KC

Skin, Hair, Nails – Comprehensive Notes

Epidermis, Dermis, Hypodermis

  • Skin has 3 main layers: Epidermis (avascular), Dermis (vascularized), Hypodermis (subcutaneous tissue)
  • Skin contains appendages and structures:
    • Hair follicles, hair shaft, hair root
    • Sweat glands: Eccrine (thermoregulation) and Apocrine (axilla, genital area; function less clear)
    • Sebaceous (oil) glands
    • Arrector pili muscle
  • Dermal papillae and cutaneous vascular plexus are in the dermis
  • Subcutaneous tissue houses adipose tissue and larger vasculature; provides insulation and energy reserve
  • Skin color is determined by: melanin amount, vascular structures/hemodynamics, carotene, and bilirubin levels
  • Nervous structures include sensory nerve fibers and specialized receptors (e.g., Lamellar corpuscle, hair follicle receptor)
  • Layers summary (from outer to inner): Epidermis → Dermis → Hypodermis

Skin Color and Circulation Changes

  • Cyanosis: decreased oxygen in the blood or decreased blood flow
  • Pallor: anemia
  • Jaundice: increased bilirubin

Hair Types

  • Vellus hair: short, fine, inconspicuous, unpigmented
  • Terminal hair: coarse, thick, pigmented

Nail Anatomy and Clubbing

  • Nail plate, nail bed, lunula, proximal nail fold, cuticle, hyponychium, free edge, matrix
  • Normal angle between nail fold and nail plate is < 180°
  • Clubbing: angle > 180°

Glands and Skin Secretions

  • Pilosebaceous glands: oil glands that secrete sebum onto skin surface; palms and soles lack them; lubricate and protect skin
  • Sweat glands (two types):
    • Eccrine: regulate body temperature via sweating
    • Apocrine: located in axilla and genitalia; function related to odor and other mechanisms (not fully specified in transcript)

Skin Symptoms a Patient Might Have

  • Pruritus (itch)
  • Rash
  • Pain
  • Lesions
  • Altered skin sensation or appearance such as hair changes
  • Hair loss or excessive hair growth
  • Nail changes

Primary Skin Lesions (described on Slides)

  • Macule: circumscribed flat area < 1\ \mathrm{cm}
  • Patch: circumscribed flat area > 1\ \mathrm{cm}
  • Papule: solid elevated area < 1\ \mathrm{cm}
  • Plaque: large elevation; papules coalescing can form plaques
  • Nodule: solid elevation > 1\ \mathrm{cm} extending into deeper skin layers
  • Pustule: small circumscribed elevation filled with purulent fluid
  • Vesicle: small circumscribed elevation containing clear fluid, < 1\ \mathrm{cm}
  • Bulla: circumscribed elevation containing clear fluid > 1\ \mathrm{cm}
  • Wheal: circumscribed raised lesion due to dermal edema

Secondary Skin Lesions

  • Erosion: loss of epidermis
  • Ulcers: deeper loss of epidermis

Vascular/Hemorrhagic Lesions

  • Petechia: non-blanchable hemorrhage
  • Purpura: non-blanchable raised and palpable hemorrhage
  • Ecchymosis: non-blanchable large hemorrhage

Describing a Lesion: Size, Distribution, Configuration, Texture, Color

  • Size: Measure with a ruler; use metric system; typical reference sizes include < 1\ \mathrm{cm} for macules
  • Distribution: how lesions are scattered or spread; note if any body parts are involved (palms, soles, face, scalp)
  • Pattern/Configuration: random, patterned (varicella, zoster), symmetric vs asymmetric
  • Configuration terms: linear, annular, discoid, target/bull’s eye, serpiginous, grouped, etc.
  • Texture: smooth, fleshy, scaly, greasy, hard; examples like Auspitz sign (psoriasis) show pinpoint bleeding on scale scraping
  • Color: erythematous, purple, skin-colored; note blanching on pressure
  • Documentation example structure (from slide):
    • 1. Number
    • 2. Size: 2\times 5\ \mathrm{cm}
    • 3. Color: tan to dark brown
    • 4. Shape: oval
    • 5. Texture: verrucous (rough, irregular)
    • 6. Primary Lesion: plaques (large, raised lesion)
    • 7. Location: abdomen
    • 8. Configuration: confluent (lesions connected)

How to Measure and Document Lesions

  • Use a ruler and the metric system
  • If ruler is unavailable, estimate with a 4x4 gauze pad as measurement
  • Note distribution across body regions (e.g., sun-exposed areas) for differential considerations

Skin Cancer Screening (ABCDE and beyond)

  • ABCDEFG principle mentioned for screening: Asymmetry, Border, Color, Diameter, Elevation, Evolution (and sometimes F/G extensions as per slides)
  • Key screening concept: monitor any lesion for irregularities and changing characteristics over time

7 Questions of History (Chapter 10 review notes)

  • Listed questions (from slide):
    • 1) Duration
    • 2) Evolution
    • 3) Periodicity
    • 4) Social history
  • Other items are not shown in transcript; note that the slide indicates a 7-question framework but only the first four are explicitly provided

Patient Examination Techniques and Positioning

  • Positioning for skin exam:
    • Sitting to examine head, neck, upper body, arms, chest, abdomen, legs
    • Standing to examine lower back, posterior thighs and legs, breast, axillae, and genitalia
    • If patient is bed-bound or immobile, examine in supine head-to-toe and prone in the same manner

Possible Differential Diagnoses (skin symptoms)

  • Pruritus without rash: consider dry skin, pregnancy, uremia
  • Jaundice: consider liver disease
  • Lymphoma and leukemia as potential systemic explanations for skin findings

Hair Loss: Common Causes

  • Most common diffuse hair loss: male pattern baldness (frontal hairline recession and posterior vertex)
  • Female pattern baldness: typically starts at the crown
  • Other causes:
    • Alopecia: sudden hair loss in localized patches, smooth skin
    • Tinea capitis (ringworm): round hair loss with scaly skin and broken hairs
    • Scarring alopecia: complete loss of hair follicles with itching, redness, pustules

Other Skin Findings and Conditions

  • Keloids, Lipomas, Warts (HPV)
  • Vascular lesions: Spider angioma, Spider vein, Cherry angioma
  • Precancerous and skin cancers: Actinic keratosis, Seborrheic keratosis, Squamous cell carcinoma, Basal cell carcinoma, Melanoma

Nail Findings Overview

  • Onychomycosis
  • Habit-tic deformity
  • Paronychia
  • Clubbing (seen in COPD)
  • Melanonychia
  • Onycholysis
  • Terry’s nails (cirrhosis)
  • Pitting
  • Beau lines

Detailed Nail Findings (additional notes)

  • Nail plate, nail bed, lunula, proximal nail fold, cuticle, hyponychium are key landmarks
  • The nail angle relationship is clinically important for detecting clubbing

Final Recap: Chapter 10 Focus Points

  • Remember the three skin layers: Epidermis, Dermis, Hypodermis
  • Know the core primary lesion definitions and their distinguishing features
  • Be able to describe lesions using Size, Distribution, Configuration, Texture, and Color
  • Be familiar with common skin, hair, and nail findings and their clinical significance
  • Be prepared to discuss differential diagnoses for pruritus, jaundice, hair loss, and nail changes
  • Review typical exam techniques: patient positioning, full-body skin examination approach, and documentation conventions