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