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A wrinkle, also known as a rhytid, is a fold, ridge or crease in an otherwise smooth surface, such as on
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...
or
fabric Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the ...
. Skin wrinkles typically appear as a result of
ageing Ageing ( BE) or aging ( AE) is the process of becoming older. The term refers mainly to humans, many other animals, and fungi, whereas for example, bacteria, perennial plants and some simple animals are potentially biologically immortal. In ...
processes such as
glycation Glycation (sometimes called non-enzymatic glycosylation) is the covalent attachment of a sugar to a protein or lipid. Typical sugars that participate in glycation are glucose, fructose, and their derivatives. Glycation is the non-enzymatic proces ...
, habitual sleeping positions, loss of body mass,
sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
damage, or temporarily, as the result of prolonged immersion in
water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
. Age wrinkling in the skin is promoted by habitual facial expressions, aging, sun damage, smoking, poor hydration, and various other factors. In humans, it can also be prevented to some degree by avoiding excessive solar exposure and through
diet Diet may refer to: Food * Diet (nutrition), the sum of the food consumed by an organism or group * Dieting, the deliberate selection of food to control body weight or nutrient intake ** Diet food, foods that aid in creating a diet for weight loss ...
(in particular through consumption of
carotenoids Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, ...
,
tocopherols Tocopherols (; TCP) are a class of organic chemical compounds (more precisely, various methylated phenols), many of which have vitamin E activity. Because the vitamin activity was first identified in 1936 from a dietary fertility factor in rats, ...
and
flavonoids Flavonoids (or bioflavonoids; from the Latin word ''flavus'', meaning yellow, their color in nature) are a class of polyphenolic secondary metabolites found in plants, and thus commonly consumed in the diets of humans. Chemically, flavonoids ...
, vitamins (A, C, D and E), essential omega-3-fatty acids, certain proteins and lactobacilli).


Skin


Causes for aging wrinkles

Development of facial wrinkles is a kind of fibrosis of the skin. Misrepair-accumulation aging theory suggests that wrinkles develop from incorrect repairs of injured elastic fibers and collagen fibers. Repeated extensions and compressions of the skin cause repeated injuries of extracellular fibers in derma. During the repairing process, some of the broken elastic fibers and collagen fibers are not regenerated and restored but replaced by altered fibers. When an elastic fiber is broken in an extended state, it may be replaced by a "long" collagen fiber. Accumulation of "long" collagen fibers makes part of the skin looser and stiffer, and as a consequence, a big fold of skin appears. When a "long" collagen is broken in a compressed state, it may be replaced by a "short" collagen fiber. The "shorter" collagen fibers will restrict the extension of "longer" fibers, and make the “long" fibers in a folding state permanently. A small fold, namely a permanent wrinkle, then appears.


Sleep wrinkles

Sleep wrinkles are created and reinforced when the face is compressed against a pillow or bed surface in side or stomach sleeping positions during sleep. They appear in predictable locations due to the underlying superficial musculoaponeurotic system (SMAS), and are usually distinct from wrinkles of facial expression. As with wrinkles of facial expression, sleep wrinkles can deepen and become permanent over time, unless the habitual sleeping positions which cause the wrinkles are altered.


Water-immersion wrinkling

The wrinkles that occur in skin over prolonged exposure to water are sometimes referred to as ''pruney fingers'' or water aging. This is a temporary
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...
condition where the skin on the palms of the hand or feet becomes wrinkly. This wrinkling response may have imparted an evolutionary benefit by providing improved traction in wet conditions, and a better grasp of wet objects. These results were called into question by a 2014 study that failed to reproduce any improvement of handling wet objects with wrinkled fingertips. However, a 2020 study of gripping efficiency found that wrinkles decreased the force required to grip wet objects by 20%, supporting the traction hypothesis. Prior to a 1935 study, the common explanation was based on water absorption in the
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...
-laden
epithelial Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellula ...
skin when immersed in water, causing the skin to expand and resulting in a larger surface area, forcing it to wrinkle. Usually the tips of the fingers and toes are the first to wrinkle because of a thicker layer of keratin and an absence of hairs which secrete the protective oil called
sebum A sebaceous gland is a microscopic exocrine gland in the skin that opens into a hair follicle to secrete an oily or waxy matter, called sebum, which lubricates the hair and skin of mammals. In humans, sebaceous glands occur in the greatest nu ...
. In the 1935 study, however, Lewis and Pickering were studying patients with
palsy Palsy is a medical term which refers to various types of paralysisDan Agin, ''More Than Genes: What Science Can Tell Us About Toxic Chemicals, Development, and the Risk to Our Children;; (2009), p. 172. or paresis, often accompanied by weakness and ...
of the
median nerve The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus. The median nerve originates from the lateral and medial cords of the brachial plexus, and has contr ...
when they discovered that skin wrinkling did not occur in the areas of the patients' skin normally innervated by the damaged nerve. This suggested that the nervous system plays an essential role in wrinkling, so the phenomenon could not be entirely explained simply by water absorption. Recent research shows that wrinkling is related to
vasoconstriction Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessel ...
. Water probably initiates the wrinkling process by altering the balance of
electrolytes An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon di ...
in the skin as it diffuses into the hands and soles via their many sweat ducts. This could alter the stability of the membranes of the many neurons that synapse on the many blood vessels underneath skin, causing them to fire more rapidly. Increased neuronal firing causes blood vessels to constrict, decreasing the amount of fluid underneath the skin. This decrease in fluid would cause a decrease in tension, causing the skin to become wrinkly. This insight resulted in bedside tests for nerve damage and vasoconstriction. Wrinkling is often scored with immersion of the hands for 30 minutes in water or
EMLA Lidocaine/prilocaine is a eutectic mixture of equal quantities (by weight) of lidocaine and prilocaine. A 5% emulsion preparation, containing 2.5% each of lidocaine/prilocaine, is marketed by APP Pharmaceuticals under the trade name EMLA (an ...
cream with measurements steps of 5 minutes, and counting the number of visible wrinkles in time. Not all healthy persons have finger wrinkling after immersion, so it would be safe to say that sympathetic function is preserved if finger wrinkling after immersion in water is observed, but if the fingers emerge smooth it cannot be assumed that there is a lesion to the autonomic supply or to the peripheral nerves of the hand.


Animals with wrinkles

Examples of wrinkles can be found in various animal species that grow loose, excess skin, particularly when they are young. Several breeds of
dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
, such as the
Pug The Pug is a breed of dog originally from China, with physically distinctive features of a wrinkly, short-muzzled face and curled tail. The breed has a fine, glossy coat that comes in a variety of colors, most often light brown (fawn) or blac ...
and the
Shar Pei The Shar Pei (Cantonese: ''shā pèih'' or Mandarin: 沙皮 ''shā pí'') is a dog breed from southern China. Traditionally kept as a property guardian, the Shar Pei was driven to the brink of extinction in the 20th century. The breed is known i ...
, have been bred to exaggerate this trait. In dogs bred for
fighting Combat ( French for ''fight'') is a purposeful violent conflict meant to physically harm or kill the opposition. Combat may be armed (using weapons) or unarmed ( not using weapons). Combat is sometimes resorted to as a method of self-defense, or ...
, this is the result of selection for loose skin, which confers a protective advantage. Wrinkles are also associated with
neoteny Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compared ...
, as they are a trait associated with juvenile animals.


Techniques for reducing the appearance of aging wrinkles

Current evidence suggests that
tretinoin Tretinoin, also known as all-''trans'' retinoic acid (ATRA), is a medication used for the treatment of acne and acute promyelocytic leukemia. For acne, it is applied to the skin as a cream, gel or ointment. For leukemia, it is taken by mouth f ...
decreases cohesiveness of follicular epithelial cells, although the exact mode of action is unknown. Additionally, tretinoin stimulates mitotic activity and increased turnover of follicular epithelial cells. Tretinoin is better known by the
brand name A brand is a name, term, design, symbol or any other feature that distinguishes one seller's good or service from those of other sellers. Brands are used in business, marketing, and advertising for recognition and, importantly, to create an ...
Retin-A. Topical
glycosaminoglycan Glycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case ...
s supplements can help to provide temporary restoration of enzyme balance to slow or prevent matrix breakdown and consequent onset of wrinkle formation. Glycosaminoglycans (GAGs) are produced by the body to maintain structural integrity in tissues and to maintain fluid balance. Hyaluronic acid is a type of GAG that promotes collagen synthesis, repair, and hydration. GAGs serve as a natural moisturizer and lubricant between epidermal cells to inhibit the production of matrix metalloproteinases (MMPs). Dermal fillers are injectable products frequently used to correct wrinkles, and other depressions in the skin. They are often a kind of soft tissue designed to enable injection into the skin for purposes of improving the appearance. The most common products are based on
hyaluronic acid Hyaluronic acid (; abbreviated HA; conjugate base hyaluronate), also called hyaluronan, is an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. It is unique among glycosaminoglycans ...
and calcium hydroxylapatite.
Botulinum toxin Botulinum toxin, or botulinum neurotoxin (BoNT), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromusc ...
is a neurotoxin protein produced by the bacterium ''
Clostridium botulinum ''Clostridium botulinum'' is a Gram-positive, rod-shaped, anaerobic, spore-forming, motile bacterium with the ability to produce the neurotoxin botulinum. The botulinum toxin can cause botulism, a severe flaccid paralytic disease in humans an ...
''. Botox is a specific form of botulinum toxin manufactured by
Allergan Allergan plc is an American, Irish-domiciled pharmaceutical company that acquires, develops, manufactures and markets brand name drugs and medical devices in the areas of medical aesthetics, eye care, central nervous system, and gastroenterology. ...
for both therapeutic and cosmetic use. Besides its cosmetic application, Botox is used in the treatment of other conditions including migraine headache and cervical
dystonia Dystonia is a neurological hyperkinetic movement disorder in which sustained or repetitive muscle contractions result in twisting and repetitive movements or abnormal fixed postures. The movements may resemble a tremor. Dystonia is often inten ...
(spasmodic
torticollis Torticollis, also known as wry neck, is a dystonic condition defined by an abnormal, asymmetrical head or neck position, which may be due to a variety of causes. The term ''torticollis'' is derived from the Latin words ''tortus, meaning "twisted ...
) (a neuromuscular disorder involving the head and neck). Dysport, manufactured by Ipsen, received
FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
approval and is now used to treat cervical dystonia as well as glabellar lines in adults. In 2010, another form of botulinum toxin, one free of complexing proteins, became available to Americans. Xeomin received FDA approval for medical indications in 2010 and cosmetic indications in 2011. Botulinum toxin treats wrinkles by immobilizing the muscles which cause wrinkles. It is not appropriate for the treatment of all wrinkles; it is indicated for the treatment of glabellar lines (between the eyebrows) in adults. Any other usage is not approved by the FDA and is considered
off-label use Off-label use is the use of pharmaceutical drugs for an unapproved indication (medicine), indication or in an unapproved age group, dose (biochemistry), dosage, or route of administration. Both prescription drugs and over-the-counter drugs (OTCs) ...
. Laser resurfacing is FDA-cleared skin resurfacing procedure in which lasers are used to improve the condition of the skin. Two types of lasers are used to reduce the appearance of fine lines and wrinkles on the face;
laser ablation Laser ablation or photoablation (also called laser blasting) is the process of removing material from a solid (or occasionally liquid) surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser ...
, which removes thin layers of skin, and nonablative lasers that stimulate
collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...
production. Nonablative lasers are less effective than ablative ones but they are less invasive and recovery time is short. After the procedure people experience temporary redness, itching and swelling.


See also

*
Botulinum toxin Botulinum toxin, or botulinum neurotoxin (BoNT), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromusc ...
*
Injectable filler Injectable filler (injectable cosmetic filler, injectable facial filler) is a soft tissue filler injected into the skin at different depths to help fill in facial wrinkles, provide facial volume, and augment facial features: restoring a smoother ap ...


References


External links


Skin Ageing
at
Medline MEDLINE (Medical Literature Analysis and Retrieval System Online, or MEDLARS Online) is a bibliographic database of life sciences and biomedical information. It includes bibliographic information for articles from academic journals covering medic ...
{{DEFAULTSORT:Wrinkle (Skin) Ageing Skin