what is at the end of a hair follicle
Leg hair


hair follicles divide and multiply. When the space fills up in the follicle it pushes older cells out and that is what becomes the leg hair. After the older cells become hard and leave the follicle, they form a hair shaft. The hair shaft is mostly made up of dead tissue and a protein that is known as keratin. It is said that hair growth occurs during the "growing" phase of the follicle, and then retained as dead club hair during the "resting" phase. The old club hair might
12163444
Hair follicle


in this active phase of growth for 2–7 years; this period is genetically determined. At the end of the anagen phase an unknown signal causes the follicle to go into the catagen phase. The catagen phase is a short transition stage that occurs at the end of the anagen phase. It signals the end of the active growth of a hair. This phase lasts for about 2–3 weeks while the hair converts to a club hair. A club hair is formed during the catagen phase when the part of the hair follicle in contact
10526669
Stem cell theory of aging


-strand breaks by non-homologous end joining (NHEJ). Lig4 deficiency in the mouse causes a progressive loss of HSCs during aging. These findings suggest that NHEJ is a key determinant of the ability of HSCs to maintain themselves over time. A key aspect of hair loss with age is the aging of the hair follicle. Ordinarily, hair follicle renewal is maintained by the stem cells associated with each follicle. Aging of the hair follicle appears to be primed by a sustained cellular response to the DNA damage that accumulates in
11531907
Hair follicle


of the scalp, forearms, legs and genitalia have abundant hair follicles. There are many structures that make up the hair follicle. Anatomically, the triad of hair follicle, sebaceous gland and arrector pili muscle make up the pilosebaceous unit. A hair follicle consists of : Other structures associated with the hair follicle include the cup in which the follicle grows known as the infundibulum, the arrector pili muscles, the sebaceous glands, and the apocrine sweat glands. Hair follicle receptors sense the position of the hair. Attached to the follicle
10526662
Hair plexus


A hair plexus or root hair plexus is a special group of nerve fiber endings and serves as a very sensitive mechanoreceptor for touch sensation. Each hair plexus forms a network around a hair follicle and is a receptor, which means it sends and receives nerve impulses to and from the brain when the hair moves. Endings of sensory nerve fibers which form a plexus around a hair follicle in hairy skin. They are mechanoreceptors conveying touch sensation. Specifically, crude touch and pressure sensation conveyed through the spinocervical tract, which is located in
15858428
Human hair growth


when the anagen phase ends and the catagen phase begins. The first sign of catagen is the cessation of melanin production in the hair bulb and apoptosis of follicular melanocytes. Ultimately, the follicle is 1/6 its original length, causing the hair shaft to be pushed upward. While hair is not growing during this phase, the length of the terminal fibers increase when the follicle pushes them upward. During the telogen or resting phase (also known as shedding phase) the follicle remains dormant for one to four months. Ten to fifteen
6603491
Hair follicle


, the epithelium and underlying mesenchyme interact to form hair follicles. A key aspect of hair loss with age is the aging of the hair follicle. Ordinarily, hair follicle renewal is maintained by the stem cells associated with each follicle. Aging of the hair follicle appears to be primed by a sustained cellular response to the DNA damage that accumulates in renewing stem cells during aging. This damage response involves the proteolysis of type XVII collagen by neutrophil elastase in response to the DNA damage in the hair follicle stem cells. Proteolysis of collagen
10526665
Hair follicle


are found. There are ethnic differences in several different hair characteristics. The differences in appearance and texture of hair are due to many factors: the position of the hair bulb relative to the hair follicle, size and shape of the dermal papilla, and the curvature of the hair follicle. The scalp hair follicle in Caucasians is elliptical in shape and, therefore, produces straight or wavy hair, whereas the scalp hair follicle of people of African descent is more curvy, resulting in the growth of tightly curled hair. In utero
10526664
Human hair growth


or other parts of the body, and can ultimately cause baldness across the entire body. This disease interferes with the hair growth cycle by causing a follicle to prematurely leave the anagen, or active growth, phase and enter the resting, or telogen phase. The hair growth in the affected follicles is lessened or stopped completely. Traction alopecia is caused by adding too much strain on the hair on one's head. Tight ponytails and other styles that require added tension to the hair are often what cause this disease. It can
6603495
Hair follicle


leads to elimination of the damaged cells and then to terminal hair follicle miniaturization. Hair grows in cycles of various phases: anagen is the growth phase; catagen is the involuting or regressing phase; and telogen, the resting or quiescent phase (names derived using the Greek prefixes ana-, kata-, and telos- meaning up, down, and end respectively). Each phase has several morphologically and histologically distinguishable sub-phases. Prior to the start of cycling is a phase of follicular morphogenesis (formation of the follicle). There
10526666
Hair


additional disulfide bond, becomes curlier in form. As the hair follicle shape determines curl pattern, the hair follicle size determines thickness. While the circumference of the hair follicle expands, so does the thickness of the hair follicle. An individual's hair volume, as a result, can be thin, normal, or thick. The consistency of hair can almost always be grouped into three categories: fine, medium, and coarse. This trait is determined by the hair follicle volume and the condition of the strand. Fine hair
14493760
Hair follicle


determine the observed ethnic differences in scalp hair appearance, length and texture. There are many human diseases in which abnormalities in hair appearance, texture or growth are early signs of local disease of the hair follicle or systemic illness. Well known diseases of the hair follicle include "alopecia" or hair loss, "hirsutism" or excess hair growth and "lupus erythematosus". The position and distribution of hair follicles changes over the body. For example, the skin of the palms and soles do not have hair follicles whereas skin
10526661
Hair follicle


This condition is called telogen effluvium. The club hair is the final product of a hair follicle in the telogen stage, and is a dead, fully keratinized hair. Fifty to one-hundred club hair are shed daily from a normal scalp. There are many human diseases in which abnormalities in hair appearance, texture or growth are early signs of local disease of the hair follicle or systemic illness. Well known diseases of the hair follicle include "alopecia" or hair loss, "hirsutism" or excess hair growth, and
10526671
Bolognese dog


mammals. These cycles are: "anagen", growth of normal hair; "catagen" growth slows, and hair shaft thins; "telegen", hair growth stops, follicle rests, and old hair fall off—is shed. At the end of the telegen phase, the follicle begins the cycle again. The length of time of the growing and shedding cycle varies by age and other factors. There is no such thing as a completely non-shedding breed. The coat requires daily brushing with monthly grooming recommended
1747056
Frictional alopecia


Frictional alopecia is the loss of hair that is caused by rubbing of the hair, follicles, or skin around the follicle. The most notorious example of this is the loss of ankle hair among people who wear socks constantly for years. The hair may not grow back even years after the source of friction has ended. Hair loss on men's legs went largely undiagnosed, but is now thought to be quite common. While the overall causes are still being explored, the primary culprit is currently thought to be friction from socks
8638815
Hair follicle


The hair follicle is a dynamic organ found in mammalian skin. It resides in the dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a complex interaction between hormones, neuropeptides and immune cells. This complex interaction induces the hair follicle to produce different types of hair as seen on different parts of the body. For example, terminal hairs grow on the scalp and lanugo hairs are seen covering the bodies of fetuses in the uterus and in
10526658
Lykoi


Breed and can begin competing against other Championship breeds in May 2017, with TICA. Work is currently being done to expand the breeding program. At the University of Tennessee, dermatologists examined them for any skin abnormalities. Along with biopsy samples of the skin, the dermatologists could find no reason for the coat pattern. What they did find is that some hair follicles lacked all the necessary components required to create hair (which is why Lykoi lack an undercoat). They also found that the follicles that were able to produce hair
12887933
Hair transplantation


being harvested. There are several different techniques for harvesting hair follicles, each with their own advantages and disadvantages. Regardless of the harvesting technique, proper extraction of the hair follicle is paramount to ensure the viability of the transplanted hair and avoid transection, the cutting of the hair shaft from the hair follicle. Hair follicles grow at a slight angle to the skin's surface, so transplanted tissue must be removed at a corresponding angle. There are two main ways in which donor grafts are extracted today: strip excision harvesting, and
7535768
Hypertrichosis


There are three stages of the hair cycle: the anagen phase (hair growth), the catagen phase (hair follicle death), and the telogen phase (hair shedding). If the anagen phase increases beyond what is normal, that region of the body will experience excessive hair growth. Hypertrichosis is diagnosed clinically by the occurrence of hair in excess of what is expected for age, sex, and ethnicity in areas that are not androgen-sensitive. The excess can be in the form of excessive length or density and
3565065
Hair cloning


Hair multiplication or hair cloning is a proposed technique to counter hair loss. The technology to clone hair is in its early stages. Experts previously assumed that in the case of complete baldness, follicles are completely absent from the scalp, so they cannot be regenerated. However it was discovered that the follicles are not entirely absent, as there are stem cells in the bald scalp from which the follicles naturally arise. Abnormal behavior of these follicles is suggested to be the result of progenitor cell deficiency in these areas. The basic
610303
Hair loss


of coronary heart disease (CHD) and the relationship depends upon the severity of baldness, while frontal baldness is not. Thus, vertex baldness might be a marker of CHD and is more closely associated with atherosclerosis than frontal baldness. A key aspect of hair loss with age is the aging of the hair follicle. Ordinarily, hair follicle renewal is maintained by the stem cells associated with each follicle. Aging of the hair follicle appears to be primed by a sustained cellular response to the DNA damage that accumulates in renewing stem cells
20514817
Pattern hair loss


units in papillae of individual hair follicles. They catalyze formation of the androgens testosterone and DHT, which in turn regulate hair growth. Androgens have different effects at different follicles: they stimulate IGF-1 at facial hair, leading to growth, but can also stimulate TGF β1, TGF β2, dickkopf1, and IL-6 at the scalp, leading to catagenic miniaturization. Hair follicles in anaphase express four different caspases. Significant levels of inflammatory infiltrate have been found in transitional hair follicles. Interleukin 1 is suspected to be a cytokine mediator that promotes
973236
Hair follicle


with the lower portion of the hair becomes attached to the hair shaft. This process cuts the hair off from its blood supply and from the cells that produce new hair. When a club hair is completely formed, about a 2-week process, the hair follicle enters the telogen phase. The telogen phase is the resting phase of the hair follicle. When the body is subjected to extreme stress, as much as 70 percent of hair can prematurely enter the telogen phase and begin to fall, causing a noticeable loss of hair.
10526670
Acne


debris and oily sebum blocks the pore of the hair follicle, thus forming the microcomedone. This is further exacerbated by the biofilm created by "C. acnes" within the hair follicle. If the microcomedone is superficial within the hair follicle, the skin pigment melanin is exposed to air, resulting in its oxidation and dark appearance (known as a blackhead or open comedo). In contrast, if the microcomedone occurs deep within the hair follicle, this causes the formation of a whitehead (known as a closed comedo). The
7723
Hair care


that not every form of cancer or cancer treatment necessarily means one will lose their hair) that caused hair loss or led to a decision to shave the head. Genetics and health are factors in healthy hair. Proper nutrition is important for hair health. The living part of hair is under the scalp skin where the hair root is housed in the hair follicle. The entire follicle and root are fed by a supply of arteries, and blood carries nutrients to the follicle/root. Any time an individual has any kind of
19772419
Hair follicle


some new born babies. The process of hair growth occurs in distinct sequential stages. The first stage is called "anagen" and is the active growth phase, "telogen" is the resting stage, "catagen" is the regression of the hair follicle phase, "exogen" is the active shedding of hair phase and lastly "kenogen" is the phase between the empty hair follicle and the growth of new hair. The function of hair in humans has long been a subject of interest and continues to be an important
10526659
Eyelash implants


with 1 to 4 hair follicles are extracted for eyelash hair transplantation. Recipient area preparation: After extraction of hair, surgeon prepares recipient area by administering local anesthesia and making extremely small incisions for implantation of follicles. While preparing recipient site, direction and angle of eyelashes are kept in mind to produce natural looking results. Graft implantation: After preparing recipient site, surgeon implants 1 to 2 hair follicles at a time in specific directions. Single procedure usually involves implantation of 30 to 40 hair follicles to get desired density of eyelashes.
5083022
Hair follicle


"lupus erythematosus". Therefore, understanding the function of the normal hair follicle is fundamental to diagnosing and treating many dermatologic and systemic diseases with hair abnormalities. Hair follicles form the basis of the two primary methods of hair transplantation in hair restoration, Follicular Unit Transplantation (FUT) and follicular unit extraction (FUE). In each of these methods, naturally occurring groupings of one to four hairs, called follicular units, are extracted from the hair restoration patient and then surgically implanted in the balding area of the patient's scalp
10526672
Hair follicle


shorter length limit compared to hair on the head. Growth cycles are controlled by a chemical signal like epidermal growth factor. DLX3 is a crucial regulator of hair follicle differentiation and cycling. Specifically, colocalization of phosphorylated Smad1/5/8 complex and DLX3 regulate role for BMP signaling to Dlx3 during hair morphogenesis in animal models. Anagen is the active growth phase of hair follicles during which the root of the hair is dividing rapidly, adding to the hair shaft. During this phase the hair grows about 1 cm every 28 days. Scalp hair stays
10526668
Human hair color


70% of cases of hair graying. The change in hair color occurs when melanin ceases to be produced in the hair root and new hairs grow in without pigment. The stem cells at the base of hair follicles produce melanocytes, the cells that produce and store pigment in hair and skin. The death of the melanocyte stem cells causes the onset of graying. It remains unclear why the stem cells of one hair follicle may fail to activate well over a decade before those in adjacent follicles less than a millimeter apart. Graying
218630
Hair follicle


, known as the recipient area. These follicles are extracted from donor areas of the scalp, or other parts of the body, which are typically resistant to the miniaturization effects of the hormone DHT. It is this miniaturization of the hair shaft that is the primary predictive indicator of androgenetic alopecia, commonly referred to as male pattern baldness or male hair loss. When these DHT-resistant follicles are transplanted to the recipient area, they continue to grow hair in the normal hair cycle, thus providing the hair restoration patient with permanent
10526673
Leg hair


lighter in color. The growth of androgenic hair is related to the level of androgens and the density of androgen receptors in the dermal papillae. Both must reach a threshold for the proliferation of hair follicle cells. Fibroblast growth factor 5 (FGF5) is a secreted signaling protein. The expression of this protein is detected in hair follicles from the mice that scientists have experimented on. The hair follicles are localized to the outer root sheath during one of the phases of the hair growth cycle. Such experiments conclude that the protein FGF5
12163446
Body grooming


be very time-consuming. The hair shaft must be long enough to grasp with tweezers. Electrolysis involves inserting a fine needle into the hair follicle and applying an electric current to the follicle root. This procedure burns the hair root, theoretically preventing it from producing more hair. Laser treatment approved by the U.S. Food and Drug Administration involves a laser beam basically killing the hair follicles. Results depend on skin pigmentation and color of hair. Depilatories use a chemical called thioglycolate mixed with sodium hydroxide or calcium hydroxide to literally melt the
22195772
Demodex folliculorum


. The adult lives for 4–6 days. "Demodex folliculorum" prefers areas where sebum production is high, and is typically found in hair follicles on the human face, generally in greater numbers around the cheeks, nose, and forehead, but also elsewhere on the face, eyelids and ears. The mites may also be found on other parts of the body, such as the chest and buttocks. Within the hair follicle, "D. folliculorum" is found above the sebaceous gland, positioned head downwards, with the end of
20460891
Bone morphogenetic protein 4


of the hair shaft in the anagen hair follicle. This is done through controlling the expression of the transcription factors which regulate hair differentiation. It is still unclear however where BMPs act within the genetic network. The signaling of bmp4 may potentially control expression of terminal differentiation molecules such as keratins. Other regulators have been shown to control hair follicle development as well. HOXC13 and FOXN1 are considered important regulators because loss-of-function experiments show impaired hair shaft differentiation that doesn’t interfere in the hair follicle formation. When BMP4 is
21279028
Sebaceous gland


There are two types of sebaceous gland, those connected to hair follicles, and those that exist independently. Sebaceous glands are found in hair-covered areas, where they are connected to hair follicles. One or more glands may surround each hair follicle, and the glands themselves are surrounded by arrector pili muscles, forming a pilosebaceous unit. The glands have an acinar structure (like a many-lobed berry), in which multiple glands branch off a central duct.The glands deposit sebum on the hairs, and bring it
10526676
DNA damage theory of aging


the aging of the hair follicle. Ordinarily, hair follicle renewal is maintained by the stem cells associated with each follicle. Aging of the hair follicle appears to be due to the DNA damage that accumulates in renewing stem cells during aging. A popular idea, that has failed to gain significant experimental support, is the idea that mutation, as distinct from DNA damage, is the primary cause of aging. As discussed above, mutations tend to arise in frequently replicating cells as a result of errors of DNA synthesis when template DNA
2404267
Arrector pili muscle


The arrector pili muscles are small muscles attached to hair follicles in mammals. Contraction of these muscles causes the hairs to stand on end, known colloquially as goose bumps. Each arrector pili is composed of a bundle of smooth muscle fibres which attach to several follicles (a follicular unit), and is innervated by the sympathetic branch of the autonomic nervous system. The contraction of the muscle is then involuntary–stresses such as cold, fear etc. may stimulate the sympathetic nervous system, and thus cause contraction. Contraction of the
11292555
Pattern hair loss


of pilosebaceous units of hair follicles begins "in utero". The physiology is primarily androgenic, with dihydrotestosterone (DHT) being the major contributor at the dermal papillae. Men with premature androgenic alopecia tend to have lower than normal values of sex hormone-binding globulin (SHBG), follicle stimulating hormone (FSH), testosterone, and epitestosterone when compared to men without pattern hair loss. Although hair follicles were previously thought to be permanently gone in areas of complete hair loss, they are more likely dormant, as recent studies
973232
Bone morphogenetic protein 4


morphogenesis. Other genes which can inhibit or interact with BMP4 are noggin, follistatin, gremlin, which is all expressed in the developing hair follicles. In mice in which noggin is lacking, there are fewer hair follicles than on a normal mouse and the development of the follicle is inhibited. In chick embryos it is shown that ectopically expressed noggin produces enlarged follicles, and BMP4 signaling shows repressed placode fate in nearby cells. Noggin has also been shown during in vivo experiments to induce hair growth in post natal skin. BMP4 is
21279030
Scarring hair loss


diagnosis of cicatricial alopecia. Diagnosis and treatment of cicatricial alopecias is often challenging. For this reason, it is helpful to be evaluated by a dermatologist with a special interest or expertise in scalp and hair disorders, and who is familiar with current diagnostic methods and therapies. Cicatricial alopecias are classified as primary or secondary. This discussion is confined to the primary cicatricial alopecias in which the hair follicle is the target of the destructive inflammatory process. In secondary cicatricial alopecias, destruction of the hair follicle is incidental to a non-follicle
16013761
Hair follicle


is also a shedding phase, or exogen, that is independent of anagen and telogen in which one or several hairs that might arise from a single follicle exits. Normally up to 90% of the hair follicles are in anagen phase, while 10–14% are in telogen and 1–2% in catagen. The cycle's length varies on different parts of the body. For eyebrows, the cycle is completed in around 4 months, while it takes the scalp 3–4 years to finish; this is the reason eyebrow hair have a much
10526667
Minoxidil


potassium channels, it allows more oxygen, blood, and nutrients to the follicles. This may cause follicles in the telogen phase to shed, which are then replaced by thicker hairs in a new anagen phase. Minoxidil is a prodrug that is converted by sulfation via the sulfotransferase enzyme SULT1A1 to its active form, minoxidil sulfate. Several studies demonstrated that the activity of sulfotransferase in hair follicles predict minoxidil response in the treatment of hair loss. Minoxidil is less effective when the area of hair loss is large. In addition, its
2448798
Hair care


, the vital organs will be attended to first, meaning that healthy, oxygenated blood may not feed into the hair follicle, resulting in less healthy hair or a decline in growth rate. While not all hair growth issues stem from malnutrition, it is a valuable symptom in diagnosis. Scalp hair grows, on average, at a rate of about 1.25 centimeters per month, and shampoos or vitamins have not been shown to noticeably change this rate. Hair growth rate also depends upon what phase in the cycle of hair growth one
19772422
Body grooming


what a man will groom. It's a personal choice and very individual. Shaving is the most commonly used hair removal technique. However, shaving is also the most temporary hair removal method since shaving cuts hair at the surface of the skin instead of removing hair by its follicles. Electric trimmers allow you to shorten your hair in certain body areas instead of getting rid of all of it. Waxing involves heated wax that is applied in the direction of hair growth over the skin. Hair becomes embedded in the wax as it
22195770
Stem cell theory of aging


renewing stem cells during aging. This damage response involves the proteolysis of type XVII collagen by neutrophil elastase in response to the DNA damage in the hair follicle stem cells. Proteolysis of collagen leads to elimination of the damaged cells and then to terminal hair follicle miniaturization. Diseases such as Alzheimer's disease, end-stage renal failure and heart disease are caused by different mechanisms that are not related to stem cells. Also, some diseases related to hematopoietic system, such as aplastic anemia and complete bone marrow failure, are not especially
11531908
Hair loss


anagen), a short transitional phase (catagen) and a short resting phase (telogen). At the end of the resting phase, the hair falls out (exogen) and a new hair starts growing in the follicle beginning the cycle again. Normally, about 40 (0–78 in men) hairs reach the end of their resting phase each day and fall out. When more than 100 hairs fall out per day, clinical hair loss (telogen effluvium) may occur. A disruption of the growing phase causes abnormal loss
20514806
Hair


the hair shaft, which exhibits no biochemical activity and is considered "dead". The base of a hair's root (the "bulb") contains the cells that produce the hair shaft. Other structures of the hair follicle include the oil producing sebaceous gland which lubricates the hair and the arrector pili muscles, which are responsible for causing hairs to stand up. In humans with little body hair, the effect results in goose bumps. The "root of the hair" ends in an enlargement, the "hair bulb
14493754
Hair


complex structure slides as the hair swells and is covered with a single molecular layer of lipid that makes the hair repel water. The diameter of human hair varies from . There are two million small, tubular glands and sweat glands that produce watery fluids that cool the body by evaporation. The glands at the opening of the hair produce a fatty secretion that lubricates the hair. Hair growth begins inside the hair follicle. The only "living" portion of the hair is found in the follicle. The hair that is visible is
14493753
Alopecia areata


scalp. In cases of alopecia areata, hair will tend to pull out more easily along the edge of the patch where the follicles are already being attacked by the body's immune system than away from the patch where they are still healthy. Nails may have pitting or trachyonychia. Alopecia areata is thought to be a systemic autoimmune disorder in which the body attacks its own anagen hair follicles and suppresses or stops hair growth. For example, T cell lymphocytes cluster around affected follicles, causing inflammation and subsequent hair loss. It has
6588565
Hair


Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and fine vellus hair. Most common interest in hair is focused on hair growth, hair types, and hair care, but hair is also an important biomaterial primarily composed of protein, notably alpha-keratin. Attitudes towards different forms of hair, such as hairstyles and hair removal, vary widely across
14493750
Eyebrow


natural-looking eyebrow of the desired shape. The process of eyebrow transplant is quite similar to the process of hair transplant. In this process as well, follicles from an active area are transferred to the area where there are no hairs. Follicles are mostly taken from the back of the head because it is the best harvesting site when it comes to hairs. The follicles are then injected into the skin. The healing process after an eyebrow transplant is similar to the process of tattoo. In this process, patients may experience
2778135
Folliculitis


Folliculitis is the infection and inflammation of one or more hair follicles. The condition may occur anywhere on the skin except the palms of the hands and soles of the feet. The rash may appear as pimples that come to white tips on the face, chest, back, arms, legs, buttocks, or head. Most carbuncles, boils, and other cases of folliculitis develop from "Staphylococcus aureus". Folliculitis starts with the introduction of a skin pathogen to a hair follicle. Hair follicles can also be damaged by friction
19702628
Hair follicle


is a tiny bundle of muscle fiber called the "arrector pili". This muscle is responsible for causing the follicle lissis to become more perpendicular to the surface of the skin, and causing the follicle to protrude slightly above the surrounding skin (piloerection) and a pore encased with skin oil. This process results in goose bumps (or goose flesh). Also attached to the follicle is a sebaceous gland, which produces the oily or waxy substance sebum. The higher the density of the hair, the more sebaceous glands that
10526663
Ophiasis


targets the body's own hair follicles, resulting in hair loss..." and although the immune system could be attacking hair follicle melanocytes, dermal papilla cells, and keratinocytes,” but the foundational cause of this disease is yet to be confirmed. This is one among many types of patterns of hair loss, “in which they have band-link hair loss across the occiput.” Hair loss can take the form of patches of hair being removed and there can also be spontaneous regrowth as well. Ophiasis hair loss is
15391662
Dihydrotestosterone


and liver, while lower expression is observed in certain brain areas, non-genital skin/hair follicles, testes, and kidneys. SRD5A1 is most highly expressed in non-genital skin/hair follicles, the liver, and certain brain areas, while lower levels are present in the prostate, epididymides, seminal vesicles, genital skin, testes, adrenal glands, and kidneys. In the skin, 5α-reductase is expressed in sebaceous glands, sweat glands, epidermal cells, and hair follicles. Both isoenzymes are expressed
16793545
Wound healing


a barrier between the wound and the environment. Basal keratinocytes from the wound edges and dermal appendages such as hair follicles, sweat glands and sebacious (oil) glands are the main cells responsible for the epithelialization phase of wound healing. They advance in a sheet across the wound site and proliferate at its edges, ceasing movement when they meet in the middle. In healing that results in a scar, sweat glands, hair follicles and nerves do not form. With the lack of hair follicles, nerves and sweat glands, the
694825
Human hair color


Hair color is the pigmentation of hair follicles due to two types of melanin: eumelanin and pheomelanin. Generally, if more eumelanin is present, the color of the hair is darker; if less eumelanin is present, the hair is lighter. Levels of melanin can vary over time causing a person's hair color to change, and it is possible to have hair follicles of more than one color on the same person. Particular hair colors are often associated with ethnic groups, while gray or white hair is associated with age.
218613
Trichotillomania


. A biopsy can be performed and may be helpful; it reveals traumatized hair follicles with perifollicular hemorrhage, fragmented hair in the dermis, empty follicles, and deformed hair shafts. Multiple catagen hairs are typically seen. An alternative technique to biopsy, particularly for children, is to shave a part of the involved area and observe for regrowth of normal hairs. Trichotillomania is defined as a self-induced and recurrent loss of hair. It includes the criterion of an increasing sense of tension before pulling the hair and gratification or relief
19419066
Canine follicular dysplasia


, for instance the neck because of contact with a collar. Hair regrowth may occur, but the hair will be even weaker and the pattern will repeat. The dogs are affected between the ages of two to four years, and it is most commonly seen on the back towards the tail. Progression of the hair loss to cover the trunk can occur. In some breeds hair follicles in certain parts of the body become progressively miniaturized, analogous to what occurs in male pattern baldness in humans. It is most commonly seen in
8961845
Management of hair loss


the recipient site. It is primarily used to treat male pattern baldness. In this condition, grafts containing hair follicles that are genetically resistant to balding are transplanted to bald scalp. It is also used to restore eyelashes, eyebrows, beard hair, chest hair, and pubic hair and to fill in scars caused by accidents or surgery such as face-lifts and previous hair transplants. Hair transplantation differs from skin grafting in that grafts contain almost all of the epidermis and dermis surrounding the hair follicle, and many tiny grafts are
9745551
Hair transplantation


Hair transplantation is a surgical technique that removes hair follicles from one part of the body, called the 'donor site', to a bald or balding part of the body known as the 'recipient site'. The technique is primarily used to treat male pattern baldness. In this minimally invasive procedure, grafts containing hair follicles that are genetically resistant to balding (like the back of the head) are transplanted to the bald scalp. Hair transplantation can also be used to restore eyelashes, eyebrows, beard hair, chest hair
7535764
Asim Shahmalak


at the University of Manchester. The research group, headed by Professor Ralf Paus, investigates the biology and pathology of the hair follicle as a microcosmic miniorgan in which many of the fundamental problems of biology can be studied in an exemplary fashion. Current research includes investigations into the neuroendocrine properties of the human hair follicle, their impact on mitochondrial function and hair follicle immune status, and the use of adult stem cells populations associated with human skin appendages for regenerative medicine purposes. In May 2018, the results of Dr Paus's research
11579336
Callophrys xami


first instar, the body of the larvae, which is covered in tiny brownish hair follicles, is pale yellow in color with some shade of brown coloring the head portion. In the case of the second instar, the body of the larvae, now covered in tiny pinkish-red hair follicles, can range from yellow-green to pale pink in color. During the last larval stage, larvae body length usually measures about 16 mm. With the larvae body now covered in dark colored hair follicles, its coloring at this
3691846
Birt–Hogg–Dubé syndrome


from both humans and mice. BHD can be suggested by clinical findings but is definitively diagnosed by molecular genetic testing to detect mutations in the FLCN gene. The classical clinical triad includes benign growths of the hair follicles; pulmonary cysts and spontaneous pneumothorax; and bilateral, multifocal renal tumors. The cutaneous manifestations of Birt–Hogg–Dubé were originally described as fibrofolliculomas (abnormal growths of a hair follicle), trichodiscomas (hamartomatous lesions with a hair follicle at the periphery, often found on the face), and acrochordons (skin
4708129
Intense pulsed light


follicles are ‘active’, and only active hair follicles can be affected by the treatment. ‘Inactive’ hair follicles can be treated as they become ‘active’ over time. For IPL treatments, an average of 8–10 treatments are required to remove most visible hair. No common treatment protocol exists and it depends on the equipment used and patient skin type. The area to be treated should be clean shaven and free of sunburn. Treatment sessions are usually 4 to 6 weeks apart. Treatments are often given in doctors'
7074466
Asclepias uncialis


types. The lower leaves are lance-shaped to oval, and the upper leaves are narrower. Flowers occur at the ends of the stems in clusters of up to 12. They are pinkish purple in color. The fruit is a follicle containing seeds which each have a tuft of silky hairs up to an inch long. The plant may be considered "semi-rhizomatous", as what appear to be separate individuals may actually be connected underground by the root crown, which may be up to a foot deep in the
5881524
Bone morphogenetic protein 4


an important component of the biological pathways that involved regulating hair shaft differentiation within the anagen hair follicle. The strongest levels of expressed BMP4 are found within the medulla, hair shaft cells, distal hair matrix, and potential precursors of the cuticle. The two main methods which BMP4 inhibit expression of hair is through restricting growth factor expression in the hair matrix and antagonism between growth and differentiation signaling. Pathways that regulate hair follicle formation and hair growth are key in developing therapeutic methods for hair loss conditions. Such conditions include the development of
21279031
Body hair


skin. Follicular nerves detect displacement of hair shafts and other nerve endings in the surrounding skin detect vibration and distortions of the skin around the follicles. Androgenic hair extends the sense of touch beyond the surface of the skin into the air and space surrounding it, detecting air movements as well as hair displacement from contact by insects or objects. Determining the evolutionary function of androgenic hair must take into account both human evolution and the thermal properties of hair itself. The thermodynamic properties of hair are based on the properties of the keratin strands
13877204
Hair transplantation


is important to prevent scabs from forming around the hair shaft. Scabs adhere to the hair shaft and increase the risk of losing newly transplanted hair follicles during the first 7 to 10 days post-op. During the first ten days, some of the transplanted hairs, inevitably traumatized by their relocation, may fall out. This is referred to as "shock loss". After two to three months new hair will begin to grow from the moved follicles. The patient's hair will grow normally, and continue to thicken through
7535779
LGR5


where most cellular proliferation takes place. However, lineage tracing had revealed LGR5 stem cells at the bottom of the gland, architecture reminiscent to that of the intestinal arrangement. This suggests that LGR5 stem cells give rise to transit-amplifying cells, which migrate towards the isthmus where they proliferate and maintain the stomach epithelium. LGR5 stem cells were pinpointed as the precursor for sensory hair cells that line the cochlea. Hair follicle renewal is governed by Wnt signalling that act upon hair follicle stem cells located in the follicle bulge. Although these
16262768
LGR5


cells are well characterised by CD34 and cytokeratin markers, there is a growing body of agreement that LGR5 is a putative hair follicle stem cell marker. LGR5 in conjunction with LRG6, is expressed in a remarkable fashion: LRG6 stem cells maintain the upper sebaceous gland whilst LRG5 stem cells fuel the actual hair follicle shaft upon migration of transit-amplifying cells into the dermal papilla. In between these two distinct populations of stem cells are the multipotent LRG5/6 stem cells that ultimately maintain the epidermal hair follicle in adults. The cancer stem cell
16262769
Absorption (skin)


: Scrotal  Forehead  Armpit ≥ Scalp  Back = Abdomen  Palm = under surface of the foot. To be absorbed through the skin, a chemical must pass through the epidermis, glands, or hair follicles. Sweat glands and hair follicles make up about 0.1 to 1.0 percent of the total skin surface. Though small amounts of chemicals may enter the body rapidly through the glands or hair follicles, they are primarily absorbed through the epidermis. Chemicals must pass through the seven cell layers of epidermis before entering the dermis where they can enter the
1823434
GLI2


aspect of the paw, resembling those of basal cell carcinoma (BCC). Unlike Gli1 transgenic mice, Gli2 transgenic mice only developed BCC-like tumors. Transgenic mice with N-terminal deletion of Gli2, developed the benign trichoblastomas, cylindromas and hamartomas but rarely developed BCCs. Gli2 is expressed in the interfollicular epidermis and the outer root sheath of hair follicles in normal human skin. This is significant as Shh regulates hair follicle growth and morphogenesis. When inappropriately activated causes hair follicle derived tumors, the most clinically significant being the
19267574
Laser hair removal


diameter and pulse duration. These three parameters determine what actually happens when the light energy is absorbed by the tissue chromophore be it melanin, hemoglobin or water, with the amount of tissue damaged being determined by the temperature/time combination. Hair grows in several phases (anagen, telogen, catagen) and a laser can only affect the currently active growing hair follicles (early anagen). Hence, several sessions are needed to damage the hair in all phases of growth and force it to revert to a vellus non-colored
21823844
Hypertrichosis


form also affects the forearms and legs, but is less common in these areas. Another deformity associated with acquired generalized hypertrichosis is multiple hairs occupying the same follicle. It may also include abnormal hair growth patterns as what happens to the eyelashes in a condition known as trichiasis. Oral minoxidil treatments for hypertension are known to cause this condition. Topical minoxidil used for alopecia causes hair growth in the areas where it is applied, however this hair disappears shortly after discontinuing the use of topical minoxidil. Acquired patterned hypertrichosis is an increase in
3565057
Hot roots


Hot roots is a term used by hair stylists to explain the condition brought about by applying an artificial pigment to the hair, whereby the roots (the sections of the hair follicles closest to the scalp) are noticeably warmer in color (more red/orange) than the ends of the hair. This can happen for a few reasons, but the two most likely causes are explained below. It is helpful to understand the general nature of the lightening, or "lifting", of natural hair color. The color of
12863608
Body grooming


cools and then quickly pulled off by a cloth or paper strip. Sugaring is similar to waxing, except that sugaring does not always require strips and it's applied against the hair and removed with the hair for less breakage and damage to hair follicles. Sugar is not hot and there is no need to ever let it cool. By removing the hair in the earliest growth stage (anagen) sugar will help diminish regrowth by letting the follicles naturally shrink. Plucking hair with tweezers is an effective way to remove hair but can
22195771
Microsporum audouinii


; it then enters a hair follicle, penetrates the hair shaft and grows down the length of the hair. The hyphae grow distally until they reach the upper limits of the zone of keratinization where the nucleated hair shaft cornifies completely and is converted into hard, anucleated keratin. The terminal end of the growing hyphae forms a ring (Adamson's Fringe). As the hair continues to grow outwards, hyphae are brought to the surface (scalp) and arthroconidia are produced. Eventually due to mechanical forces (the movement of the
15410706
Human hair growth


hallmarks of cancer; however, hair follicle cells also grow and divide quickly. Consequently, the chemotherapy drugs usually inhibit hair growth. The dose and type of medicine will determine the severity of hair loss. Once the course of chemotherapy has ended, new hair growth may begin after three to 10 weeks. Alopecia is a hair loss disease that can occur in anyone at any stage of life. Specifically Alopecia areata is an autoimmune disease that causes hair to spontaneously fall out. It is mainly characterized by bald patches on the scalp
6603494
Dog coat genetics


hairs are longer, thicker and stiffer, and called guard hairs or outer coat. Each follicle also holds a variety of silky- to wiry-textured secondary hairs (undercoat) all of which are wavy, and smaller and softer than the primary hair. The ratio of primary to secondary hairs varies at least six-fold, and varies between dogs according to coat type, and on the same dog in accordance with seasonal and other hormonal influences. Puppies are born with a single coat, with more hair follicles per unit area
12729042
Electrology


Electrology is the practice of electrical hair removal to permanently remove human hair from the body. Electrolysis is the actual process of removing hair using electricity. In electrolysis, a qualified professional called an electrologist slides a hair-thin, solid metal probe into each hair follicle without puncturing the skin (when inserted properly). Electricity is delivered to the follicle through the probe, which causes localized damage to the areas that generate hairs, either through the formation of caustic sodium hydroxide (the galvanic method), overheating (thermolysis),
13211419
Hair


a source of heat insulation and cooling (when sweat evaporates from soaked hair) as well as protection from ultra-violet radiation exposure. The function of hair in other locations is debated. Hats and coats are still required while doing outdoor activities in cold weather to prevent frostbite and hypothermia, but the hair on the human body does help to keep the internal temperature regulated. When the body is too cold, the arrector pili muscles found attached to hair follicles stand up, causing the hair in these follicles to do the same
14493764
Hair conditioner


conditioner without feeling greasy or heavy. The outermost layer of a hair follicle is called the cuticle and is composed largely of keratin. This is rich in cysteine groups which are mildly acidic. When the hair is washed these groups can deprotonate, giving the hair a negative charge. Positively charged quaternary ammonium species, such as behentrimonium or polyquaternium, can then become attached to the hair via electrostatic interactions. Once attached these compounds have several effects. Their long hydrocarbon backbone helps to lubricate the surface of each hair follicle, reducing the
18607013
Hair cloning


idea of hair cloning is that healthy follicle cells or dermal papillae can be extracted from the subject from areas that are not bald and are not suffering hair loss, they can be multiplied (cloned) by various culturing methods and the newly produced cells can be injected back in the bald scalp, where they would act healthy and produce hair. In 2015, initial trials for human hair were successful in generating new follicles, but the hairs grew in various different directions giving an unnatural look. As of 2019, scientists believe they
610304
Hair transplantation


as the new hairs grew and lasted just as they would have at their original home. Advancing the theory of donor dominance, Walter P. Unger, M.D. defined the parameters of the "Safe Donor Zone" from which the most permanent hair follicles could be extracted for hair transplantation. As transplanted hair will only grow in its new site for as long as it would have in its original one, these parameters continue to serve as the fundamental foundation for hair follicle harvesting, whether by strip method or FUE. For the next twenty
7535783
Management of hair loss


of the scalp of a bald man is reduced. This procedure can reduce the area of the scalp without hair. Radiation induces hair loss through damage to hair follicle stem cell progenitors and alteration of keratin expression. Radiation therapy has been associated with increased mucin production in hair follicles. Studies have suggested electromagnetic radiation as a therapeutic growth stimulant in alopecia. Certain hair shampoos and ointments visually thicken existing hair, without affecting the growth cycle. There have also been developments in the fashion industry with wig design. The fashion accessory has also
9745555
Bone morphogenetic protein 4


morphology and hair follicle cycling in an abnormal fashion. The cycles of hair follicles are that of growth, or anagen, regression or catagen, and rest or telogen. In mammals reciprocal epithelial and mesynchymal interactions control the development of hair. Genes such as BMP4 and BMP2 are both active within the precursors of the hair shaft. Specifically BMP4 is found in the dermal papilla. BMP4 is part of the signaling network which controls the development of hair. It is needed for the induction of biochemical pathways and signaling for regulating the differentiation
21279027
Human hair growth


percent of the hairs on one's head are in this phase of growth at any given time. In this phase the epidermal cells lining the follicle channel continue to grow as normal and may accumulate around the base of the hair, temporarily anchoring it in place and preserving the hair for its natural purpose without taxing the body's resources needed during the growth phase. At some point, the follicle will begin to grow again, softening the anchor point of the shaft initially. The hair base will break free from the root and
6603492
Hair follicle


topic in society, developmental biology and medicine. Of all mammals, humans have the longest growth phase of scalp hair compared to hair growth on other parts of the body. For centuries, humans have ascribed esthetics to scalp hair styling and dressing and it is often used to communicate social or cultural norms in societies. In addition to its role in defining human appearance, scalp hair also provides protection from UV sun rays and is an insulator against extremes of hot and cold temperatures. Differences in the shape of the scalp hair follicle
10526660
Chukat


out. Rabbi Eliezer ruled that even as many as 50 such hairs could be plucked. But Rabbi Joshua ben Bathyra ruled that even if it had only one non-red hair on its head and one on its tail, it was invalid. If the cow had two hairs in one follicle with their roots black and their tips red or with their roots red and their tips black, Rabbi Meir taught that what was visible determined validity; but the Sages ruled that validity followed the root. Rav Judah reported in Samuel's
16590572
Hyperkeratinization


Hyperkeratinization American English or hyperkeratinisation in British) is a disorder of the cells lining the inside of a hair follicle. It is the normal function of these cells to detach or slough off (desquamate) from the skin lining at normal intervals. The dead cells are then forced out of the follicle (primarily by the growing hair). However, in hyperkeratinization, this process is interrupted and a number of these dead skin cells do not leave the follicle because of an excess of keratin, a natural protein found in the skin
15307979
Melanocyte


and cause the melanocyte to produce melanosomes, which are then transferred by dendrites to the top layer of keratinocytes. The precursor of the melanocyte is the melanoblast. In adults, stem cells are contained in the bulge area of the outer root sheath of hair follicles. When a hair is lost and the hair follicle regenerates, the stem cells are activated. These stem cells develop into both keratinocyte precursors and melanoblasts - and these melanoblasts supply both hair and skin (moving into the basal layer of the epidermis). There is additionally
7373535
Dog coat genetics


H) loci cause patchy reduction of melanin to half (merle), zero (harlequin) or both (double merle). Alleles present at the Spotting (S), Ticking (T) and Flecking (F) loci determine white markings. Every hair in the dog coat grows from a hair follicle, which has a three phase cycle, as in most other mammals. These phases are: Most dogs have a double coat, each hair follicle containing 1-2 primary hairs and several secondary hairs. The primary
12729041
Frontal fibrosing alopecia


hair loss (FPHL), chronic telogen effluvium (CTE), and alopecia areata (AA). FPHL is a non-scarring progressive miniaturization of the hair follicle with one of three different characteristic patterns. CTE is an idiopathic disease causing increased hair shedding and bi-temporal recession, usually in middle aged women. AA is an autoimmune attack of hair follicles that usually causes hair to fall out in small round patches. Improvement or stabilization of the condition has been reported with topical and intralesional corticosteroids, antibiotics, hydroxychloroquine,
16970382
Laser hair removal


also allowed to perform laser hair removal in the state of Florida. Several wavelengths of laser energy have been used for hair removal, from visible light to near-infrared radiation. These lasers are characterized by their wavelength, measured in nanometers (nm): Pulse width (or duration) is one of the most important considerations. The length of the heating pulse relates directly to the damage achieved in the follicle. When attempting to destroy hair follicles the main target is the germ cells which live on the surface of the hair
21823840
Canine follicular dysplasia


red hair of the face and feet. It is caused by lipid invasion of the hair follicle cells. Color dilution alopecia is an inherited type of follicular dysplasia. It most commonly affects dogs with blue or fawn coats, which are dilutions of black and brown, respectively. Dilution is caused by irregularities in melanin transfer and storage. Melanosomes may clump within melanocytes of the skin and hair follicles, causing the hair shafts to easily fracture. Signs of color dilution alopecia include hair loss and recurrent skin infection on the back. It
8961848
Pattern hair loss


the hair follicle across gender. Also, crosstalk occurs between androgens and the Wnt-beta-catenin signaling pathway that leads to hair loss. At the level of the somatic stem cell, androgens promote differentiation of facial hair dermal papillae, but inhibit it at the scalp. Other research suggests the enzyme prostaglandin D2 synthase and its product prostaglandin D2 (PGD2) in hair follicles as contributive. These observations have led to study at the level of the mesenchymal dermal papillae.Types 1 and 2 5α reductase enzymes are present at pilosebaceous
973235
Fungal folliculitis


have keloidal features. Majocchi's granuloma is caused by a common group of fungi called dermatophytes. Unlike traditional tinea corporis (commonly known as ringworm) that resides in the top layer of the skin, Majocchi's granuloma contains dermatophytes that have invaded the hair follicle and/or dermis. The invasion of the hair follicule is what leads to the clinically evidence papules and pustules at the periphery. The most common form, the superficial perifollicular form, occurs predominately on the legs of otherwise healthy young women who repeatedly shave their legs and develop hair
10288671
Long-tailed chinchilla


, and the recessive colors include sapphire, violet, charcoal, and velvet. Their hair is long. It is silky, extremely soft, and firmly adhered to the skin. Up to 75 hairs, in diameter, emerge together from a single hair follicle. Vibrissae (whiskers) are abundant, strong, and long——and emerge from single follicles. The general color of their upper parts is bluish or silvery gray; the underparts are yellowish-white. The tail has long, coarse, gray and black hairs on
13805945