1. Ch. 5 The Integumentary System

2. Introduction Integument consists of: Skin Skin – largest organ
Accessory structures (hair/sweat glands)
Subcutaneous tissue
Skin
Barrier to many harmful substances

3. The Skin 2 major layers (Fig. 5-1) Epidermis – outer layer
Dermis – inner layer

5. Epidermis Stratified squamous keratinizing epithelium
Thickest on palms, soles
Abundant keratinocytes
No capillaries
2 sublayers
inner stratum germinativum
outer stratum corneum

6. Stratum Germinativum “stratum basale”
Base of the epidermis where mitosis occurs
older cells pushed toward skin surface
produce keratin and die
Merkel cells (Merkel discs)
touch receptors (Fig. 5-2)

8. Stratum Germinativum Keratinocytes
living cells that synthesize antimicrobial “defensins”
rupture pathogen membranes as part of inflammatory process
Living portion produces vitamin D when exposed to sunlight

9. Stratum Corneum Outermost epidermal layer
Keratin prevents evaporation and water entry
Barrier to pathogens & chemicals

10. Langerhans Cells “dendritic cells” (Fig. 5-2)
Originate in red bone marrow
Phagocytize foreign material
migrate to lymph nodes; take pathogen to lymphocytes
triggers immune response

11. Melanocytes See Fig. 5-2 Produce melanin
those with darker skin produce large amounts
production increased in when exposed to UV rays
Melanin gives color to hair, iris, choroid layer of eye
See Table 5-1

12. Dermis Made of irregular fibrous connective tissue
fibroblasts produce collagen & elastic fibers
allow strength & elasticity
Papillary layer – junction of dermis with epidermis (Fig. 5-1)
abundant capillaries
Accessory structures
hair & nail follicles, sensory receptors, glands

13. Hair Follicles Made of epidermal tissue Base of follicle (Fig. 5-3)
Hair root; mitosis occurs in matrix
Produce keratin
Get color from melanin
Die & become incorporated into hair shaft
Hair shaft pushed toward skin surface

15. Hair Follicles Eyelashes & eyebrows keep dust & sweat out of eyes
Nostril hairs keep dust from entering nasal cavities
Hair on head provides insulation
body hair doesn’t serve this purpose
Pilomotor (arrector pili muscle) attached to each follicle
pull hair follicles upright (fear, cold)

16. Nail Follicles On ends of fingers & toes
Produce nails; mitosis in nail root at the nail’s base (Fig. 5-4)
New cells produce keratin & die
Nail is dead keratin cells, but nail bed is alive

18. Nails Protect fingers & toes from mechanical injury Allow dexterity
Good for scratching

19. Receptors Cutaneous senses Specific receptor for each sensation
touch, pressure, heat, cold, pain
Specific receptor for each sensation
Receptors & sensation provide CNS with information about external environment

20. Glands Made of epithelial tissue (Fig. 5-1) Sebaceous glands
Secrete sebum (oil)
inhibits bacterial growth on skin’s surface
prevents drying of skin, hair
Ceruminous glands
in the dermis of ear canals
secrete cerumen (ear wax)
keeps outer surface of eardrum pliable; prevents drying

21. Glands Sweat glands 2 types
Apocrine – numerous in axillae (underarm), genital areas
Eccrine – numerous on forehead, upper lip, palms, soles

22. Blood Vessels Capillaries in dermis Arterioles
Smooth muscle in walls permits constriction or dilation
maintains body temp.

23. Subcutaneous Tissue “superficial fascia”
Made of areolar and adipose tissue
Connects dermis to underlying muscles
Secondary line of defense

24. Aging & The Integumentary System
Skin layers become thinner, more fragile
Fibroblasts die & are not replaced
Repair of breaks or cuts slows
Skin wrinkles
Glands become less active
Skin becomes dry
Temp. regulation becomes harder
Hair thins, turns white