails. A change in fingernail color, thinning, thickening, brittleness, splitting, grooves, Mees' lines and nail ridges, small white spots, receded lunula, clubbing (convex), flatness, spooning (concave) can indicate illness in other areas of the body, nutrient deficiencies, drug reaction or poisoning, or merely local injury.
Both Fingernails and toenails can also become thickened (onychogryposis), loosened (onycholysis), infected with fungus (onychomycosis) or degenerate (onychodystrophy)
- Onychia is an inflammation of the matrix (surrounding tissue) of the nail with formation of pus and shedding of the nail.
- Onychocryptosis, commonly known as "ingrown nails" can affect either the fingers or the toes. In this condition, the nail cuts into one or both sides of the nail bed, resulting in inflammation and possibly infection.
- Onychodystrophy is a deformation of the nails that can result from cancer chemotherapy. It can include discoloration of the nail, or dyschromia.
- Onychogryposis is a thickening and increase in curvature of the nail most commonly seen in the great toe but may be seen in other toes as well as the fingernails. An affected nail has many grooves and ridges, is brownish in color, and grows more quickly on one side than on the other.
- Onycholysis is a loosening of the exposed portion of the nail from the nail bed, it is frequently associated with an internal disorder, trauma, infection, nail fungi, allergy to nail enhancement products, or side effects of drugs.
- Onychoschizia or splitting of the nails is a very common problem often seen by dermatologists. The term onychoschizia includes splitting, brittle nails, soft or thin toenails and fingernails.
- Onychomadesis is the separation and falling off of a nail from the nail bed. Common causes include localized infection, minor injury to the matrix bed, or severe systemic illness.
- Onychomycosis, also known as tinea unguium, is a contagious infection of the nail caused by the same fungal organisms which cause ringworm of the skin.
- Onychoptosis is the periodic shedding of one or more nails, in whole or part. This condition may follow certain diseases such as syphilis, or can result from fever, trauma, systemic upsets or adverse reaction to drugs.
- Paronychia is a bacterial or fungal infection where the nail and skin meet.
- Koilonychia is when the nail curves upwards due to an iron deficiency. The normal process of change is: brittle nails, straight nails, spoon-shaped nails.
- Subungual hematoma occurs when trauma to the nail results in a collection of blood, or hematoma, under the nail. It may result from an acute injury or from repeated minor trauma such as running in undersized shoes.
Quick Facts: Human Nail
- Nail biting is called onychophagia.
- Nails grow faster in the summer than in the winter.
- White spots on your nails don't indicate a calcium deficiency.
- Finger and toenails grow at an average rate of 3 millimeters a month.
- Fingernails take 3 to 6 months to regrow completely, while toenails require around 12 to 18 months to grow back fully.
- Contrary to popular belief, nails do not continue to grow after death; the skin dehydrates and tightens, making the nails (and hair) appear to grow.
- Although it is widely believed that toenails do not grow back, this is not true. Actual growth rate is dependent upon age, gender, season, exercise level, diet, and hereditary factors.
Statistics: Longest Fingernail Length
- The fingernail length record-holder for women is Lee Redmond of the U.S., who set the record in 2001 and as of 2008 had nails with a total length on both hands of 28 feet (850 cm), with the longest nail on her right thumb at 2 feet 11 inches (89 cm).
- The current fingernail length record-holder for men, according to Guinness, is Shridhar Chillal from India who set the record in 1998 with a total of 20 feet 2.25 inches (615.32 cm) of nails on his left hand. His longest nail, on his thumb, was 4 feet 9.6 inches (146.3 cm) long.