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What is Hair? – Definition, Structure, Characteristics, and More

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Hair

Definition

Hair is a continuation of the cornified skin, formed by a keratin fiber and made up of a root and a stem.

It is formed in a follicle of the dermis and is characteristic of thin or thin skin.

The difference between the keratin of the horny layer and the Hair’s keratin is that in the Hair.

The cells are always united, giving rise to more hardened keratin.

It is complete with the following chemicals: 28% protein, 2% lipids, and 70% water.

The most abundant protein is keratin, which accounts for between 85 and 90 percent of the total hair weight.

Keratin is a protein composed of polypeptide chains very rich in cysteine.

Its main elements are carbon, hydrogen, oxygen, nitrogen, and sulfur.

In less quantity, it contains calcium, copper, cadmium, mercury, zinc, lead, iron, arsenic, silicon, magnesium, uranium, vanadium, sodium, and potassium.

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What is the Structure of Hair?

It is an excellent material that, while biologically dead, has a life of its own.

To understand it, you have to know its complex structure.

1.      Root

In the heart, there is excellent metabolic and mitotic activity.

The root ends in a bulb in whose central hollow the dermal papilla is a house, which feeds the Hair.

When blood circulation is active, hair growth is fast, being slow in the opposite case.

2.      Stem

It is the central part of the Hair and is complete up of three concentric parts.

A.      Cuticle

It occupies 9% of the Hair’s total surface and is a protective layer resistant to physical and chemical forces that could quickly damage the hair fibers as they emerge from the skin.

Its integrity provides shine to the Hair and ease of gliding when brushing.

B.      Cortex

It constitutes the middle layer of the hair shaft, occupies 70% of the Hair’s total surface, and is responsible for the Hair’s mechanical properties.

C.      Medulla

Represents 21% of the hair surface. It is located in the central part and is composed of rounded corneal cells, without a nucleus and little pigmented.

What are the Characteristics of Hair?

Each of the hairs consists of a root located in a hair follicle and a stem that projects upward above the epidermis’s surface.

The root is enlarge at its base.

The papillary area or dermal papilla comprises connective tissue and blood vessels.

Which provides the Hair with the substances necessary for its growth.

The sebaceous glands are distributing throughout the skin, except in the palmoplantar regions.

They are very abundant on the scalp, face, and in the upper area of ​​the chest, in the pubis, and the armpits.

There are smooth muscle fibers associated with each Hair (erector hair muscle).

The muscles’ contraction makes the Hair stand on end, thus changing its angle to the skin.

This process increases the Hair covering’s insulating possibilities, thus providing a better shelter against the cold.

What are the Growth phases in Hair?

It does not grow indefinitely but has a cyclical growth, which is called the hair cycle.

·         Anagen or Anagen phase

In this phase, the Hair is attach to the papilla.

It is born and grows.

It lasts between 4 and 6 years, although usually three years is taken as an average value.

In this phase, the shape of the follicle is similar to that of an onion, wider at the base than at the stem.

·         Catagen phase or Catagen

It is a transition phase.

It lasts for about three weeks, during which growth stops and separates from the papilla, ceasing the matrix’s cells’ activity, including melanocytes.

The bulb takes on a cylindrical appearance.

·         Telogen or Telogen Phase

The phase of rest and loss lasts about three months.

Type; Duration of the anagen phase

  • hair – 3 – 5 years (1095-1825 days)
  • beard – 1 year (365 days)
  • body hair – 13 – 15 weeks (91-105 days)
  • eyebrows – 1 month (30 days)
  • mustache – 4 – 14weeks (28-98 days)

Every two days and 9 ½ hours, the Hair grows at least one more millimeter.

What is the Function of Hair in Humans?

Protection function

It  protects the scalp from the sun and cold.

The eyebrows and eyelashes protect the eyes from sweat that could fall from the forehead.

The nose hairs prevent dust, particles that may contain the air, from entering the nostrils.

It also serves to dampen bumps and abrasions.

It hinders insect bites and improves body temperature control through dissipation.

Aesthetic function

In all cultures, It has had a greater or lesser degree of care and importance.

From his combed, washed, collected, and adorned.

Hair’s high or low presence has been an aesthetic symbol of multiple meanings; strength, wisdom, experience, freedom, social status, and political-philosophical ideology.

What are the Types of Hair?

In a unitary sense

a)      Deck, guard, or jug ​​Hair

It is the longest and straightest Hair, with a pointed end; this type of Hair prevents heat from escaping.

b)      Under skin or fur

It is used for thermal insulation since it is very dense; allows or prevents heat exchange to the outside.

c)       Sensory or vibrissae

It is provided with vascular sinuses and nerve fibers that surround the base of the hair follicle.

So they have a sensory function.

Depending on its structure

a.       Its structure and physical appearance

Smooth, straight, or esoteric.

The shape of the follicle is circular and orienting vertically to the skin’s surface at a right angle.

It is oval and is orienting at an acute angle.

Curly or electric, It is elliptical, and the orientation is parallel to the skin’s surface.

Depending on its epicutaneous emulsion

a.       epicutaneous emulsion

Normal The epicutaneous emulsion is balanced. The look of is shiny, smooth, and velvety Dry.

The epicutaneous emulsion contains little fat and little water.

The appearance of the Hair is rough and brittle Fatty.

The epicutaneous emulsion is high in fat. The look of the is shiny and sticky.

What are the Qualities of Hair?

The qualities of the Hair are due to the filamentous structure of keratin.

·         Elasticity

It can stretch and return to its natural shape without breaking.

For example, in most chemical beauty procedures, dyeing, bleaching, or waving, the elasticity test is done to not over-process.

·         Resistance

It is healthy because the cuticle cells are attaching, with a complex chemical that acts like cement and also holds them together to the cortex.

It is resistant to

  1. Breakage
  2. The heat
  3. Putrefaction
  4. PH changes

·         Electrical properties

Dry is not a good conductor of electricity and has a high electrical resistance.

When combing or brushing, it accumulates static electricity and repels each other.

To avoid this, it is recommending do not to use plastic combs. Lightly dampen the Hair.

·         Porosity

It can absorb liquids.

Wet Hair is a bit longer than dry and fluffier.

The absorption of water and the swelling of the fiber depends mainly on the pH of the medium.

The alkaline pH favors the swelling of the fiber.

·         Colour

The pigments responsible for color are melanins, which are producing by melanocytes in the womb.

Melanin accumulates within these cells in spherical organelles, delimited by a lipid membrane, and called melanosomes.

The activity of melanocytes adapts to the cycle, taking place during the anagen phase.

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