SKIN STRUCTURE, EPIDERMIS, LAYERS OF EPIDERMIS, STRATUM CORNEUM, STRATUM BASALE, MELANIN, FUNCTIONS OF EPIDERMIS, ANATOMY OF EPIDERMIS, DESQUAMATION, KERATINISATION, INTEGUMENTARY SYSTEM, SCIENCE OF SKIN ANATOMY,STRATUM SPINOSUM, STRATUM GRANULOSUM, HORNY LAYER, PRICKLE CELL, MELANOCYTES, LANGERHAN CELLS, KERATIN CELLS, PIGMENTS OF THE SKIN, MERKEL CELLS, KERATINOCYTES

1. The
Integumentary
System
• Integumentary system is an
organ that consists of
skin,nails, hair and glands
along with nerves and blood
vessels that support them.
• Integument is skin

2. Skin
• Skin is the largest and heaviest
organ in the body and covers the
entire external surface.
• 16% of body weight comes from
skin.
• Scientific name of skin is derma
• The cells in the skin are mainly
made of protein keratin.
There are two kinds of human skin
• Glabrous skin(non-hairy)
• Hair –bearing skin

3. Functions of the skin
Skin has the vital function to keep the physiological and biochemical conditions in the body in optimum state.
Regulates body temperature
Prevents loss of body fluids and penetration of toxic substances
Storage of lipids cholesterol vitamin and synthesis of vitamin D
Excretes toxic substances by sweat(salt, water, organic wastes)
Protection of body from harmful effects of the sun and radiation
Immunological function mediated by Langerhans cells.
Sensory organ for touch, pressure, pain , temperature
Mechanical support

4. Layers of
Skin
Skin has primarily three
layers
• Epidermis
• Dermis
• Hypodermis

5. EPIDERMIS – The first layer of Skin
• Strong superficial layer of skin serves of first line of
protection against outer environment from interior body.
• Composed of keratinized ,stratified, squamous, epithelial
cells
• Continually renewing cells that keratinizes and gives rise to
derivative appendages(hair,nails,sebaceous and sudoriferous
gland)
• Oxygen and nutrients diffuse from underlying dermis .
• It is avascular-no blood supply
• The thickness of epidermis varies 0.4 to 1.5mm
• It is thickest on the palms and soles.

6. Cells of Epidermis
• Keratinocytes
• Melanocytes
• Langerhans cell
• Merkel cells
• Corneocyte
• Basal cells

7. Layers of
Epidermis
From below up layers are:
• Stratum Basale or
Germinativum(deepest layer)-
(BASAL LAYER)
• Stratum Spinosum or Prickle Layer
(SPINOUS LAYER)
• Stratum Granulosum(GRANULAR
LAYER))
• Stratum Corneum (Horny Layer)
• Stratum Lucidum(CLEAR CELL
LAYER) is extra layer below Horny
Layer found in thick skin of palms
and soles.

8. Stratum Basale
• Also known as Stratum
Germinativum
• The cells are cuboidal or columnar in
shape, with dark staining nuclei and a
dense cytoplasm.
• It is generally 1-2 cell layers thick
• Cells are active in mitosis constantly
producing keratinocytes to replenish
the cells shed from epidermis
• The keratin produced hardens and
flattens the cells as it moves
outwards and waterproofs the skin.
• This layer also has melanocytes and
merkel cells.
• It is attached to the underlying
Dermis by basement
membrane(basal lamina)
• The melanocytes produces melanin
which gives colour to the skin

9. Stratum Spinosum
Also known as prickle layer
It is about 8-10 cell layer, polyhedral cell
The cells are shrunken with spine like
projection
The spine connects to the neighbouring cells
with desmosomes
Functions as adhesion of epidermal cells and
resistance to mechanical stress.
Partly responsible for skins strength and
flexibility
Langerhans cells are found in this layer
Keratin synthesis begins in this layer

10. Stratum Granulosum
• Also known as Granular Layer
• It is 3-5 cell layer
• Cells are diamond in shape
• Cells has keratohyaline granules and lamellar
granules
• Keratinocytes has keratohyaline granules which
clusters to form keratin filament.
• Lamellar granules are present in the intercellular
space which secretes glycolipids acting as a glue
keeping the cells stuck together
• Cornified envelope begins to form.

11. Stratum Lucidum
It has 2-3 cell layers
Present in thicker skin of palms and
soles, and lips
It is a transparent thin layer
Translucent protein called eleidin is
present in the cell

12. Stratum Corneum
• Also known as horny layer
• The outermost layer of the skin
• Made of 15-20 layers of flattened, anucleated
squamous cells(dead keratinocytes)or corneocyte
• The cells are made of mature protein –keratin
• This keratin secretes defensins which immunes our
body.
• Cornification takes place as keratinization keeps
happening
• Desquamation takes place continuously
• Average duration for cells to replace from basal
layer to corneum layer for adults is 4-6 weeks and
for babies is 7-10 days.

13. To
remember
• Keratinization
• Cornification – development of skin barrier,
nails and hair
• Desquamation
• These are certain processes which keeps
happening for proper functioning of
integumentary system in the epidermis layer

14. Cells of epidermis
Keratinocytes
• Predominant cell of epidermis
• Originates in Basal Layer
• Protective barrier by secreting
defensins
• The mature keratin acts as water
barrier by making and secreting
lipids
• Gives toughness to skin because of
hardened keratin
• Regulates calcium absorption
needed for formation of vitamin D
by UVB rays

15. Langerhan’s
cells
• Present in Stratum Spinosum
• They are dendritic cells.
• It protects the skin by
producing antigen
presentation through allergic
reaction and stimulates the
immune cells into action.
• It guards the cutaneous
membrane(epidermis,
dermis&hypodermis)

16. Merkel Cells
Found in Stratum Basale
• Oval shaped mechano receptors for
light touch
• Found mostly in finger tips, palms,
soles, oral.
• Has keratin and desmosomes
• Desmosomes connects merkel cells to
adjoining keratinocytes
• Their membrane interacts with free
nerve endings

17. Melanocytes
• Found in Stratum Basale
• Produces pigment “Melanin”which gives color to
the skin
• UVB stimulates melanin secretion which protects
skin from harmful UV radiation acts as a built in
sunscreen
• The amount of melanin transfer to keratinocytes
defines the skin color
• There are two types of melanin
Eu melanin ( brown&black)
Pheo melanin ( red and yellow)

18. Coloration of skin
Combination of three pigments
• Melanin
• Carotene
• Haemoglobin
Carotene
A yellowish pigment found in epidermal cell
and fatty cell of dermis
Abundant in skins of Asians
Together with melanin accounts for
yellowish tan color.
Haemoglobin
Not a pigment, but its oxygen binding
capacity in RBC’s gives pinkish tone to the
skin.