The normal cycle of hair growth lasts approximately 2 to 3 years. Each hair grows approximately 1 centimeter per month during this phase. About 90 percent of the hair on your scalp is growing at any one time. About 10 percent of the hair on your scalp, at any one time, is in a resting phase. After 3 to 4 months, the resting hair is shed and new hair starts to grow in its place. Loss of hair is basically a result ot the hair follicle loosing its capacity to initiate new growth. It is normal to shed some hair each day as part of this cycle. Every day, normal hair loss is about 50 to 100. However, some people may experience excessive (more than normal) hair loss. Hair loss of this type can affect men, women and children. Hair fall and scalp disorders are very much related to changes taking place in the normal functions of the distinct population of cells that make up the skin and its structural elements. The scalp layer divides into 4 zones, layered one on top of the other; the epidermis, the basement membrane zone, dermis and subcutaneous tissue. On certain parts of the body these regions and zones are highly modified, reflecting special needs, i.e. the scalp is ordinarily covered with thick hair (a product of the epidermis) and the palm is covered with a highly thickened epidermis. On the other hand, the face contains large numbers of subaceous glands and are susceptible to inflammation (acne). Hair, sweat glands and subaceous glands are all specialized structures that are produced through the coordinated efforts of both epidermis and dermis.Not only do they protect the skin by regulating heat exchange; important special diseases, such as alopecia (hair loss) and acne (hair follicle inflammation) often affect them. The skin, whose function is to create a barrier between the human body and the environment, can also be affected by *autoimmune diseases, allergies, infections and metabolic and genetic disorders.
Hair Growth cycle