This
is a diagram of the cross section of a hair.
On the
outer layer you have the cuticle which acts as a protective barrier to the
inner layers of the hair.
The
inner lauer is called the cortex. The cortex is filled with strands of keratin
and gives the hair its elasticity and shape. For example, curly or wavy hair.
The
center layer of the hair is called the medulla which is only present in some hair.
The function is not entirely sure of.
Looking
further into the anatomy of the hair you come to the hair follicle.
"The human hair follicle is a dynamic structure that generates hair
through a complex and exquisitely regulated cycle of growth and remodelling
governed by numerous genes," Siobh�n
A. Jordan has noted in Molecular Medicine Today.
The
hair follicle is a cavity or sac in the epidermis where a hair will develop.
The
middle part of the follicle is related to the sense of touch.
The lower
part is the active part of the follicle and the upper part is dendritic cells
which are the immune cells.
Hair types.
Lanugo
hair- hair on the baby in the foetus. Usually shed by the 8th month
of pregnancy.
Vellus
hair- The soft downy found all over the face and body, except the soles of
feet, palms, lips, eyelids and nipples.
Terminal
hair- longer, course hairs on the scalp and eyebrows.
Cycle of the hair.
Anagen
(Active)
· It
takes 4-5 months for eyelash
· 5-7
years for scalp.
· Follicle
reforms
· Matrix
divides to create new hair.
· As
cells reach upper part of the bulb they kerintinise
· As
new hair grows up in the follicle the old hair is pushed out to appear on the
skins surface.
Catagen
(changing)
· The
inbetween stage from active to resting
· Lasts
about 2 weeks
· The
hair is now fully grown and cell division has stopped
· The
hair starts to separate from follicle
Telagen
(tired/resting)
· Resting
stage lasts 3-4 months
· Hair
moves up the follicle
· Hair
falls out when it is brushed
· New
hair begins to grow
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