The integumentary system consists of the skin, hair, nails, and glands. The skin is composed of two layers - the epidermis and dermis. The epidermis is made of epithelial cells and lacks blood vessels. It contains keratin and is thicker in areas with more wear. The dermis lies below and contains blood vessels, nerves, hair follicles, and glands. Accessory structures in the skin include sebaceous glands which secrete oil, sweat glands which cool the body, and hair and nails made of keratin. The skin functions to protect the body, regulate temperature, and sense the environment.

1. INTEGUMENTARY
SYSTEM
Norelie Ibacarra

2. INTEGUMENTARY SYSTEM
• Skin
• Epidermis
• Dermis
• Accessory structures (appendages)
• Glands
• Hair
• Nails

3. EPIDERMIS
• Outermost layer of the skin
• Comprised of epithelial cells
• Contains no blood vessels (avascular)
• Nutrients diffuse over from dermal blood vessels
• Is thicker in areas of significant wear and tear
(palms of hands and soles of feet)
• Keratin
• Protein that replaces epidermal cell cytoplasm in
order to thicken and protect the skin
• Also comprises hair and nails

4. EPIDERMIS – THICK VS.
THIN SKIN
• Thick Skin (aka, glabrous [hairless] skin)
• 5 layers
• Stratum corneum
• Stratum lucidum
• Stratum granulosum
• Stratum spinosum
• Stratum basale (stratum germinativum)
• Thin Skin (aka, vellus [hairy] skin)
• 4 layers (stratum lucidum is absent and stratum corneum
is much thinner)

5. Dermis
SB
SS
SG SL
SC

6. EPIDERMIS
Thick Skin Thin Skin

7. EPIDERMAL CELLS
• Keratinocytes
• Major epidermal cell type
• ~28 day transit time from stratum basale to stratum corneum
• Melanocytes
• Scattered between cells of stratum basale
• Contain organelles called melanosomes, in which the melanin
pigment is synthesized
• Melanosomes are quickly released and phagocytized by
neighboring keratinocytes (epidermal melanocytes do not
retain their melanosomes)
• Langerhans cell – involved in immune response
• Merkel cell – touch receptor

8. EPIDERMAL CELLS
Melanocyte
Keratinocytes

9. MELANIN IN STRATUM
BASALE KERATINOCYTES

10. DERMIS
• Comprised of elastic connective tissue
• Allows for skin to stretch
• Contains blood vessels (vascular) and nerves
(innervated)
• Location of accessory structures (sweat glands, oil
glands, and hair)
• Dermal papillae
• Extensions of dermis into epidermal layer
• Are what form fingerprints

11. DERMIS

12. DERMAL PAPILLAE

13. HYPODERMIS
• aka, subcutaneous layer
• NOT part of the skin
• Connects skin to surface muscles
• Consists of loose connective tissue and fat (adipose) tissue

15. ACCESSORY STRUCTURES
(APPENDAGES)
• Glands
• Sebaceous (Oil)
• Sudoriferous (Sweat)
• Eccrine
• Apocrine
• Hair
• Nails

16. SEBACEOUS (OIL) GLANDS
• Sebum – oily secretion
• Lubricates skin and coats hair
• Prevents drying
• It is believed that bacterial lipases break down
triglycerides of sebum into irritative fatty acids that cause
acne.
• Ducts open into hair follicles
• Meibomian glands
• Modified sebaceous glands
• Lubricate eyes

19. SEBACEOUS (OIL) GLANDS

20. SUDORIFEROUS (SWEAT)
GLANDS
• Cool the body via evaporation
• Eccrine Sweat Glands
• Distributed over entire body except lips and parts of external
genitalia
• Ducts open directly onto surface of skin
• Excrete salts, urea, ammonia, and uric acid along with water

23. SUDORIFEROUS (SWEAT)
GLANDS (CONT.)
• Apocrine Sweat Glands
• Located in armpits (axillae), nipples, and groin area
• Duct empties into hair follicle superficial to sebaceous
gland
• Become active at puberty
• Secretion is initially odorless; bacteria on the skin
metabolize secretory products to produce malodorous
compounds
• Secrete in response to emotional stimuli (not heat)
• Modified apocrine sweat glands
• Ceruminous glands – ear canal; produce cerumen (ear wax)
• Ciliary glands - eyelids
• Mammary glands – produce milk (breasts)

25. HAIR
• Two types in adults
• Vellus hairs – thin, short and poorly pigmented
• Terminal hairs – thicker, longer and more heavily
pigmented
• Composed mainly of “hard keratin” (as opposed
to “soft keratin” in the epidermal cells)
• Arrector pili muscle causes hair to raise,
forming goose bumps
• Hair color is determined by relative amounts of
eumelanin (black/brown) & pheomelanin
(reddish color)

26. HAIR (CONT.)
• Shaft – portion of hair above the skin
• Root – portion of hair below the skin
• Follicle – sheath of epithelial and connective tissue that
surrounds the hair
• Bulb – located at base of follicle
• Three phases in life cycle of each hair
• Anagen – the period of active growth (0.04 cm per day)
• Catagen – the period of involution (degeneration) when the
lower part of the follicle below the arrector pili muscle atrophies
• Telogen – the resting period between the end of follicular
atrophy and the shedding of the hair

27. HAIR

28. NAILS
• Comprised of hard keratin from stratum corneum
• Nail plate – hard portion of nail
• Nail bed
• Comprised of stratum basale and stratum spinosum
• Nail plate rests on the nail bed
• Nail root – proximal part of nail (covered by skin)
• Nail matrix – contains stem cells that cause nail
to grow

29. NAILS

30. FUNCTIONS OF SKIN
• Protect against infection
• Protect against dehydration
• Membrane-coating granules (MCG’s) seal spaces between
keratinocytes to prevent entry of pathogens and loss of water
• Regulate body temperature
• Vasoconstriction (blood vessels become narrower) – conserve
heat
• Vasodilation (blood vessels open wider) – promotes
radiation/dissipation of heat to surrounding air
• Sweat
• Sensory reception
• Pain
• Temperature changes
• Touch (and pressure)