Melanocytes are pigment-producing cells found in the basal layer of the oral epithelium. They contain melanin granules called melanosomes and transfer melanin to surrounding keratinocytes. Melanocytes develop from neural crest cells during embryogenesis and their main function is to absorb ultraviolet radiation and protect against DNA damage. The document discusses the structure, development, and role of melanocytes in determining skin and oral pigmentation. It also covers genetic and environmental factors that influence melanin production.
4. Introduction
Two types of cells broadly constitutes the
oral epithelium:
1)Keratinocytes
2)Non-
keratinocytes
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5. Non-keratinocytes -
Lack desmosomal attachments &
tonofilaments
Do not participate in the process of
maturation of oral epithelium
10% of total population of oral epithelium
Consists of melanocytes, merkel cells,
Langerhans cells, lymphocyteswww.indiandentalacademy.com
6. Stratum basale
(germinativum)
Single layer of cells on
basal lamina
Stems cells which give rise
to keratinocytes
Contain melanin
transferred from
melanocytes
May see mitotic figures
Desmosomes and
hemidesmomes
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7. Melanocytes are…
Melanin pigment forming cells
Present in epidermis, its appendages, oral
epithelium, some mucous membrane,, parts
of middle and internal ear, etc.
Melanocytes contribute color to the skinMelanocytes contribute color to the skin
and serve to decrease the amount ofand serve to decrease the amount of
ultraviolet light that can penetrate intoultraviolet light that can penetrate into
deeper layers of the skindeeper layers of the skin
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8. They are…
Capable of producing the brown pigment,
melanin
Melanin can absorb energy from ultraviolet
(UV) light
UV light contains high energy photons that
can damage DNA – mutations
Melanin can prevent damage to DNA, helps
to prevent skin cancer
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11. Embryology
Develops from neural crest cells
Appears in cranio-caudal direction
Can be identified in epidermis of head in 3rd
month of IU life and in caudal body parts in 4th
fetal month
Functionally immature during their migration
through the fetal dermis
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12. Structure
Randomly dispersed cells within basal &
parabasal layer, in people of certain races
found through epidermis
Small darkly stained nucleus, clear cytoplasm,
no mitotic activity.
Found wedged between basal cell of
epidermis, at the tips of rete pegs.
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13. No. of melanocytes varies with body
region and increases with repeated
exposure to light
Lack desmosomes and tonofilaments
but possess long dendritic processes
that extend in several directions
across several layers of cells
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14. Ultrastructure
Dendritic nonkeratinocytes lacking desmosomal
attachments with adjacent keratinocytes
Hang down into superficial dermis and are separated
from the extracellular dermal matrix by the basement
membrane
Nucleus large ,round and euchromatic
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15. Cytoplasm has intermediate filaments, prominent
golgi complex, vesicles. endoplasmic reticulum,
mitochondria and melanosomes
Melanosomes are often aggregated above the
nucleus to form supranuclear caps .
Melanosomes during their maturation move from
cytoplasm to the dendritic processes .
At the base where they lie in close apposition with
the lamina densa, show structures resembling
hemidesmosomes.
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20. Melanogenesis
Melanosome - membrane bound vesicle which undergoes a
sequence of 4 developmental stages during which melanin is
synthesized and deposited within it by the tyrosin-tyrosinase
reaction
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22. Melanin Increase: Sunlight; Addison Disease;
Hemachromatosis
Melanin Decrease:
Albinism –Melanocytes present but no tyrosinase.
Leukoderma (Vitiligo)- Melanocytes absent; destruction of
melanocytes- patchy expansive
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23. Melanin
The brown color of the skin is due to melanin, which is produced
in the skin itself in cells called melanocytes. These cells are
located in the epidermis.
In the melanocytes, the melanin is located in membrane-bound
organelles called melanosomes.
Melanocytes can transfer melanin to keratinocytes - mainly to the
basal cells
Melanin protects the chromosomes of mitotically active basal
cells against light-induced damage.
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24. Types of melanin
TypeType ColorColor SolubilitySolubility CompositionComposition
EumelaninEumelanin BrownBrown
blackblack
InsolubleInsoluble
in allin all
solventssolvents
NitrogenNitrogen ++++
to otherto other
componentscomponents
PhaeomelaninPhaeomelanin RedRed
yellowyellow
AlkaliAlkali
solublesoluble
Sulphur inSulphur in
addition toaddition to
nitrogennitrogen
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25. The regulation of the production of eumelanin versus
pheomelanin involves the interaction of the melanocortin 1
receptor (MC1R) on the surface of the melanocyte with
melanocyte stimulating hormone (MSH) or with the agouti
signaling protein. The binding of MSH to MC1R results in the
formation of eumelanin while the binding of the agouti protein
to MC1R leads to the production of pheomelanin.
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26. Melanin unit
• Each epidermal melanocyte is
surrounded by a group of keratinocytes
with which it maintains functional
contact- melanin unit
• A melanocyte supplies melanosomes to
app. 30-40 keratinocytes
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27. Functions of melanin
Absorption of uv light
Scavenger of damaging free radical
Can oxidize NADH in vitro and
participate in other oxidation reduction
reactions
Melanocytes in stria vascularis also
known as intermediate cells
Melanocytes help proper routing of optic
nerves at the chaisma during early
development of optic cup.www.indiandentalacademy.com
28. Melanin transfer
Result of active phagocytosis of the tips of the
melanocytic dendrites by keratinocytes
In EM, pseudopod-like cytoplasmic projections
of keratinocytes are wrapped around the tips
of the dendrites
After such projection has enveloped the tip, it
is pinched off
Melanosomes in pinched-off dendrite are
separated from the cytoplasm of keratinocyte
by plasma membrane of dendrites & of
keratinocytes
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29. Due to the breakdown of plasma
membrane, the melanosomes are
dispersed in keratinocytes cytoplasm
In lightly pigmented skin, transferred
melanosomes are found in basal &
parabasal layer
In Africans,melanosomes are found
throughout the skin including stratum
corneum www.indiandentalacademy.com
31. Control of melanin pigmentation
Can be analyzed on 2 basis:
1)Constitutive a) genetics
b) hormones
2)Facultative a) uv radiations
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32. Genetics:
Specific genes influence differentiation
of neural crest cells into melanoblasts,
migration of melanoblasts into skin and
differentiation into melanocytes.
Other genes acting primarily within the
melanocytes control synthesis of
tyrosinase.
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33. Hormones
Increased ACTH secretion causes
hyper-pigmentation by increasing the
melanocytic activity
Increased estrogen & progesterone
levels causes hyperpigmentation which
is due to increased melanization of
keratinocytes
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34. UV radiation: It shows two types of
reactions:
- Immediate tanning
- Delayed tanning
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35. Regional variation
High conc. Of melanocytes found on face and male
genital app 2000/mm sq, lower trunk about 800/mm sq
No significant difference exists between density of
distribution of melanocytes for area of skin for lightly &
dark pigmented persons.
The differnce in degree of pigmentation is due to a
combination of size & no. of dentritic processes and
size of melanosomes and its degree of dispersion
Related exposure to uv light causes an increase in
concentration of melanocytes and increase in their size
and functional activity
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37. Loss of melanocytes
Physical causes like burns , trauma
Ionising radiations
Chemicals – phenols etc.
Inflammatory disorders of skin
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38. HYPERMELANOSIS
Condition Location Clinical Features
Racial Any area Diffuse pale to dark brown
discoloration
Oral melanotic
macule
Any area Discrete/diffuse localized
brown to black macule.
Freckles Cheek,temples, nose Small, flat brown to tan
patches
Cholasma Face Localized increase in
pigmentation during
pregnancy.
Mongolian spot Sacral region Bluish grey to brownish area in
sacral region of mongolian
people.
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39. Blue nevus Localized raised blue
black area.
Melanocytic nevus Skin Seen in
adoloscents,flat/slightly
elevated lesion of about 3-
5mm in diameter.
Combined nevus Blue –black circumscribed
area.
Melasma Forehead,cheek,
temples,upper lip
Bilaterally symmetrical
patches seen in females
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40. Albinism
Vitiligo - partial or complete loss of melanin
in an area
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41. Malignancy:
Melanoma is a malignant tumour that arises
from a mutant melanocyte. Melanoma occurs
in all races but is most common in people
with fair skin. Most melanomas present as a
dark, mole-like spot that spreads and tends
to have an irregular border. The risk of
melanoma increases with overexposure to
the sun and sunburn.
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