dermis<\/span>.<\/p>\nThe follicle is covered by inner and outer sheaths, which protect and shape the growing hair.<\/p>\n
A muscle called the arrector pili attaches to the external root sheath below the sebaceous<\/span> gland. When the erector pili muscle contracts, e.g. when it is cold, the hair shaft stands up (goosebumps).<\/p>\nA single hair is made up of three parts:<\/p>\n
\n- Marrow<\/li>\n
- Cortex<\/li>\n
- Cuticle.<\/li>\n<\/ul>\n
The medulla and cortex have pigment<\/span> cells responsible for hair color.<\/p>\nThe cuticle is the outer and strongest part of the hair shaft. It is made up of flattened dead cells that overlap each other. The cuticle is keratinized, that is, the cells are mainly made up of a protein called curb<\/span>; Keratin is also an important component of the skin and nail<\/span>.<\/p>\nThe sebaceous gland produces tallow<\/span>, which protects the hair and acts as a natural conditioner.<\/p>\n\n<\/span>Hair structure and growth.<\/span><\/h5>\n<\/section>\n\n\n
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the hair bulb<\/p>\n
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Phases of the hair cycle.<\/p>\n<\/p><\/div>\n<\/section>\n
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Hair grows in cycles, thus the structure of an individual hair apparatus varies.<\/p>\n
\n- \nAnagen<\/span> \u2013 growth phase (4 to 7 years for scalp hair)<\/li>\n
- \nCatagen<\/span> \u2013 intermediate phase (a few weeks)<\/li>\n
- \nTelogen<\/span> \u2013 resting phase (a few months)<\/li>\n<\/ul>\n
The new anagen hair shaft then begins to germinate within the same follicle, expelling the telogen hair, resulting in normal hair shedding or shedding.<\/p>\n
<\/span>What is a hair shaft defect?<\/span><\/h2>\nA hair shaft defect is any structural abnormality of the hair shaft. Some hair shaft defects are easily diagnosed with the naked eye, others may require microscopic<\/span> exam.<\/p>\nHair shaft defects can cause:<\/p>\n
\n- There are no visible hair abnormalities.<\/li>\n
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Hair loss (alopecia<\/span>)<\/li>\n- thick or curly hair<\/li>\n
- Uncombinable hair: when bundles of messy hair grow in all directions and cannot be fixed by combing<\/li>\n
- Brittle hair: hair shafts with reduced tensile strength. A gentle tug on several hair shafts will help determine if the hair is abnormally brittle.<\/li>\n<\/ul>\n\n
<\/span>Frizzy hair of unknown cause<\/span><\/h5>\n<\/section>\n\n\n
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Frizzy hair of unknown cause<\/p>\n
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Frizzy hair of unknown cause<\/p>\n<\/p><\/div>\n<\/section>\n
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<\/span>What causes hair shaft defects?<\/span><\/h2>\nHair shaft defects may be due to external injury or genetic<\/span> anomaly.<\/p>\n<\/span>External injury to the hair shaft.<\/span><\/h3>\nRepeated physical injury is the most common cause of hair growth. fragility<\/span>. This may be due to:<\/p>\n