The hair follicle can be divided into 3 regions: the lower segment (bulb and suprabulb), the middle segment (isthmus), and the upper segment (infundibulum). The lower segment extends from the base of the follicle to the insertion of the erector pili muscle (also known as the arrector pili muscle). The middle segment is a short section that extends from the insertion of the erector pili muscle to the entrance of the sebaceous gland duct. The upper segment extends from the entrance of the sebaceous gland duct to the follicular orifice. 

Therefore, the degeneration of the nipple (dermal papilla) results in the loss of this hair (Leonhardt, 1985).

What does a hair follicle consist of?

A hair follicle consists of :

  • The papilla is a large structure at the base of the hair follicle. The papilla is made up mainly of connective tissue and a capillary loop.
  • Around the papilla is the hair matrix.
  • A root sheath composed of an external and internal root sheath.
  • The bulge is located in the outer root sheath at the insertion point of the arrector pili muscle. It houses several types of stem cells, which supply the entire hair follicle with new cells, and take part in healing the epidermis after a wound.

The strain of hair protrudes obliquely from the skin. As the hair grows, the shaft lengthens until it reaches its normal length. Then comes the resting phases of the hair. The resting period is longer for young and healthy people. In the end, the root drops. Usually, 85% of the hairs are in the growing season and 15% in the resting period. Every day, there is a loss of about 50-100 hairs. Usually the hair grows about one centimeter per month (Leonhardt, 1985).

Therefore, when a person sees hair on their comb or brush, there is not always a cause for concern about hair loss. According to dermatologists, from the Hellenic Dermatological & Venereological Society (EDAE), each hair has its own life cycle, which can be affected by various individual, environmental, psychological and other factors. In particular, age, gender, heredity, hormonal disorders, certain autoimmune diseases, various diseases (such as thyroid disorders, diabetes, anemia, iron deficiency, and intake of certain medications), burns or trauma, stress or a diet low in proteins may play a vital role in the hair loss of any person.

In short, the life cycle of the hair is divided into three phases.

  • The first stage is Anagen, which lasts for 3 to 5 years and is the hair growth phase.
  • The second phase is Catagen, which lasts about 1 to 2 weeks and is defined as the phase of hair weakening and "preparing" for future hair loss.
  • Finally, the third phase is Telogen, lasting about 2 to 4 months and is the final phase of hair loss. However, the root of the (follicle) still exists and so, after a while, the hair regenerates. This regeneration can occur up to 20 times, but is not necessarily continuously.

What are the types of alopecia (hair loss)?

Below, we will talk in detail about the types of alopecia and their features, as well as their causes. At any given time, almost 90% of our hair is in the growth phase, but over time, that rate slows down.

Additionally, a person may notice hair loss due to physiological or pathological causes.

In particular, alopecia may be:

  • Involutional alopecia. It is a natural condition in which the hair gradually become thinner with time. A large number of hair follicles go into the resting phase, and the remaining hairs become shorter and fewer. It is considered normal hair loss and can occur in both men (more often) and women. In addition, the remaining hair is thinner and shorter than the rest.
  • Androgenetic Alopecia. It is the most common type of alopecia. Due to genetic factors, it occurs equally in both men and women. Specifically, it is estimated that 70% of men and 40% of women will experience alopecia at some point in their lives, with one in two men suffering from alopecia at the age of 50. Men who are likely to develop androgenetic alopecia (AA) may begin losing hair at the age of 20 or even earlier. In contrast, women who suffer from AA do not show significant scalp thinning before their 40s (most of them develop it after menopause), whereas thinning involves the entire head with emphasis on top.
  • Alopecia Areata. Alopecia Areata, as a major cause of heredity, is defined as an autoimmune dermatological disease, which affects 2% of the world's population. The patient, who suffers from alopecia areata, may notice hair loss around the scalp, face or even other parts of the body. It can occur at any time, without prior notice, by the formation of scattered hairless parts of few centimeters (usually 1-5 cm). At the same time, it can lead to complete loss of hair in the scalp (alopecia totalis), a very rare case where the patient loses even his or her eyelashes and eyebrows.
  • Diffuse alopecia. Diffuse alopecia is defined as a condition in which, over time, we observe thinning of the hair and a decrease in the hair density throughout the scalp.  A large number of hairs are in the telogen phase of their growth at the same time. The causes of this type of alopecia vary with the main ones being severe stress, lack of iron, hypothyroidism, malnourishment and others.
  • Cicatricial alopecia. It appears in both men and women. It is a form of hair loss that usually affects the front of the hair, causes scarring and stops hair regeneration in the future. The hair follicles are replaced with scar tissue (hence the name). In some cases the hair loss is without symptoms and can go unnoticed for long periods. In other cases the hair loss is accompanied by burning, itching and pain and is more progressive. It occurs in men and women of all ages.

In every case and for any hair condition you are concerned about, you should visit a specialized and certified Dermatologist, who will examine your case individually and give you the most appropriate treatment for your type of alopecia.

Sources: Hellenic Dermatological & Venereological Society (EDAE) & ISHRS, International Society for Hair Restoration Surgery


Our 25 years of clinical experience in hair transplantation, combined with our highly trained medical and paramedical staff, are a strong warranty for restoring androgenetic alopecia (of all types) and treating scalp diseases, achieving successful and natural looking results.

For the hair transplantations, we use the two basic techniques of FUE or FUT (STRIP) methods, or a combination of the two, depending on the needs of each patient.


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