Anatomy of Nail And Applied Aspects

1. ANATOMY & APPLIED ASPECTS
OF NAIL
Dr. Yugandar

2.  Hard & Durable Epidermal Appendages
 Similar to Claws & Hooves of animals
 Covers 1/5th of dorsal surface of the digits (Great
toes upto 30% )
 It is difficult to obtain nail producing substance &
grow nails and nail matrix keratinocytes in culture
 Mouse nails display amazing homology with human
nails,Mouse models and mouse genomics used for
nail research

3. Components of Nail
• Nail Matrix
• Nail Bed
• Cuticle
• Nail Plate
• Nail Folds
• Lunula

5. Anatomy of the Nail

8.  Lunula: it is visible part of nail matrix,best
seen in thumb,poorly in little finger
 Cuticle: the fold of skin tissue at base of the
nail that overlaps lunula & protects nail bed
 Nail Matrix:
- It is tissue which is protected by nail
- Contains nerves,lymphatics & blood vessels
- It is responsible for production of nail plate

9.  Nail bed: skin beneath the nail plate
 Nail plate: it is hard part of nail,made of
translucent keratin protien
 Distal edge: anterior margin of nail plate
 Proximal nail fold:
- Epithelium with a granular layer
- Corresponds to skin of digit
- Contains sweat glands

11.  Hyponychium: it is epithelium located
beneath nail plate at junction b/w distal edge
& skin of fingertip
 Eponychium: small band of epithelium from
post nail wall onto the base of nail
 Paronychium: it is border tissue around nail
 Perionyx: it is projecting edge of the
eponychium covering the proximal strip of
lunula

12. Nail Matrix differentiation
• As new plate cells formed old cells push
forward & compressed become flat,
translucent, that makes nail bed capillaries
visible pink colour

13. Direction of differentiation & cell movement with in nail apparatus

14. Histological section of proximal nail matrix

15. Histologic section shows dorsal & ventral portions
of the proximal nail fold

16. Proliferating epithelial cells of matrix & ventral aspect of the PNF
Staining with antibody MIB-1

17. Development
 Nail apparatus develops & matures from
Primitive epidermis b/w 9th & 20th week of
intrauterine life
 First identified at 10th week of IUL as a
primary nail fields of proliferative ectoderm
on tips of terminal segments of digits

18. Development
 Due to slow growth rate,Primary nail fields
become depressed & Epidermis overlaps their
sides & Proximal ends forms nail folds
Proximal part of each nail field forms root of
nail,becomes germinative portion
 From germinative portion actual substance of
nail develops

19. Development
Keratin synthesis identified in early embryonic
differntiation
 Fetal growth of nail is gradual,finger nails
appear longer than toe nails,at birth nail
edges reaches tips of digits

21. Functions of Nail
• Protection
• Sensory Perception
• Manual Dexterity
• Scratching
• Picking up small objects
• Augments sensation of touch

22. Blood Supply of Nail
Lateral digital arteries supply nail through
superficial,proximal & distal arcades
Vasculature of nail bed is unique in that it
must supply a vascular structure b/w two hard
surfaces ie nail plate & distal phalanx

23. Blood Supply of Nail
Large AV anastomoses with glomusbodies,
play key role in peripheral circulation &
thermoregulation
Glomus bodies called as Peripheral heart of
masson

24. Blood Supply of Nail
Vasculature of nail

25. Blood Supply of Nail
Vasculature of nail

26. Blood Supply of Nail
Capillary microscopy of the proximal nail fold
showing longitudinally oriented capillary loops

27. Nerve Supply of Nail
Nail unit is richly innervated by nerves which are
branches of median,ulnar & radial nerves
Innervation of nail unit is through two laterally
positioned sensory nerves
Digital nerves divides in to three branches just
distal to the interphalangeal joint to supply
different constituents of the nail unit

28. Nerve supply of nail through branches of
Median,Ulnar & Radial nerves

29. Nail Growth
 Nail growth is continuous,it ceases at death(
skin tightens & dehydrates appear nails grow)
 Finger nail grows at rate of 0.1 mm/ day,
3mm/ month
 Toe nail grows at rate of 0.033 mm/
day,1mm/month

30. Nail Growth
 It is proliferating cells of germinative matrix
most contributes to nail growth
 Thinning of nail plate usually sign of nail
matrix disease,Nail thickening sign of nail bed
disease

31. Nail Growth
Complete replacement finger nails- 6
months,toe nails-18 months
 Nails grow more in summer than other
season

32. Nail Growth - Physiological factors
Increase : Right hand,Dominant
hand,Pregnancy,2nd & 3rd
decade,Youth,Fingers,Male upto 19 years
Decrease : At birth,After age 60
yrs,Lacatation,Left hand,Non Dominant
hand,Old age,Toes,Females upto 69 yrs,Thumb
& Little fingers

33. Nail Growth - Other Factors
Decrease : Cooler temp,Finger
Paralysis,Hypothyroidism,Fever,Measles,Mumps,
CRF,Pneumonia,TB,Malnutrition,Yellow nail
syndrome,Onychomycosis
Increase : Warm temp,AV shunts,
Hyperthyroidism,Psoriasis,P. Rubra Pilaris,Drugs (
L- Dopa,Retinoids,Itraconazole), Finger Trauma

34. Reasons : Nails grow always forward
& flat
• Guiding restraint of proximal nail fold
• Influence of underlying phalanx
• Adherence of nail plate to nail bed
• Containment by Lateral nail folds

35. Reasons : Nails Pointed & Rounded
• No Clear reason for it
• Function of Lunula
• Nail bed may have role
• Iso Kikuchi syndrome – Abnormally shaped
Lunula – Hemionychogryphosis

36. Nails in Childhood & Adults
In Early Child – Nail plate thin & temporary
Koilonychia ( More Prominent Great Toes)
Prominence of nail surface markings –
Herringbone or Chevron Nails
Solitary beau’s lines – Infancy

37. Nails in Childhood & Adults
 Onychophagia,Punctate
Leuconychia,Pitting,Lamellar Splitting of free
edge of nail – normal in children
 Elderly – Slow rate of growth
 Neapolitan nails : Proximal half – White,No
Lunula,Distal Edge is opaque,Central portion –
Pink.

40. Nail Composition
• Lamellar sheets of tightly adherent dead
corneocytes containing large amount of
protien ( 78 % ),Small amounts of water ( 18
%),Very Little Lipid ( < 5 % )

41. Nail Composition
• Hardness due to structural protiens alfa helical
keratin,Cystiene rich amorphous matrix
protien
• Mineral content of nail Zn,Fe,Cu & Mg in small
quantites

42. Nail Composition
Nail Matrix
 Dorsal ( undersurface of
proximal nail fold )
 Intermediate or germinative
 Ventral (nail bed
epithelium)
Nail Plate
 Dorsal lamina : Dorsal
matrix derived
 Intermediate layer:
Germinative matrix derived
 Ventral layer: Ventral matrix
derived

43. Nail Matrix
Nail Matrix Keratinocytes
Melanocytes
Langerhans cells
Merkel cells

44. Biochemistry of Nail
• Low sulfur keratins,High sulfur keratins
• High glycine tyrosine matrix protiens
• Presence of K6/K16 keratins in nail bed
demonstrates hyperkeratotic state in diseases
• Mutation in K16 gene observed in
pachyonychia congenita

45. Keratin gene expression at different locations with in nail

46. Importance of Nail Composition
• Cystic fibrosis – Na,Cu Elements Increased
• Wilsons disease – Cu increased
• Iron def anemia – Fe decreased
• Acrodermatitis enteropathica – Zn decreased
• Environmental Exposure – As,Pb increased

47. Importance of Nail Composition
• Cocaine in nail clipping in newborn indicative
of Cocaine exposure during embryogenesis
• X linked Icthyosis – Steroid
sulfatese,Cholesterol sulfatase

48. Nail signs – Deposition of pigments
 Pigmentation from external staining typically
follows shape of proximal nail fold eg: yellow
brown discolouration in smokers d/t
Nicotine,Darkening of nail plate in hairdressers
 Metals Gold (Chrysiasis),Silver(Argyria)

49. Nail signs – Deposition of pigments
 Subungual deposition of Green pigment seen
in Pseudomonas colonization d/t
Pyocyanin,Yellow Subungual pigment d/t
Dermatophytes
 Exogenous – Convex Proximal Border,
Endogenous – Concave Proximal border,
Subungual deposition- a/w onycholysis

50. Nail signs – Deposition of pigments
Dermoscopy very useful for assessment of nail
plate pigmentation & nail bed changes

51. Nail plate in Forensic Medicine
 Due to Slow Growth rate of nails makes it
possible to utilize nail clippings to detect
previous exposure to drugs,metals and toxins
eg Heroin,cocaine,amphetamine
 Drug exposure,Poisoning,Genetic analysis
 Finger nail clippings of victims for
identification of accused by DNA method

52. Nail plate in General Medicine
 Nail clippings used for identification of
Alcohol dehydrogenase enzyme defect in
hepatic dysfunction
 Long term control of blood glucose levels in
diabetes
 HBV DNA

53. Nail plate in General Medicine
 Creatine levels in renal dysfunction
 Porphyrin levels in PC Tarda
 Assesment of Environmental exposure to
pollutants eg: Pb,Nicotine

54. Nail signs as an aid to diagnosis of congenital heart
diseases

55. Correlation of nail findings with anatomic site of nail damage

56. Applied aspects of Nail
Congenital disorders of nail unit:
Anonychia,Congenital malalignment of bigtoe,
IsoKikuchi syndrome,Micronychia,
Macronychia,
Polyonychia,Onychoheterotopia,Racket
nails,Periodic shedding

57. Applied aspects of Nail
 Congenital disorders of nail unit:
Dolichonychia,Circumferential nails,Nail
patella syndrome
Alterations in Nail shape: Clubbing,Shell
nails,Racket nails

58. Applied aspects of Nail
Alterations in Nail size:
Anonychia,Micronychia,Polyonychia,Nail
patella syndrome,Iso Kikuchi syndrome

59. Applied aspects of Nail
Alterations in the Nail Plate: Beau’s
lines,Onychomadesis,Washboard nails,
Koilonychia,Pincer nails,Brittle nails,
Platyonychia,Pitting,Multiple longitudinal nail
grooves,Onychorrhexis,Trachyonychia,20-nail
dystrophy of childhood,Pachyonychia
congenita

60. Applied aspects of Nail
Disease of Nail bed:
 Trauma – Sportsman’s toe
 Primary skin diseases – Psoriasis,Alopecia
Areata,Lichen planus,Dermatitis,Porphyria,
Pachyonychia congenita,Epidermolysis bullosa
 Drugs – Retinoids,Doxycycline,
Chemotheraphy,Na Valproate
 Chemicals

61. Applied aspects of Nail
Systemic – Fe def anemia,Connective tissue
diseases,hypo or hyper thyroidism
Infections – Candida,Herpes,Warts,Bacterial
Paronychia,Onychomycosis