Human hair growth

Human Hair Growth

Human hair growth is a complex process that involves various biological systems and structures. It is a dynamic process, with hair follicles cycling between periods of growth (anagen), regression (catagen), and rest (telogen).

Anatomy of the Hair Follicle

Anatomy of a hair follicle

The hair follicle is a dynamic organ found in mammalian skin. It resides in the dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a complex interaction between hormones, neuropeptides, and immune cells.

Phases of Hair Growth

Hair growth occurs in cycles consisting of three phases:

1. Anagen Phase: This is the growth phase. The length of this phase is genetically determined and lasts between two and seven years.
2. Catagen Phase: This is a short transition stage that occurs at the end of the anagen phase. It signals the end of the active growth of a hair.
3. Telogen Phase: This is the resting phase before the hair falls out. The follicle then remains inactive for about three months before the whole process is repeated.

Factors Affecting Hair Growth

Several factors can affect the growth of hair, including:

1. Genetics: Certain genetic factors can influence the length and thickness of hair.
2. Hormones: Hormones play a key role in regulating hair growth. For example, androgens have a direct effect on the growth of hair.
3. Nutrition: A lack of proper nutrition can also affect hair growth.

Hair Disorders

There are several disorders that can affect hair growth, including:

1. Alopecia Areata: This is a condition in which hair falls out in patches.
2. Androgenetic Alopecia: This is also known as male or female pattern baldness.
3. Telogen Effluvium: This is a condition in which hair falls out excessively due to stress or shock.

See Also

• Hair follicle
• Anagen
• Catagen
• Telogen
• Alopecia Areata
• Androgenetic Alopecia
• Telogen Effluvium

References

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