Structure of the human hair

About the structure of the hair.

Facts about hair:

Diameter: 0.1 mm, growth per day: 0.3 mm, growth per month: 1 cm, hair density: 200 hair follicles per cm², life span: 2 to 5 years, carrying capacity: 100 g per hair.

Structure of the hair

The hair visible from the outside is only a small part of the total hair. The hair roots (also called hair follicles) reach deep into the skin.

The hair consists of hair follicles and the hair papilla. The hair papilla is located in the lower part of the dermis. It forms the hair and is thus, so to speak, the base of the hair. The hair shaft is formed by keratin-rich cells within the hair follicle upward toward the skin surface. The hair follicle is a rectangular recess in the epidermis through which the hair shaft passes.

People with brown or black hair have about 100,000 hair follicles, those with blond hair have slightly more (150,000) and those with red hair have slightly fewer (75,000). Hair color is mainly determined by the pigment melanin. Melanin is formed in the melanocytes and released to the hair roots.

The different hair colors are hereditary and result from different types, amounts and distributions of melanin. A decrease in melanin production causes hair to turn gray later in life.

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The hair cycle

Every day new hair grows and every day hair falls out. This cycle repeats itself constantly and is completely natural. The hair cycle consists of three phases: (1) the growth phase (2) the transition phase (3) the rest phase. Each hair goes through its own independent cycle. Perennial growth phases alternate with shorter transitional and resting phases. Finally, after the resting phase, the hair is shed. The length and thickness of the hair is determined by the length of the growth phase.

Growth phase

During the growth phase, the hair grows by division of the hair cells. At any given time, about 80 % of the hair on the head is in this phase. It is the longest phase of the hair cycle, lasting between 2 and 5 years. The longer the growth phase, the longer the hair will naturally grow. Roughly speaking, the hair grows about 1 cm in a month.

The transition phase

The transition or resting phase lasts about 14 days and is therefore the shortest phase. Only a small proportion of all hair follicles are in this phase at any one time. In the transition phase, the hair follicle shrinks and the skin surface is closed. The hair has reached its maximum length and stops growing.

The resting phase

The resting phase follows directly after the transition phase. It is the last phase after which the old hair is expelled by a new one. This marks the beginning of a new cycle. The duration of a hair cycle varies according to age. The length of the cycle also determines the length and thickness of the hair.

As you can see, losing hair is quite normal. In a normal hair cycle, hair grows, rests and then falls out to make room for new hair. In a normal hair cycle, 80-100 hairs fall out per day. If this number is significantly higher, there may be a disruption in the cycle, i.e. an unusually strong Hair Loss.

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