Lecture Notes: Structure of Nails

Overview

• Nails are similar to hair in formation but are scale-like modifications of the epidermis, unlike the tubular structure of hair.
• Both nails and hair are composed of hard keratin.

Function

• Nails provide a protective cover for the distal dorsal surfaces of fingers and toes (phalanges).

Structure of Nails

• Components
  • Free Edge
  • Nail Plate
  • Root: Embedded within the dermis.
• Nail Bed: Extension of the epidermis under the keratinized nail plate.
• Nail Matrix: Thickened portion of the bed responsible for nail growth, similar to the hair matrix.

Nail Anatomy

• Nail Fold: Skin fold that overlaps the border of the nail, known as the cuticle.
  • Epinychium: Part of the cuticle projecting onto the surface of the nail body.
• Nail Color
  • Typically appears pink due to underlying capillaries.
  • Lunula: Whitish, thickened nail matrix on the proximal end of the nail.

Health Indicators

• Abnormal nail color and shape can indicate cardiovascular disease.
• Nail health reflects overall health; abnormalities may suggest hormonal disturbances or nutritional deficiencies.

Visual Description

• Image shows the distal end of a finger or phalanx with various nail parts:
  • Free edge, body, matrix, root, lateral nail fold, epinychium (cuticle), and lunula.
• Cross-section depicts the nail bed, superficial to the bone, subcutaneous tissue, and stratified squamous epithelium.

Growth Process

• Root traces back to the matrix as the site of new nail growth.
• Cells divide in the matrix, incorporating dead keratinocytes full of hard keratin into the growing nail, pushing it outward distally.