Hair Loss: the Science Of Hair

The complexity of hair is much greater than what it seems on the surface. It is important for both genders to have hair.

Hair Origins

Week 22 is when a developing fetus will have all of its hair-follicles formed. The body has approximately five million hair follicles. A total of 1 million hair follicles are on your head. One hundred thousand reside on your scalp. Since we don't generate hair follicles at any time during our lifetime, this is the most hair follicles that a person will ever own.

Most people will see a reduction in hair density as they get older. This is because our scalps grow as we age.

Hair Follicles

Two distinct structures exist in hair. First, there is the follicle which is found under the skin and then, there is the shaft. This is visible on the top of the head.

The hair follicle, a section of the epidermis which looks tunnel-like and extends to the dermis, is the epidermis' tunnel-like portion. There are several layers to the structure, each with its own functions. The base of the hair is the papilla. This contains the capillaries or small blood vessels that provide nourishment to the cells. The bulb is the part that lives in the hair. It's the part closest to the papilla. It is remarkable that the cells of the bulb can divide in 23-72 hours. This is faster than any other type of cell.

A follicle's inner and outer are protected by two sheaths. These sheaths protect and shape the growth hair shaft. The hair shaft is followed by the inner sheath, which ends at the sebaceous oil gland. Sometimes an apocrine gland (scent gland) can be found below. The outer sheath extends all the way to the gland. Below the gland is attached a muscle known as the erector Pili muscle. This connects to a fibrous membrane around the outer layer. This muscle contract causes hair to rise and the oil glands to release oil.

Sebum is the main ingredient in hair and skin health. The gland produces sebum which helps to condition it. Our bodies produce more sebum after puberty, but we lose some of it as we get older. As they get older, women produce far less sebum than do men.

Hair Shafts

Keratin is a protein that is hard to find in hair shafts. It is composed of three layers. It is a dead protein, which is why the hair you see does not look like a living one. This is the inner layer. The cortex is the second layer, while the cuticle is the outermost layer. The majority of hair shaft is made up by the cortex. Cuticle is an intricately formed structure of tightly overlapping, shingle-like scales. The cortex is the structure that gives hair its pigment.

Hair Growth Cycle

Scalp hair grows at a rate of.3 to.4 mm per day, which is approximately 6 inches each year. Human hair growth and shedding are not like that of other mammals. They happen randomly and do not follow a seasonal pattern. A random number of hairs may be at any one time in each of the following stages: anagen (catagen), telogen (telogen).


Anagen, the hair's active stage is called. Rapid division is taking place in the roots of hair cells. The new hair forms and pushes out the club hair, which is a hair that is not growing properly or has reached the end of its anagen phase.

The hair will grow about 1 cm each 28 days during this stage. This active growth phase lasts between two and six years.

People with short active phases of hair growth may have trouble growing long hair. People with long hair experience a longer active growth phase. Hair on the legs, arms, eyebrows, eyelashes and eyes have an active growth phase that lasts between 30 and 45 days. This is why they grow so quickly compared to scalp hair.


This transitional phase, which is about 3% in all hairs at any one time, is called the catagen phase. This stage lasts approximately 2 to 3 weeks. As the growth stops, the outer root sheath shrinks around the root and becomes attached to it. This is what we call a "club hair".


The resting phase of hairs is called Telogen and accounts for between 6% and 8%. For hairs on your scalp this phase takes around 100 days. It lasts longer for hairs on your eyebrow, eyelash or arm. The hair follicle will be completely still during this phase and the club hairs are fully formed. A solid, hard, dry, and white root can be seen if you pull out hairs in this phase. Every day 25 to 100 telogen-hairs are shed.