Dermatology Guide: Skin Anatomy & Pathologies

Introduction to Skin Anatomy

The skin, the body's largest organ, is a complex and dynamic barrier that protects us from the environment, regulates temperature, enables sensation, and contributes to overall health. Understanding its intricate anatomy is crucial for comprehending its various pathologies.

Anatomy of the Skin

The skin is composed of three primary layers, each with distinct structures and functions:

1. Epidermis (Outer Layer)

  • Stratum Basale: Deepest layer, contains basal cells, melanocytes, and Merkel cells.
  • Stratum Spinosum: Several layers thick, contains keratinocytes and Langerhans cells.
  • Stratum Granulosum: 2–5 layers with keratohyalin and lamellar granules.
  • Stratum Lucidum: Thin, clear layer in thick skin (palms/soles).
  • Stratum Corneum: 10–30 layers of dead keratinocytes forming a waterproof barrier.

2. Dermis (Middle Layer)

Contains collagen, elastin, blood vessels, nerve endings, hair follicles, sebaceous glands, sweat glands, lymphatics.

  • Papillary Layer: Loose connective tissue and dermal papillae.
  • Reticular Layer: Dense connective tissue for strength and elasticity.

3. Hypodermis (Subcutaneous Layer)

  • Adipose tissue for insulation and energy storage.
  • Loose connective tissue, large vessels, nerves.
  • Anchors skin to underlying structures.

Common Dermatological Conditions

Inflammatory Skin Conditions (Dermatitis/Eczema)

Inflammatory
  • Atopic Dermatitis: Chronic, itchy, dry skin in flexural areas, often linked to allergies.
  • Contact Dermatitis: Rash from irritants/allergens (e.g., poison ivy).
  • Seborrheic Dermatitis: Flaky, oily, red skin on scalp, face, chest.

Papulosquamous Diseases

Autoimmune
  • Psoriasis: Autoimmune plaques with silvery scales.
  • Lichen Planus: Itchy, purple papules on wrists, ankles, mouth.

Infections

Infectious
  • Bacterial: Impetigo, cellulitis, folliculitis.
  • Fungal: Ringworm, athlete's foot, candidiasis.
  • Viral: Herpes simplex, warts, shingles.

Acne Vulgaris

Inflammatory

Inflammation of sebaceous glands; includes comedones, papules, pustules, cysts. Caused by sebum, bacteria, and clogged pores.

Pigmentary Disorders

  • Vitiligo: Loss of pigment due to melanocyte destruction.
  • Melasma: Dark patches from sun and hormones (e.g., pregnancy).

Skin Cancers

Cancer
  • Basal Cell Carcinoma: Pearly bump, slow-growing.
  • Squamous Cell Carcinoma: Scaly nodule, risk of metastasis.
  • Melanoma: Dangerous, pigmented lesion following ABCDE rule:
A: Asymmetry
B: Border irregularity
C: Color variation
D: Diameter > 6 mm
E: Evolving features

Remember: Early detection saves lives! Regular skin checks are recommended, especially for those with risk factors