Download 25 square feet.

Chapter 5
INTEGUMENTARY SYSTEM
FUNCTIONS OF THE SKIN
• The skin has 7 functions:
1 - Covers underlying tissues to protect
against dehydration, injury, and germ
invasion
2 - Regulates body temperature,
controlling amount of heat loss.
(evaporation)
3 - Helps manufacture vitamin D
FUNCTIONS OF THE SKIN
4- Serves as the site of many nerve
endings
5- Temporarily stores fat, glucose,
water, and salts
6- Screens out ultraviolet radiation
7 -Absorbs certain drugs and chemical
substances
STRUCTURE OF THE SKIN
• Layers of the skin:
– Epidermis - the outermost covering of
epithelial cells with no blood vessels
– Dermis - true skin made of connective
tissue and is vascular
– Subcutaneous (hypodermal layer) lies
under the dermis and consists of
loose connective tissue
STRUCTURE OF THE SKIN
Epidermis
• Consists of 4 distinct cell types and
five layers
• Thickness varies – thinnest on
eyelids and thickest on palms of
hands and soles of feet
Epidermis
• Keratin – protein that keeps the
skin dry and provides a waterproof
covering, resisting evaporation and
preventing excess water loss.
– Also serves as a barrier against UV
light, bacteria, abrasions, and some
chemicals.
Trivia
Trivia
• The largest human organ is the
skin, which has a surface area
averaging ___ square feet.
Trivia
• The largest human organ is the
skin, which has a surface area
averaging 25 square feet.
Epidermal Cells
• Keratinocytes – comprise most of
the epidermis and produce the
protein keratin
• Merkel cells – are the sensory
receptors for touch.
Epidermal Cells
• Melanocytes – make the protein
melanin, which protects the skin
against the UV rays of the sun.
• Langerhans cells – are macrophages
which are effective in the defense
of the skin against macrophages.
Epidermal layers
1 -Stratum germinativum – (AKA
stratum basale)
– Undergoes continuous cell division
(mitosis)
– Deepest epidermal layer
– Consists of cells that are mostly
keratinocytes, can find melanocytes
and merkel cells
Epidermal layers
– Lower edge contains ridges –
papillae.
• Arise from the dermal layer and
push into the str. germ.
• Provide max. resistance to
slipping when grasping and holding
objects.
• AKA friction ridges
• Fingerprints
Epidermal layers
• 2 – stratum spinosum
– Cells look like have spines (due to
fixation preparation)
– Contain keratinocytes
– Also some melanin granules and
Langerhans’ cells
– 8-10 cell layers thick
Epidermal layers
3- stratum granulosum
– 3-5 cell layers of keratinocytes.
– Cells are flat
– Cells begin to die here due to being so
far away from capillaries of dermis
Epidermal layers
• 4- stratum lucidum
– Appears translucent
– Consists of a few rows of dead
keratinocytes
– Only visible on thick skin
Epidermal layers
• 5- stratum corneum
– 10 -30 cell layers thick
– Prevents water loss, protection from
external environment
– Cells are slightly acidic for protection
– Can be keratinized or non-keratinized
• Keratinized on hands/feet
Dermis
• Thicker, inner layer of skin
• Contains matted masses of
connective tissue, collagen tissue
bands, elastic fibers, blood vessels,
nerve endings, muscles, hair
follicles, oil and sweat glands, and
fat cells.
Sensory Receptors of Dermis
1. Free dendritic nerve endings of
sensory neurons
– Located in dermis,epithelia, glands
– Sense pain, heat and cold, and
pressure
2. Merkel discs
– At base of epidermis of skin
– Sense light pressure
Sensory Receptors of Dermis
3. Root hair plexuses
-In and surrounding hair follicles
-Feel hair deflection
4. Meissner’s corpuscles
-Dermal papillae of hairless skin –
lips, eyelids, nipples, fingertips
-Light pressure, vibration
Sensory Receptors of Dermis
5. Pacinian corpuscles
-Subcutaneous tissue of skin
-Deep pressure, stretch, vibration
Pop Quiz
1. What are the layers of the skin,
in order from outside world
inward?
2. What are the 3 main types of
fingerprints?
3. What types of tissues can be
found in a skin sample?
TRIVIA
Trivia
• Based on the selling price of
cowhide, which is approximately
$.25 per square foot, the value of
an average person’s skin is about
________.
Trivia
• Based on the selling price of
cowhide, which is approximately
$.25 per square foot, the value of
an average person’s skin is about
$6.25.
Subcutaneous layer
•
•
•
•
Aka hypodermal layer
Lies under the dermis
Not a true part of the IS
Consists of loose connective tissue and
contains about ½ of the body’s stored
fat.
• Attaches IS to the surface muscles
underneath.
• Injections – hypodermic or
subcutaneous (subcu)
Pop Quiz
1. What are the 4 cells types found
in the epidermis?
2. What is another name for the
subcutaneous layer of the skin?
3. Name the layers of the skin from
inner to outermost.
4. What is the white part of hair
called?