1. Chapter 5: The Integumentary System
BIO 210 Lab
Instructor: Dr. Rebecca Clarke

2. Parts of the Integumentary System
Cutaneous membrane (integument, skin)
(outer) epidermis = superficial epithelium
(inner) dermis = underlying area of connective tissues
Accessory structures – located primarily in dermis, protrude through epidermis to skin surface
Hair
Nails
(Multicellular) exocrine glands
Also
Blood vessels throughout dermis
Sensory receptors – monitor touch, pressure, temperature, pain

3. Integumentary System Cutaneous membrane = epidermis + dermis
Figure 5–1

4. Layers (Strata) of Epidermis
From basal lamina to free surface:
stratum germinativum
stratum spinosum
stratum granulosum
stratum lucidum
stratum corneum

5. Stratum Germinativum (Basale)
Single layer of basal (germinative, stem) cells
Site of cell division; replenishes epidermis
Attached to basal lamina by hemidesmosomes
Forms strong bond between epidermis and dermis

6. Stratum Germinativum Forms epidermal ridges (Fig 5-2)
fingerlike projections into dermis underneath; intermesh with dermal papillae
 ridge-shaped pattern (fingerprint) on surface of skin which is unique for each individual (genetically determined) (Fig 5-4)
increase strength and bond between epidermis and dermis
Has melanocytes (with melanin pigment) – give skin its color (Fig 5-5)

7. Organization of the Epidermis
Figure 5–2

8. Ridges and Ducts
Figure 5–4

9. Stratum Spinosum “Spiny layer” 8-10 cell layers of keratinocytes
cells shrink until cytoskeletons stick out (spiny)
8-10 cell layers of keratinocytes
Dividing cells from stratum germinativum push up through this layer
Still some cell division

10. Stratum Granulosum “Grainy layer” 3-5 cell layers thick
Cells stop dividing, start producing proteins  grainy appearance
keratin:
tough, fibrous protein
makes up hair and nails
 water resistant, not waterproof
keratohyalin
dense granules
cross-link keratin fibers
 tightly interlocked cell layers
Cells
thinner, flatter, less permeable
further from papillary plexus, start to die

11. Stratum Lucidum “Clear layer”
Cells flattened, densely packed, filled with keratin  barrier to water
Only in thick skin (on palms and soles)

12. Stratum Corneum “Horn/hard layer” on exposed surface of skin
15-30 cell layers of dead cells (far from nutrients in dermis); durable, expendable  protective function
Cells filled with keratin (= keratinized)  water-resistance (not waterproof)
Cells tightly interconnected by desmosomes so are sloughed off in sheets
Cells remain for 2 weeks (total of 6 weeks from origin in stratum germinativum to sloughing)

13. 2 Kinds of Skin Thin skin Thick skin
Has 4 layers of keratinocytes (missing stratum lucidum)
Covers most of body
Thick skin
Has all 5 layers of keratinocytes
Covers heavily abraded body surfaces, e.g., palms of hands, soles of feet

14. Dermis Located between epidermis and subcutaneous layer Contains
Blood and lymph vessels
Nerve fibers and sensory receptors
Tactile (Meissner’s) corpuscles – sensitive to light touch; located in dermal papilla
Lamellated (Pacinian) corpuscles – sensitive to deep pressure and vibration
Accessory organs (of epidermal origin), e.g., hair follicles, sweat glands

15. Components of Dermis 2 major components – boundaries indistinct
Papillary layer
Reticular layer
Associated structures
Papillary plexus = branching network of small arteries in papillary layer of dermis which provide blood to capillary loops that follow contours of epidermis-dermis boundary

16. Papillary Layer
Has dermal papillae projecting between epidermal ridges
Consists of areolar tissue
Contains smaller capillaries, lymphatics, and sensory neurons

17. Reticular Layer Deep to papillary layer
Consists of dense irregular connective tissue
Contains
Larger blood vessels, lymph vessels, and nerve fibers
Collagen and elastic fibers 
Strength and elasticity
Flexibility

18. Dermatitis An inflammation of the papillary layer
Caused by infection, radiation, mechanical irritation, or chemicals (e.g., poison ivy)
Characterized by itch or pain

19. Subcutaneous Layer aka hypodermis (“below dermis”), superficial fascia
Highly vascularized – contains large arteries and veins; site of subcu injections
Separates integument from deep fascia around other organs, e.g., muscles and bones
Stabilizes position of skin relative to underlying tissues, e.g., skeletal muscles or other organs, while permitting independent movement

20. Structure of Subcutaneous Layer
Consists of
Elastic areolar (loose) connective tissue
Adipose tissue (energy reserve, shock absorber)

21. Accessory Structures of the Integumentary System
Derived from epidermis
Located in dermis
Extend through epidermis to skin surface
Include:
Hair follicles and hairs
Exocrine glands
Nails

22. Structure of a Hair and Follicle
Figure 5–10a

23. Hair Follicles Living organs
Produce “nonliving” hairs; complex process involving dermis and epidermis
Extend deep into/through dermis and into underlying subcutaneous layer
Wrapped in dense connective tissue sheath of dermis

24. Follicle Wall Composed of epithelial cells
Cells organized into 3 concentric layers (from outside in)
Glassy membrane:
Thickened basal lamina
External root sheath:
Widest layer
Internal root sheath:
Contacts cuticle (outer layer of hair)

25. Structure of a Hair and Follicle
Figure 5–10

26. Structure of a Hair Follicle
Hair bulb
Bulbous mass of epithelial cells
Hair matrix
Layer of epithelial cells in central, deepest part of follicle
Site where cell division begins that produces hair
Cells gradually pushed toward surface as hair gets longer
Hair papilla
At base of follicle (below matrix)
“Peg” of connective tissue that contains capillaries and nerves
If damaged, hair will not grow

27. Structure of a Hair and Follicle
Figure 5–10

28. Hair Structure Hair root Hair shaft Lower part of hair
Begins at base of hair (bulb) and extends about halfway to skin surface
Anchors hair into skin;
Hair shaft
Upper part of hair
Extends from above the root to above the skin surface

29. Structure of a Hair and Follicle
Figure 5–10

30. Layers Within Hair Cuticle Cortex Medulla Outer surface
Layer of overlapping, dead keratinized cells
Contains hard keratin  hair stiffness
Cortex
Intermediate layer below cuticle
Also contains hard keratin
Medulla
Middle layer, central core
Contains soft keratin
Flexible

31. Structure of a Hair and Follicle
Figure 5–10

32. Associated Structures
Arrector pili muscle
Involuntary smooth muscle
Contractions cause hairs to stand up  “goose bumps”

33. Exocrine Glands Sebaceous (oil) glands: Sweat (sudoriferous) glands:
holocrine glands
secrete sebum
Sweat (sudoriferous) glands:
merocrine glands
apocrine glands

34. Types of Sweat Glands Apocrine: Merocrine:
Associated with hair follicles
Found in armpits, around nipples, and groin
Merocrine:
Widely distributed on body surface
Especially on palms and soles

35. Merocrine Sweat Glands
Also called eccrine glands
Smaller but more numerous
Coiled, tubular glands
Watery secretion = sensible perspiration (produced by glands) vs. insensible perspiration which is the loss of fluid by evaporation through the stratum corneum

36. Nails Nonliving structures; made of dead cells packed with keratin
Form on dorsal surface of tips of fingers and toes
Function = protect fingers and toes
Metabolic disorders can change nail structure, e.g., shape, appearance; can assist in diagnosis

37. Nail Structure Nail body - Superficial, visible portion
Nail bed – area of epidermis under nail body
Nail root – epidermal fold not visible from surface; where nail production occurs
Eponychium – extends over exposed nail forming cuticle
Hyponychium – skin beneath free edge of nail
Lunula (“moons”) pale crescent at base of nail where underlying blood vessels may be obscured

38. Structure of a Nail
Figure 5–13