6. Mitotic index
Is the fraction of basal cells that is in mitotic
phase at any time.
Labelling index
Fraction of basal cells in DNA synthesis
7. Turnover time of the germinative epithelium
Epidermal turnover time
( transit time= 14 days)
The time taken for a cell to pass from basal
layer to the surface of the skin
next 14 days
Subsequent desquamation
8. Normal vs psoriatic cell
cycle time
Labelling
Index( %)
S
phase
hr
G2
Phase
hr
M
Phase
hr
G1
Phase
hr
TOTAL
TIME
DURATI
ON(hr )
NORMAL
EPIDERMIS
5.2 8.5 6 - 8 1 146 163
PSORIATIC
EPIDERMIS
22.7 8.5 4 0.3 25 37.5
15. 4.Changes in expression of
Intracellular lipid
Membrane glycoproteins
Growth factor receptors
Adhesion protein
Blood group antigens
Desmosomes.
16.
17. KERATINOCYTES
Any one of the cells in the skin that
synthesize keratin.
Contains actin ,tubulin , intermediate
filaments.
Keratin is one of the 6 types of
intermediate filaments.
18. KERATIN (CYTOKERATINS)
54 functional keratin genes.
Two gene family :-
type 1(basic)
type 2(acidic)
Retinoic acid , growth factors ,hormones
regulate keratin gene expression.
22. DIFFERENTIATING EPIDERMAL
KERATINOCYTES
Basal layer as proliferative cells express K-5 and
K-14
The process of differentiation starts with the
K – 10/K-1 expression (in TA cells)
K-2 is expressed at later stages of
differentiation( granular layer)
24. BASIC
K
ACIDIC
K
TISSUE EXPRESSION DISEASE ASSOCITION
1 10 Suprabasal keratinocytes Bullous congenital icthyosiformis
erythroderma ;
Diffuse non epidermolytic PPK
1 9 Suprabasal keratinocytes
(palmo-plantar skin)
Epidermolytic PPK
2 10 Upper spinous , granular Icthyosiform bullosa of siemens
3 12 cornea Meesmann’s corneal dystrophy
4 13 Mucosal epithelium White sponge nevus
5 14 Basal keratinocytes Epidermolytic bullosa complex
6a 16 Outer root
sheath,hyperproliferative,
palmo-plantar
keratinocytes
Paronychia congenita type 1 ;
Focal non-epiderdermolytic PPK
6b 17 Nail bed ,epidermal
appendages
Paronychia congenita type II,
Steatocystoma multiplex
8 18 Simple epithelium Cryptogenic cirrhosis
25. Keratohyaline granules
Keratinocytes of stratum granulosum.
Disappear in cornified squames.
They contain granules rich in histidine .
Keratin filament are aggregate into bundles
by the action of the histidine rich basic
protein callled filaggrin.
26. Membrane – coating granules
Also called as lamellar granules or odland
bodies.
Found in spinosum and Granulosum layers
of skin.
Contains phospholipids, glycolipids and free
sterols.
Forming an important barrier to permeability.
27.
28. CORNIFIED ENVELOPE
Highly insoluble cell envelope.
Present in stratum corneum.
It’s development is triggered by intracellular calcium.
Involucrin is main envelope precursor.
Others include
1. Loricin 6. Envoplakin
2. Cornifine 7. Periplakin
3. Pancornulin 8. 61KDa protein
4. Elafin
5. Keratolini
29. Transglutaminases cross-link plakins and
involucrin.
Other desmosomal proteins are also cross-
linked ,forming a scaffold along the entire
inner surface of the plasma membrane.
High calcium level increases differentiation.
30.
31. PROTEIN DISEASE ASSOCIATION
CYSTATIN A Harlequin ichthyosis
PROFILAGGRIN
/FILAGGRIN
Ichthyosis vulgaris
Atopic dermatitis
LORICIN Mutilating keratoderma with ichthyosis;
Progressive symmetric erythroderma
35. DISTURBANCE IN EPIDERMAL DIFFERENTIATION
2. PARAKERATOSIS
Incomplete differentiation in post mitotic phase
Faulty and accelerated cornification
Retension of of pyknotic nuclei of epidermal cells
Leads to gap between cells
Loss of barrier function of the epidermis
37. Conditions associated with Parakeratosis
1. Psoriasis
2. Pellagra
3. Epidermolytic hyperkeratosis
4. Scurvy
Note – it can be normally found in hard palate
38. 3. DYSKERATOSIS
Morphologic presentaion of apoptosis of
keratinocytes
Eosinophilic cytoplasm ,pyknotic nucleus
Cells are packed with keratin filaments
Cell will tent to round up
Loose it’s attachment with surrounding cells
40. CANCERS OF THE EPIDERMIS
Squamous cell cancer
Irregular masses of epidermal cells.
Differentiation is in direction of keratinization
Horn pearls – concentric layers of squamous
cells with increasing keratinization at centre.
Keratohyaline granules are sparse or absent.
41. Basal cell cancer
Predominent basal cell type
Keratotic basal cell carcinoma
Parakeratotic cells
Horn cysts – fully keratinized cells, represent
attempt at hair shaft formation.
42. DRUGS ACTING ON EPIDERMAL CELL
Retinoic acids
Acts on retinoic acid receptors RAR and RXR
CRABP II – in human epidermis
Epidermal differentiation
Increased in –
1. Psoriasis
2. Lamellar ichtyosis
3. Darier’s disease
4. PRP
44. Vitamin D analogues(calcitriol,calcipotriol)
Acts on vit D receptors on keratinocytes
MOA-
Regulate keratinocyte proliferation.
Epidermal differentiation.
Formation of cornified membrane.
45. Tazarotene
Acts on retinoic acid receptors
Modulate abnormal epidermal differentiation
and proliferation.
Upregulation of K-10 terminal differentiation.