1. The Integumentary System
Exercise 7
The Integumentary System

3. What is the integumentary system?
An organ system
Several tissue types functioning together
Largest organ of body
Many functions:
Protection, insulation, cushion, prevent water loss, regulate heat loss, excretion through pores, vitamin D synthesis, sensory input

4. 2 Main Regions
Epidermis
Dermis

5. EPIDERMIS: 4-5 layers SUPERFICIAL DEEP Stratum corneum Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale

6. Figure 7.2 The main structural features in epidermis of thin skin.
Keratinocytes
Dendritic cell
Stratum corneum Most superficial layer; 20–30 layers of dead cells, essentially flat membranous sacs filled with keratin. Glycolipids in extracellular space.
Stratum granulosum One to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellar granules (release lipids) and keratohyaline granules.
Stratum spinosum Several layers of keratinocytes joined by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin.
Stratum basale Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers.
Dermis
Dermis
Tactile (Merkel) cell
Melanin granule
Sensory nerve ending
Desmosomes
Melanocyte 6

7. TOP: Stratum corneum Stratum corneum Most superficial layer;
20–30 layers of dead cells,
essentially flat membranous sacs
filled with keratin. Glycolipids in extracellular space.

8. 2nd (if present) Stratum lucidum
Thin, clear layer
Flattened dead cells, filled with keratin
Only in “thick skin”: palms, soles
Fig. 5-4

9. 3rd (if thick skin) Stratum granulosum
Stratum granulosum One to five layers of flattened cells, organelles deteriorating;
Cytoplasm full of lamellar granules
(release lipids) and
keratohyaline granules.
Fig. 5-4

10. 4th Stratum spinosum
Dendritic cell
Stratum spinosum Several layers of keratinocytes joined by desmosomes.
Cells contain thick bundles of intermediate filaments made of pre-keratin.
Keratinocytes

11. 5th (bottom) Stratum basale
Stratum basale Deepest epidermal layer;
one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers.
Tactile (Merkel) cell
Melanocyte
Dermis
Melanin granule
Sensory nerve ending
Desmosomes

12. Epidermal cells Keratinocytes: most abundant, produce keratin
Melanocytes: produce melanin, shield nuclei from UV, freckle = many in one spot
Langerhans cells: macrophages (immune system) that help stimulate a defense; in s. spinosum
Merkel cells: sensory touch receptors; in s. basale

13. DERMIS: 2 layers Papillary layer Reticular layer
superficial, just below the epidermis
Reticular layer
deep, below the papillary layer

14. • Sebaceous (oil) gland • Hair follicle
Figure 7.1 Skin structure.
Hair shaft
Dermal papillae
Epidermis
Subpapillary plexus
Papillary layer
Sweat pore
Dermis
Appendages of skin
Reticular layer
• Eccrine sweat gland
• Arrector pili muscle
• Sebaceous (oil) gland
• Hair follicle
Hypodermis (subcutaneous tissue; not part of skin)
• Hair root
Cutaneous plexus
Nervous structures
Adipose tissue
• Sensory nerve fiber with free nerve endings
• Lamellar corpuscle
• Hair follicle receptor (root hair plexus)

15. Papillary Layer
Dermal papillae (projections) extend from upper dermis into epidermal ridges
Epidermal ridges formed by stratum basale, at junction of epidermis & dermis  FINGERPRINTS!
Areolar tissue

16. Reticular Layer Thicker layer Dense irregular connective tissue Fibers
Vascular, glandular (sweat/sebaceous)
Stretch marks: dermis is torn because stretched too far…then repaired

17. Dermal Cells
Meissner’s corpuscles: light touch receptors in dermis—PAPILLARY LAYER
Pacinian (lamellar) corpuscles: deep pressure receptors in dermis—RETICULAR LAYER

18. Hypodermis Deep to the dermis (below it) Superficial fascia layer
Primarily adipose tissue
NOT a part of the “skin”

19. Accessory Skin Organs
Hair
Nails
Cutaneous Glands

20. Hair follicle Tubular depression in epidermis & dermis
Where a hair develops
Follicle wall

21. Hair bulb (root), within the hair follicle, the enlarged base

22. Root sheath
Inner cylinder of epidermis surrounding hair root in the follicle
• External epithelial root sheath
• Internal epithelial root sheath

23. Arrector pili Smooth muscle cells
Arrector pili muscle
Arrector pili
Smooth muscle cells
Connect hair follicle to papillary layer
Muscles contract  hair stands up, goosebumps b/c skin dimpled

24. Hair shaft
Hair shaft
Visible, dead (keratinized) portion of the hair

25. Figure 7.6 Photomicrographs of skin.
Sloughing stratum corneum cells
Epidermis
Hair follicle
Hair shaft
Dermis
Epidermis
• Stratum corneum
• Stratum lucidum
• Stratum granulosum
• Stratum spinosum
• Stratum basale
Dermis 25

26. NAILS Are in the integumentary system
Don’t need to know the specifics FOR LAB

27. Cutaneous Glands
Sebaceous Glands
Sweat Glands
Eccrine
Apocrine

28. Sebaceous Glands “oil glands” Associated with hair follicle
Secrete sebum into hair follicle to keep hair from being brittle (holocrine gland)
Sebaceous gland

29. Sweat Glands Exocrine glands, all over body (pores) 2 types of fluid:
Eccrine glands
Forehead, back, palms, soles
Clear perspiration (water, salts, urea: exocytosis), controls body temperature
Merocrine glands
Apocrine glands
Much larger
Axillary, pubic, mammary (specialized, produces milk)
“cloudy” perspiration, odorous
Olfactory communication--pheromones
Eccrine gland

31. Skin Model Key: I. Epidermis II. Dermis III
Skin Model Key: I. Epidermis II. Dermis III. Hypodermis (subcutaneous) 1. Stratum corneum 1a. Stratum lucidum 2. Stratum germatativum 2a. Stratum granulosum 2b. Stratum spinosum 2c. Stratum basale 3. Papillae 4. Touch (Meissner) corpuscle 5. Adipose tissue 6. Laminated (Pacinian) corpuscle 7. Sweat (Eccrine) gland 8. Hair (longitudinal section)
8a. Medulla 8b. Cortex 8c. Cuticle 8d. Internal epithelial root sheath 8e. External or outer epithelial root sheath 8f. Glassy (hyaloid) membrane 8g. Fibrous connective tissue root sheath 9. Hair (cross-section) 10. Hair shaft 11. Root 11a. Hair bulb 12. Hair papilla 13. Sebaceous glands 14. Arrector pili muscle 15. Sweat (apocrine) gland 15a. Smooth muscle cells 15b. Hyaline top 15c. Part of the pushed out cell body

32. Interactive website—quiz yourself!

36. Review Figure 7.1 36