Skin Structure and Function

• Normal human skin consists of two sections: the epidermis and the dermis.

Epidermis

• The layers of the epidermis include the stratum corneum, stratum granulosum, and the basal layer.

Dermis

• The dermis contains the dermal papilla.

Functions of Skin

• Protection from environmental factors such as chemical, thermal, physical, and UV injury.
• Thermoregulation is achieved through blood shunting and hair follicles.
• Neuroreceptors in the skin respond to external stimuli.
• Skin plays a role in antigen processing for immunization.
• Skin contributes to the synthesis of vitamin D.
• Cosmetic appearance, such as the absence of bruises, is a function of the skin.

Monomorphic vs Polymorphic Skin

• Monomorphic skin conditions present with lesions of the same type.
• Polymorphic skin conditions feature lesions of different types.

Macule and Patch

• Macules and patches are flat, non-palpable lesions visible as circumscribed areas on the skin.
• A macule is a flat lesion less than 1cm in size.
• A patch is a flat lesion larger than 1cm.

Plaque

• A plaque is a slightly raised, flat-topped lesion with a diameter greater than 1cm.
• Chronic plaque psoriasis is an example of a condition presenting with plaques.

Papule

• A papule is a circumscribed, palpable elevation smaller than 1cm.
• Lichen planus is associated with flat-topped papules.

Nodule

• A nodule is a palpable, brown elevation that may be eroded on the surface.
• Nodular malignant melanoma is an example of a disease presenting with nodules.

Vesicle

• A vesicle is a blister less than 0.5cm in diameter.
• Pompholyx eczema on the palm manifests with vesicles.

Bulla

• A bulla is a blister greater than 0.5cm in diameter.
• Angine bullosa haemorrhagica presents with blood blisters in the oral cavity.

Scaling

• Scaling involves the peeling of the stratum corneum.
• Eczema can result in scaling due to skin dehydration.

Lichenification vs Excoriation

• Lichenification is the thickening of the skin, often seen in areas like the popliteal fossa, due to scratching.
• Excoriation is a shallow breach in the skin surface caused by scratching, often with hemorrhagic crusting.
• Both lichenification and excoriation can occur in atopic eczema.

Ulcer

• An ulcer is characterized by full-thickness loss of the epidermis.
• Ulcerated nodular basal cell carcinoma is an example of a condition presenting with ulcers.

Scar

• A scar represents a permanent change in skin surface or texture.
• Lichen planus in the scalp, known as lichen planopilaris, can result in scarring.

Topical Tests for Diagnosis

• Skin swabs or scrapings are taken to confirm bacteriology, virology, and mycology.
• Skin biopsies are performed to confirm histology, culture, or immunofluorescence.
• Patch tests are used to confirm contact allergies.
• Photo-tests are conducted to confirm sensitivity to UV light.

Blood Tests for Ill Patients

• Haematology tests, including FBC (full blood count) and ESR (erythrocyte sedimentation rate).
• Biochemistry tests: U+E (urea and electrolytes), LFT (liver function test), glucose, and CRP (C-reactive protein).
• Immunology tests: ANA (antinuclear antibody), DNA antibodies, and organ-specific antibodies.
• Virology tests: Herpes simplex serology.

Topical Agents to Manage Infection

• Antibacterial agents.
• Candida corticosteroids creams.
• Mouthwash.

Systemic Agents to Manage Infection

• Prednisolone, possibly with steroid-sparing agents.
• Antibiotics.

Common Skin Complaints

• Eczema
• Psoriasis
• Lichen planus
• Pruritus (itching)
• Skin infections

Eczema

• Eczema is a pruritic inflammatory condition characterized by dryness and erythema of the skin.
• Scratching of eczema can lead to lichenification and excoriation.

This material covers the structure and function of human skin, including the epidermis and dermis layers. It also discusses skin functions such as protection, thermoregulation and sensation. Finally, monomorphic and polymorphic skin conditions, macules, and patches are also touched upon.