Hair

This ppt gives information about the hair structure, function of hair, hair cycle(all phase are explain in this ppt) how to maintain healthy hair during all the phase of the hair cycle.

1. HAIR

2. Hair is one of the characteristic features of mammals and has various functions such as protection against external factors; producing sebum, apocrine sweat and pheromones; impact on social and sexual interactions; thermoregulation and being a resource for stem cells. Hair is a derivative of the epidermis and consists of two distinct parts: the follicle and the hair shaft. The follicle is the essential unit for the generation of hair. The hair shaft consists of a cortex and cuticle cells, and a medulla for some types of hairs. Hair follicle has a continuous growth and rest sequence named hair cycle. The duration of growth and rest cycles is coordinated by many endocrine, vascular and neural stimuli and depends not only on localization of the hair but also on various factors, like age and nutritional habits. Distinctive anatomy and physiology of hair follicle are presented in this chapter. Extensive knowledge on anatomical and physiological aspects of hair can contribute to understand and heal different hair disorders.

3. Nearly whole body surface is coated with the hairs except a few areas like palms, soles and mucosal regions of lips and external genitalia. Most of these are tiny, colorless vellus hairs. The ones located in several areas like scalp, eyebrows and eyelashes are thicker, longer and pigmented and are called terminal hairs. Humans have approximately 5 million hair follicles and 100,000 of them are located on the scalp

4. HAIR STRUCTURE The three inner layers become the  hair , made up of the cuticle, the cortex and the medulla

5. Cosmetologists should study the properties of the hair and scalp so that they can differentiate between normal and abnormal hair loss, offer a varity of chemical services to clients , and aid a client in caring for their scalp and hair well-clients, and aid a client in caring for their scalp and hair well-being. Trichology- study of hair and its diseases and care. Human hair is divided into two parts: (epi- means above or outer ; and derm- means skin so epidermis is the OUTER layer of skin) HAIR ROOT HAIRSHAFT

6. STRUCTURE OF THE HAIR ROOT Hair follicle Hair bulb Dermal papilla Arrector pili muscle Sebaceous glands

7. STRUCTURE OF THE HAIR SHAFT Hair cuticle – Cortex Medulla

8. The Hair Bulb The hair bulb is a structure of actively growing cells, which eventually produce hair. Cells continually divide in the lower part of the bulb and push upwards, gradually hardening. When they reach the upper part of the bulb they arrange themselves into six cylindrical layers The three inner layers become the hair, made up of the cuticlethe cortex and the medulla – although the medulla isn’t always present in hairs with a thinner diameter. The outer three layers become the lining of the follicle and form the inner root sheath and basement membrane, around which lie undifferentiated cells. Specific cells in the hair bulb, melanocytes, make the pigment called melanin that gives your hair its colour.

9. Hair Shaft Your hair shaft is the part of your hair that can be seen above your scalp. It’s made of a protein called keratin, compacted and cemented together. Keratin is a remarkably strong protein, which is very resistant to wear and tear. It’s the same material that feathers, claws, nails and hoofs are composed of! Keratin is a sulphur -rich protein, with strong ‘ disulphide ’ bonds holding the protein strands together.   This plays an important role in any chemical processing like perming and relaxing, which break disulphide bonds and reset them to a different configuration to change the shape of your hair. Your hair shaft is also made of hydrogen bonds, which help to give your hair its flexibility. They are weaker and more numerous than disulphide bonds and are easily broken with the application of water – this is what allows you to temporarily change the natural configuration of your hair with heated styling aids after washing. H air shaft consists of three layers:

10. The Cuticle A protective layer composed of overlapping cells, like fish scales or roof tiles, but facing downwards. The outer cuticle holds your hair in your hair follicle by means of a Velcro-like bond. It also minimizes the movement of water (moisture) in and out of the underlying cortex. However, chemical processes and weathering can lift the cuticle and disrupt this balance. When healthy, i.e. smooth and intact, your outer cuticle gives your hair shine and protects the inner layers from damage. The Cortex Forms your hairs’ main bulk and pigment (colour). It consists of long keratin filaments, which are held together by disulphide and hydrogen bonds. The health of your cortex depends largely on the integrity of the cuticle protecting it. The Medulla A thin core of transparent cells and air spaces.

11. Chemical Composition of the Hair Keratinization- Process by which newly formed hair cells in the hair bulb mature, fill with keratin, move upward, lose their nucleus and die COHNS- major elements that make up the human hair Carbon, Oxygen , Hydrogen, Nitrogen, Sulphur

12. HAIR PIGMENT Melanin- The tiny grains of pigment in the cortex that give hair its natural colour. Eumelanin- Provides natural dark brown to black hair colour. Pheomelanin- Provides natural colours ranging from red to ginger to yellow and blonde tones.

13. HAIR GROWTH CYCLE

14. Anagen: Growing phase  The stages of hair growth begin with the anagen phase. It’s the longest phase, lasting about 3 to 5 years for the hairs on your head, though for some people a single hair could continue growing for 7 or more years. Fortunately, the anagen phase differs with different types of hair. For example, the anagen phase for eyebrow hairs and pubic hairs is much shorter than the phase for your scalp hairs. During the anagen phase, your  hair follicles  are pushing out hairs that will continue to grow until they’re cut or until they reach the end of their lifespan and fall out. At any time, about  90 percent Trusted Source  of the hairs on your head are in the anagen phase.

15. Catagen: Transition phase  The catagen phase starts when the anagen phase ends, and tends to last about 10 days or so. During this chapter, hair follicles shrink and hair growth slows. The hair also separates from the bottom of the hair follicle, yet remains in place during its final days of growing. Only about 5 percent of the hairs on your head are in the catagen phase at any given time.

16. Telogen: Resting phase  The telogen phase typically lasts around 3 months. An estimated 10 to 15 percent of your scalp hairs are in this phase. Hairs don’t grow during the telogen phase, but they don’t usually fall out either. The telogen phase is also when new hairs start to form in follicles that have just released hairs during the catagen phase. Some  health experts  consider the telogen phase the shedding phase, as well, but many scientists have divided this stage into two parts: the telogen and exogen stages. 4. Exogen: Shedding phase 

17. Exogen: Shedding phase  The exogen phase is essentially an extension or a part of the telogen stage of hair growth. During the exogen phase, hair is shed from the scalp, often helped along by washing and brushing. Losing 50 to 100 hairs per day during the exogen phase is normal. During the exogen phase, which can last about 2 to 5 months, new hairs are growing in the follicles as old hairs fall away.

18. How to maintain hair health during all four stages Having  healthy, fuller hair  depends on genetics and hormone levels, which are largely beyond your control, as well as manageable factors related to a healthy lifestyle and proper hair care. Some of the best strategies for all four stages include: Good nutrition Because hair is largely made of protein, you should keep up your protein intake by focusing on  healthy proteins . That includes: lean meats fish beans legumes low-fat dairy products A 2019 study in the journal  Dermatology and Therapy Trusted Source  also found that sufficient intake of the following nutrients was associated with healthy hair growth: Vitamin D Vitamin C Iron  (especially in women) Zinc ,  folic acid , and  vitamin B12  may also be associated with promoting healthy hair growth.