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How much of each hair type you have varies from person to person and also depends on your age and sex. About 30 percent of the body’s surface is covered with terminal hair in women, compared to about 90 percent in men. Hair is continually shed and renewed by the operation of alternating cycles of growth, rest, fallout, and renewed growth. The average life of different varieties of hair varies from about four months for downy hairs to three to five years for long scalp hairs.
Root of the hair
The wall of the hair follicle is made of three concentric layers of cells. The cells of the internal root sheath surround the root of the growing hair and extend just up to the hair shaft. The external root sheath, which is an extension of the epidermis, encloses the hair root. It is made of basal cells at the base of the hair root and tends to be more keratinous in the upper regions.
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What causes increased hair loss?
The cuticle is of considerable cosmetic importance as it gives the hair an untangled appearance and shape. The first is the hair shaft, which comprises the visible part outside the skin, and the second is the hair follicle, which lies underneath the skin's surface. Additionally, the hair follicle contains an inner and outer root sheath. The hair follicles in your skin contain living cells to allow your hair to grow.
Definition of hair – Learner’s Dictionary
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The hair shaft is the part of the hair not anchored to the follicle, and much of this is exposed at the skin’s surface. The rest of the hair, which is anchored in the follicle, lies below the surface of the skin and is referred to as the hair root. The hair root ends deep in the dermis at the hair bulb, and includes a layer of mitotically active basal cells called the hair matrix. The hair bulb surrounds the hair papilla, which is made of connective tissue and contains blood capillaries and nerve endings from the dermis (Figure 1). Hair grows and is eventually shed and replaced by new hair. The first is the anagen phase, during which cells divide rapidly at the root of the hair, pushing the hair shaft up and out.
Protection
Hair is most noticeable on 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, ears, head, eyebrows, 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. Shaving is accomplished with bladed instruments, such as razors. The blade is brought close to the skin and stroked over the hair in the desired area to cut the terminal hairs and leave the skin feeling smooth. Depending upon the rate of growth, one can begin to feel the hair growing back within hours of shaving.
Structure of Hair
On adult whales, elephants, sirenians, and rhinoceroses body hair is limited to scattered bristles. In most other mammals the hair is abundant enough to form a thick coat, while humans are among the most hairless of all mammals. Nerve supply to the hair follicles is similar to that of the surrounding network of dermal nerves in that it is composed of both sensory afferents and autonomic sympathetic nerves.
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Hair care involves 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. Similar to the skin, hair gets its color from the pigment melanin, produced by melanocytes in the hair papilla. Different hair color results from differences in the type of melanin, which is genetically determined. As a person ages, the melanin production decreases, and hair tends to lose its color and becomes gray and/or white.
Clinical Significance
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. The first to develop is the lanugo, a layer of downy, slender hairs that begin growing in the third or fourth month of fetal life and are entirely shed either before or shortly after birth. During the first few months of infancy there grow fine, short, unpigmented hairs called down hair, or vellus. Vellus covers every part of the body except the palms of the hands, the soles of the feet, undersurfaces of the fingers and toes, and a few other places.
The shaft is composed predominantly of macrofibrils, which are rods of microfibrils meshed together in a matrix. Healthy hair indicates health and youth (important in evolutionary biology). White or gray hair is a sign of age or genetics, which may be concealed with hair dye (not easily for some), although many prefer to assume it (especially if it is a poliosis characteristic of the person since childhood). Although pattern baldness can be slowed down by drugs such as Finasteride and Minoxidil or treated with hair transplants, many men see this as unnecessary effort for the sake of vanity and instead shave their heads. In early modern China, the queue was a male hairstyle in which the hair at the front and top was shaved every 10 days in a style mimicking pattern baldness, while the remaining hair at the back was braided into a long pigtail. Jablonski's assertions[52] 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.
Guard hairs give warnings that may trigger a recoiling reaction. 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. Telogen effluvium is when hair roots are pushed into the telogen resting phase. This usually occurs after some stress and can be acute or chronic.
Being knowledgeable of an individual's hair type is a good start to knowing how to take care of one's hair. There 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. Hair grows everywhere on the external body except for mucus membranes and glabrous skin, such as that found on the palms of the hands, soles of the feet, and lips. Each of the thread-like things growing on your head and body is a hair.
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