What is skin?
Nature's miracle wrap, skin shields the dog from its environment.
It functions to provide form and contour to the body while elasticity
allows movement. The epidermis
also possess several appendages which further assist in its function
to control inward or outward diffusion of fluids, regulate body temperature,
lubricate the skin's surface, and generally provide additional protection
from its environment. The skin's sensory capabilities allow the perception
of pain, heat, touch and together with it's hair, provides insulation
and protection from external elements. But most importantly, it is the
barrier that typically prevents the loss of essential water and body
The skin is comprised of the epidermis, dermis and hypodermis. The topical
management and conditioning takes place on the epidermal layer. Couple
with its specialized appendages/coat, the epidermis/skin forms the first
line of defense against the environment as the body's protective wrap.
The epidermal appendages consist of the:
Follicle which unlike human follicles that support only one hair
per follicle, canine hair follicles are compound supporting one primary
coarse hair sometimes referred to as guard hair and many (from seven
to twenty) secondary fine soft hairs(undercoat). Whiskers also called
vibrissae are abundant with nerve endings and as such provide specialized
sensory capabilities; however, they are present in only a few prime
sensory areas (nose, eyelashes, etc.). The hair follicle unit also known
as the pilosebaceous
unit consist of the hair follicle, its arrector pili muscle together
with apocrine and sebaceous glands.
and secondary hairs share the same common opening, below the skin's
surface, the secondary hairs form their own philosebaceous units.
Sebaceous Gland is connected to the upper part of the hair follicles
by a duct. They have a central mass of foamy lipid cells that are surrounded
by a layer of basal
cells. When foamy cells become too plentiful and/or are disrupted,
their oily material is pushed upward through their connective duct and
deposited within the hair follicle. The oils spread themselves along
the hair shafts and are pushed upward to spread over the surface of
the skin. Sebaceous oils help waterproof the skin, thereby maintaining
proper hydration. The oily secretion also keeps the skin soft and pliable,
and is spread onto each hair shaft imparting a glossy sheen.
Inadequate functioning of the sebaceous glands may cause
the hair to become dull and dry due to the lack of oily secretions.
Conversely, overproduction and constant disruption of the sebaceous
glands may result in abnormal sebum production causing the skin and
hair to appear excessively greasy while altering the normal, healthy
flora of the follicle and skin surface.
3) The Apocrine Gland
is located deep within the dermis. One gland is associated with each
hair follicle unit, and the proteinaceous, white odorless milky fluid
secreted by the apocrine glands is responsible for body odors when it
combines with bacteria on the skin's surface.
Pheromones, a sexually attracting chemical, is produced
and emitted by the apocrine glands.
4) Eccrine Sweat Glands are numerous in man and aid the
body's mechanisms to dissipate heat. However, in dogs these glands are
only present in the footpads and nose. The distinct absence of eccrine
sweat glands greatly hinders the dogs' ability to dissipate
heat thereby increasing the risk of being overcome by excessive temperatures.
Erector Pili Muscle while not specifically an epidermal component,
its influence is visualized as a function of the epidermis. It is an
involuntary, smooth muscle closely associated with each hair follicle.
Constriction of the muscle causes the hair to stand erect thus improving
the insulating properties of the skin. Over activity of this muscle
whether by stress, irritation, etc. can cause excessive pressure on
the pilosebaceous unit resulting in excessive glandular material (oils,
cholesterol esters, and squalene waxes) being dispensed into the follicle
causing an oily skin and coat. On the other hand, inactivity of the
erector pili muscle could be responsible for reduced oils being dispersed
on the skin and coat causing brittle hair and dry skin.