An appendage of our skin and also made of keratin. Our hair and hair follicles make up the Pilary system. Most of our skin surface is covered with some type of hair.
(See book).
Our Hair Functions:
- Sensory receptors inform us of small objects
- Protecting and insulating areas
- Attracting others
Two Main Types:
Vellus Hair – soft hair found on body of children and women. We call “peach fuzz” on cheeks of face. Grows short, fine and usually has a light color. These do not have a central medulla.
Terminal Hair – coarse hair that is most of the body hair found on men due to sex hormones (testosterone). It grows on the head, eyelashes and eyebrows, as pubic and axillary (armpit) hair. Terminal hair does contain the central medulla in it’s shaft.
Hair Structure:
Dermal Papilla – a cone shaped indention that feeds blood to the bulb.
Hair Bulb – If you have ever plucked out a gray hair or even an eyebrow hair you have seen the little bulb ( matrix). The expanded end that takes nourishment from capillaries. The growing part at the base. Epithelial cells here divide forming our hair.
Hair Root – found inside the skin.
Hair Follicle – a tubular shape running from deep in the dermis to the skin surface. Here keratin makes our hair.
Sebaceous Glands – next to hair follicle produces sebum (oil) to lubricate skin and hair through a small duct.
Arrector Pili Muscle – this muscle is attached to each hair follicle. When cold or fear stimulate many hair follicles we develop “goose bumps”. This muscle is responsible for erecting the hair when this happens.
Hair Shaft – what we see above the skin. Mostly keratin at this point and no longer living (like the top layer of our skin).
Hair Layers:
There are three main circling layers.
Cuticle – Outer layer. The ends made from a single layer of cells that overlap. Where “split-ends” may be seen, once the layer has worn away.
Cortex – Center layer. Several different layers of melanocytes are found here giving the shaft its color.
Hair color depends on these melanocytes that we inherit. The hair follicle also plays a part in its color. Blond and red hair is produced by melanocytes containing sulfur and iron. Grey and white hair is due to the decrease in melanin production when the cells are replaced by air bubbles in the shaft.
Adults can have about 120,000 hairs on the head. Keratin production depends on our genes and can vary person to person. Keratin and the shape of our hair follicle is responsible for our hair texture. A shaft that is smooth will result with straight hair. A oval will have wavy or curly hair.
Medulla – Inner layer. The central core only found in terminal hair.
Hair Stages:
Our hair grows in different stages. Our hair is going through one of these stages all the time. Each hair does not go through the same stage at the same time. This is why a percentage falls out and others don’t. Our hairs growth can also be affected by stress, medications and other conditions.
Anagen – (growth phase) cells join at the root and form the hair. This can be around 2-7 years.
Catagen – (transitional phase) growth of hair slows and the follicle shrinks to about half its size. Last about 2-4 months.
Telogen – (resting phase) growth stops. Last about 3-4 months.
Exogen- (shedding phase) I have found websites mentioning this other phase. Studies have shown an additional phase. While in the anagen, catagen and telogen phases the hair is still firmly attached to the scalp. In a normal healthy scalp the hair is released while in the Exogen phase. Becoming the hair in your brush, sink and so on.
References:
https://www.healthline.com/health/stages-of-hair-growth
https://donovanmedical.com/hair-blog/2017/6/6/hair-shedding-and-the-exogen-phase
https://www.sciencedirect.com/science/article/pii/S0022202X15417737
The cycle begins again.
In our 40s our hair follicles age. Our hair growth rate begins to fall. We may notice thinning.
Conditions Affecting Our Hair:
Hair Loss (Alopecia)
Male Pattern Baldness (Androgenetic alopecia)
Seborrheic dermatitis (dandruff)
Piedra (trichomycosis nodularis)
Hirsutism
References:
How the Body Works A Comprehensive Illustrated Encyclopedia of Anatomy General Editor Dr. Peter Abrahams Metro Books @2007 by Bright Star Publishing pic Body Systems, Hair pgs. 420-421, How Hair Grows pgs. 422-423 https://www.goodreads.com/book/show/16004050-how-the-body-works (See book).
Modern Esthetics A Scientific Source for Estheticians Henry J Gambino, PhD Milady @1992 Delmar Ch 10, Hair Structure pgs. 188-189
