Anatomy

Nail Anatomy

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Nail Anatomy, Fingernail, Toenail, Nail Growth, Hyponychium, Eponychium, Nail Cuticle, Toe Cuticle, Finger Cuticle

  • Anatomy
  1. Images
    1. DermNailAnatomy.jpg
    2. dermNailBaseGrayBB943.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  2. Cuticle
    1. Intersection between nail plate and overlying skin at proximal nail
  3. Germinal matrix
    1. Root of the nail
    2. Forms nail plate from base of nail bed
    3. Distal matrix produces deeper nail plate
      1. Disruption may cause deep nail ridges
    4. Proximal matrix produces superficial nail plate
      1. Disruption may cause superficial Nail Pitting
  4. Eponychium
    1. Skin just proximal to cuticle
    2. Dorsal fold at proximal surface of nail
    3. Binds nail to underlying skin at proximal margin
  5. Paronychial edge or Perionychium
    1. Lateral borders of nail
    2. Site of hangnails and Paronychia
  6. Hyponychium
    1. Area beneath free edge of nail
    2. Junction where nail bed meets tip of digit skin
  7. Nail Plate
    1. Hard and translucent
    2. Composed of dead keratin
    3. Surrounded by perionychium
  8. Nail Bed (Sterile Matrix)
    1. Adheres to underside nail with squamous epithelium
    2. Makes nail plate thicker and stronger
    3. Contains blood vessels and nerves
  • Physiology
  • General
  1. Nail is keratinized squamous cells
  2. Forms protective plate
    1. Prevents infection of underlying skin
  3. Enhances fingertip sensation
    1. Nail acts as counterforce to fingertip
    2. Two Point Discrimination decreased when nail absent
  4. Attachment of nail to skin
    1. Proximal: Eponychium
    2. Distal: Anterior ligament, distal nail fold
    3. Lateral: Lateral nail folds
  • Physiology
  • Nail Growth
  1. Normal Nail Growth
    1. Fingernails
      1. Grow 3 mm per month
      2. Require 6 months for complete re-growth
    2. Toenails
      1. Require 12-18 months to replace (2-3 times as long to re-grow as Fingernails)
  2. Arrested Nail Growth
    1. Caused by any systemic illness
    2. Results in deep transverse grooves (Beau's Lines)