Summary Dermatology physiology and pathology

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Skin physiology

Contains three layers:

1. Epidermis: keratinocytes (squamous epithelial cells)

2. Dermis: connective tissue, vessels

3. subcutaneous fat

Stratum Basalis:

contains stem cells that can
regenerate keratinocytes

Stratum Spinosum:

This contains cells with spines, the
spines are formed by desmosomes.
Desmosomes are connections
between keratinocytes.

Stratum Granulosum:

Cells contains keratohyalin granules,
which are used to form keratin
filaments.

Stratum Lucidum:

Clear layer of dead skin cells

Stratum Corneum:

Anucleated cells

Cells are filled with keratin filaments.
(tough outer layer of skin)



Skin physiology 1

, Dermis:

Contains blood vessels (unlike
epidermis)

Connective tissue




Skin lesions:
Primary lesions:

Directly caused by disease

Macules, papules, vesicles and bulla

Secondary lesions:

modification of primary lesion, or
caused by trauma/external factor

Scale, crust, erosion, fissure and
ulcer



Primary skin lesions:
Macules and Patches:

Flat lesions (not raised)

Macule < 1cm

Patch > 1cm



Papules and Plaques:

Raised lesions

Papule < 1cm

Plaques >1cm



Skin physiology 2

, Maculopapular rash:

Collection of macules (flat) and
papules (raised) lesions

Sometimes described as Morbilliform
(looks like measles)

Common in:

Drug rash

Scarlett fever

Measles

Syphilis

Rubella



Vesicles and Bulla:

Fluid filled lesions (blisters)

Vesicle < 1cm (chicken pox)

Bulla > 1cm (bullous pemphigoid)



Pustule:

Pus filled vesicle

Normally contains a white centre




Secondary skin lesion:
Scale:

Secondary lesion




Skin physiology 3