In hair that is curly/kinky, the hair follicles grow from the scalp at a much stronger angle. The fol-
licle is almost parallel to the surface of the scalp. Furthermore, the hair bulb itself is nearly doubled
back over the follicle in a growth shape resembling a golf club.
The hair follicle that produces a
curly/kinky hair has a flattened, elliptical shape.
Hair Growth
As this primitive hair germ con-
tinues its growth downward into
the dermis and joins a small
number of dermal cells, these
cells eventually become the
dermal papilla.
The papilla is
filled with capillaries (small
blood vessels) that supply
nourishment to the cells
around it, called germinal matrix cells.
The germinal matrix is the area of the bulb where cell
division (mitosis) takes place. These germinal matrix cells produce the cells that ultimately kera-
tinize (harden) and form the three major layers of the hair:
1.
Cuticle
- the outer covering of the hair shaft made up of
overlapping layers of transparent scales
2.
Cortex
- the second layer consisting of unique protein
structures (gives hair most of its pigment and strength [elasticity]
3.
Medulla
- the central core of the hair shaft, also called the
pith or marrow (often absent in fine or very fine hair)
Attached to the side of the root sheath are bulges. These bulges are the beginnings of the sebaceous
glands.
The sebaceous, or oil, glands produce sebum (oil) and send it up through the hair
follicles to the surface of the skin to prevent the hair and skin from becoming too dry. Sebum
mixes with the body's perspiration to form the "acid mantle." The acid mantle is important
because it protects the cuticle, or outer covering, of the hair fiber and maintains the acid
balance of hair and skin.
The arrector pili muscle comes from cells in the dermis that attach to the follicle just below
the sebaceous gland. This is the muscle that causes the hair to stand on end when a person
is scared or cold.
It also aids in the secretion of sebum from the sebaceous glands. The other
end of the arrector pili muscle attaches to the dermis (or lower layer) just beneath the basal layer of
the epidermis.
Cells Form Parts of the Hair
As cells begin their journey upward through the hair follicle, they are separated into specific types.
In other words, some cells will become cuticle scales, others will make up the cortex and others will
182
SALON FUNDAMENTALS
"Hair pulled out from the
roots will grow again unless
the papilla (origin of hair) is
destroyed."
MEDULLA
CORTEX
CUTICLE
