55-441: A bristle is a stiff hair or feather (natural or artificial), either on an animal, such as a pig, a plant, or on a tool such as a brush or broom . Synthetic materials such as nylon are also used to make bristles in items such as brooms and sweepers. Bristles are often used to make brushes for cleaning purposes, as they are strongly abrasive; common examples include the toothbrush and toilet brush . The bristle brush and
110-543: A brown-haired person has 110,000, a black-haired person has 100,000, and a redhead has 90,000. Hair growth stops after a human's death. Visible growth of hair on the dead body happens only because of skin drying out due to water loss. The world record for longest hair on a living person stands with Smita Srivastava of Uttar Pradesh, India . At 7 feet and 9 inches long, she broke a Guinness World Record in November 2023, having grown her hair for 32 years. Hair exists in
165-914: A cotton thread, but is not stiff or rough. It is neither fine nor coarse. Thick strands whose shed strands usually are easily identified. Coarse hair feels hard and wiry. Hair is mainly composed of keratin proteins and keratin-associated proteins (KRTAPs). The human genome encodes 54 different keratin proteins which are present in various amounts in hair. Similarly, humans encode more than 100 different KRTAPs which crosslink keratins in hair. The content of KRTAPs ranges from less than 3% in human hair to 30–40% in echidna quill. Many mammals have fur and other hairs that serve different functions. Hair provides thermal regulation and camouflage for many animals; for others it provides signals to other animals such as warnings, mating, or other communicative displays; and for some animals hair provides defensive functions and, rarely, even offensive protection. Hair also has
220-435: A flat cross-section, while people of mostly European or Middle Eastern ancestry tend to have hair with a diameter of 70–100 μm and an oval cross-section, and people of mostly Asian or Native American ancestry tend to have hair with a diameter of 90–120 μm and a round cross-section. There are roughly two million small, tubular glands and sweat glands that produce watery fluids that cool the body by evaporation. The glands at
275-447: A sensory function, extending the sense of touch beyond the surface of the skin. Guard hairs give warnings that may trigger a recoiling reaction. While humans have developed clothing and other means of keeping warm, the hair found on the head serves primarily as 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
330-400: A variety of textures. Three main aspects of hair texture are the curl pattern, volume, and consistency. All mammalian hair is composed of keratin , so the make-up of hair follicles is not the source of varying hair patterns. There are a range of theories pertaining to the curl patterns of hair. Scientists have come to believe that the shape of the hair shaft has an effect on the curliness of
385-610: 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 different cultures and historical periods, but it
440-423: Is a method which classifies the hair by curl pattern, hair-strand thickness and overall hair volume. Curliness Strands Thin strands that sometimes are almost translucent when held up to the light. Shed strands can be hard to see even against a contrasting background. Fine hair is difficult to feel or it feels like an ultra-fine strand of silk. Strands are neither fine nor coarse. Medium hair feels like
495-490: Is a trait that may be associated with neoteny . Primates are relatively hairless compared to other mammals, and Hominini such as chimpanzees, have less dense hair than would be expected given their body size for a primate. Evolutionary biologists suggest that the genus Homo arose in East Africa approximately 2 million years ago. Part of this evolution was the development of endurance running and venturing out during
550-438: Is cognate with terms such as Old Norse and Norwegian : fax . Each strand of hair is made up of the medulla , cortex , and cuticle . The innermost region, the medulla , is an open and unstructured region that is not always present. The highly structural and organized cortex , or second of three layers of the hair, is the primary source of mechanical strength and water uptake. The cortex contains melanin , which colors
605-419: 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. These hairs then form a heat-trapping layer above
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#1733094226053660-469: Is interpreted in the neocortex , a section of the brain that expanded markedly in animals like Morganucodon and Hadrocodium . The more advanced therapsids could have had a combination of naked skin, whiskers , and scutes . A full pelage likely did not evolve until the therapsid-mammal transition. The more advanced, smaller therapsids could have had a combination of hair and scutes, a combination still found in some modern mammals, such as rodents and
715-478: Is more complex, since not all hair grows at once. Scalp hair was reported to grow between 0.6 cm and 3.36 cm per month. The growth rate of scalp hair somewhat depends on age (hair tends to grow more slowly with age), sex, and ethnicity. Thicker hair (>60 μm) grows generally faster (11.4 mm per month) than thinner (20-30 μm) hair (7.6 mm per month). It was previously thought that Caucasian hair grew more quickly than Asian hair and that
770-455: Is not just one method to discovering one's hair type. Additionally it is possible, and quite normal to have more than one kind of hair type, for instance having a mixture of both type 3a & 3b curls. The Andre Walker Hair Typing System is the most widely used system to classify hair. The system was created by Oprah Winfrey 's hairstylist, Andre Walker . According to this system there are four types of hair: straight, wavy, curly, kinky. This
825-448: Is often used to indicate a person's personal beliefs or social position, such as their age, gender , or religion . The word "hair" usually refers to two distinct structures: Hair fibers have a structure consisting of several layers, starting from the outside: The word "hair" is derived from Middle English : heer and hêr , in turn derived from Old English : hǽr and hér , with influence from Old Norse : hár . Both
880-409: Is the outer covering. Its 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 0.017 to 0.18 millimeters (0.00067 to 0.00709 in). Some of these characteristics in humans' head hair vary by race: people of mostly African ancestry tend to have hair with a diameter of 60–90 μm and
935-416: Is the outermost part of the hair shaft . It is formed from dead cells , overlapping in layers, which form scales that strengthen and protect the hair shaft. These layers are formed of keratin proteins. The hair cuticle is also known to contain anteiso-18-methyleicosanoic acid which contribute to the hydrophobic properties of hair. While the cuticle is the outermost layer, it is not responsible for
990-545: The Upper Permian , shows smooth, hairless skin with what appears to be glandular depressions, though as a semi-aquatic species it might not have been particularly useful to determine the integument of terrestrial species. The oldest undisputed known fossils showing unambiguous imprints of hair are the Callovian (late middle Jurassic ) Castorocauda and several contemporary haramiyidans , both near-mammal cynodonts , giving
1045-441: The anagen , catagen , and telogen phases. Each strand of hair on the human body is at its own stage of development. Once the cycle is complete, it restarts and a new strand of hair begins to form. The growth rate of hair varies from individual to individual depending on their age, genetic predisposition and a number of environmental factors. It is commonly stated that hair grows about 1 cm per month on average; however reality
1100-409: The epidermis called the hair follicle . The bulb of hair consists of fibrous connective tissue, glassy membrane, external root sheath, internal root sheath composed of epithelium stratum ( Henle's layer ) and granular stratum ( Huxley's layer ), cuticle, cortex and medulla. All natural hair colors are the result of two types of hair pigments. Both of these pigments are melanin types, produced inside
1155-517: The epidermis . This process is formally called piloerection , derived from the Latin words 'pilus' ('hair') and 'erectio' ('rising up'), but is more commonly known as 'having goose bumps ' in English. This is more effective in other mammals whose fur fluffs up to create air pockets between hairs that insulate the body from the cold. The opposite actions occur when the body is too warm; the arrector muscles make
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#17330942260531210-418: The fiber based on the number, distribution and types of melanin granules. The melanin may be evenly spaced or cluster around the edges of the hair. The shape of the follicle determines the shape of the cortex, and the shape of the fiber is related to how straight or curly the hair is. People with straight hair have round hair fibers. Oval and other shaped fibers are generally more wavy or curly. The cuticle
1265-423: The hygiene and cosmetology of hair including hair on the scalp , facial hair ( beard and moustache ), pubic hair and other body hair. Hair care routines differ according to an individual's culture and the physical characteristics of one's hair. Hair may be colored, trimmed, shaved, plucked, or otherwise removed with treatments such as waxing, sugaring, and threading. Cuticle (hair) The hair cuticle
1320-406: The opossum . The high interspecific variability of the size, color, and microstructure of hair often enables the identification of species based on single hair filaments. In varying degrees most mammals have some skin areas without natural hair. On the human body, glabrous skin is found on the ventral portion of the fingers , palms , soles of feet and lips , which are all parts of
1375-461: The EDAR locus, a region of the modern human genome that contributes to hair texture variation among most individuals of East Asian descent, support the hypothesis that (East Asian) straight hair likely developed in this branch of the modern human lineage subsequent to the original expression of tightly coiled natural afro-hair . Specifically, the relevant findings indicate that the EDAR mutation coding for
1430-461: The Old English and Old Norse words derive from Proto-Germanic : * hēran and are related to terms for hair in other Germanic languages such as Swedish : här , Dutch and German : haar , and Old Frisian : her . The now broadly obsolete word "fax" refers specifically to head hair and is found in compounds such as Fairfax and Halifax . It is derived from Old English : feax and
1485-445: The age as no later than ≈220 ma based on the modern phylogenetic understanding of these clades. More recently, studies on terminal Permian Russian coprolites may suggest that non-mammalian synapsids from that era had fur. If this is the case, these are the oldest hair remnants known, showcasing that fur occurred as far back as the latest Paleozoic . Some modern mammals have a special gland in front of each orbit used to preen
1540-414: The belly and lower tail of a pelycosaur , possibly Haptodus shows the basal synapsid stock bore transverse rows of rectangular scutes , similar to those of a modern crocodile , so the age of acquirement of hair logically could not have been earlier than ≈299 ma, based on the current understanding of the animal's phylogeny. An exceptionally well-preserved skull of Estemmenosuchus , a therapsid from
1595-493: The body most closely associated with interacting with the world around us, as are the labia minora and glans penis . There are four main types of mechanoreceptors in the glabrous skin of humans: Pacinian corpuscles , Meissner's corpuscles , Merkel's discs , and Ruffini corpuscles . The naked mole-rat ( Heterocephalus glaber ) has evolved skin lacking in general, pelagic hair covering, yet has retained long, very sparsely scattered tactile hairs over its body. Glabrousness
1650-425: The circulation of cool air onto the scalp. Further, wet Afro-hair does not stick to the neck and scalp unless totally drenched and instead tends to retain its basic springy puffiness because it less easily responds to moisture and sweat than straight hair does. In this sense, the trait may enhance comfort levels in intense equatorial climates more than straight hair (which, on the other hand, tends to naturally fall over
1705-453: The condition of the strand. Fine hair has the smallest circumference, coarse hair has the largest circumference, and medium hair is anywhere between the other two. Coarse hair has a more open cuticle than thin or medium hair causing it to be the most porous. There are various systems that people use to classify their curl patterns. Being knowledgeable of an individual's hair type is a good start to knowing how to take care of one's hair. There
Bristle - Misplaced Pages Continue
1760-527: The density is less than with fur, pigs are vulnerable to sunburn . One breed, the Tamworth pig , is endowed with a very dense bristle structure such that sunburn damage to skin is minimized. Animals named for their bristles include bristlebirds , the bristle-thighed curlew , the bristle-spined porcupine , and the Trinity bristle snail . Bristles also anchor worms to the soil to help them move. Hair Hair
1815-506: The ears and neck to a degree that provides slightly enhanced comfort levels in cold climates relative to tightly coiled hair). Further, it is notable that the most pervasive expression of this hair texture can be found in sub-Saharan Africa; a region of the world that abundant genetic and paleo-anthropological evidence suggests, was the relatively recent (≈200,000-year-old) point of origin for modern humanity. In fact, although genetic findings (Tishkoff, 2009) suggest that sub-Saharan Africans are
1870-457: The edges of the eyelid and protects the eye from dirt. The eyelash is to humans, camels, horses, ostriches etc., what whiskers are to cats ; they are used to sense when dirt, dust , or any other potentially harmful object is too close to the eye. The eye reflexively closes as a result of this sensation . Eyebrows and eyelashes do not grow beyond a certain length (eyelashes are rarely more than 10 mm long). However, trichomegaly can cause
1925-560: The equator, straight hair may have (initially) evolved to aid the entry of UV light into the body during the transition from dark, UV-protected skin to paler skin. Jablonski's assertions suggest that the adjective "woolly" in reference to Afro-hair is a misnomer in connoting the high heat insulation derivable from the true wool of sheep. Instead, the relatively sparse density of Afro-hair, combined with its springy coils actually results in an airy, almost sponge-like structure that in turn, Jablonski argues, more likely facilitates an increase in
1980-491: The first years of life. Hair grows everywhere on the external body except for mucous membranes and glabrous skin, such as that found on the palms of the hands, soles of the feet, and lips. The body has different types of hair, including vellus hair and androgenic hair , each with its own type of cellular construction. The different construction gives the hair unique characteristics, serving specific purposes, mainly, warmth and protection. The three stages of hair growth are
2035-425: The fur, called the harderian gland . Imprints of this structure are found in the skull of the small early mammals like Morganucodon , but not in their cynodont ancestors like Thrinaxodon . The hairs of the fur in modern animals are all connected to nerves, and so the fur also serves as a transmitter for sensory input. Fur could have evolved from sensory hair (whiskers). The signals from this sensory apparatus
2090-420: The growth rate of women's hair was faster than that of men. However, more recent research has shown that the growth rate of hair in men and women does not significantly differ and that the hair of Chinese people grew more quickly than the hair of French Caucasians and West and Central Africans. The quantity of hair hovers in a certain range depending on hair colour. An average blonde person has 150,000 hairs,
2145-514: The hair follicle and packed into granules found in the fibers. Eumelanin is the dominant pigment in brown hair and black hair , while pheomelanin is dominant in red hair . Blond hair is the result of having little pigmentation in the hair strand. Gray hair occurs when melanin production decreases or stops, while poliosis is white hair (and often the skin to which the hair is attached), typically in spots that never possessed melanin at all, or ceased for natural reasons, generally genetic, in
2200-415: 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 , which is whiter in color and softer in texture than the shaft and is lodged in a follicular involution of
2255-423: 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
Bristle - Misplaced Pages Continue
2310-520: The hair lie flat on the skin which allows heat to leave. In some mammals, such as hedgehogs and porcupines , the hairs have been modified into hard spines or quills. These are covered with thick plates of keratin and serve as protection against predators. Thick hair such as that of the lion's mane and grizzly bear's fur do offer some protection from physical damages such as bites and scratches. Displacement and vibration of hair shafts are detected by hair follicle nerve receptors and nerve receptors within
2365-501: The hot times of the day that required efficient thermoregulation through perspiration . The loss of heat through heat of evaporation by means of sweat glands is aided by air currents next to the skin surface, which are facilitated by the loss of body hair. Another factor in human evolution that also occurred in the prehistoric past was a preferential selection for neoteny , particularly in females. The idea that adult humans exhibit certain neotenous (juvenile) features, not evinced in
2420-438: The individual's hair. A very round shaft allows for fewer disulfide bonds to be present in the hair strand. This means the bonds present are directly in line with one another, resulting in straight hair. The flatter the hair shaft becomes, the curlier hair gets, because the shape allows more cysteines to become compacted together resulting in a bent shape that, with every additional disulfide bond, becomes curlier in form. As
2475-429: The lashes to grow remarkably long and prominent (in some cases the upper lashes grow to 15 mm long). Hair has its origins in the common ancestor of mammals, the synapsids , about 300 million years ago. It is currently unknown at what stage the synapsids acquired mammalian characteristics such as body hair and mammary glands , as the fossils only rarely provide direct evidence for soft tissues. Skin impression of
2530-510: The most genetically diverse continental group on Earth, Afro-textured hair approaches ubiquity in this region. This points to a strong, long-term selective pressure that, in stark contrast to most other regions of the genomes of sub-Saharan groups, left little room for genetic variation at the determining loci. Such a pattern, again, does not seem to support human sexual aesthetics as being the sole or primary cause of this distribution. A group of studies have recently shown that genetic patterns at
2585-607: The most successful species on the planet (and which also is very vulnerable at birth) was arguably a more urgent issue (axillary hair in the underarms and groin were also retained as signs of sexual maturity). Sometime during the gradual process by which Homo erectus began a transition from furry skin to the naked skin expressed by Homo sapiens , hair texture putatively gradually changed from straight hair (the condition of most mammals, including humanity's closest cousins—chimpanzees) to Afro-textured hair or 'kinky' (i.e. tightly coiled). This argument assumes that curly hair better impedes
2640-406: 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 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
2695-595: The other great apes, is about a century old. Louis Bolk made a long list of such traits, and Stephen Jay Gould published a short list in Ontogeny and Phylogeny . In addition, paedomorphic characteristics in women are often acknowledged as desirable by men in developed countries. For instance, vellus hair is a juvenile characteristic. However, while men develop longer, coarser, thicker, and darker terminal hair through sexual differentiation , women do not, leaving their vellus hair visible. Jablonski asserts head hair
2750-424: The passage of UV light into the body relative to straight hair (thus curly or coiled hair would be particularly advantageous for light-skinned hominids living at the equator). It is substantiated by Iyengar's findings (1998) that UV light can enter into straight human hair roots (and thus into the body through the skin) via the hair shaft. Specifically, the results of that study suggest that this phenomenon resembles
2805-426: The passage of light through fiber optic tubes (which do not function as effectively when kinked or sharply curved or coiled). In this sense, when hominids (i.e. Homo erectus ) were gradually losing their straight body hair and thereby exposing the initially pale skin underneath their fur to the sun, straight hair would have been an adaptive liability. By inverse logic, later, as humans traveled farther from Africa and/or
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#17330942260532860-612: The predominant East Asian 'coarse' or thick, straight hair texture arose within the past ≈65,000 years, which is a time frame that covers from the earliest of the 'Out of Africa' migrations up to now. Ringworm is a fungal disease that targets hairy skin. Premature greying of hair is another condition that results in greying before the age of 20 years in Europeans, before 25 years in Asians, and before 30 years in Africans. Hair care involves
2915-667: The scrub brush are common household cleaning tools, often used to remove dirt or grease from pots and pans. Bristles are also used on brushes other than for cleaning, notably paintbrushes. Bristles are distinguished as flagged (split, bushy ends) or unflagged; these are also known as flocked or unflocked bristles. In cleaning applications, flagged bristles are suited for dry cleaning (due to picking up dust better than unflagged), and unflagged suited for wet cleaning (due to flagged ends becoming dirty and matted when wet). In painting, flagged bristles yield more even application. Bristles are found on pig breeds, instead of fur. Because
2970-602: The skin. Hairs can sense movements of air as well as touch by physical objects and they provide sensory awareness of the presence of ectoparasites . Some hairs, such as eyelashes , are especially sensitive to the presence of potentially harmful matter. The eyebrows provide moderate protection to the eyes from dirt , sweat and rain . They also play a key role in non-verbal communication by displaying emotions such as sadness, anger, surprise and excitement. In many other mammals, they contain much longer, whisker-like hairs that act as tactile sensors. The eyelash grows at
3025-410: Was evolutionarily advantageous for pre-humans to retain because it protected the scalp as they walked upright in the intense African (equatorial) UV light . While some might argue that, by this logic, humans should also express hairy shoulders because these body parts would putatively be exposed to similar conditions, the protection of the head, the seat of the brain that enabled humanity to become one of
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