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Chapter 5:
The Integumentary System
https://www.youtube.com/watch?v=dIJhAWrsm0&list=PLF2F5D171DA2715B7
Size of the Integument
 The integument is the largest system of the body:
 16% of body weight
 1.5 to 2 m2 in area
Connections to other systems
 Circulatory system:
 blood vessels in the dermis
 Nervous system:
 sensory receptors for pain, touch, and
temperature
Functions of Skin
 Protects underlying tissues and organs
 Excretes salts, water, and organic wastes (glands)
 Maintains body temperature (insulation and
evaporation)
Functions of Skin
 Synthesizes vitamin D3
 Stores lipids
 Detects touch, pressure, pain, and temperature
Parts of the Integument

The integument is made up of
2 parts:
1. cutaneous membrane (skin)
2. accessory structures
hair, nails and glands
Parts of the
Cutaneous Membrane
 Outer epidermis:
 superficial epithelium (epithelial tissues)
 Inner dermis:
 connective tissues
Skin Structure
 Epidermis—outer layer
 Stratified squamous
epithelium
 Outer layers
keratinized
(hardened by keratin)
 Dermis
 Dense connective
tissue (beneath thin
layer of loose CT)
Layers of the Epidermis
 Stratum corneum – outer 2030 layers of dead, heavily
keratinized cells
 Stratum lucidum - thick,
hairless, “clear layer” skin of
palms and feet only
 Stratum granulosum –
“grainy layer” produces keratin
 Stratum spinosum – “spiny
layer” has an immune
response
 Stratum basale – a.k.a.
stratum germinativum; stem
cells here give rise to all other
epidermal cells. Melanocytes
located here.
Thin Skin
 Covers most of the body
 Has 4 layers of keratinocytes
Thick Skin
 Covers the palms of the hands and soles of the
feet
 Has 5 layers of keratinocytes
Keratin, Melanin, and an Amazing Factoid!
Keratin – tough, pliable protein;
water resistant; gives skin, hair,
and nails protective properties
Stratum corneum is ‘cornified’
= filled with keratin
Cells are shed everyday;
stratum basale totally replaces
epidermis every 25 – 45 days!!
Melanin – pigment of skin color
 Produced by melanocytes (usually in stratum basale)
 Color is yellow to brown to black
 Amount depends upon genetics and exposure to sunlight
 Protects skin from sun damage
Dermis – deep to epidermis: 2 layers (has capillaries and
sensory neurons)
1. Papillary layer (upper dermal
region)
 Projections called dermal
papillae
 Capillary loops, pressure
and pain receptors,
fingerprints, made of areolar
tissue
2. Reticular layer (deepest skin layer).
Made of collagen & elastic fibers.
 Blood vessels
 Sweat and oil glands
 Hair follicles
 Deep pressure receptors
Damage to the Dermis:
Skin Damage
 Sagging and wrinkles (reduced skin elasticity) are
caused by:
 dehydration
 age
 hormonal changes
 UV exposure
Stretch Marks
 Thickened tissue resulting from:
 excessive stretching of skin due to:
 pregnancy
 weight gain
Lines of Cleavage
Clinically significant:
A cut parallel to a cleavage line
will usually remain closed and
heals with little scarring.
A cut at a right angle to a cleavage
line will be pulled open as severed
elastic fibers recoil and will result
in greater scarring.
The skin contains two types of exocrine glands:
1. Sebaceous glands (oil glands):
 secrete sebum -- inhibits bacteria growth, lubricates and protects
hair and skin.
2. Sweat glands: (2 types)
I.
apocrine – located in armpits and pubic region, produce a sticky,
cloudy, and potentially odorous secretion. Begin secreting at puberty.
I.
II.
Mammary glands of the breast are modified apocrine sweat
glands, a complex interaction between sex and pituitary hormones
controls their development and secretion.
merocrine – secrete “sweat” onto the skin, composed of 99% H2O.
Found all over the skin, the palms and soles have the highest number
per cm2. Cools the skin surface, flushes the surface of the skin.
Hair
 Produced by hair
follicles
 Consists of keratinized
epithelial cells
 Melanocytes provide
pigment
Arrector pili – smooth muscle attached to follicle
and papillary layer cause ‘goosebumps’
Nails – heavily keratinized modifications of
epidermis
 Stratum basale in nail matrix responsible for
growth, nail itself is mostly dead cells (like hair)
The Subcutaneous Layer
 Subcutaneous layer (hypodermis):
 Not part of the skin
 Composed of loose connective
tissue: areolar & adipose tissue.
 ½ of your fat is stored here
 Lots of blood vessels, location of hypodermic
injections.
Review
Burns – damage from heat, electricity, UV, chemicals
Burns – damage from heat, electricity, UV, chemicals
Severity of Burns
 First-degree burns
 Epidermis only
 Red and swollen (typical sunburn)
 Second-degree burns
 Epidermis and upper dermis damaged
 Red with blisters
 Third-degree burns
 Entire skin layer destroyed
 Burn is gray-white or black
Rule of 9’s to estimate burn area.
Skin Cancer
Figure 5–6
Skin Cancer – uncontrolled cell division in skin
Skin cancer = #1 cancer
 Basal cell carcinoma – least malignant, most common,
(stratum basale)
 Squamous cell carcinoma – easy cure early, but does
metastasize to lymph nodes, (stratum spinosum)
 Malignant melanoma – most deadly, rapid
metastasis to lymph and blood, (melanocytes)
ABCD Rule: detecting malignant melanoma
 A = Asymmetry – opposite sides don’t match
 B = Border irregularity – borders not smooth
 C = Color – one mole, several colors
 D = Diameter - >6mm (pencil eraser)
Hair and Hair Follicles
Figure 4.7c