Structure of Nail

Nishkarsh Chugh

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

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: Onychocytes Hard Keratins Phosphate Calcium It comprises three horizontal layers: A thin dorsal lamina The thicker intermediate lamina 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: Proximal Matrix Distal Matrix It has the following cells: Melanocytes Langerhans Cells Merkel Cells 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. Proximal Nail Fold Distal Nail Fold 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

13. 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.

14. 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 bed 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.

15. Functions of Nail Aesthetics of the hand Protection of the distal phalanges Tactile discrimination and the capacity to pick up small objects Scratching Grooming As a weapon Normal biomechanics of gait

16. Nail Signs in Health and Disease

17. Alterations of nail surface

18. Alterations of nail shape and size

19. Alterations of nail surface

20. Alterations of nail plate/bed adhesion

21. Change in periungual tissue

22. THANK YOU Nishkarsh Chugh PGJR1 Dermatology