Anatomy of Human Hair
The pilosebaceous unit consists of the hair shaft, the hair follicle, the sebaceous gland, and the erector pili muscle. Hairs take birth in a sac-like structure called a hair follicle that surrounds the hair root and is found below the skin, Hair is a compact strand made up of keratin and melanin filled dead cells. Hair shaft consists of 3 layers: The medulla, the cortex and the cuticle.
Hair follicles are often between 3mm or 4 mm long and consist of: Inner root sheath, outer root sheath, fibrous root sheath, suprabulb region, isthmus and infundibulum.
Hair, Eyelashes, Eyebrows and Beard growth.
The hair growth cycle can be divided into 3 phases: catagen, telogen, and anagen. The anagen phase is the longest of the cycle and can take from 2 to 7 years. During this phase the hair grows about 1 cm every month ( 0,35 per day).
The catagen phase lasts aproximately 2 to 3 weeks and is the shortest of the cycle. During this phase the hair stops growing, the hair follicle shrinks and the melanine production and mitotic activity ceases.
The telogen is a resting phase and represents the end of the cycle, during this phase the hair follicle is completely at rest and the club hair is completely formed. A club hair is a hair that has matured and no longer has access to the blood supply because there is no longer a need to grow, about 100 telogen hairs (club hairs) are shed normally each day.
We have an average of 200 hairs per square centimeter
On average we have about 200 hairs per square centimeter, and a total of 75.000 to 150.000 hairs per person.
Eyelash growth is very slow and its life cycle lasts aproximately 4 to 5 months, in the place where the dead eyelashes fall out, new ones start to grow, every eyelash reaches its full length and developement in 2 months and a half. On average each eye has aproximately 280 eyelashes from which 200 of them are located in the upper lid, each eyelash can measure 5, 9 or 10mm in length.
The eyebrows have an aproximate growth of 1.16mm per day, they reach their total growth in a month and its total length varies from 0,5 mm to 2.0 mm, in each eyebrow we have an average of 400 to 600 hairs.
The hair of the beard has a very fast growth, it can reach a daily growth of 0.38mm , reaching an anual growth of 15 cm.The quality of the hair is often rough and curly.
Funtion of Hair, Eyelashes, Eyebrows and Beard
In general the funtion of hair, eyelashes, eyebrows and beard are aesthetic and protective. The aestehic funtions provide an improvement of the autoexpresion, and the protective functions contribute to regulate the temperature and to protect from the cold, dust and sun. It can also help to protect from physical trauma.
Miniaturization of Hair Follicles
Is a process where hair follicles start to srink and close, as a result they begin to produce thinner, shorter, more brittle hairs with weaker shafts. These hairs are less dense and lead to the appearance of hair loss.
Genetic and Psychological Effects
There are a significant number of theoretical models that suggest the intervention of multiple genes associated with hair loss, it is clear that androgenetic alopecia with a male pattern, is genetically inherited , however, still is not clear how having a close relative with patterned hair loss appears to be a risk factor for developing this condition.
Hair loss has a psychological effect in relation with the selesteem and confidence of an individual. People with this condition often feel less atractive, aged, less competitive and depressed.