SKIN - RELATED TO AESTHETIC MEDICINE - PRACTICE

1. SKIN BASIC STRUCTURE
AND FUNCTION
I. INTRODUCTION
II. EPIDERMIS AND ITS LAYERS
III. EPIDERMAL CELLS
IV. BASEMENT MEMBRANE
ZONE
V. DERMIS
VI. VESCULAR SUPPLY OF
DERMIS
VII. ULTRA STRUCTURE OF DEJ
VIII. CUTANEOUS GLANDS, HAIR
& NAIL

2. • Skin is the largest organ in the body.
• A 70 kg individual the Skin weighs over
5 kg & surface area 2 meter square.
• The skin is composed of two basic layers
1. outermost layer-Epidermis
2. underlying connective tissue-Dermis
BELOW THE DERMIS Subcutaneous fatty
layer is Hypodermis

4. Layers of
epidermis
• Stratum basale (the deepest layer)
• Stratum spinosum
• Stratum granulosum
• Stratum lucidum (only in thick skin)
• Stratum corneum (most superficial
layer of epidermis).

5. Layers of
epidermis
SPINOUS
LAYER
Upper most STRATUM
CORNEUM
GRANULAR LAYER
Lowest BASAL LAYER
Epidermis formed by the division of cells in the basal
layer. which give rise to the spinous layer. This
layer contains cells that move outwards and
progressively differentiate, forming the granular layer
and the stratum corneum.

6. EPIDERMI
S :-
• Epidermis derived from ectoderm
• The epidermis is mainly
composed of keratinocytes ,
• Thickness is 0.05–0.1 mm .
• Thickest on plams and soles (approx-
1.5mm)
• Thinnest on eyelids & scrotum
(approx- 0.1mm)
• The cellular progression from the basal
layer to the skin surface takes about 30

7. DESMOSOM
ES
HEMI
DESMOSOMES

8. Stratum
Basale
• The stratum germinativum (basal layer)
- single layer of basophilic columnar or
cuboidal cells
• All cells contain intermediate
keratin filaments.
• Number of keratin filaments increases as
cells progress upward.

9. Stratum
Spinosum
• Also contain the dividing cells as in basale.
Cells contain bundles of intermediate filament
(tonofilaments) projecting into the processses
of cells which give attachment to the
desmosomes, so giving spined appearance
hence called Prickle Layer
• Tonofilaments provide resistant to the
abrasion so this layer is thicker in the areas
prone to abrasion (thick skin) .
• Keratinization begins in the stratum spinosum

10. stratum
granulosum
• Consists of polygonal cells , cytoplasm of
which
is filled with the basophilic granule
,keratohyaline granules.
• It is rich in phosphorylated histidine and
cystine.
Cells contain, lamellated bodies, made
up of lipid.
• It fuses with the cell membrane and it come
out of cells and function as a intercellular
cement or sealing agent.

11. Stratum
Lucidum
• More prominent in thick skin .
• Cellular organells and nuclei are
not prominent.
• It is composed of clear non-nucleated
cells.
• In the palms and soles, the
stratum lucidum is present.
• The tan colored protein blocks the
underlying melanocytes from view

12. Stratum
corneum
• The main difference between thick skin and thin
skin relates to the thickness of the Stratum
corneum.
• These are the dead cells, flaking off. The cells
lose their nucleus and fuse to form squamous
sheets, which are eventually shed from the
surface (desquamation).
• The mean turnover or renewal time of
epidermis is 28-30 Days i.e. time for a cell
to move from the stratum basale to the distal
edge of the stratum
corneum and shed.

13. CELLS OF
EPIDERMIS
• A. Keratinocyte
• B. Melanocyte
• C. Langerhans Cells
• D. Merkel Cells ( Haascheiben
cells)

14. A.
Keratinocyte
• The cells are named after its intermediate
filament called keratin which provides
mechanical strength to this cells ( strength is
required for resisting daily trauma and
mechanical pressure on the epidermis ).
• Keratinocytes devide and generate the
upper layers. Transit time / turnover time is
the time it takes for basal cells to reach the
skin surface it is 28 days.
• More the need for strength, more the need
for keratin

15. S
G
s
s
S
B
S
C
14
DAYS
14
DAYS
2
8
DAY
S

16. • Since SC require the maximum strength
maximum keratin is in SC and least
amount of keratin is in SB.
• This process of increasing the keartin in
the cells from SB upward to SC is
called keratinization of epidermis
• As function of SC is protection and it does
not divide, it sheds off its nucleus .

17. Keratin filamentsjoin together in the
upper epidermis by Filaggrin.
Since upper layers require more strength than
lower layer, Filaggrin synthesis is in upper layer

18. Disease with abnormal
keratinization
• A. Parakeratosis:- in psoriasis the basal
layer divides too fast

19. • In psoriasis the basal layer divides too fast.
Hence the basal layer reach the SC faster
and donot shed the nucleus
• Hence as nuclei are retained in
psoriasis, nucleated stratum corneum
is seen on histopathology this is
called parakeratosis
• In the granular layer the keratohyaline
granules contain these filaggrin molecules
(Hence granular layer is called granular)

20. B.
Melanocytes
• Present in basal layer
• Derived from the neural crest
• Produce Melanin
• Package it in organells (Melanosomes)
and Transfer it via finger-like
processes called Dendrites to
Keratinocyes
• Each melanocyte transfer melanin to
36 keratinocytes
• Forming the epidermal-melanin unit
[1:36]

21. Through these
Dendrites
melanin
transfer to
keratinocytes
Keratinocyt
es
Dendriti
c
process
Melanocyte in basal
layer

22. • Melanin protects cells form Uv light.
• They differ from keratinocytes by
possessi
ng no desmosomes.
• Colour of skin depends on :-
1. Amount of melanin inside melanocytes
2. Number and size of melanosomes
3. Degree of transfer into keratinocytes

23. • It does not depend on the number
of melanocyte (all humans have
the same number of melanocytes)
Types of melanin :-
1. Eumelanin:- brown or black
pigment found in dark colored
races.
2. Pheomelanin:- yellow-red in
caucasian
skin

24. C. Langerhans
Cells
• Derived from bone marrow
• Dendritic cells expressing
:-CD45, HLA-DR, CD
1C
• Role in adaptive immune responses in the
skin since they are antigen-presenting
cells (APC) Processing antigens and
transporting them to local lymph nodes
• Like melanocytes they are not
connected to adjacent keratinocyte by
the desmosomes.
• Contain tennis racket shaped “Birbeck

25. D. Merkel Cells ( Haascheiben
cells)
• Seen amongst the basal keratinocytes.
contain desmosomes
• Derivation of this cell is controversial-
evidence supports both differentiation
from epidermal keratinocytes as well
as migration from the neural crest.
• Slow adapting touch receptors.

26. Dermi
s
• It is connective tissue that support the epidermis and
attaches the epidermis to the hypodermis.
• Dermis is 15-40 times thicker than the epidermis
• Its surface consists of many ridges (dermal papillae)
which interdigitate with epidermal ridges.
• The dermis is also the area where all the glands of the
body are located.
• Has 2 layers/compartments
1.A thin zone immediately beneath the epidermis the
papillary dermis
2. A thick zone of Reticular dermis that extends from the
base of
the papillary dermis to the surface of the subcutaneous fat

27. Papillary
dermis
• Papillary layer –The papillary dermis is the
uppermost layer of the dermis,composed of thin
haphazardly arranged collagen bundles,delicate
branching elastic fibers,numerous
fibrocytes,abundant ground substance.
• A highly developed microcirculation composed
of arterioles,capillaries and venules Its superior
surface is uneven (fingerlike projections) which
forms the characteristic fingerprint of the finger.
• This layer provides the epidermis with nutrients.
Pain and touch receptors are found here

28. Reticular
dermis
• Dense irregular Connective Tissue Has thick
bundles of Collagen and coarse Elastic fibers.
• Proportionally, there are fewer fibrocytes and
blood vessels and less ground substance
compared to papillary dermis
• Arrangement of bundle in the direction of
mechanical force give rise to the cleavage lines
of Langer.
• Strongest layer of the Dermis. Gives the
area strength.Contains sweat,sebaceous
glands and pressure receptors
• Leather is made of this layer.

29. HYPODER
MIS
• Consists of loose connective tissue
which helps in sliding the skin over
the deep structure.
• Consists of layer of fat according to
the nutritional status of the person.
• Also called as superficial fascia or
panniculus adiposus

30. VESSELS IN
SKIN
• Arteries form the 2 plexuses One at
the junction of papillary and reticular
layer( sub- papillary plexus) and another
at junction of dermis and hypodermis
(cutaneous plexus).
• Veins form the 3 plexuses –
2 in same position as for arterial and
another in the middle of the dermis

31. BASEMENT MEMBRANE
ZONE
• THE JUNCTION BETWEEN
EPIDERMIS AND DERMIS IS
CALLED THE BASEMENT
MEMBRANE ZONE
• ULTRASTRUCTURALLY THIS ZONE IS
COMPOSED OF THREE
COMPONENTS FROM TOP TO
BOTTOM

32. 1. BASAL
KERATINOCYTE
2.
DEJ
3. DERMAL CONNECTIVE
TISSUE

33. ULTRA STRUCTURE
OF DEJ
HEMIDESMOSO
MES
LAMINA
DENSA
LAMINA LUCIDA
DE
J
TYPE 4 COLLAGEN
FIBER
ANCHORING FIBER
DERMAL
CONNETIVE
TISSUE

34. • PLASMA MEMBRANE OF BASAL KERATINOCYTE WITH
THE
SPECIALIZED ATTACHMENT PLATES =
HEMIDESMOSOMES
• DE JUNCTION:- IT IS DEVIDED INTO THE
UPPER – LAMINA
LUCIDA LOWER –
LAMINA DENSA
TYPE –IV COLLAGEN IS THE MAJOR COMPONENT OF
LAMINA
DENSA
• ANCHORING FIBERS:-ATTACHES THE LAMINA
DENSA ABOVE TO THE UNDERLYING CONNECTIVE
TISSUES
TYPE VII COLLAGEN IS THE MAJOR PROTEIN IN
THE ANCHORING
FIBER

35. BASAL
KERATINOCYTE
TYPE -4 COLL.FIBER
BP-
1
BP-
2
LAMINI
N
DERMAL
CONNECTIVE
TISSUE
ANCHORING
FIBER
BP (anti body against
BP-1)
BP,CP,LAD (anti-b against
BP-2)
EBA (antibody against collagen
7) EBD (absent collagen 7
since birth)
EBJ
(Absent
laminin
since
birth)

36. Cutaneous
Glands
• 1. Sebaceous (oil) glands- Sebaceous
glands are microscopic glands in
the skin which secrete an oily matter,
called sebum, In the hair follicles to
lubricate the hair.
• In humans, they are found in greatest
abundance on the face and scalp, though
they are distributed throughout all skin
sites except the palms and soles.
• infection causes acne

37. 2. Sweat
glands –
• Sweat glands are exocrine glands, found in the skin , that
are used
for body temperature regulation.
a)Eccrine glands -Eccrine glands (or merocrine
glands) are found at virtually all sites on the human
body. They produce clear liquid (perspiration),
consisting of water, salts, and urea.
b)Apocrine glands- Apocrine glands are found in
axillary and genital areas, secrete a milky protein and fat
substance. This mixture is an excellent source of
nutrients for bacteria which produce body odour.

38. HAI
R
• Follicle- A hair follicle is a part of the
skin that grows hair by packing old cells
together

39. • Arrector pili -Arrectores pilorum
(singular Arrector pili) are tiny smooth
muscle fibers attached to each hair
follicle, which contract to make the hairs
stand on end, causing goose bumps.

40. Nail
s
• Fingernails and toenails are made of a
tough protein called keratin. Along with
hair and teeth they are an appendage of
the skin.

41. • Free edge- The part of the nail that extends
past the finger, beyond the nail plate. There
should always be a free edge present to
prevent infections.
• Nail folds (cuticle)- A fold of hard skin
overlapping the base and sides of a
fingernail or toenail.
• Nail Matrix- This is the only living part of the
nail. It is situated behind and underneath the
Nail Fold and produces protein keratin which
makes up the Nail Plate

42. Embryology of
skin

43. • The skin of the embryo begins to form during the
first 20 to 30 days of embryonic life, the period of
active organogenesis in human development
• The skin arises by the juxtaposition of two
major embryological elements
1. The prospective epidermis, originates
from a
surface area of the early gastrula; ectoderm.
2. The prospective mesoderm, which is
brought into
contact with the inner surface of the epidermis.
• The neural crest also makes contribution to
the skin

44. Development of
epidermis
EMBRYONIC GESTATIONAL AGE EVENTS
3 Weeks Single Layer Of
Flattened Epithelial
Cells
4 Weeks Basal Germinative
Layer & Periderm
3 Months Intermediate Cells
Tonofilaments-
desmosomes
5 Months Keratohyaline Granules,
signs Of Cornification
Starts
6 Months Cornification Completed
Term Increase In Thickness Of Cornified
Layers

45. Physiological function of
skin
Epidermis is a barrier to water loss and also
barrier to prevent entry of harmful substance like
microbes and UV light into the body .
Loss of this barrier will lead to increase of
infection and more loss of fluids from skin (in
burn patient)
This barrier is created by polygonal shape of
keratinocytes and better sticking together by glue
like lipid secreted by keratinocytes.
It is compared to a brick and cement model
where bricks are synonymous with keratinocytes
and cement is the glue.

46. BRICK=KERATINOCY
TE
CEMENT = INTER
CELLULAR LIPID
LAMELLAR BODY IN
KERATINOCYTE SYNTHESIZES
LIPID AND EXPELS IT INTO
LIPID INTO
INTERCELLULAR
SPACE

47. BARRIER
LOSS
• Barrier loss can either be due to problem in the
keratinocytes (brick damage) or problem in the
glue (cement collapse).
A. Problem in the keratinocytes (brick damage) :-
1.Damage to intercellular junction desmosomes
2. Primary destruction of the keratinocyte itself (cytolysis)
3. Problem in calcium pump

48. • B. Problem in the Glue (cement damage) :-
– Intercellular cement contain ceramide, Squalene,
fatty acids.
– Loss of intercellular glue cause eczema. The small
gap creates a barrier function loss. This Gap then fill
up with fluid this is called intercellular edema or
spongiosis.
– Fluid can ooze out of skin clinically. These
microscopic gap also allows entry of organism in to
skin [ Pt. with atopic eczema have more infectious
especially staphylococcal ].
– In eczema to replace this loss of ceramide
moisturising containing ceramide are often given
to replace this intercellular cement.

49. • Langerhans cells which serve as sentinel cells whose
prime function is to survey the epidermal environment and
to initiate an immune response against microbial threats.
• Melanin, which is mostly found in basal keratinocytes, also
provides some protection against DNA damage from
ultraviolet radiation.
• Thermoregulation:-Vasodilatation or vasoconstriction of the
blood vessels in the deep or superficial plexuses helps
regulate heat loss.
• Skin lubrication and waterproofing is provided by sebum
secreted from sebaceous glands.
• Subcutaneous fat has important roles in cushioning
trauma aswell as providing insulation and a calorie reserve.
• Endocrine function:- releasing the hormone leptin, which
acts on the hypothalamus to regulate hunger and energy
metabolism
• Vitamin D synthesis from UV-B