The document discusses the anatomy and development of nails. It describes the main structures of the nail unit including the nail plate, proximal nail fold, nail matrix, nail bed, and hyponychium. It discusses their structure, blood supply, nerve supply, and development from early gestation through maturity. The nail matrix is identified as the primary site of nail growth through keratinization. Factors that can increase or decrease nail growth rates are also outlined.

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

5. ANATOMY OF
NAIL

6. 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

7. 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.

8. 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.

9. 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.

10. 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.

11. NAIL
MATRIX
• The germinative portion of the nail is the nail matrix.
• It is divided into three regions
1)Dorsal matrix
2)Intermediate matrix
3)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.

12. 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.

13. 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 .

14. 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.

15. 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.

16. 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.

17. HYPONYCHI
UM
• 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 10th
week
gestation onwards.
• It is the seat for subungual hyperkeratosis.

18. ARTERIAL SUPPLY OF
DISTAL FINGER

19. 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.

20. 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.

21. 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
cm3.
• Glomus bodies play a critical role in maintaining peripheral
circulation and are involved in thermoregulation under cold
conditions.

22. 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.

23. BLOOD
SUPPLY

24. 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.

25. 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.

26. BIOCHEMISTRY OF THE
NAIL
• The protein constituents of the nail unit can be categorised into
three
1) Low sulfur keratin ( 40-60 kDa)
2) High sulfur keratin (10-25 kDa)
3) 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

27. BIOCHEMISTRY OF
THE NAIL
10 hair specific keratins are expressed in the human nail-
1) Four acidic
2) Four basic keratins labelled as HaKa 1-4 and HaKb 1-4.
3) 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.

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

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

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

31. 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

32. 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

33. 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

34. 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.

35. 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.

36. 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.

37. • 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.

38. • 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.

39. Thank
You