Integumentary
System

• Sites used
http://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/skinlsn/sknls
n.htm
• http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Integumentary/Integum.htm

Skin
• ~9 lbs. (4.1 kgs)
• Covers S.A. of 15-20 ft2 (1.4 to 1.9 m2)
• Every square inch contains 15’ blood
vessels, 12’ nerves, 650 sweat glands,
100 oil glands, 1500 sensory receptors,
& 3 million cells
• Thickness varies from 1/32” to 1/8”
• Skin cells die & replaced continuously
• 3 layers = epidermis, dermis &
hypodermis

Skin-Major Functions
• Protects
• Excretion/Secretion
• Helps regulate body
temperature
• Sensation (Cutaneous sensation)
• Promotes vitamin D synthesis
• Acts as reservoir for blood

Protects
• 3 ways
• Chemically
• Physically
• Biologically

Protects-Chemically
• Acidic skin secretions inhibit
bacteria from multiplying
• Substances in sebum (oil) kill
some bacteria
• Melanin-shield skin from UV
rays

Protects-Physically
• Keratinized cells-
ex.epidermis, hair and nails
•Barrier to invading
organisms

Protects-Biologically
• Dermal macrophages-2ndline of
defense against bacteria
• Epidermis contains macrophage
like Langerhan’s cells =
immunity

Excrete/Secrete
• Sweat-nitrogenous waste,
sodium chloride
• Sebum-secreted by sebaceous
glands

Regulate Body Temp.
• Evaporation of sweat
• Dermal blood vessels dilate and
constrict

Cutaneous Sensation
• Sensory receptors-Meissner’s,
Pacinian, Ruffini’s, Krauses,
free nerve endings

Vitamin D Synthesis.
• Exposed to UV-skin converts
cholesteral molecules to Vitamin
D

Reservoir for blood
• Shunted from skin to general
circulation ex. To working
muscles

Skin
•3 layers
•Epidermis
•Dermis
•Hypodermis

1. Epidermis
• Most superficial layer of skin
• First barrier of protection
• Principle (main) cell type in epidermis
= keratinocytes
• 4-5 layers
• 4 types of epidermal cells

2. Dermis
• Contains sebaceous and sweat glands
• Sensors:
2-A) Pacinian corpuscle – heavy
touch & vibratiions
2-B) Meissner’s corpuscle – light
touch

3. Hypodermis
• Most of the blood flow (arteries &
veins)
• Contains fat for insulation &
cushioning

4. Hairs
• Protection
• Decrease heat loss
• Errector pilius – pulls
hair errect during stress

Common Disorders:
1. Eczema
2. Psoriasis
3. Freckles/Moles
4. Athelete’s
Foot/Jock Itch
5. Melanoma
1. Calluses/Corns
2. Bruising
3. Impetigo

Epidermal Cells
• Keratinocytes: compose most of
epidermis; make protein keratin
• Keratin: waterproofs and protects skin
• Melanocytes:synthesize melanin
• Melanin protects against UV damage
• Merkel cells: associated with sensory
receptors (touch)
• Langerhan’s cells: macrophages used
in defense against microorganisms