Hair

From Wikipedia, the free encyclopedia

Hair is a protein filament that grows through the epidermis from follicles deep within the dermis. The fine, soft hair found on many nonhuman mammals is typically called fur; wool is the characteristically curly hair found on sheep and goats. Found exclusively in mammals, hair is one of the defining characteristics of the mammalian class.^[1] Although other non-mammals, especially insects, show filamentous outgrowths, these are not considered "hair" in the scientific sense. So-called "hairs" (trichomes) are also found on plants. The projections on arthropods such as insects and spiders are actually insect bristles, composed of a polysaccharide called chitin. There are varieties of cats, dogs, and mice bred to have little or no visible fur. In some species, hair is absent at certain stages of life. The main component of hair fiber is keratin.

Cross section of hair follicle

The hair can be divided into three parts length-wise, (1) the bulb, a swelling at the base which originates from the dermis, (2) the root, which is the hair lying beneath the skin surface, and (3) the shaft, which is the hair above the skin surface. In cross-section, there are also three parts, (1) the medulla, an area in the core which contains loose cells and airspaces (2) the cortex, which contains densely packed keratin and (3) the cuticle, which is a single layer of cells arranged like roof shingles.

[edit] Social role of hair

Hair has great social significance for human beings. It can grow on most areas of the human body, except on the palms of the hands and the soles of the feet (among other areas), but hair is most noticeable in most people in a small number of areas, which are also the ones that are most commonly trimmed, plucked, or shaved. These include the face, nose, ears, head, eyebrows, eyelashes, legs and armpits, as well as the pubic region. The highly visible differences between male and female body and facial hair are a notable secondary sex characteristic.

[edit] Hair as indicator

Healthy hair indicates health and youth (important in evolutionary biology). Hair colour and texture can be a sign of ethnic ancestry. Facial hair is a sign of puberty in men. White hair is a sign of age, which can be concealed with hair dye. A well known old wives' tale often told to children claims that eating a large portion of bread crusts can make hair curly.^{[citation needed]} Male pattern baldness is a sign of age, which can be concealed with a toupee, hats or religious/cultural adornments. In modern times, it can be reversed in some men with minoxidil (marketed as Rogaine or Regaine) or finasteride (marketed as Propecia); see Baldness treatments. Rather than these options, many men simply shave their heads for a clean look. Males in some religious groups, for example Sikhs and Orthodox Jews, may follow certain rules regarding hair as part of their faith, e.g. never cut their hair, or shave some or all of it. Some groups, such as women in the Muslim and orthodox Jewish communities, cover their hair as part of religious observance. Hair whorls have been discovered to be associated with brain development.

Hairstyle can be an indicator of group membership:. Metalheads can often feature long hair for headbanging, although long hair is commonplace for many men and women outside of heavy metal (ex: Indian sadhus, the hippie subculture, etc). Beatle "mop-top" haircuts. Mohawk haircuts, often associated with punk rock and the punk subculture. Skinhead haircuts, where the head is often shaved completely bald, or "buzzed". Mullet hairstyles, which have stereotypically been portrayed as pertaining to rednecks. Deathhawk A larger, fuller, back combed version of a mohawk - popular in the gothic sub-culture, and heavily featured in deathrock and gothic rock bands in the 1980s. Undercut where the sides and back of the head are shaved short or bald, and the top hair is allowed to grow long. Common among so-called "cybergoths" and followers of Industrial and heavy electronic music scenes. This is especially true of women in these subcultures, although the undercut is accepted as a unisex hair style. Fascinator (hair style) where the hair is short at the back and long at the front and the front forms itself into a point. It is similar to a mullet in reverse (also known as a frullet) or a devil lock. Hair that is usually short with a long side fringe [American: bangs] is a cut often associated with emo music and its fan basis. It is often dyed black or vibrant and contrasting colours such as pink or blue. It is considered a unisex haircut and often appears similar to the mop-top.

[edit] Growing and removing

In Western society, men's hair is generally kept short. This is due in part to the English Civil War. The followers of Oliver Cromwell decided to crop their hair close to their head, as an act of defiance to the curls and ringlets of the king's men. The Cromwell followers won.^[14] The Cavaliers and Roundheads are another example of politically-motivated hairstyles. Long hair on men had a resurgence in the 1960s. Some notable hairstyles include skinheads and mullets. Members of the Sikh religion don't cut their hair. Having bobbed hair was popular among the flappers in the 1920s as a sign of rebellion against traditional roles for women. Female art students known as the "cropheads" also adopted the style, notably at the Slade School in London, England. Regional variations in hirsutism cause practices regarding hair on the arms and legs to differ.

[edit] Hair, power, punishment, and status

Samson and Delilah. Shaved heads in concentration camps. Head-shaving as punishment - especially for women with long hair. Military haircuts, monastic tonsures. Kovstro and his Seven Hounds. Extremely long hair of some Indian holy men. Regular hairdressing as sign of wealth. The dreadlocks of the Rastafari were despised early in the movement's history. Having one's own hair cut in order to liberate oneself from their past, usually after a trying time in one's life. Having hair cut as a sign of mourning, which was practiced in a number of cultures. Yoko Ono famously cut her very long hair after the assassination of her husband John Lennon, saying, "John loved my long hair, so I gave it to him.". Tightly coiled hair in its natural state can be worn in an Afro. This hairstyle was once worn among African Americans as a symbol of racial pride. Given that the coiled texture is the natural state of most African Americans' hair, this simple style is now often seen as a sign of self-acceptance and an affirmation that the beauty norms of dominant (northern/European) culture are not absolute. Flappers of the 1920s cut their traditional long hair into short bob cuts to show their independence and sexual freedom. Hippies of the 1960s grew their hair long in order to illustrate their distance from mainstream society. The film Easy Rider (1969) includes the description of one Hippie forcibly having his head shaved with a rusty razor to indicate the intolerance of some conservative groups towards the Hippie movement. At the conclusion of the Oz obscenity trials in the UK, the defendants had their heads shaved by the police, causing an outcry. During the appeal trial, they appeared in the dock wearing wigs.

[edit] Religious practices

Women's hair may be hidden using headscarves, a common part of the hijab in Islam and a symbol of modesty required for religious rituals in Orthodox Christianity. Orthodox Judaism endorses the use of wigs for women for modesty reasons as in Islam. Hassidic Judaism, on the other hand, discourages the trimming of head hair, and practitioners typically wear their hair in ringlets. Sikhs generally keep their hair uncut and tied in a bun on the head, which is then covered appropriately using a turban.