INTRODUCTION TO SKIN Part 1- Epidermis

SKIN ANATOMY

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EPIDERMIS

Stratum Corneum

Stratum Granulosum

Stratum Spinosum

Stratum Basale

Stratum Lucidum

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THE RELATION BETWEEN THESE 5 LAYERS

Stratum CorneumStratum GranulosumStratum SpinosumStratum Basale

Stage 1

Stage 2Stage 3

Stage 4

1 2 3 4

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STRATUM BASALE

• Made up of keratinocyte stem cell.

• Undergoes mitosis division to constantly renew epidermal cells.

• Half of the cells differentiate and move to the next layer (stratum spinosum) to begin the maturation process- Keratinisation/ desquamation

• Other cell in stratum basale: Melanocyte Keratinocyte

SKIN DESQUAMATION

• is a natural process where skin cells are sloughed away and replaced.

• It takes approx. 28 days.

• The duration of keratinisation process will vary with different lifestyle, sun exposure, ageing and etc.

• Dead skin cells accumulation will result in pigmentation, dull skin, dehydration and etc. - Exfoliating can help in normalise skin regeneration.

MELANOCYTE• is a melanin producing cells.

• melanin is a pigment found in eyes, skin, and hair.

• Function is to protect skin cells and tissues from harmful UV radiation- transform the UV energy to heat.

• Almost everyone has the same amount of melanocyte,while the size and amount of melanosomes can be different.

• Most of the whitening products act on the process of melanogenesis.

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STRATUM SPINOSUM

• Retaining moisture and protect against foreign bodies and substances.

• Begin to synthesise keratin, which can hold water and retain moisture.

• Langerhans cells to detect skin penetration by foreign matter and transport the invaders to the lymph node.

• The malfunction/activation of langerhans cells can lead to sensitive skin.

Desmosomes

STRATUM GRANULOSUM

• Contain granules, which to bind keratin filaments together.

• Lamellar bodies are formed in the keratinocytes of stratum granulosum.

• When it matures to the stratum corneum, enzyme degrade the outer layer of lamellar bodies, releasing lipids such as ceramides, essential fatty acids and cholesterol.

• The lipids fuse with stratum corneum to form a continuous layer of lipids- called lamellar lipid bilayer- which is lipid soluble.

• impermeable to water soluble substances.

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STRATUM CORNEUM

• Outermost layer of epidermis, consist of 15-20 layers dead cells.

• Corneocyte/Keratinocyte- protein complex that made of keratin. These keratin can hold large amounts of water between fibre. Contain NMF.

• Natural moisturizing factor (NMF)- water soluble compound that absorb water from the atmosphere to stay hydrate. Yet, they are easily leached from the cells with water contact.

• Intercellular lipid- consist of ceramide, free fatty acids and cholesterol. It can maintain the water balance by trapping water molecule

• Corneodesmosome- Diversify desmosome that hold the corneocyte together

Brick and mortar structure

STRATUM CORNEUM

• Water content in stratum corneum should remain approx 15-20%.

• The main functions of stratum corneum are

• to provide hydration to skin and prevent loss of water through the water holding/absorb properties and lipid bilayer.

• to protect skin against foreign bodies through the brick and mortar structure.

• The incomplete of stratum corneum can lead to several skin problems- such as dehyrated skin, aging skin, sensitive skin, oily skin and etc.

Brick and mortar structure

SEBUM• A combination of sebum that secrete by

the sebaceous gland and sweat.

• It’s slightly acidic (pH 4.5-6.5)

• Function:

• to inhibit the growth of bacteria due to the acidic environment

• Prevent water loss from the epidermis due to it’s waterproof nature

• Sebum is odorless, but it breakdown by bacteria can product strong odor

• The incomplete of sebum can lead to acne skin.Keratinocyte

Intercellular matrix

Sebum

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CONTENT OF STRATUM CORNEUM

Sebum Corneocyte/Keratinocyte Intercellular Matrix

41% Triglyceride21% Wax estersAmino acids Lactic acid Cholesterol 12% Squalane Uric acid

80% Keratin protein20% amino acidsUric acidNMFPyrrolidone Carboxylic Acid

55% CeramidesCholesterolFree fatty acids

Keratinocyte

Intercellular matrix

Sebum

Brick and mortar structure

REVISION

Stratum basale • Skin regeneration• Secrete melanin

Stratum spinosum • Provide nutrients• Detect allegens

Stratum granulosum • Provide structural protection• to create skin barrier

Stratum corneum • Provide hydration• 1st layer to protect skin from

foreign bodies.

Stratum lucidum • Reduces effect of friction• Provides protection

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REFERENCE

• https://www.youtube.com/watch?v=OKosGSm7Ps4

• http://dermatology.about.com/

• http://www.taiwanlaser.com/

• http://www.wisegeek.com/

• https://www.wikipedia.org