Salon Fundamentals
TM
Esthetics
s k i n p h y s i o l o g y
260
pores. Sweat is water mixed with salt and other
chemicals that have built up in the body. Have you
ever eaten a lot of garlic and then actually smelled
like garlic the next day? This is an example of the
body excreting waste from the system.
Regulation
The body maintains an internal temperature of
98.6 degrees Fahrenheit (37 degrees Celsius). Skin
regulates the body's temperature through mechan-
isms such as shivering and goosebumps. The
contraction of a muscle called the arrector pili causes
goosebumps, while shivering releases energy that
warms the body. The skin also changes blood flow to
regulate body temperature. For example, when body
temperature drops, blood flow increases. When body
temperature increases, the sudoriferous glands secrete
sweat. When water from sweat on the skin evaporates,
it gives off heat and cools the body as it evaporates.
Sensation
The surface of the skin contains millions of nerve
end fibers that transport stimuli sent from the brain
and spinal cord to the corresponding parts
of the body. These nerve end fibers allow humans
to detect sensations such as heat, cold, pain,
pressure and touch.
Protection
The skin shields internal tissues from toxins such
as pollutants, smoke, ultraviolet radiation and other
harmful chemicals and substances. It also acts as a
barrier to infectious bacteria and to extreme heat
and cold. The layers of the skin contain cells that
provide immune functions to the entire body.
Immune cells, such as Langerhans (which are
explained later in this chapter), provide the body
with its first line of defense against infection by
identifying foreign substances in the skin.
Absorption
For many years it was believed that substances
applied to the body could not penetrate the skin
and, therefore, were not absorbed. Now it is
known that certain types of ingredients, such as
vitamins and acids, along with water and
oxygen, are absorbed by thousands of pores on
the surface of the skin to provide necessary
moisture, nourishment and protection.
Secretion
The skin secretes sebum, a complex mixture of
fatty substances that keeps the skin soft, supple
and pliable. This layer of sebum on the skin,
known as the acid mantle, affects the skin's pH
level. A normal pH range is approximately 4.5 to
5.5, which is the result of a sufficient amount of
sebum on the skin. This serves as a protective
barrier to prevent bacteria from invading the skin.
Excretion
The skin is the body's largest waste removal
system. Toxins and waste material, such as carbon
dioxide, are released through the sweat glands and
As you learned in
Chapter 5, Anatomy, the major
systems of the body are the integumentary
(skin), skeletal, circulatory, muscular, nervous,
endocrine, excretory, digestive, respiratory and
reproductive systems.
Amazingly, one square inch (2.5 cm) of skin
contains approximately 1,250 pain receptors, 155
pressure receptors and 12 cold and heat receptors.
