nail anatomy.pptx

NAIL ANATOMY

1. ANATOMY - NAIL AND ITS DEVELOPMENT DR PDIANGTY GIRI MAWLONG PG DERMATOLOGY 1ST YEAR PGIMS ROHTAK

2. ANATOMY OF NAILS Nail unit consists of – Nail plate Proximal nail fold Nail matrix Nail bed Hyponychium

3. ANATOMY OF NAIL

4. ANATOMY OF NAIL

5. NAIL PLATE Nail plate- It is a rectangular, translucent and relatively inflexible structure. It varies in thickness from 0.5 to 0.75mm The nail plate arises from beneath the proximal nail fold and is bordered on both sides by the lateral nail folds A whitish and crescent-shaped area called the lanula is seen just distal to the proximal nail fold (distal portion of nail matrix) The dorsal surface of the nail appears pink in colour because of the enhanced vasculature of the underlying nail bed. At the tip of digit, nail plate separates from the underlying tissue at the hyponychium

6. NAIL PLATE Upper dorsal surface of the nail plate is smooth and may have a variable number of longitudinal ridges that are specific enough to allow forensic identificaption Onychodermal band- It is a thin, transverse, deep pink or brownish line, just proximal to the distal free edge. It is structurally important for the adherence of the nail plate to the nail bed and acts as a barrier to exogenous substances trying to enter the nail.

7. NAIL PLATE Consists of 3 portions Dorsal Intemediate Ventral Above the lunula, the nail plate is thinner and consists only of the dorsal and intermediate portions. The Ventral layer makes up one fifth of the nail thickness,is derived from the nail bed The rest of the nail is derived from the the nail matrix Over 80% of the nail developed from the nail matrix.

8. PROXIMAL NAIL FOLD The proximal nail fold is a skin fold that consists of a dorsal and a ventral portion . The dorsal portion is anatomically similar to the skin of the dorsum of the digit but thinner and devoid of pilosebaceous units. The ventral portion, cannot be seen from exterior,which proximally is in continuity with the germinative matrix. Eponychium- Anterior extension of roof of proximal nail fold on to the nail plate.

9. PROXIMAL NAIL FOLD.. Cuticle – tissue distal to the eponychium in contact with the nail plate. The horny layer of the proximal nail fold forms the cuticle, which is firmly attached to the superficial nail plate and prevents the separation of the plate from the nail fold thereby protecting the underlying germinative matrix from environmental insult. The dermis of this contains numerous capillaries that run parallel to the surface of the skin. The morphology of proximal nail fold capillaries is typically altered in connective tissue diseases.

10. NAIL MATRIX The germinative portion of the nail is the nail matrix. It is divided into three regions Dorsal matrix Intermediate matrix ventral matrix The dorsal section of the nail matrix contributes to the most of the superficial layers of the nail plate The intermediate region of the matrix forms the deeper layers.

11. NAIL MATRIX The ventral subdivision is the most distal part of the nail matrix ( derived from the nail bed) The nail matrix produces the major part of the nail plate through onychokeratinization. The nail matrix extends 1-2 mm proximally to the beginning of the nail plate and its distal end extends to the outer edge of the lanula. The germinative epithelium of the nail matrix consists of basal cells that diffentiate, harden and die to form the nail plate.

12. NAIL MATRIX The nail matrix contains melanocytes in the lowest two cell layers. Matrix melanocytes are unable to produce melanin in normal circumstances, especially in white people. Average density in an adult is about 217/mm. Melanocytes are more numerous and more strongly dopa positive in the distal than in the proximal matrix. There are no melanocytes in the nail bed. Langerhans cells are also demonstrable in the matrix .

13. NAIL MATRIX.. The nail plate and matrix volumes are generally higher in men than in women. In some fingers, the distal matrix is not completely covered by the proximal nail fold, but is visible through the nail plate as a white half- moon-shaped area, the lunula. The white color of the lunula results from two main anatomic factors: The keratogenous zone of the distal matrix contains nuclear fragments that cause light diffraction. The nail matrix capillaries are less visible than nail bed capillaries due to the relative thickness of the nail matrix epithelium.

14. NAIL BED The nail bed is the area underneath the nail plate ( between the lanula and the hyponychium) Its thin epidermal layer represent the ventral portion of the nail matrix The nail bed epithelium is so adherent to the nail plate that it remains attached to the undersurface of the nail when a nail is avulsed. It is composed of a thin epidermal and a dermal layer but there is no subcutaneous fat.

15. NAIL BED The epidermis of the nail bed contains parallel longitudinal ridges from the lanula to the hyponychium. These ridges interlock to provide strong binding between the nail bed and the nail plate.. The dermal layer of the nail bed contains blood vessels to supply the nail unit, as well as lymphatics.

16. HYPONYCHIUM The region underlying the frees edges of the nail plate distal to the nail bed and proximal to the epidermis of the tip of the digit is referred to as the hyponychium It is the residuum of the distal ridges seen from the 10 th week gestation onwards. It is the seat for subungual hyperkeratosis.

17. ARTERIAL SUPPLY OF DISTAL FINGER

18. BLOOD SUPPLY The nail matrix and the nail bed are richly supplied with blood. The arterial supply originates from the two main arterial arches (proximal and distal) lying below the nail plate. The anastomotic arteries forming these arches are the branches of the digital arteries after the latter reaches the pulp space of the terminal phalanx.

19. BLOOD SUPPLY The capillary blood supply to the tissue around the nail is abundant . A capillary loop system supplies blood to the whole of the nail fold, but the loops to the roof and matrix are flatter compared to those below the exposed nail. In the matrix and the proximal nail folds the ccapillaries are mostly oblique, whereas in the nail bed they run parallel to each other in a longitudinal direction.

20. BLOOD SUPPLY The nail bed is richly supplied with glomus bodies. Glomus bodies are the neurovascular bodies and represent arteriovenous anastomoses without intervening capillaries. Digital nail bed contains as many as 93- 501 glomus bodies per cm 3. Glomus bodies play a critical role in maintaining peripheral circulation and are involved in thermoregulation under cold conditions.

21. BLOOD SUPPLY The venous blood efflux is less precise. The blood is collected into a deep and superficial system that drains into a few larger veins that run subcutaneously on the dorsal and volar aspect of the digits.

22. BLOOD SUPPLY

23. NERVE SUPPLY The perionychial area is innervated by dorsal branches of the paired digital nerves. The digital nerve divides into three branches just distal to the interphalangeal joint to supply the different constituents of the nail unit.

24. LYMPHATIC SUPPLY There are numerous lymphatics vessels in the nail bed, especially near the free edge of the nail. The superficial network joins the deep trunks by anastomotic rami.

25. BIOCHEMISTRY OF THE NAIL The protein constituents of the nail unit can be categorised into three Low sulfur keratin ( 40-60 kDa) High sulfur keratin (10-25 kDa) High glycine tyrosine matrix protein (6-9 kDa) Over 30 high sulfur protein have been identified in the human nail. Both soft epithelial keratin and hard trichocyte keratins occur in the nail unit. The nail plate epithelium expresses approximately 20% epidermal and 80% hair keratins The epithelial keratins expressed in the nail are K5/14,K6/K16, and K19

26. BIOCHEMISTRY OF THE NAIL 10 hair specific keratins are expressed in the human nail- Four acidic Four basic keratins labelled as HaKa 1-4 and HaKb 1-4. Two minor keratins identified as HaX and HbX HaKa 1 and HaKb 1 quantitatively represent the largest fraction of nail trichocyte keratins The main lipid of the nail is cholesterol.

27. BIOCHEMISTRY OF THE NAIL The fat content is only 0.1%-1%. The water content is 7%-12%.

28. BIOPHYSICAL PROPERTIES Rigidity and strength of the nail plate are due to- Double curvature of the nail plate A very cohesive cellular structure with interlacing plasma membrane. The orientation of the keratin fibrils in a plane parallel to the surface and perpendicular to the direction of the growth. Very low water content. The nail shows significant permeability characteristics It is highly permeable to water. It is also able to absorb radiation.

29. FUNCTION OF NAILS Protection of phalanges and fingertips. Enhancement of fine touch and fine digital movements. Scratching and grooming. Esthetic and cosmetic organ.

30. FUNDAMENTALS OF NAIL GROWTH Nail growth is continuous throughout life and only ceases at death The rate at which nail grows varies considerably from person to person and in the same person under different physiological and environmental conditions. Finger nails grow at a rate of approximately 0.1mm/ day and toe nail one – third of this rate. It is the intermediate matrix that contribute most to nail growth

31. FACTORS AFFECTING NAIL GROWTH Pathological factors affecting nail growth rate Increase Decrease Localized finger trauma Finger immobilization or paralysis Raised blood supply(e.g., arteriovenous shunts) Reduced blood supply(e.g., peripheral vascular disease) or peripheral neuropathy Hyperthyroidism Hypothyroidism Psoriasis Acute infections(e.g., fever, mumps, measles) Pityriasis rubra pilaris Systemic disorders(e.g., chronic renal failure, pneumonia, tuberculosis) Treatment with oral retinoids, l-dopa, itraconazole Treatment with antimitotics Malnutrition Onychomycosis Yellow nail syndrome

32. FACTORS AFFECTING NAIL GROWTH Physiological factors affecting nail growth rate Increase Decrease Between second and third year At birth and after the age of 60 decade Pregnancy Lactation Right hand/dominant Left hand/nondominant Male (up to 19 years) Females (up to 69 years) Youth Old age Fingers Toes Middle, ring and index finger nails Thumb and little finger nails Warmer temperature Cooler temperature

33. NAIL GROWTH Thinning of the nail plate is usually a sign of nail matrix disease whereas thickening of the nail plate is a sign of nail bed disease. Nail plate grows in the direction from proximal to distal. Due to their slow growth rate, the nails may provide information on pathologic conditions ,nail clippings can be used to detect previous exposure to drugs or chemicals. The nail of the big toe is the best site for investigation because of its size and slow growth rate.

34. NAIL GROWTH Nail clippings may also be used for genetic analysis and determination of blood groups. DNA can, in fact, be extracted easily from fingernail clippings and used for enzymatic amplification and genotypic or individual identification.

35. DEVELOPMENT OF NAIL The earliest sign of finger nail development occurs at 8- 9 week gestation. There is an invagination of the primitive epidermis to form an uninterrupted groove delineating a flattened surface at the end of each digit,known as nail field. A group of cells from the proximal part of the nail fold then grow proximally into the digit, stopping approximately 1 mm from the phalanx. This give rise to matrix primordium. This site will eventually contribute to the epithelium of the proximal nail fold as well as distal and intermediate matrix epithelium.

36. At 13 weeks gestation bthe proximal nail fold is formed band the first sign of nail plate growth are observed from the lanula. At this stage the stratum corneum and stratum granulosum start to materialize from the nail field epithelium,beginning distally and advancing towards the proximal nail fold. At 18 weeks gestation the granular layer recedes and the nail bed epithelium takes on a post natal appearance. At 20 weeks gestation the process of cellular differentiation and maturation within the matrix is similar to that seen in adult nails.

37. At 32 weeks gestation virtually all the components of the nail can be recognised. Toe nail development is similar to that of finger nails but the stages occur about 4 weeks later.

38. Thank You