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Home arrow Basics arrow Hair arrow Anatomy & Development
Anatomy & Hair Development

That part of the hair, which we see on the surface of the skin is called the shaft of the hair. Similar to the fingernails, hair is mainly made up of a dead horn substance known as keratin. The inner part of the hair is composed of the medulla, which is surrounded by a layer of keratin fibers called the cortex. The cortex contains among other things the color pigments. The cortex is in turn enclosed from the outside by a transparent multi-layered squamous set of horn cells, whose arrangement somehow resembles that of a fir cone.

Haar in 400-facher Vergrößerung
  Fig. 3: Human hair fiber (400 x magnification):
To be seen clearly are the transparent fircone-like squamous layer and the fine brown pigments


That part of the hair stuck in the skin is surrounded by the hair root sheath. It is joined at its lower part by the hair bulb. Hair root sheath and hair bulb are in the contrary to the hair fibre living tissues. The hair bulb is considered as the "reactor" for the growing hair. It is in this part of the hair, where the cells divide most rapidly and these cells differentiate itself further as dead horn cells. These horn cells are pushed upwards as long as the cells in the hair bulb continue to divide. In the end, they come out to the surface of the skin and is seen as the hair shaft. It is also in the hair bulb, where lots of melanocytes are to be encountered. These melanocytes deliver their pigments to the hair cells.
The hair bulb encompasses the hair papilla like a claw. Small blood vessels can be seen as clusters in the hair papilla. They are very important for the supply, development and growth of the hair. Many researchers are of the opinion that it is in the papilla where cells responsible for the growth of hair follicles are to be found.

In contrast to the hair root sheath, hair bulb and hair papilla, which are living tissues, the hair itself is a dead one. The functional unit is called hair follicle. And it is the hair follicle, which produces hair. Attached to each hair follicle is a tiny muscle that is entwined by fine nerve fibres and small blood vessels. The nerves are so sensitive that even the slightest touch on the hair or a light breeze wafting in the air can be perceived. Aside from this, each hair has sweat glands, which make the hair smooth and protects the scalp.


klick to enlarge 

Fig. 4: Hair bulb and hair papilla. 200 x magnification and corresponding schematic drawing with markings