Integumentary System, Parts and Functions of the skin, epidermis, dermis.

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)