1. Anatomy and Physiology of the Skin

2. Structure of skin Epidermis
Basement membrane (dermoepidermal junction)
Dermis
Subcutaneous fat
Epidermis: Four layers (from outside – inside)
Cornified layer
Granular layer
Spinous layer
Basal layer
Dermis contains:
Collagen fibers
Elastic fibers
Ground substances
Blood vessels
Nerves.

3. Skin appendages:
Hair follicle
Sebaceous gland
Arrector pili muscle
Eccrine sweat gland
Apocrine sweat glands
Nail

4. Epidermis (thinner outer layer of skin)
Dermatology deals with disorders of skin, hair, nails, and mucous membranes.
Structure
Epidermis (thinner outer layer of skin)
Dermis (thicker connective tissue layer)
Hypodermis (subcutaneous layer)

5. Dermatological disorder = 10% -15% of primary care consultations
Skin is the largest organ in human body
Dermatological diseases can cause social and psychological problems, also it may affect ability to work (e.g. Chronic hand dermatitis.)
Skin is the gate of the body(might reflect systemic disease).

6. Physiology (function)
1- Protection
- physical barrier that protects underlying tissues from injury, UV light and bacterial invasion.
- mechanical barrier and immunity
2- Excretion
- sweat removes water and small amounts of salt, uric acid and ammonia from the body surface
3- Synthesis of Vitamin D

7. 4- Regulation of body temperature
- high temperature or strenuous exercise; sweat is evaporated from the skin surface to cool it down.
- vasodilation (increases blood flow) and vasoconstriction (decrease in blood flow) regulates body temp.
5-Sensation
- nerve endings and receptor cells that detect stimuli to temp., pain, pressure and touch.

8. Epidermis
Basement membrane (dermoepidermal junction)
Dermis
Subcutaneous fat

10. Stratum lucidum :
Found in thick skin of palms and soles above granular layer

11. Epidermis: Consist of several zones
Cornified layer (Stratum corneum )
Granular layer (Stratum granulosum)
Spinous layer (Stratum spinosum)
Basal layer (Stratum basale) 7

12. Basal layer
Rest on the basement
membrane they divide
continuously and move
upwards.
Melanocytes are dendritic
cells lying between basal
cells in a ratio of 1:10 .
Melanocytes synthesize
melanin stored in
melanosomes.

13. Basal Cell layer
Melanosomes are
transferred to adjacent cells
forming the Epidermal
Melanin unit.
Small, unmelanized,
clumped melanosomes are
found in white skin
Large melanized, dispersed
melanosomes in dark skin

15. The Spinous cell layer:
Usually layers thick .
Adhere to each other by
desmosomes (complex
modification of the cell
membrane ).
Desmosomes appear like spines.

16. Cytoplasm is filled with keratohyaline granules.
Granular Cell layer : Diamond
shaped cells.
Cytoplasm is filled with
keratohyaline granules.
In thin skin it is cell layers and 10 cell layers in thick skin like palms and soles.

17. Stratum Corneum layer:
The cells in this layer have no nucleous .
Cells have thick envelope
that resist chemicals.
Cells are held together by
desmosomes.
It is 25 cell layer .

18. Basement Membrane (BM)
Pink homogenous area between epidermis and dermis .
Consists of number of
proteins like BP antigens, collagen 4
The site of attack injury
in blistering diseases.

19. Skin Structure Components of BM
Lamina lucida: thin clear amorphous space
Lamina densa: an electron dense area containig type4 collagen
Anchoring fibrils : anchors epidermis to dermis ,type 7 collagen

20. Skin Structure Dermis is divided into Papillary dermis .
Reticular dermis
Consists of :
Collagen fibers Provides strength .
Elastic Fibers:
Provides elasticity,
protection against shearing
forces.

21. Skin Structure Ground substance : Binds water and maintains
the skin turgor.
Blood vessels:
To nourish the overlying
epidermis.

22. Skin Structure
The function of dermis:
It provides nourishment to the epidermis and interact with it during wound repair.
It gives the skin its strength elasticity, and softness.

23. Skin structure
Subcutaneous Fat:
Composed of lipocytes

24. Skin Structure Skin Appendages include: Eccrine/ apocrine sweat
glands.
Sebaceous glands.
Hair Follicles.
Nails

25. Skin appendages Eccrine sweat glands Tubular structures open
freely on the skin ;not
attached to hair follicles.
Under the influence of
cholinergic stimuli.

26. Skin appendages Eccrine sweat glands Present everywhere except
the vermilion border ; nail
beds ; labia minora ; glans
Abundant in palms ; soles.

27. Skin appendages Present in the axillae ; anogenital area modified
Apocrine glands:
Present in the axillae ;
anogenital area modified
glands in the external ear
canal the eye lids(moll’s
glands ) and areolae.

28. Attached to hair follicles; or open freely.
Sebaceous glands:
Attached to hair follicles; or open freely.
Present in the scalp ; forehead face upper chest except palms and soles.
Under the control of androgens.
Ectopic glands in the mucous
membrane are called fordyce spots.

29. Present in the areola as Motgomery’s tubercles ;in the
Sebaceous glands:.
Present in the areola as
Motgomery’s tubercles ;in the
eye lids as Meibomian glands.

30. Skin appendages Hair follicles: The hair follicle with it’s
attached sebaceous gland
form the Pilosebaceous
Unit.
Structure :
Infundibulum : Region between skin surface and sebaceous gland.

31. Skin Appendages Isthmus begin at sebaceous
glands and end at bulge (site of
insertion of arrector pilli
muscle)
Hair bulb envelopes the dermal papilla

32. Skin Appendages
Arrector pili is smooth muscle located in the dermis and is attached to the side of the hair shaft. - Cold and emotions will contract muscle and pull hair in vertical position.

33. Skin Appendages Hair shaft has: Cuticle Cortex contain pigment cells
Medulla found only in terminal hair

34. Skin appendages: Nails Anatomy
Nail plate made up of dead keratinized cells of matrix.
Nail bed is visible through nail plate.
Nail matrix lies above the midportion of distal phalanx

36. Skin appendages: The lunula is the visible part of the matrix
Proximal nail fold can be
altered in connective tissue
Fingernails grow 3 mm/m
Toenails grow 1 mm/m

37. Cornification (keratinization)
Occur in the cytoplasm of epidermal keratinocytes during their terminal differantiation into dead horny cell(corneocyte)

38. Cornification (keratinization)
The total process takes
approximately 2 months.
It involves the formation of keratin polypeptides.
Abnormalities in this process leads to roughness and scaling of the skin e g psoriasis.

39. Skin immune system
Langerhans cells interact with keratinocytes, which secrete a number of immunoregulating cytokines, and T-cells forming the skin immune system.

40. Thank You