LET’S LOOK AT THE SKIN
CHAPTER 17
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OBJECTIVES
 Describe
the skin
the structure & composition of
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INTRODUCTION
One of the largest and most important organ of the
body
 Healthy skin is slightly moist, soft, and flexible, is
acid, and free from disease
 Skin has immunity responses to organisms that touch
or try to enter it
 Unbroken skin is the bodies best defense against
disease
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INTRODUCTION
Its texture ideally is smooth and fine grained
 Appendages of the skin are hair, nails, sweat, and
oil glands
 Scientific study of skin is called histology
 The study of skin is important to form an
effective program of skin care, beauty services,
and scalp treatments
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INTRODUCTION
Medical branch of science that deals with the study of
skin and its nature, structure, functions, diseases, and
treatment is called dermatology
 Dermatologist is a physician that treats the skin, its
structures, & diseases
 Esthetician is a specialists in the cleansing,
preservation of health, & beautification of the skin &
body
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FACTS ABOUT THE SKIN
Skin varies in thickness
 Thinnest on the eyelids and thickest on the
soles of the feet
 Continued pressure on any part of the skin
can cause it to thicken and develop a callus
 Skin on the scalp is constructed similar to the
skin on the body, except the scalp has larger
and deeper hair follicles
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Skin
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Skin is the largest organ in the body, both by
weight and surface area. In adults, the
weight of your skin accounts for about 16%
of your total body weight. Normally the skin
separates the internal environment from the
external. However, skin diseases and
infections can compromise that barrier.
Infections and diseases also affect the nails
and hair.
The skin serves many purposes:
 - serves as a barrier to the environment, and
some glands (sebaceous) may have weak antiinfective properties.
- acts as a channel for communication to the
outside world.
- protects us from water loss, friction wounds,
and impact wounds.
- uses specialized pigment cells to protect us
from ultraviolet rays of the sun.
- produces vitamin D in the epidermal layer,
when it is exposed to the sun's rays.
- helps regulate body temperature through
sweat glands.
- helps regulate metabolism.
- has esthetic and beauty qualities
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HISTOLOGY OF THE SKIN
The skin contains two main divisions:
Epidermis and Dermis
 Epidermis is the outermost layer
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Also called the cuticle or scarf layer
It is the thinnest layer of the skin
 Is protective covering for the body
 Contains no blood vessels, but has nerve
endings
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LAYERS OF THE EPIDERMIS
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Stratum corneum or horny layer
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Outer layer, scale-like cells are being shed
Contains protein keratin
Cells combine w/ a thin layer of oil to help make it
waterproof called the “acid mantle”
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pH of the acid mantle ranges from ph 4.5 –5.5
Toughest layer and protective layer for the layers below it
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Stratum Corneum
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This stratum corneum may be as thin as a few cells,
or as thick as 50 or more, again depending on its
location on the body. The corneum of the scalp, for
instance, may be very thin, perhaps five cells thick,
while that of the elbow is more likely to be upwards
of 50 cells thick. So the body provides for highcontact areas by maintaining a thicker and, therefore,
more durable layer of protection.
LAYERS OF THE EPIDERMIS
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Stratum lucidum
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Under the stratum corneum
Clear layer
Small transparent cells through which light can
pass
Only in the palms of the hands and soles of the
feet
These cells are known as squamous due to their
flat, scale-like appearance
LAYERS OF THE EPIDERMIS
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Stratum granulosum or granular layer
Cells look like granules
 Cells are almost dead & are pushed to the
surface to replace cells that are shed from the
stratum corneum
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LAYERS OF THE EPIDERMIS
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Stratum germinativum
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Formerly known as the stratum mucosum
Also referred to as basal or Malpighian layer
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Single cell layer thick
This is where mitosis or cell division takes place
Cells are constantly dividing a& producing new cells which are
pushed towards the surface of the skin to replace cells that have been
shed as flake-like, lifeless residue
This process takes 15-25 days
Deepest layer, responsible for growth, & skin color
Contains melanocytes, which produce melanin ( dark skin
pigment ) which protects the sensitive cells below from the
ultraviolet rays of the sun
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As pigment granules move upward melanosomes are “picked up”
Dermis
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The second, larger layer of skin is called the dermis.
Its main roles are to regulate temperature and to supply
the epidermis with nutrient-saturated blood.
The dermis is made up of fibroblasts, which produce
collagen connective tissues and which lend elasticity and
support to the skin.
It is the seat of hair follicles, nerve endings, and
pressure receptors.
Furthermore, the dermis defends the body against
infectious invaders that can pass through the thin
epidermis, the first defense against disease.
DERMIS LAYER
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The underlying, or inner layer
 Also called true skin or corium
25 times thicker than epidermis
Highly sensitive layer of connective tissues
Contains blood vessels, lymph vessels, nerves,
sweat glands, oil glands, hair follicles, arrector pili
muscles, and papillae
Made up of two layers
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Papillary layer
Reticular layer
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The dermis is also subdivided into two divisions, the
papillary dermis, and the reticular layer.
 The papillary dermis is the main agent in dermis
function.
 It is from here that the dermis (1) supplies nutrients
to select layers of the epidermis and (2) regulates
temperature.
 Both of these functions are accomplished with a thin
but extensive vascular system that operates like
vascular systems throughout the body.
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Constriction and expansion control the amount of
blood that flows through the skin and dictate
whether body heat is dispelled carefully in times of
heat or conserved for the cold.
The reticular layer is much denser than the papillary
dermis; it strengthens the skin, providing structure
and elasticity.
As a foundation, it supports other components of the
skin, such as hair follicles, sweat glands, and
sebaceous glands.
PAPILLARY LAYER
Outer layer of the dermis
 Called superficial layer
 Lies directly beneath the epidermis
 Contains small cone-shaped projections of elastic
tissue called papillae
 These contain looped capillaries
 Contain nerve fiber ending, called tacticle corpuscles
that provide the body with the sense of touch
 Also contains some melanin
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RETICULAR LAYER
Deeper layer
 Supplies the skin with oxygen and nutrients
 Contains fat cells, blood vessels, lymph
vessels, oil glands, sweat glands hair follicles
and arrector pili muscles
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TISSUES IN THE SKIN
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Subcutaneous tissue
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Fatty layer found below the dermis
Also called adipose or subcutis
 Varies in thickness according to the age, sex
and general health of a person
 Gives smoothness and contour to body, uses
fats for energy, and is a protective cushion
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NERVES OF THE SKIN
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MOTOR NERVE FIBERS
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Distributed to the arrector pili
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SENSORY NERVE FIBERS
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Causes goose bumps, cold or frightened
Reacts to heat, cold, touch, pressure, and pain
SECRETORY NERVE FIBERS
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Distributed to sweat and oil glands
Regulate excretion of perspiration from sweat
glands and controls flow of sebum
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Strength & flexibility of the skin & collagen
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Two specific structures composed of flexible protein
fibers found within the dermis
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Collagen
Elastin
Collagen
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Collagen
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Fibrous protein gives the skin form and strength
Triple helix formed by three extended protein chains
that wrap around on another
Large portion of the dermis & gives structural
support to the skin
Holds together all the structures found in this layer
Healthy collagen fibers allow the skin to stretch &
contract
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Unhealthy due to lack of moisture, environmental damage,
or frequent changes in weight
Skin will begin to lose its tone & suppleness, wrinkles &
sagging begin forming
Strength & flexibility of the skin & collagen
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Elastin
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Collagen fibers are interwoven w/elastin
Elastin polypeptide chains are cross-linked together to
form rubber-like, elastic fibers
Protein similar to collagen
Gives skin flexibility & elasticity
Helps the skin regain its shape
GLANDS OF THE SKIN
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Two types of duct glands that extract
materials from the blood to form new
substances
 Sudoriferous or sweat glands
 Excrete
sweat, consist of a coiled base or
fundus and a tube-like duct that terminates
at the skin surface
 Most numerous on the palms, soles,
forehead, and armpits
 Regulate body temp
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Sudoriferous or sweat glands
 Help
to eliminate waste products from
the body
– Increased by heat, exercise, emotions &
certain drugs
 Controlled
by nervous system
– One to two pints of liquids containing
salts are eliminated daily
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Sebaceous or oil glands
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Consist of little sacs whose ducts open into the hair follicles,
not right into the skin like sweat glands
Secrete sebum
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Fatty or oily secretion that lubricates the skin and preserves
smoothness of hair
Found in all parts of the body, except on the palms & soles
Sebum flows through the oil ducts leading to the mouths of
the hair follicles
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If duct becomes clogged a blackhead is formed
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Summary
A cosmetologist who has a thorough
understanding of the skin, its structure
has a better position to give clients
professional advice on scalp, facial and
hand care