Weatherly's Woes - Layers of Skin

Epidermis

Stratum Basalis - stem cells sitting on the basement membrane, secured with hemidesmosomes

Stratum Spinosum - nucleated cells with desmosomes, connected to each other by desmosomes

Stratum Granulosum - contain granules of keratohyalin, which eventually merge and forms filaments

Stratum Lucidum - clear, dead cells

Stratum Corneum - dead, and anuclear. They’re filled with keratin instead

Basement Membrane - proteins anchoring epidermis to the dermis

a. Basal Lamina - top layer. Contains laminin proteins and Type 4 collagen (Goodpasture’s)

b. Reticular Lamina - bottom layer

Dermis - full of connective tissues, nerves and blood vessels (no vessels in the epidermis)

Subcutaneous Fat - under the dermis, full of adipose tissue

Derm Pathology Terms

Hyperkeratosis - thick stratum corneum (too much keratin). Occurs in psoriasis and in calluses

Parakeratosis - nucleated cells in the stratum corneum. Indicates hyperproliferation! Usually seen alongside hyperkeratosis. Common in psoriasis.

Hypergranulosis - thick stratum granulosum. Classic in Lichen Planus

Spongiosis - Edema of epidermis. Seen in eczema

Acantholysis - Loss of connections (desmosomes) between Keratinocytes. Keratinocytes become rounded, detached and free-floating. Leads to blisters. Key feature of pemphigus vulgaris.

Acanthosis - epidermal hyperplasia. Stratum Spinosum thickens. Long “Rete Ridges” poke down into the dermis. Acanthosis Nigricans is a classic example (dark skin folds assc. w/ DM2 or CA (rare))

CELL JUNCTIONS

Tight Junctions - waterproof seal
Adherens Junctions - a continuous belt under the tight junction
Desmosomes - spot seals between Epi cells, especially in the stratum spinosum. Deficient in Pemphigus Vulgaris
Gap Junctions - hollow tubes, ions and water can pass through (eg, in the heart)
Hemidesmosomes - anchors Epithelium to the BM. Deficient in Bullous pemphigoid

Granulation Tissue is the raw, beefy, pinkish-colored skin that appears a few days after a skin wound appears. You're looking directly at the statum basale, stripped bare of the layers above it!