Some skincare and health information

Here are is some useful information about hair. To see a list of all skincare articles, please go here. To see a list of general health information, please go here.

ABOUT HAIR AND HAIR GROWTH

The hair is a part of the skin, and to understand the hair anatomy and physiology, one must understand the skin structure and functions.

The skin consists of 3 layers. The outer layer, the epidermis, consists of flat epitelial cells. These cells are renoved from the bottom and as new cells are made, existing cells are pushed upwards. As they move to the surface, they are gradually filled with the protein keratin so that the outermost cells are dead plates of keratine. This kerastine layer is also steadily shed or worn off at the surface while it is renoved from the bottom.

The layer under consists of connective tissue. It contains strong and elastic protein fibres between the cellls, and has blood vessels. The lowest layer conists mostly of fat cells, but it has also blood vessels and some amount of fibres.

The hairs grow up from deep pouches in the skin going down through the epidermis, through the dermis and reach the fat layer, the hair follicles. The hair follicles have an inside covered by epidermial cells. High up at one side of the follicle there is a gland, the sedaceous gland, that excrete the vaxy blending called sebum. The sebum lubricates and protects the hairs and the skin. Each hair follicle is also connected to a little muscle going from a place a distance under that gland up to the epidermis. It makes the hair rise when it contracts, the arrector pili muscle.


THE STRUCTURE OF AND GROWTH OF THE HAIR

Most of the hair consists of keratine. The hair is mostly a thin thread, but the lowest part has the shape of a bulb and is called the hair bulb. The hair bulb is the part that fixes the hair to the inside and bottom of the hair follicle. The hair parts over the bulb consist of dead cells that are mostly dry and contain much keratine. Hairs can be round and then they will be streight. A person with mostly round hairs will therefore have smooth hair on the head. Hairs can alo be somewhat flattended, and then the hairs will easily bend and a person with flat bending hair will have curly hair on the head.

The hair has three main layers of cells. The innermost one is the medulla where the cells are round and loosely packed and with little keratine. The medulla can lack and then the hair is hollow in the mid. The the mid layer is the cortex, where the cells are cubic and stacked in a regular fashion over and outer each other.

The outter layer is very thick and is called the cuticle. In this layer the cells are mostly flat and are stacked over and outer each other so that the sides of each cell covers the borders of the cells inner and outer for it. The cuticle is very complex and consists of several sub-layers.

Also the hair bulb has these keratine filled layers. But the bottom and inside of the bulb consist of living cells without much keratine, and the further up in the bulb, the more are the cells of the three layers filled with keratine. Inside the hair bulb is also a living structure called the hair papilla. Blood vessels go in and out of the papilla to nourish the living cells and the hair growth activity. Around the papilla there is an area called the matrix.

At the bottom cells are steadily formed. Older cells in the bulb are pushed up as new are formed, and they are graduallly filled by keratine during this process. Instead of being shed, the old cells go upwards and become a part of the hair that will be stedily longer during this process.

But at some stage the hair stops to grow, and the entire hair is shed, but the papila remains. Then a new hair bulb is formed from the papilla, and then a new hair grows up.


THE PHYLOGENY OF HAIR, SHELLS, FEATHERS AND TEETH

Early in the evolution of vertebrates, the skin was covered by small structures that resamble teeth, and the mouth also had these structures. Sharks and mantas still have these skin teeth instead of shells. The structures in the mouth evolved into real teeth in all types of fish. The skin teeth evolved into shells in the higher groups of fishes.

The amfibia and reptiles have inherited the shells. But in the mammals the shells later evolved into hairs. In some higher prehistorian reptils, the shells evolved into feathers and the birds have inherited those structures. Thus hairs, chells, feathers and even teeth have the same origine and have similar anatomical structures.



These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. This information is nutritional in nature and should not be construed as medical advice. This notice is required by the Federal Food, Drug and Cosmetic Act.