Hair (lat. pili) is long horn threads. They essentially consist of Keratin. With few exceptions (palms, finger insides, soles, nipples, lips) the entire outside skin of humans is behaart.

Structure

The hair is roughly in three layers developed.

The first layer, shed layer or Cuticula mentioned, consist of flat, overlapping cells, comparably with a Tannenzapfen. It consists of six to ten such cell situations. The shed layer is in as much important as this shows the state of health of the hair most obviously. With the healthy hair the shed layer fits flat and results in so a flat surface. The light is reflected optimally and results in so the healthy gloss of the hair.

The bulk of the hair is the fiber layer (or fiber trunk, lat. Cortex). Here all for the relevant take place chemical process. The Cortex consists of a large number of finest Keratinfasern, the Fibrillen. These result probably from the fact that Cortexzellen together-store themselves. The connection between the two cells is made by the cell membrane complex, which one can understand oneself as a kind cement substance. The ultimate tensile strength and elasticity of the hair are to be due to this cementing.

Inside the hair we find the Mark channel (lat. Medulla). It consists of cell walls, dismantling products of the Cortexzellen and fats. The Mark channel is supposed for the structure and the structure of the hair without meaning.

Fine structure

• Peptidspirale
• Protofibrille
• Makrofibrille
• Cortexzelle
• Nearly first ranks
• Nearly first rank bundle
• Cortexzelle
• Fasterstamm

Numbers

Humans have approx. 25,000 and (dependent on the hair color) 90,000 (red) to 140,000 (blond) Kopfhaare.

• daily hair loss: 60-100 pieces
• Growth rate: approx. 0.33 mm/day
• Hair thickness: 0.07 mm (Vellushaare) up to 0.12 mm (terminal hair)
• Tensile strength per hair: 200g

Hair grows constantly, also with patients, who are appropriate in coma.

Only few body places are complete without Behaarung:

• Eyeball, teeth, sole, hand inner surface, toe nail bed
• Mucous membranes of the body openings and/or - excavate (exception nose)

The hair organ

Hair root

Within the lower range of the leather skin the hair develops to the Haarpapille. Within the education range, the matrix, stores numerous Melanozyten, which delivers its pigments to the developing hair. The keratinreichen horn cells move upward and form thereby the hair shank, which pushes itself within the follicle to the skin surface.

Hair follicle (hair bellows)

The hair shank lies in an oblong a inverting of the Oberhaut, which hair follicles or hair bellows, at whose lower end the hair in the hair root is formed. Into the follicle a tallow gland, occasionally also a smell gland flows.

At the outside edge, except with primary hair (covering and skin hair), the small hair putting up muscle (Musculus arector pili, also hair bellows muscle) sets. It consists of smooth musculature and rises from the superficial layer of the leather skin and sets underneath the tallow gland at the hair. The Musculus arector pili puts the hair up with psychological influences such as excitation and rage ("the hair stands to mountains", "the skin itself"). The innervation takes place automatically via sympathetic nerve fibers. Also with cold weather the hair straightens up by this muscle. With humans one calls the Hautstruktur resulting from putting the hair up also goose skin. The sense of this putting the hair up exists in an increased inclusion of air, which increases the isolation against cold weather. With humans this mechanism has an effect however due to the small hair density hardly.

Finally some nerve fibers tape the follicle and fulfill as hair follicle receptors palpation functions.

Hair shank

One can differentiate three hair places:

• To terminal hair (main hair) to it all belong "thicken hair ", like e.g. the Kopfhaar, beard, nose, ear hair, lashes, brows and shame hair. Terminal hair is hormone dependent in their growth (puberty - Geschlechtsbehaarung, beard stature, Glatzenbildung). In the cross section of a terminal hair a Dreischichtigkeit is recognizable:

• • Mark (Medulla): The central part of the hair shank.
  • Crust (Cortex): The principal part of the hair shank (above all Keratin fibers).
  • Cuticula: Cell shed at the hair exterior, whose shed is oriented toward hair point. The Cuticula serves the protection of the hair and encloses it with a smooth layer.
• Vellushaar (woolly hair) all remaining villi of the body surface are called Vellushaare. They are substantially thinner and shorter than the terminal hair, and their hair shank contains no Marks.

• Lanugohaar (Flaumhaar) the fine villi, which carry earlyborn still at the whole body surface.

Hair forms (with humans)

The kind of the hair training (smoothly, curved, lured) depends considerably on the hair form, thus the hair cross section. Hair of east Asians has a round cross section, whereby they are usually very smooth. The European type exhibits mostly a round to oval cross section, whereby the hair is smooth or is inclined to the formation of curls. African humans have against it hair with strongly elliptical cross section. Therefore their hair forms also very strong, small curls.

Tasks and functions of the hair (with humans)

• Light protection: Hair absorbs UV-RADIATION and protects thus the head against harmful influences of the sunlight.
• Lagging: They prevent a too rapid cooling of the head.
• Humidity adjustment: The skin is provided with sweat glands. Surplus humidity is absorbed by the hair. General mistake: unbehaarte bodies smell more strongly than behaarte.
• Hautflora: On each healthy skin bacteria live. They are held by the hair in the correct relationship.

How, when and for what the hair itself

The hair of humans itself, if it freezes or frightens. Colloquially this also goose skin is called. In order to set up the hair, the muscle at the hair root contracts. Between the put up hair thereby an air cushion is formed which works heat insulating. However in addition much close hair is, like it with modern humans only on the head occur, necessarily. This mean-light protection against cold weather is to be regarded thus rather as a Relikt from the time, when humans were strongly behaart still at the whole body. In this time it was also useful to work threateningly if one were attacked. Setting up hair could early humans in such a dangerous situation be looked larger and broader.

Hair growth

Hair grows in cycles, a hair follicle goes through thereby several phases which are called hair cycle. Hair grows approx. 15 cm in one year. Hair growth is often different with humans, this difference is however usually only half to whole millimeters.

Hair cycle

• Anagenphase: In this growth phase a new hair root forms, and the production of a hair begins. The Anagenphase lasts approx. between three and six years (the duration is hereditary given). 85-90% of the hair on the scalp are on the average in this phase.

• Katagenphase: In this transitional phase the matrix stops its cell production and the hair follicles narrows itself in the lower range. The hair separates from the Papille and diminishes. The Haarfolikel shortens.

• Telogenphase: With this final phase, in which up to 18% the Kopfbehaarung is, the Haarpapille and the Haarfolikel renew themselves regenerate. The matrix develops again and begins with the cell division, whereby a new hair develops.

Trichogramm

With suspicion on structural damage of the hair or for the clarification of a hair loss a Trichogramm is put on. In addition with tweezers 50 to 100 hair are plucked out (after three days long one did not wash and one did not comb only carefully). Under the microscope afterwards the hair roots are judged and assigned to the individual growth phases. Normal values: Anagenhaare 85 per cent, Katagenhaare 1 per cent, Telogenhaare 13 per cent. The remainder is allotted to defective hair.

Articles in category "Hair"

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