Hair Growth Cycle

Hair does not grow at the same rate all over the body. Each stage of hair growth lasts for a different length of time. There are three different stages of hair growth:

  • ANAGEN: Early anagen and anagen are often referred to as the active stages of hair growth. The follicle is either forming or fully formed and the cells are still attached to the base of the follicle. Cell mitosis occurs in this stage. New cells allow the hair to grow up towards the skin’s surface, while the follicle grows down towards the dermis and forms the dermal papilla. This provides nourishment for the hair to grow.
  • DERMAL PAPILLA: The base of the follicle is attached to the blood supply and provides oxygen and nutrients, stimulating hair growth throughout the anagen phase.
  • CATAGEN: Catagen is also called the transitional stage because the hair begins to detach from the life-giving dermal papilla and causes the follicle to begin to shrink. The hair rises towards the skin’s surface while it’s still attached to the follicle wall.
  • TELOGEN: Telogen is the final stage of the hair growth cycle and is known as the resting stage because the hair is dead. The dermal papilla has completely withdrawn from the follicle and will only be stimulated again at the start of a new hair growth cycle. It’s at this point that the hair is shed from the follicle and the cycle starts again.

The hair is made of three layers of keratinised cells: the medulla, the cortex and the cuticle.

The hair bulb is the base of the hair follicle that is present in hair that is removed by waxing or tweezing during the anagen phase of hair growth. It houses the dermal papilla and its lower part is called the matrix. The epithelial root sheath is made up of two parts: an outer area and an inner area. The outer area forms the wall of the hair follicle and doesn’t grow upwards with the hair but instead remains in place. The inner area grows from the dermal papilla with the hair follicle until it becomes level with the sebaceous gland. It interlocks with the cuticle of the hair and anchors it in place.

Matrix: Where cell mitosis occurs to create the hair. Underneath the matrix there are dividing cells which form the hair.

Hair structure

  • MEDULLA: The medulla is the innermost layer of the follicle but isn’t always found in vellus hair. It’s formed of loosely connected, keratinised cells with air spaces in between. The medulla determines the sheen and colour tones of the hair by light reflection.
  • CORTEX: This middle layer forms the bulk of the hair. It contains melanin that gives hair its natural colour and elongated keratinised cells that are bound together.
  • CUTICLE: This outermost layer is made up of scale-like cells that point towards the tip of the hair and interlock with the cuticle of the hair follicle, anchoring it into place. There’s no pigment in the cuticle and its job is to protect the cortex. There are three types of hair found on the body, depending on the location: lanugo vellus terminal. Pigment A substance that produces colour.
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