Integumentary System
A. Includes skin, hair, nails, glands; also contains sensory receptors &
vascular network
B. Skin
1. Functions of the skin
A) Protection
B) Thermoregulation – via blood vessels in skin
C) Sensation
1) Tactile – touch & pressure
2) Thermal – warmth & coolness
3) Pain
D) Excretion
1) Water and some wastes
E) Absorption
1) Fat-soluble vitamins, O2, CO2 and some toxins – acetone, lead,
mercury and poison ivy & oak
2. 3 distinct layers
A) Epidermis
B) Dermis
C) Hypodermis
3. Epidermis
A) Thinnest & outermost layer
B) Composed of keratinized stratified squamous epithelium (30-50
cells thick)
C) 4 specialized cell types
1) Keratinocytes – produce keratin
2) Melanocytes – produce melanin
3) Langerhans cells – arise from bone marrow and help to activate
the immune system
4) Merkel cells – associated with sensory neurons to aid in our
sense of touch
D) 4 or 5 distinct layers dependent on location
1) Stratum basale – deepest
a) 1 cell layer thick
b) Constantly reproducing
c) 10-25% melanocytes
2) Stratum spinosum
a) Several cell layers thick
b) Large number of Langerhans cells
3) Stratum granulosum
, a) 3-5 cell layers thick
b) Keratinization begins
i) Process by which cell’s internal structures die, degrade,
and are replaced with keratin
c) Last layer with blood nutrient supply
4) Stratum lucidum – only in thick skin
a) Thin band of flattened cells
5) Stratum corneum – outermost
a) 20-30 cell layers thick, 3/4 of epidermis
4. Dermis
A) Deeper & thicker than epidermis
B) Contains vascular network that “feeds” the epidermis & sensory
receptors
C) 2 layers
1) Papillary layer (20%)
a) Areolar connective tissue – flexibility
b) Dermal papillae – extensions into the epidermis
c) Contain blood vessels, free nerve endings (pain) and
Meissner’s corpuscles (touch receptors)
2) Reticular layer (80%)
a) Dense irregular connective tissue
b) Contains blood vessels, glands, hair follicles, and Pacinian
corpuscles (pressure receptors)
c) Has some flexibility but can be torn or damaged
i) Scaring/Stretch marks
ii) Blister
5. Hypodermis
A) Composed primarily of adipose tissue
B) Contains major blood vessels
6. Skin color
A) Results from a combination of 3 pigments
1) Melanin
a) Produced by melanocytes in stratum basale
b) Red to yellow to brown-black
2) Carotene
a) Found in plants (carrots)
b) Yellow to orange
3) Hemoglobin
a) More prominent in fair-skinned people
b) Crimson
A. Includes skin, hair, nails, glands; also contains sensory receptors &
vascular network
B. Skin
1. Functions of the skin
A) Protection
B) Thermoregulation – via blood vessels in skin
C) Sensation
1) Tactile – touch & pressure
2) Thermal – warmth & coolness
3) Pain
D) Excretion
1) Water and some wastes
E) Absorption
1) Fat-soluble vitamins, O2, CO2 and some toxins – acetone, lead,
mercury and poison ivy & oak
2. 3 distinct layers
A) Epidermis
B) Dermis
C) Hypodermis
3. Epidermis
A) Thinnest & outermost layer
B) Composed of keratinized stratified squamous epithelium (30-50
cells thick)
C) 4 specialized cell types
1) Keratinocytes – produce keratin
2) Melanocytes – produce melanin
3) Langerhans cells – arise from bone marrow and help to activate
the immune system
4) Merkel cells – associated with sensory neurons to aid in our
sense of touch
D) 4 or 5 distinct layers dependent on location
1) Stratum basale – deepest
a) 1 cell layer thick
b) Constantly reproducing
c) 10-25% melanocytes
2) Stratum spinosum
a) Several cell layers thick
b) Large number of Langerhans cells
3) Stratum granulosum
, a) 3-5 cell layers thick
b) Keratinization begins
i) Process by which cell’s internal structures die, degrade,
and are replaced with keratin
c) Last layer with blood nutrient supply
4) Stratum lucidum – only in thick skin
a) Thin band of flattened cells
5) Stratum corneum – outermost
a) 20-30 cell layers thick, 3/4 of epidermis
4. Dermis
A) Deeper & thicker than epidermis
B) Contains vascular network that “feeds” the epidermis & sensory
receptors
C) 2 layers
1) Papillary layer (20%)
a) Areolar connective tissue – flexibility
b) Dermal papillae – extensions into the epidermis
c) Contain blood vessels, free nerve endings (pain) and
Meissner’s corpuscles (touch receptors)
2) Reticular layer (80%)
a) Dense irregular connective tissue
b) Contains blood vessels, glands, hair follicles, and Pacinian
corpuscles (pressure receptors)
c) Has some flexibility but can be torn or damaged
i) Scaring/Stretch marks
ii) Blister
5. Hypodermis
A) Composed primarily of adipose tissue
B) Contains major blood vessels
6. Skin color
A) Results from a combination of 3 pigments
1) Melanin
a) Produced by melanocytes in stratum basale
b) Red to yellow to brown-black
2) Carotene
a) Found in plants (carrots)
b) Yellow to orange
3) Hemoglobin
a) More prominent in fair-skinned people
b) Crimson
