hair
The coalesced horny cells, which contain the
protein keratin along with 0.75 to 2.0% mineral
salts. Although hair is an epidermal structure, it
is seated deep in the papillary layer of the
dermis. It consists of two continuous regions, the
root and a long projection. which is the shaft.
The lower part of the shaft is enclosed in a
follicle which is a sheath of epidermal cells
continuous with those in other parts of the
epidermis. Most animal hairs are of two types:
primary and secondary. Primary hairs are the more
numerous and vary in structure depending on the
age and species of the animal. Secondary hairs.
which are similar in structure to the primary, are
only about one-third their diameter.
The positions which the primary and secondary
hairs occupy relative to each other as they enter
the surface of the skin, together with their
different thicknesses, determine the
characteristic grain pattern of the dermal surface
after the hair and other epidermis have been
removed. Due to the general complexity of the
papillary region, including hairs of various
diameters at different stages of growth and
located at different depths in the papillary
layer, their removal by mechanical means is
difficult. See also: HAIR-ON LEATHER ; HAIR SHEEP ; SHORT HAIR ; UNHAIRING . (248 , 291 , 363 )
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