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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 different cultures and historical periods, but it is often used to indicate a person's personal beliefs or social position, such as their age, gender, or religion. Overview Meaning The word "hair" usually refers to two distinct structures: #the part beneath the skin, called the hair follicle, or, when pulled from the skin, the bulb or root. This organ is located in the dermis and maintains stem cells, which not only re-grow the hair afte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hairstyle
A hairstyle, hairdo, haircut, or coiffure refers to the styling of hair, usually on the human head but sometimes on the face or body. The fashioning of hair can be considered an aspect of personal grooming, fashion, and cosmetics, although practical, cultural, and popular considerations also influence some hairstyles. The oldest known depiction of hair styling is hair braiding, which dates back about 30,000 years. Women's hair was often elaborately and carefully dressed in special ways, though it was also frequently kept covered outside the home, especially for married women. Prehistory and history People's hairstyles are largely determined by the fashions of the culture they live in. Hairstyles are markers and signifiers of social class, age, marital status, racial identification, political beliefs, and attitudes about gender. Some people may cover their hair totally or partially for cultural or religious reasons. Notable examples of head covering include women in Islam w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hair Care
Hair care or haircare is an overall term for hygiene and cosmetology involving the hair which grows from the human scalp, and to a lesser extent Facial hair, facial, Pubic hair, pubic 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 Hair coloring, colored, trimmed, Shaving, shaved, plucked or otherwise removed with treatments such as waxing, Sugaring (epilation), sugaring and threading. Hair care services are offered in Beauty salon, salons, barbershops and day spas, and products are available commercially for home use. Laser hair removal and Electrology, electrolysis are also available, though these are provided (in the US) by licensed professionals in medical offices or specialty spas. Hair cleaning and conditioning Biological processes and hygiene Care of the hair and care of the scalp skin may appear separate, but are actually intertwined because hair grows from beneath the skin. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hair Removal
Hair removal is the deliberate removal of body hair or head hair. This process is also known as epilation or depilation. Hair is a common feature of the human body, exhibiting considerable variation in thickness and length across different populations. Hair becomes more visible during and after puberty. Additionally, men typically exhibit thicker and more conspicuous body hair than women.) Both males and females have visible body hair on the head, eyebrows, eyelashes, armpits, genital area, arms, and legs. Males and some females may also have thicker hair growth on their face, abdomen, back, buttocks, anus, areola, chest, nostrils, and ears. Hair does not generally grow on the lips, back of the ear, the underside of the hands or feet, or on certain areas of the genitalia. Hair removal may be practiced for cultural, aesthetic, hygienic, sexual, medical, or religious reasons. Forms of hair removal have been practiced in almost all human cultures since at least the Neo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hair Growth
The growth of human hair occurs everywhere on the body except for the soles of the feet, the palms of the hands, the inside of the mouth, the lips, the backs of the ears, some external genital areas, the navel, and, apart from eyelashes, the eyelids. Hair is a stratified squamous keratinized epithelium made of multi-layered flat cells whose rope-like filaments provide structure and strength to the hair shaft. The protein called keratin makes up hair and stimulates hair growth. Hair follows a specific growth cycle with three distinct and concurrent phases: anagen, catagen, and telogen. Each phase has specific characteristics that determine the length of the hair. The body has different types of hair, including vellus hair and androgenic hair, each with its own type of cellular construction. This varied construction gives the hair unique characteristics, serving specific purposes, mainly warmth (redundant in modern humans) and physical protection. Most humans develop the l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hair Follicle
The hair follicle is an 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 some newborn babies. The process of hair growth occurs in distinct sequential stages: ''anagen'' is the active growth phase, ''catagen'' is the regression of the hair follicle phase, ''telogen'' is the resting stage, ''exogen'' is the active shedding of hair phase and ''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 impor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cuticle (hair)
Comparison of sheep (top) and human (bottom) hairs with different cuticle textures The hair cuticle is the outermost part of the hair shaft.James, William; Berger, Timothy; Elston, Dirk (2005) ''Andrews' Diseases of the Skin: Clinical Dermatology'' (10th ed.). Saunders. Page 8. . 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. Diagram of the hair shaft, indicating medulla (innermost), cortex, and cuticle (exterior) While the cuticle is the outermost layer, it is not responsible for the color of the hair. Melanin is the pigment A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vellus Hair
Vellus hair is short, thin, light-colored, and barely noticeable hair that develops on most of a human's body during childhood. Exceptions include the lips, the back of the ear, the palm of the hand, the sole of the foot, some external genital areas, the navel, and scar tissue. The density of hair – the number of hair follicles per area of skin – varies from person to person. Each strand of vellus hair is usually less than 2 mm (1/13 inch) long and the follicle is not connected to a sebaceous gland. Vellus hair is most easily observed on children and adult women, who generally have less terminal hair to obscure it. Vellus hair is not lanugo hair. Lanugo hair is a much thicker type of hair that normally grows only on fetuses. Vellus hair is differentiated from the more visible terminal or androgenic hair, which develops only during and after puberty, usually to a greater extent on men than it does on women. The Latin language uses the word ''vellus'' to designate "a f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terminal Hair
In humans, terminal hair is a variant of hair that is thick and long such as that growing on the scalp, as compared with vellus hair, colloquially known as peach fuzz, growing elsewhere.Marks, James G; Miller, Jeffery (2006)''Lookingbill and Marks' Principles of Dermatology''(4th ed.), Elsevier Inc., p. 11. During puberty, the increase in androgenic hormone levels causes vellus hair to be replaced with terminal hair in certain parts of the human body.Hiort, O. "Androgens and Puberty". ''Best Practice & Research Clinical Endocrinology & Metabolism'', Vol. 16, No. 1, pp. 31–41. These parts will have different levels of sensitivity to androgens, primarily of the testosterone family.Neal, Matthew; Lauren M. Sompayrac''How the Endocrine System Works'' Blackwell Publishing, 2001, p. 75. The pubic area is particularly sensitive to such hormones, as are the armpits which will develop axillary hair.Randall, Valerie A.; Nigel A. Hibberts, M. Julie Thornton, Kazuto Hamada, Alison E. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keratin
Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. It is the key structural material making up Scale (anatomy), scales, hair, Nail (anatomy), nails, feathers, horn (anatomy), horns, claws, Hoof, hooves, and the outer layer of skin in vertebrates. Keratin also protects epithelial cells from damage or stress. Keratin is extremely insoluble in water and organic solvents. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and form strong mineralization (biology), unmineralized epidermal appendages found in reptiles, birds, amphibians, and mammals. Excessive keratinization participate in fortification of certain tissues such as in horns of cattle and rhinos, and armadillos' osteoderm. The only other biology, biological matter known to approximate the toughness of keratinized tissue is chitin. Keratin comes in two types: the primitive, softer forms found in all vertebrates and the harder, derived forms fou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stem Cell
In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell in a cell lineage. They are found in both embryonic and adult organisms, but they have slightly different properties in each. They are usually distinguished from progenitor cells, which cannot divide indefinitely, and precursor or blast cells, which are usually committed to differentiating into one cell type. In mammals, roughly 50 to 150 cells make up the inner cell mass during the blastocyst stage of embryonic development, around days 5–14. These have stem-cell capability. '' In vivo'', they eventually differentiate into all of the body's cell types (making them pluripotent). This process starts with the differentiation into the three germ layers – the ectoderm, mesoderm and endoderm – at the gastrulation stage. However, whe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medulla (hair)
The medulla is the innermost layer of the hair shaft. This nearly invisible layer is the most soft and fragile, and serves as the pith or marrow of the hair. Some mammals don't have a medulla in their hair. The presence or absence of this layer and the characteristics of the medulla can aid taxonomists in identifying what taxa a hair comes from. Characteristics include whether the medulla contains air pockets as well as the histology of the medulla. Scientists are still uncertain about the exact role of the medulla, but they speculate that it is primarily an extension that is more prominent in depigmented (grey or white) hair .James, William; Berger, Timothy; Elston, Dirk (2005) ''Andrews' Diseases of the Skin: Clinical Dermatology'' (10th ed.). Saunders. Page 8. . See also List of distinct cell types in the adult human body The list of human cell types provides an enumeration and description of the various specialized cells found within the human body, highlighting thei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cortex (hair)
The cortex of the hair shaft is located between the hair cuticle and medulla and is the thickest hair layer. It contains most of the hair's pigment, giving the hair its color. The major pigment in the cortex is melanin, which is also found in skin. The distribution of this pigment varies from animal to animal and person to person. In humans, the melanin is primarily denser nearer the cuticle whereas in animals, melanin is primarily denser nearer the medulla.James, William; Berger, Timothy; Elston, Dirk (2005) ''Andrews' Diseases of the Skin: Clinical Dermatology'' (10th ed.). Saunders. Page 8. . See also * List of distinct cell types in the adult human body The list of human cell types provides an enumeration and description of the various specialized cells found within the human body, highlighting their distinct functions, characteristics, and contributions to overall physiological processes. Cell ... References Hair anatomy {{Dermatology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
