The document summarizes the structure and function of human skin. It describes the three layers of skin - epidermis, dermis and hypodermis. The epidermis contains keratinocytes, melanocytes and other cells. The dermis contains collagen, elastic fibers and blood vessels. Photoaging is caused by UV radiation damage from the sun and leads to wrinkles, pigment changes and loss of collagen over time. Prevention involves limiting sun exposure, wearing sunscreen and protective clothing.

5. Skin
 Largest organ completely covering the body continuous with
membranes lining body orifices.
 Average thickness:1-2mm, 0.5mm on eyelids & 6mm on
palms & soles.
 pH-4 to 5.6
 Renewal of skin takes place in 28-50 days by shedding of
outer layer.

6. Layers of skin
Epidermis:
Stratified squamous
epithelium; outer layer is
"keratinized" or
"cornified"
Dermis:
Dense irregular
connective tissue
Hypodermis:
Adipose connective
tissue

7. Epidermis
Epidermis:
Avascular layer that depends on
blood vessels in underlying
dermis for its nutrition.
Cells formed by mitosis in deepest,
or basal, layer, then get pushed
into more superficial layers or
"stata"

8. Epidermis
Stratum Corneum: 15 -20 layers of
dead cells mechanical protection
and water proof. Thickening of
corneal layer – Ichthyoses
Stratum Lucidum: flat epithelial
cells, homogenous translucent
appearance
Stratum Granulosum: 2-5 layers of
flattened rhomboid cells

9. Epidermis
Stratum Spinosum: spinous or
prickle-cell layer
Stratum basale: Usually one cell
thick, 2-3 cell thick in glabrous skin
and hyperproliferative epidermis

10. Epidermis
Keratinocytes Primary cell type
in epidermis which produce large
amounts of protein keratin
Melanocytes produce pigment
melanin & transfer it to
keratinocytes
Langerhans cells (really
macrophages) clean up debris
Merkel cells detect touch and
pressure; transfer this information
to sensory receptors in the dermis

11. Dermis
Dense irregular connective tissue.
Separated from epidermis by
basement membrane
Highly vascular, Highly
innervated
Contains many types of sensory
receptors for
touch, pressure, vibration, pain,
temperature, etc.

12. Dermis
Cells
Fibroblasts
(Fibrocytes), Macrophages, Mast
cells, Lymphocytes
Fibers
Collagen: Strong, Flexible
Elastic: Stretchable
Tears in collagen fibers
producing striae
(Stretch marks)

13. Functions of Skin
● Protection against physical damages and abrasion, infections, UV
and other radiations, oozing body fluid and solutes in.
● Sensory Perception (touch, temperature, pressure, pain, etc.)
● Vitamin D Synthesis
● Temperature regulation
● Excretion (lactic acid, sodium chloride, urea)
● Blood reservoir

14. Intrinsic Aging
 Chronological aging
 Hormonal aging
Decreased estrogens during menopause
contribute to collagen loss in women

15. Extrinsic Aging
 Photodamage - 80%
 Smoking
 Stress
 Poor nutrition
 Pollution
 Excess alcohol

16. Photoaging
● Sun-induced skin aging
● Dermatoheliosis
 ―Photoaging‖ term is described in 1986
by Kligman

17. Definition of Photoaging
Photoageing is due to (oxidative) damage
caused by short wavelength ultraviolet
radiation (UVB) injury to the outside layers
of the skin (epidermis), longer wavelength
ultraviolet radiation (UVA) to the middle
layers (dermis) and infra-red A radiation to
the deeper dermis and subcutaneous tissue.

18. Solar Radiation
 Acute exposure
 Immediate




Vitamin D synthesis
Immediate darkening reaction
Antidepressant action
Immunosuppressive action
 Delayed



Sunburn reaction
Delayed pigmentation
Hyperplastic reaction
 Chronic exposure
 Photoaging (dermatoheliosis)
 Photocarcinogenesis

19. Ultraviolet Radiation (UVR)
ELECTROMAGNETIC RADIATION

20. Ultraviolet Radiation (UVR)
 UV :wavelength range 100–400 nm
• UVC (100–280 nm)
• UVB (280–315 nm)
• UVA (315–400 nm)

21. Health Effects of UV Radiation
 SKIN
 SUNBURN, SUNTAN AND SKIN AGEING
 NON-MELANOMA SKIN CANCERS (basal cell carcinoma and
squamous cell carcinoma)
 MALIGNANT MELANOMA
 EYE
 Photokeratitis and Photoconjunctivitis
 Cataracts (UVB)
 IMMUNE SYSTEM
 Immunosuppressive effect
 Higher risk of infection (viral, bacterial, parasitic or fungal)

22. Ultraviolet Radiation (UVR)
Photobiological effects of UV
UVA: Causes skin aging & wrinkles. Used in tanning beds.
UVB: Causes sunburns, cataracts, immune system
damage, skin cancers.
UVC: These rays are the most dangerous. Fortunately, these
rays are blocked by the ozone layer and don’t reach the
earth.

23. Ultraviolet Radiation (UVR)
UV RADIATION LEVELS ARE INFLUENCED BY:
• SUN ELEVATION (Time of Day, Time of Year)
• LATITUDE
• CLOUD COVER
• ALTITUDE
• OZONE
• GROUND REFLECTION

24. Clinical Signs of Photoaging
 Texture changes
 dryness, enlarged pores, wrinkles (deep and coarse)
 pigment changes (dark/light), sun spots, freckles, melasma,
sallowness (elastosis/heliosis), atrophy, Leathery appearance, solar
comedones, colloid milia.
 Vascular changes
 spider veins, red spots, rosacea, purpura
 Degenerative changes
 Benign- seborrheic keratosis, skin tags, moles
 Precancerous- actinic keratosis
 Cancerous- melanoma, basal cell, squamous cell

25. Clinical Signs of Photoaging
Wrinkles
Elastosis
Telangiectases
Purpura
Solar comedones
Colloid milia

26. Facts About Photoaging
 20 minutes of sun exposure is enough to cause
damage to the skin.
 Sunburn and sun-tanning causes wrinkles
skin.
 Number one risk factor for all skin cancers is
SUN EXPOSURE! (one blistering sunburn
doubles the risk of skin cancer)

27. Histologic Changes in Photoaging
● Thickened stratum corneum
● Thin atrophic epidermis with cellular atypia
● Irregular dispersion of melanin
● Loss of dermal glosaminoglycans and collagen
● Loss of normal dermal vasculature
● Elastosis (abnormal elastic fibres in dermis)

28. Mechanisms Photoaging of Skin
 Collagen
 Main building blocks of human skin (skin’s strength)
 Deraml fibroblasts make procollagen
 Two important regulators of collagen
 Transforming growth factor (TGF)-β
(A cytokine that promotes collagen production)
 Activator protein (AP)-1
(a transcription factor that inhibits collagen production and up-regulates
collagen breakdown)
 TGF-β promotes collagen formation, while AP-1 promotes collagen
breakdown by upregulating enzymes called matrix metalloproteinases
(MMPs).

29. Mechanisms Photoaging of Skin
 Reactive oxygen species (ROS):
harmful compounds by UV
exposure of skin
 “Oxidative Damage” to cellular
cell walls, lipid
membranes, mitochondria, an
d DNA.

30. Chronological Aging
 Fine wrinkles
 Laxity
 Benign neoplasms
 Thin skin
 Mild dryness

31. Prevention
 Limit exposure during midday hours.
 Seek shade.
 Wear protective clothing.
 Wear a broad-brimmed hat to protect the eyes, face and neck.
 Protect the eyes with wrap-around design sunglasses or
sunglasses with side panels.
 Avoid tanning beds.
 Use and reapply broad-spectrum sunscreen of sun protection
factor (SPF)15+

32. Sunscreens
CLASSIFICATIONS
Physical: Scatters or reflects UV radiation due to large particle size
titanium dioxide
talc, kaolin
zinc oxide
ferric chloride
icthyol, red petrolatum
Chemical: absorbs UV radiation
PABA, PABA esters
benzophenones
cinnamates
salicylates
digalloyl trioleate
anthranilates

33. Sunscreens

Sun Protection Factor (SPF) =
MED of Protected Skin (Sunscreen)
MED of Unprotected Skin


MED is minimum dose of radiation which produces erythema
SPFs are determined indoors using xenon lamps which
approximate the spectral quality of UV radiation

34. Sunscreens
 SPF 15 blocks 93%, SPF 30 blocks 97% for 2 hours
 Suggestions to improve sunscreen effectiveness:
 Apply sunscreen 20 minutes before you go outdoors
 Use about 1 ounce (enough to fill a shot glass) to cover the entire body.
Cover all exposed areas liberally. Pay special attention to
face, ears, nose, arms and legs. Remember that lips can burn, too, so
cover lips with a lip balm sunscreen or SPF 30 or higher
 Reapply approximately every 2 hours, or after swimming or heavy
sweating (reapplying does not increase the SPF—it just keeps the SPF at
its maximum level)

35. Sunscreens
Criteria for Selecting a Sunscreen to Prevent Photoaging
 SPF of 30 or higher
 Broad-spectrum, providing both UVA and UVB protection
 Does not cause skin irritation
 Does not worsen an existing skin condition

36. Teatment for Photoaging
 Diet high in fruits and vegetables
 Adequate oral hydration ( 64 oz + daily)
 Good daily skin care regimen
 No Smoking
 Rejuvenation procedures
 Protection/Prevention

37. Teatment for Photoaging
 Alpha Hydroxy Acids (AHA)
 Glycolic Acid
 Retinoids (Stimulates collagen production, Decreases cell damage
from sun exposure, Increases skin cell turnover)
• Tretinoin (Retin-A, Renova)
• Terazatane (Tazorac)
• Differin (Adapalene)
 5-Fluorouracil
 Imiquimod

38. Teatment for Photoaging
Rejuvenation Procedures
 Botulinum Toxins (Botox, Myobloc, Reloxin)
 Dermal Fillers (Collagen, Hyaluronic
Acid, Radiesse, Sculptra, Hylaform, Captiqu, Cos
moplast, Juvederm)
 Laser & Light treatments