Dermatology

1. Dr. BIJAY KR YADAV

2. Introduction to skin:
 Largest organ of our body.
 It weighs an average of 4 kg
 Area- 2m2
 It acts as a barrier (external environment as well
as preventing loss of important body
constituents)

4. Structure of skin
 Composed of 3 layers: Epidermis, dermis
and subcutaneous tissue.
 Epidermis: Outer layer.
 Is a continually renewing structure
 gives rise to derivative structures called
appendages (pilosebaceous units, nails, and
sweat glands).
 The epidermis ranges in thickness from 0.4
to 1.5 mm.

5. Epidermis composed of 4 layers
• St. corneum
• St. granulosum
• St. spinosum/pickle cell layer
• St. basalis
 St lucidum( palms and soles)
Composed of 4 cell types- .
• Keratinocytes
• Melanocytes
• Langerhans cells
• Merkel cells

6. Stratum corneum
 Outermost layer
 The epidermis is stacked layers of anucleate,
flattened cornified cells
 It provides mechanical protection to the skin
and a barrier to water loss and permeation of
soluble substances from the environment

7. Stratum granulosum
• 1-2 cell layer thick
• Consists of keratihyaline granules
• consisting of profillagrin, keratin
filaments, loricrin
• These are the precursors of lipids of cell
envelop.

8. Stratum spinosum
 They are named for the spine-like
appearance of the cell margins.
 As these cells differentiate and move
upward through the epidermis, they
become progressively flatter and
develop organelles known as lamellar
granules.
 These secretory organelles deliver
precursors of stratum corneum lipids
into the intercellular space.

9.  Stratum germinativum/basalis –
 innermost layer in which cells undergo
mitosis continually.
 This allows for replacement of upper layers
that are sloughed and repair of damage.
 New cells move toward the surface and their
cytoplasm is replaced by keratin – a protein
that makes them tough and waterproof.
 30% of basal cells are actively dividing.

10. Keratinocytes/ squamous
cells
 Principal cells of the epidermis*(85%)
 Flattened dead cells
 Arranged like bricks and stuck together by
lipids
 Ectodermal in origin
 Special function is to produce keratin.

11. Melanocytes:
 They are pigment producing cells
 Derived from neural crest
 Are dendritic cells
 Reside in basal layer at 1:10 every basal
keratinocytes
 Contain melanosomes ( size and no
determine the color)

12. Langerhans cells
 Found scattered among keratinocytes in st.
spinosum
 Constitute 3-5% of cells
 Characterised by intracytoplasmic
organelle Langerhans/ Birbeck granules
 Responsible for delayed type
hypersensitivity( antigen presenting cells)

13. DERMAL-EPIDERMAL
JUNCTION
 The dermal-epidermal junction (DEJ) is a
basement membrane zone that forms the
interface between the epidermis and dermis.
 The major functions of the DEJ are to attach
the epidermis and dermis to each other and to
provide resistance against external shearing
forces

14. D-E junction……..
• Junction is formed by basement memb
zone.
• Ultrastructurally, composed of 4 components.
1. memb of basal cells with hemidesmosomes
2. lamina lucida
3. lamina densa
4. fibrous components ass with anchoring
fibrils, dermal microfibrills, collagen fibres.

16. Functions of skin
1.Protection- against chemicals, particles, uv rays, microbes
2. Homeostasis- prevents loss of water, electrolytes,
macromolecules
3. Shock absorber- by dermis & sc tissue.
4. Temperature regulation- bl.vs ,sweat glands.
5. Sensation- thru specialized nerve endings
6. Protection and prising- nails
7. Insulation and calorie reserve- sc fat
8. Vit D synthesis- keratinocytes
9. Body odour- apocrine sweat glands
10.Lubrication- sebaceous glands.

19. Sebaceous glands are holocrine in association with the hair
follicles and produced an oily secretion called sebum.
• The glands are present all over the body except the palm,
the soles, the eyelids and the fingertips.
• These are most numerous on the scalp, the face, the upper
middle portion of the chest and the back.
• The sebaceous glands are rudimentary at birth but start
functioning at the age of puberty under the influence of sex
hormones.
• Androgens increases the size of sebaceous glands, while
estrogens reduces the size of the sebaceous glands.

20. Primary Lesions
Macule: A circumscribed, flat, non palpable area of altered colour with
variable size and shape. It can be either hyper, hypo or depigmented like
café au lait macules in neurofibromatosis, tan brown in melasma.
Papule: A palpable small, solid, elevated lesion of <0.5 cm, with well
defined margins which projects above the surface of the surrounding skin
like the lesions of molluscum contagiosum, miliaria, acne, scabies etc.
Vesicle: It is a circumscribed, well defined, raised, fluid filled lesion, of size
<0.5 cm in diameter. It is found in diseases like chicken pox, herpes
simplex, herpes zoster, pemphigus etc.
Wheal: An erythematous, edematous, evanescent, well circumscribed,
raised, round to oval lesion which disappears within 24 hours. Wheal is a
primary lesion of urticaria.

21. Secondary Lesions
Scale: Scales are the flakes of lesion that are formed secondary to some
infammatory process. They are of various types like silvery scales as seen
in psoriasis, greasy yellow scales in seborrhoeic dermatitis, collarete scales
in pityriasis rosea, fish like scales in icthyosis .
Crust: Crust is formed due to any discharge like pus, serum or blood. It is
seen in eczematous dermatitis, impetigo, pemphigus and pemphigoid
group,etc
Excoriation: A superficial excavation of epidermis which may be linear or
punctate resulting from scratching. It is commonly seen in scabies, atopic
dermatitis, lichen planus,etc.
Lichenification: It is the thickening of epidermis with hyperpigmentation
and loss of skin marking in response to prolonged itching.
Ulcer: A skin defect where there has been loss of the epidermis and dermis

22. Macule:
Non-palpable change in skin color with distinct borders

23. Morphology

24. Macule:
Non-palpable change in skin color with distinct borders

25. Papule:
Palpable, solid lesion less than 0.5 cm in diameter

26. Papule:
Palpable, solid lesion less than 0.5 cm in diameter

27. Papule:
Palpable, solid lesion less than 0.5 cm in diameter
blue nevus

28. Vesicle: Fluid-containing, superficial, thin-walled
cavity less than 0.5 cm

29. Vesicle: Fluid-containing, superficial, thin-walled
cavity less than 0.5 cm

30. Vesicle: Fluid-containing, superficial, thin-walled
cavity less than 0.5 cm
varicella with vesicles and bullae

31. Ulcer: A skin defect where there has been loss of the
epidermis and dermis

32. Ulcer
 A focal loss of epidermis and dermis, and
heal with scarring
 Examples
 Decubitus
 Ischemic
 Stasis ulcers
 Neoplasms

33. Ulcer: A skin defect where there has been loss of the
epidermis and dermis
pyoderma gangrenosum

34. Crust
 Is a collection of dried serum and cellular
debris- a scab
 Examples
 Acute eczematious inflammation
 Atopic on the face
 Impetigo- golden or honey colored
 Tinea capitis

35. Morphology

36. CRUSTING
SCALING

37. Excoriation
 An erosion caused by scratching
 Are often linear
 Examples
 Scabies
 Atopic dermatitis
 Dry skin

38. Lichenification
 An area of thickened epidermis induced
by scratching
 Skin lines are accentuated so it looks like
a washboard
 Examples
 Atopic dermatitis, chronic eczematous
dermatitis

39. LICHENIFICATION

40. FISSURE ULCER

41. ATROPHY LICHENIFICATION

42. Thank you
Have a good day