Understanding the Skin structure

One of the most important aspects of high Skin Care, is to understand the constituents of the skin itself, this learning helps to achieve better results in choosing the correct products for your specific problem or goal and also helps one to treat ones skin better with a more in-depth knowledge and greater understanding.

Structure of the Skin

Outer layers

(a) Epidermis - most superficial
(b) Dermis
(c) (Hypodermis/Subcutaneous Tissue)


Five layers

Stratum Germinativum (Basal Layer)
Stratum Spinosum (Prickly Layer)
Stratum Granulosum (Granular Layer)
Stratum Lucidum
Stratum Corneum (Horny Layer)

Stratum Germinativum (Basal Layer)

Innermost layer to the Dermis
Separated from the underlying Dermis by a basement membrane

Cuboidal shaped cells, with large nuclei & distinct cell content, particularly Ribosome's for Keratin production

Mitotic activity most evident in this layer, replacing cells in upper layers

Approx 14 days for cells to move through this layer

As the cells hit the upper part of this layer, they increase the amount of Keratin in them as Keratin granules

Melanocytes are scattered throughout this layer which synthesize the black pigment Melanin

Stratum Spinosum (Prickly Layer)

This second layer is sometimes considered to be part of the st. germinativum.

Polyhedral shaped cells held together by intercellular bridges (or prickles) but become flattened towards the top

Prominent nuclei and cytoplasmic basophilia indicate active protein synthesis

A fibrillar protein aggregates in these cells to form intracellular fibrils known as tonofibrils which converge upon the desmasomes of the prickles. These tonofibrils become more prominent toward the st. granulosum

Stratum Granulosum (Granular Layer)

Third layer

Contains melanocytes and basophilic granules which are thought to be the precursor to Keratin

Flattened and diamond shaped cells which are characterized by numerous, dense basophilic granules which crowd the cytoplasm and tend to obscure the tonofibrils

Stratum Lucidum

Questionable fourth layer which is often so thin that it is sometimes considered not to be a transitional layer between the st. granulosum and the st. Corneum

It is so thin that there is debate currently that the layer is an artefact of the electron microscope and doesn’t in fact exist

Supposedly most pronounced in the palms of the hands and the soles of the feet

Cells show signs of disintegration and have lost their nuclei and organelles

Stratum Corneum (Horny Layer)

Final layer or the Horny layer

Cells are non-nucleated disintegrated, fused, flattened squamous cells which are filled with Keratin fibres (matured Keratin)

Little water

Forms the protective barrier for the skin

As the junctions become interrupted, the cells are desquamated


Contains two layers

Papillary Layer which is closest to the Epidermis

Reticular Layer

Papillary Layer

Consists of loose connective tissue with fine Collagen and Elastin fibres

Folded into ridges or papillae which extend in to the Epidermis

Especially noticeable in the palms and soles (fingerprints)

Contains nerve fibres and blood vessels which extend into the folds, supplying the Epidermis which is avascular

Rete pegs (?)

Reticular Layer

No defined boundary between the two layers

Contains denser connective tissue and many thick Collagen fibres


Technically not part of the skin

Composed of loose connective tissue and contain lots of Adipose Tissue for metabolism, insulation,


description - colour, shape, number, size, grouping

abscess - a localized collection of pus formed by necrosis of tissue

atrophy - loss of Epidermis, Dermis or both. Atrophic skin is thin, translucent and wrinkled with easily visible blood vessels

cellulitis - a purulent inflammation of the skin and subcutaneous tissue

crust - dried exudate (normally sebum, blood or pus) on the skin surface

ecchymosis - a macular red or purple haemorrhage, more than 2mm in diameter, in the skin or mucous membrane

erythema- redness of the skin due to vascular dilation

excoriation - a superficial abrasion, often linear, which is due to scratching

fissure - a linear split in the Epidermis, often just extending into the Dermis

folliculitis - an inflammation of the hair follicles

furuncle - a pyogenic infection localised in a hair follicle

keloid - an elevated and progressive scar not showing regression

lichenification - chronic thickening of skin with increased skin markings, result of rubbing/scratching

petechia - a haemorrhagic punctate spot measuring 1-2 mm in diameter

purpura - extravasation of blood resulting in red discolouration of the skin or mucous membranes

telangiectasia - dilated dermal blood vessels giving rise to a visible lesion

Immunology of Skin


Epidermal barrier - innate immunity, protective barrier


Langerhans cell

Outermost immune cell

Important role in antigen presentation

T lymphocyte

Circulate through normal skin

Different types are present

Mast cell

Normal residents of the Dermis

Part of the inflammatory reaction


Have an immunological function

Can produce pro-inflammatory Citokines

Can express immune reactive molecules & intercellular adhesion molecules

Functional Systems

Skin-associated Lymphoid Tissue

Skin has a regulatory immunological function

Blood, Lymphatic drainage, circulating Lymphocytes & resident immune cells

Cytokines & eicosanoids

Mediate inflammatory response as well as action between cells


Activation of a complement cascade of events in the inflammatory response eg. Lysis & Chemotaxis for Neutrophils & Macrophages

Adhesion molecules

Help bind T cells & increase cell trafficking to the area


Tissue type Antigens of an individual

These Antigens are found in the major histocompatibility complex (MRC)

MRC located on the HLA gene cluster on chromosome 6

Vital for immunological recognition

eg. Psoriasis is associated with the B13 HLA Antigen

Hypersensitivity reactions and the Skin

Inappropriate or exaggerated response where tissue damage results

4 types

Type I (immediate)

Type II (antibody-dependent cytotoxicity)

Type III (immune complex disease)

Type IV (cell mediated or delayed)

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