A wrinkle, also known as a rhytid, is a fold, ridge or crease in an otherwise smooth surface, such as on skin or fabric. Skin wrinkles typically appear as a result of ageing processes such as glycation,^[1] habitual sleeping positions,^[2] loss of body mass, sun damage,^[3] or temporarily, as the result of prolonged immersion in water. Age wrinkling in the skin is promoted by habitual facial expressions, aging, sun damage, smoking, poor hydration, and various other factors.^[4] In humans, it can also be prevented to some degree by avoiding excessive solar exposure and through diet (in particular through consumption of carotenoids, tocopherols and flavonoids, vitamins (A, C, D and E), essential omega-3-fatty acids, certain proteins and lactobacilli).^[5]

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.^[6][7][8] 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 are created and reinforced when the face is compressed against a pillow or bed surface in side or stomach sleeping positions during sleep.^[9] They appear in predictable locations due to the underlying superficial musculoaponeurotic system (SMAS), and are usually distinct from wrinkles of facial expression.^[10] 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.^[11]

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 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,^[12] and a better grasp of wet objects.^[13] These results were called into question by a 2014 study that failed to reproduce any improvement of handling wet objects with wrinkled fingertips.^[14] However, a 2020 study of gripping efficiency found that wrinkles decreased the force required to grip wet objects by 20%, supporting the traction hypothesis.^[15]

Prior to a 1935 study, the common explanation was based on water absorption in the keratin-laden epithelial skin when immersed in water,^[16] 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.

In the 1935 study, however, Lewis and Pickering were studying patients with palsy of the median nerve 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.^[17][18] Water probably initiates the wrinkling process by altering the balance of electrolytes 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.^[19]

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 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.^[20]

Examples of wrinkles can be found in various animal species that grow loose, excess skin, particularly when they are young. Several breeds of dog, such as the Pug and the Shar Pei, have been bred to exaggerate this trait. In dogs bred for fighting, this is the result of selection for loose skin, which confers a protective advantage.^[21]

Current evidence suggests that tretinoin 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.^[22] Tretinoin is better known by the brand name Retin-A.

Topical glycosaminoglycans 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 and calcium hydroxylapatite.

Botulinum toxin is a neurotoxin protein produced by the bacterium Clostridium botulinum. Botox is a specific form of botulinum toxin manufactured by Allergan 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 (spasmodic torticollis) (a neuromuscular disorder involving the head and neck).^[23]

Dysport, manufactured by Ipsen, received FDA 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.

Laser resurfacing is FDA-cleared skin resurfacing procedure in which lasers are used to improve the condition of the skin.^{[citation needed]} Two types of lasers are used to reduce the appearance of fine lines and wrinkles on the face; laser ablation, which removes thin layers of skin, and nonablative lasers that stimulate collagen 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.

• Botulinum toxin
• Injectable filler
• Wrinkly skin syndrome

Look up wrinkle in Wiktionary, the free dictionary.

Wikimedia Commons has media related to Wrinkles (skin).

• Skin Ageing at Medline

A clinic (or outpatient clinic or ambulatory care clinic) is a health facility that is primarily focused on the care of outpatients. Clinics can be privately operated or publicly managed and funded. They typically cover the primary care needs of populations in local communities, in contrast to larger hospitals which offer more specialized treatments and admit inpatients for overnight stays.

Most commonly, the English word clinic refers to a general practice, run by one or more general practitioners offering small therapeutic treatments, but it can also mean a specialist clinic. Some clinics retain the name "clinic" even while growing into institutions as large as major hospitals or becoming associated with a hospital or medical school.

The word clinic derives from Ancient Greek κλίνειν klinein meaning to slope, lean or recline. Hence κλίνη klinē is a couch or bed and κλινικός klinikos is a physician who visits his patients in their beds.^[1] In Latin, this became clīnicus.^[2][3]

An early use of the word clinic was "one who receives baptism on a sick bed".^[4]

Clinics are often associated with a general medical practice run by one or several general practitioners. Other types of clinics are run by the type of specialist associated with that type: physical therapy clinics by physiotherapists and psychology clinics by clinical psychologists, and so on for each health profession. (This can even hold true for certain services outside the medical field: for example, legal clinics are run by lawyers.)

Some clinics are operated in-house by employers, government organizations, or hospitals, and some clinical services are outsourced to private corporations which specialize in providing health services. In China, for example, owners of such clinics do not have formal medical education. There were 659,596 village clinics in China in 2011.^[5]

Health care in India, China, Russia and Africa is provided to those regions' vast rural areas by mobile health clinics or roadside dispensaries, some of which integrate traditional medicine. In India these traditional clinics provide ayurvedic medicine and unani herbal medical practice. In each of these countries, traditional medicine tends to be a hereditary practice.

The function of clinics differs from country to country. For instance, a local general practice run by a single general practitioner provides primary health care and is usually run as a for-profit business by the owner, whereas a government-run specialist clinic may provide subsidized or specialized^{[dubious – discuss]} health care.

Some clinics serve as a place for people with injuries or illnesses to be seen by a triage nurse or other health worker. In these clinics, the injury or illness may not be serious enough to require a visit to an emergency room (ER), but the person can be transferred to one if needed.

Treatment at these clinics is often less expensive than it would be at a casualty department. Also, unlike an ER these clinics are often not open on a 24/7/365 basis. They sometimes have access to diagnostic equipment such as X-ray machines, especially if the clinic is part of a larger facility. Doctors at such clinics can often refer patients to specialists if the need arises.^[6]

Large outpatient clinics vary in size, but can be as large as hospitals.

Typical large outpatient clinics house general medical practitioners (GPs) such as doctors and nurses to provide ambulatory care and some acute care services but lack the major surgical and pre- and post-operative care facilities commonly associated with hospitals.

Besides GPs, if a clinic is a polyclinic, it can house outpatient departments of some medical specialties, such as gynecology, dermatology, ophthalmology, otolaryngology, neurology, pulmonology, cardiology, and endocrinology. In some university cities, polyclinics contain outpatient departments for the entire teaching hospital in one building.

Large outpatient clinics are a common type of healthcare facility in many countries, including France, Germany (long tradition), Switzerland, and most of the countries of Central and Eastern Europe (often using a mixed Soviet-German model), as well as in former Soviet republics such as Russia and Ukraine;^[7] and in many countries across Asia and Africa.^[8]

In Europe, especially in the Central and Eastern Europe, bigger outpatient health centers, commonly in cities and towns, are called policlinics (derived from the word polis, not from poly-).

Recent^[when?] Russian governments have attempted to replace the policlinic model introduced during Soviet times with a more western model. However, this has failed.^[9]

In the Czech Republic, many policlinics were privatized or leasehold and decentralized in the post-communist era: some of them are just lessors and coordinators of a healthcare provided by private doctor's offices in the policlinic building.^[10]

India has also set up huge numbers of polyclinics for former defense personnel. The network envisages 426 polyclinics in 343 districts of the country which will benefit about 33 lakh (3.3 million) ex-servicemen residing in remote and far-flung areas.^[11]

Policlinics are also the backbone of Cuba's primary care system and have been credited with a role in improving that nation's health indicators.^[12]

Providing health services through mobile clinics provides accessible healthcare services to these remote areas that have yet to make their way in the politicized space. For example, mobile clinics have proved helpful in dealing with new settlement patterns in Costa Rica. Before foreign aid organizations or the state government became involved in healthcare, Costa Rica's people managed their own health maintenance and protection.^[13] People relied on various socio-cultural adaptations and remedies to prevent illnesses, such as personal hygiene and settlement patterns.^[13] When new settlements that sprang up along the coast became "artificial" communities, and due to lack of traditional home healing practices here, alternative methods such as mobile clinics had to be implemented in these communities for the protection and prevention of diseases.^[13]

A study done in rural Namibia revealed the health changes of orphans, vulnerable children and non-vulnerable children (OVC) visiting a mobile clinic where health facilities are far from the remote villages.^[14] Over 6 months, information on immunization status, diagnosis of anemia, skin and intestinal disorders, nutrition, dental disorders was collected and showed that visits to mobile clinics improved the overall health of children that visited regularly. It concluded that specified "planning of these programs in areas with similarly identified barriers may help correct the health disparities among Namibian OVC and could be a first step in improving child morbidity and mortality in difficult-to-reach rural areas."^[14]

Food supplementation in the context of routine mobile clinic visits also shows to have improved the nutritional status of children, and it needs further exploration as a way to reduce childhood malnutrition in resource-scarce areas. A cross-sectional study focussed on comparing acute and chronic undernutrition rates prior to and after a food-supplementation program as an adjunct to routine health care for children of migrant workers residing in rural communities in the Dominican Republic.^[15] Rates of chronic undernutrition decreased from 33% to 18% after the initiation of the food-supplementation program and shows that the community members attending the mobile clinics are not just passively receiving the information but are incorporating it and helping keep their children nourished.^[15]

There are many different types of clinics providing outpatient services. Such clinics may be public (government-funded) or private medical practices.

• A CLSC are in Quebec; they are a type of free clinic funded by the provincial government; they provide service not covered by Canada's healthcare plan including social workers
• In the United States, a free clinic provides free or low-cost healthcare for those with little or without insurance.
• A retail-based clinic is housed in supermarkets and similar retail outlets providing walk-in health care, which may be staffed by nurse practitioners.
• A general out-patient clinic offers general diagnoses or treatments without an overnight stay.
• A polyclinic or policlinic provides a range of healthcare services (including diagnostics) without need of an overnight stay
• A specialist clinic provides advanced diagnostic or treatment services for specific diseases or parts of the body. This type contrasts with general out-patient clinics.
  • A sexual health clinic deals with sexual health related problems, such as prevention and treatment of sexually transmitted infections.
  • A gender identity clinic provides services relating to transgender health care.
  • A fertility clinic aims to help women and couples to become pregnant.
  • An abortion clinic is a medical facility providing abortion services to women.
  • An ambulatory surgery clinic offers outpatient or same day surgery services, usually for surgical procedures less complicated than those requiring hospitalization.
  • An ultrasound clinic offers medical ultrasound investigations for patients. An ultrasound clinic is normally run privately.

Wikimedia Commons has media related to Clinics.

• Healthcare provider
• Health center
• Health systems management
• Healthcare system
• Nurse-led clinic
• Polyclinics in England
• Walk-in clinic