This document provides an overview of the structure and anatomy of the nail unit. It describes the key components of the nail including the nail plate, nail matrix, nail bed, eponychium, hyponychium, nail folds, and nail isthmus. It discusses the development, blood and nerve supply, growth, and functions of the nail. Finally, it outlines common nail signs that can be seen in health and disease such as Beau's lines, onychorrhexis, nail pitting, clubbing, and melanonychia.

1. STRUCTURE
OF NAIL
DR. NISHKARSH CHUGH
PGJR1 DERMATOLOGY

2. Introduction
An appendage of the skin better known as the Nail Unit
A translucent, protective plate that protects the tips of the fingers
and toes
Onyx is the technical term for nail
Onychology is the study of nail

3. Development of Nail
9 weeks
• First embryonic rudiment of the nail unit becomes evident,
known as the nail anlage
10 weeks
• Primary nail field becomes evident as a distinct region
13 weeks
• Proximal and lateral nail folds differentiate due to a
differential growth of the primary nail field and its adjacent
tissues
14 weeks
• The nail plate is formed, and emerges from beneath the
proximal nail plate

4. Anatomy

5. 1. Nail Plate
It is the visible part of the nail and its free edge extends beyond the distal end of the digits
The nail plate is formed by keratinisation of the nail matrix cells which loose their nuclei and get progressively
elongated and compacted with minor contribution from the nail bed
The nail plate is a fully keratinized structure consisting of:
1. Onychocytes
2. Hard Keratins
3. Phosphate
4. Calcium
It comprises three horizontal layers:
1. A thin dorsal lamina
2. The thicker intermediate lamina
3. A ventral layer from the nail bed

6. Chemical Properties of the Nail Plate
The nail plate, like hair, consists mainly of fibrillary low-sulfur protein, globular
high-sulfur matrix protein and high-glycine/tyrosine rich matrix protein.
The nail matrix, and hence the nail plate, express hard keratins.
The nail bed, nail matrix and nail plate expresses epithelial/ soft keratins.
However, these areas do not express the keratins 1 and 10 like the suprabasal
epidermis.
The flexibility of nail plate is related to its water content.

7. 2. Nail Matrix
Germinative epithelium of the nail unit, located above mid distal phalanx.
The nail matrix has 2 portions:
1. Proximal Matrix
2. Distal Matrix
It has the following cells:
1. Melanocytes
2. Langerhans Cells
3. Merkel Cells
4. No Granular Layer

8. 3. Nail Bed
The nail bed consists of the dermis and the soft tissue that lie
beneath the nail plate.
The epithelium is thin and consists of two to five cell layers.
The nail bed also has a minor contribution to the nail plate
formation.
Its keratinization is also not associated with a granular layer.

9. 4. Eponychium
It is also known as the cuticle
A strip of cornified epithelium that acts as a seal.
It emerges from the proximal nail fold and
subsequently adheres to the superficial surface of
the proximal nail plate.

10. 5. Hyponychium
Keratotic natural barrier at the physiological point of
separation of the nail plate from the underlying distal nail
fold
It seals the free edge, preventing external moisture,
bacteria, or fungi from getting under the nail

11. 6. Nail Folds
They ensheathe and hold the nail plate in
place.
1. Proximal Nail Fold
2. Distal Nail Fold
3. 2 Lateral Nail Folds

12. 7. Nail Isthmus
In the distal part of the nail, a transverse band is seen which is
more pink (or brown) than the rest of the nail-bed. This is called the
onychodermal band.
Proximal to this pink band is a transverse white zone, namely the
onychocorneal junction which represents the most distal point of
attachment between the nail bed and the nail plate.
The onychocorneal junction, in histology, corresponds to a
transitional zone between the nail bed and the hyponychium called
the nail isthmus

14. Blood and Nerve Supply
The nail apparatus has an abundant blood supply
provided by the lateral digital arteries.
The nail-fold capillary network can be visualized using a
dermoscope over the proximal nail fold. The morphology
of these capillary loops are important in conditions such
as scleroderma and dermatomyositis
The nerve supply is through sensorimotor nerves which
run parallel to the digital vessels. The origin of the nerve
supply is from the dorsal branches of paired digital
nerves.

15. Nail Growth
Growth of nail plate is a continuous process that happens throughout
life, with the newly formed plate moving distally.
This continuous distal movement is aided by two factors— proximal
proliferation and differentiation of nail matrix keratinocytes and the nail
epithelium which drags the nail plate forward like a conveyor belt.
 The mean growth rate of the nail plate is 1.5 mm per month for toenails
and 3.5 mm per month for fingernails.
The total regeneration time for a fingernail is around 6 months and 12–
18 months for toenails.

16. Functions of Nail
1. Aesthetics of the hand
2. Protection of the distal phalanges
3. Tactile discrimination and the capacity to pick up small objects
4. Scratching
5. Grooming
6. As a weapon
7. Normal biomechanics of gait

17. Nail Signs in Health
and Disease

18. Alterations of nail surface
Beau’s lines Onychorrhexis
Trachyonychia Nail pitting

19. Alterations of nail shape and size
Increased transverse
curvature of nail
Increased
Flattening/Concavity of Nail
Anonychia
Clubbing Pachyonychia

20. Alterations of nail surface
Leukonychia Melanonychia
Erythronychia

21. Alterations of nail plate/bed adhesion
Onycholysis
Subungual
Hyperkeratosis

22. Change in periungual tissue
Paronychia
Changes in Nail Fold
Capillary Patterns

23. THANK YOU
Nishkarsh Chugh
PGJR1 Dermatology