1. I. General Concepts and Considerations
Skin & Appendages
I. General Concepts and Considerations

2. A. Heaviest single organ of body
16% of total body weight
m2 surface area
Epidermis
Dermis
Hypodermis

3. C. Functions of the skin
Protection from injury, desiccation, infection
Regulation of body temperature
Absorption of UV radiation for synthesis of vitamin D
Reception of sensory stimuli
Secretion of protective lipids, milk
Dermis and epidermis interdigitate via dermal papillae - best developed in areas exposed to shearing stress
Classified as thick or thin depending on the thickness of epidermis

4. Skin & Appendages
II. Epidermis

5. A. Characteristics Keratinized stratified squamous epithelium
Regenerated by keratinocytes
Formed by five layers or strata
turnover from basal to superficial varies from site to site
25-30 days fastest; days slowest
Downgrowths produce sweat glands and hair follicles

6. Epidermis

7. B. Stratum Basale
Deepest layer, attached to basement membrane by hemidesmosomes
Keratinocytes, large euchromatic nuclei, mitotically active
Melanocytes and Merkel cells

8. C. Stratum Spinosum A few layers of prickly keratinocytes
Intercellular bridges formed by desmosomes
Round, euchromatic nuclei, mitotically active
Concentrated tonofilaments in cytoplasm
Upper cells cemented together to waterproof the skin
Langerhans cells & cytoplasmic projections of melanocytes
Psoriasis

9. D. Stratum Granulosum
Cells accumulate keratohyalin granules and bundles of intermediate keratin filaments
All cells produce membrane-coated granules
Keratohyalin granules composed of histidine- & cystine-rich proteins that glue keratin filaments together
Nuclei are present

10. E. Stratum Lucidum Clear homogenous layer
Nuclei and organelles are not present
Cells contain eleidin

11. F. Stratum Corneum – Thick Skin
Outermost layer, formed of dead cells
Surface cells continuously desquamated

12. F. Stratum Corneum – Thin Skin

13. G. Other cellular components
Melanocytes
Langerhans cells
Merkel's cells
Melanocytes
Langerhans
Cell

14. 1. Melanocytes structure derivation melanosomes keratinocytes
skin color
distribution
races
tanning

15. 1. Melanocytes

16. 2. Langerhans cells
dendritic-shaped cells derived from the bone marrow
present in all layers but mainly in stratum spinosum
ovid, pale-staining nuclei, cytoplasm with granules, processes
function as APCs
increase in number in chronic inflammatory skin diseases

17. 3. Merkel's cells
found in thick skin; scanty and difficult to find in thin skin
present in stratum basale
contain small dense-core granules
receive afferent nerve terminals, believed to function as sensory - mechanoreceptors

18. H. Types of Skin

19. H. Types of Skin Thin Skin Thick Skin
Covers entire body except palms and soles On palms and soles of the feet
(0.5 mm on the eyelid, 5 mm on the back) (0.8 mm to 1.5 mm thick)
Thin epidermis, dermis can be thick Thick epidermis
Hair follicles with sebaceous glands Hairless thus no sebaceous glands
Sweat glands Sweat glands
Epidermis

20. Skin & Appendages
III. Dermis

21. A. Characteristics
Dense irreg. FECT
Contents
Aging
Blood vessels

22. Epidermal-Dermal Junction
Scalloped margin consisting of epidermal pegs and dermal papillae
Strengthens attachment of epidermis to the underlying dermis
40X
400X
Epidermal
peg
Dermal
papilla

23. Dermis

24. Blood Vessels of Dermis

25. B. Layers
Papillary Layer - loose FECT that forms the dermal papillae, loops of small blood vessels and capillaries, nerve endings

26. B. Layers
Reticular Layer - dense irregular FECT that forms bulk of dermis, with blood vessels and a-v shunts, lymphatics and nerves

27. B. Layers Erector Pili Muscle
bundles of smooth muscle, attached to hair follicles in dermis and papillary layer of dermis
contraction elevates hairs (makes them more vertical) and produces goose bumps

28. 3. Erector Pili Muscle

29. C. Nerve Supply Sympathetic NS Afferent fibers Free nerve endings
Pacinian Corpuscles
Meissner's Corpuscles

30. Paccinian Corpuscle

31. Meisner’s Corpuscle

32. D. Blisters

33. E. Dermatitis

34. Wound Repair

35. Skin & Appendages
IV. Glands

36. Eccrine sweat glands Characteristics Dark cells Clear cells
Myoepithelial cells
Ducts
Dermis & epidermis
Produce sweat
Sweat

37. B. Apocrine Sweat Glands
Hair follicle
Hair follicle
Sebaceous gland
Sebaceous
gland
In axillary, areolar & anal regions
Viscous secretion
Empty into hair follicles

38. C. Sebaceous Glands Holocrine gland Hair follicle Non-hair Activity
Sebum
Number & size
Locations
Absent
Acne

39. C. Sebaceous Glands

40. Skin & Appendages
V. Appendages

41. A. Hair Derived from epidermal epithelium Locations
Medulla, cortex, & cuticle
Root of hair, hair bulb, dermal papilla
Rate of growth
Hair color due to melanin

42. B. Nails Location Nail plate & nail bed Eponychium (cuticle)
Hyponychium
Growth

43. B. Nails