Insights to the Stratum Corneum Layer of skin.

1. Vikhyati Patel
15MCT111
SEM II
CE-1 of PDCF
STRATUM CORNEUM

2. CONTENT
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3. PERMEATION BARRIER
• Stratum corneum is the horny layer of the
epidermis.
• Acts as the primary permeability barrier of
the skin.
3
"Delivery system Handbook for personal care and cosmetic products", Meyer R. Rosen, William Andrew Publishing, NY. USA, 2005 edition, Skin physiology and
penetration pathway- Stratum corneum.

4. ULTRA-STRUCTURE
• Corneocytes: cell of this layer.
• Corneocytes are hexagonal or pentagonal in shape; aligned
and stacked like plates.
• Intercellular spaces of the stratum corneum contain many
stacked membranous structures.
• Membrane lipids are organized into trilaminar units
4"Delivery system Handbook for personal care and cosmetic products", Meyer R. Rosen, William Andrew Publishing, NY. USA, 2005 edition, Skin physiology and
penetration pathway- Stratum corneum.

5. • The abundant lamellar arrangement include ones with three,
six and nine lucent band pattern.
• The three band pattern is mainly seen between the ends of the
adjacent Corneocytes.
• Six-band pattern is found between the broad, flat surfaces of
adjacent Corneocytes.
• Nine-band pattern contain 3 broad-narrow-broad lucent band
units.
• The first lucent band adjacent to the electron-dense protein
band of the cornified envelope is covalently attached lipids.
• The paired bilayer are attached by edge-to-edge fusion of
flattened lipid vesicles extruded from the lamellar granules.
• The narrow lucent band bands in the centre of the nine-band
pattern is formed by the eversion of the linoleate chains from
acyl ceramide molecules in the adjacent lamellae to form a
zipper-like central narrow lamella.
5
• "Delivery system Handbook for personal care and cosmetic products", Meyer R. Rosen, William Andrew Publishing, NY. USA, 2005 edition, Skin physiology and
penetration pathway- Stratum corneum.
• https://books.google.co.in/books?id=As1eHSlUIggC&pg=PA83&lpg=PA83&dq=linoleate+chains+in+stratum+corneum+ultrastructure&source=bl&ots=b-
Sj5wPMSh&sig=UQjFPpF5UxlDreFAsJwpuuSIoA&hl=en&sa=X&ved=0ahUKEwi9v6GQgqLKAhWBbY4KHfWmA9QQ6AEIHjAA#v=onepage&q=linoleate%20chains%20in
%20stratum%20corneum%20ultrastructure&f=false

6. STRUCTURAL PROTEINS OF SC
• Keratin is the major structural protein of SC.
• They are a type of intermediate filament.
• There are approximately 30 different keratin genes.
• 50% code for Type I Acidic keratin
• 50% code for Type II Neutral-Basic keratin polypeptide.
acidic-basic genes
heteroduplexes
building blocks for keratin fibres
6
"Delivery system Handbook for personal care and cosmetic products", Meyer R. Rosen, William Andrew Publishing, NY. USA, 2005 edition, Skin
physiology and penetration pathway- Stratum corneum.

7. • At the end of the differentiation, proteins are
deposited at the cell periphery-
 Involucrin
 Envoplakin
 Periplakin
• 80% of the protein I the epidermal cornified envelope
is loricrin.
• There are two linkages- 1. Isopeptide linkages
2. Disulphide linkages
between envelope proteins
• The cross-linked proteins of the envelope is 10-12nm.
• Covalently bound lipids are 4-5nm thick.
• Epidermis keratin filaments are anchored to the
cytoplasmic sides of the desmosomes through
specialized adapter proteins.
• This network provides physical strength to the
epidermis and important in the dissipation of
shearing forces.
• Desmosomes are made up of three protein families:
cadherins, plakins, armadillo.
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"Delivery system Handbook for personal care and cosmetic products", Meyer R. Rosen, William Andrew Publishing, NY. USA, 2005 edition, Skin
physiology and penetration pathway- Stratum corneum.

8. MODELS
1. TWO COMPARTMENT MODELS:
o Bricks-and-mortar model
o Impermeable, keratin-filled cells.
o Cells embedded in continuous lipid phase
o Corneocytes= bricks
o Lipids= mortar
o Provides tortuous pathway.
o Hence helps in skin barrier function.
8
• "Delivery system Handbook for personal care and cosmetic products", Meyer R. Rosen, William Andrew Publishing, NY. USA, 2005 edition, Skin
physiology and penetration pathway- Stratum corneum.
• http://www.medscape.org/viewarticle/473453_1

9. 2. Domain Mosaic model
• Ceramides or free fatty acids are rod-like or
cylindrical in shape.
• Therefore, they form relatively impermeable,
membrane domain.
• Cholesterol fluidize the stratum corneum
membrane.
• This model was proposed by Forslind.
• Gel phase domain are embedded in in a
continuous liquid crystalline phase.
• Penetrants diffuse primarily through the
liquid crystalline phase.
9
"Delivery system Handbook for personal care and cosmetic products", Meyer R. Rosen, William Andrew Publishing, NY. USA, 2005 edition, Skin
physiology and penetration pathway- Stratum corneum.

10. 2. Single- gel phase model
• Lamella have low water content and
low lipid mobility due to close
packing of the lipid chains.
3. Sandwich model
• Based on molecular geometry.
• Outer two lamellae of tri-lamellar
membrane unit are in the gel phase
while central lamella in liquid
crystalline state.
10
"Delivery system Handbook for personal care and cosmetic products", Meyer R. Rosen, William Andrew Publishing, NY. USA, 2005 edition, Skin
physiology and penetration pathway- Stratum corneum.

11. STRATUM CORNEUM LIPIDS
• In epidermal SC, lipids
compromise 10-15% of the dry
weight of the tissue.
• Ceramides (50%), cholesterol
(25%) and saturated fatty acids
(10%) are the principle lipids of
SC.
• Cholesterol esters, cholesterol
sulphate, glycosylceramides are
present in minor amounts.
• Pig skin is excellent model for
human skin.
11
"Delivery system Handbook for personal care and cosmetic products", Meyer R. Rosen, William Andrew Publishing, NY. USA, 2005 edition, Skin
physiology and penetration pathway- Stratum corneum.

12. CERAMIDES
• Structurally heterogeneous.
• Nomenclature was proposed by Motta, et.
Al
• Base is designated as S: Sphingosine, P:
phytosphingosine or H:6-
hydroxysphingosine.
• Amide- linked fatty acid are designated as
N: normal fatty acid, A: α-hydroxyacid or
O: ω-hydroxyacid.
• Ester-linked fatty acid is designated with
prefixed E.
• Least polar is CES EOS.
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"Delivery system Handbook for personal care and cosmetic products", Meyer R. Rosen, William Andrew Publishing, NY. USA, 2005 edition, Skin
physiology and penetration pathway- Stratum corneum.

13. • CER-EOS: 34- carbon ω- hydroxyacid amide-
linked to sphingosine bases with linoleic acid
ester- linked to the ω- hydroxyl group.
• CER-NS: linked to sphingosine and
dihydroxysphingosine bases.
• CER-NP: similar to CER-NS but linked to
phytosphingosine bases.
• CER-EOP: minor component and is a
phytosphingosine containing variant acyl-
ceramide.
• CER-AS: short C16 and long C24-28 α-
hydroxyacid amide. They are linked to
sphingosines and dihydroxysphingosine.
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"Delivery system Handbook for personal care and cosmetic products", Meyer R. Rosen, William Andrew Publishing, NY. USA, 2005 edition, Skin
physiology and penetration pathway- Stratum corneum.

14. CHOLESTEROL
• Sterol found in porcine and
Human stratum corneum.
• Widely distributed membrane
component.
• It either increases or decreases
membrane fluidity, depending
on proportion of cholesterol.
• Variation in fluidity has major
impact on molecular diffusion
across the membranes.
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"Delivery system Handbook for personal care and cosmetic products", Meyer R. Rosen, William Andrew Publishing, NY. USA, 2005 edition, Skin
physiology and penetration pathway- Stratum corneum.

15. FATTY ACIDS
• Contains aliphatic chains longer than 18C
• They are entirely saturated chains.
• Fatty acids that are abundant are generally 22-24C entities.
• Fatty acids and cholesterol sulphate are ionizable lipids in Stratum corneum.
Therefore, they are important for formation of lamellae.
• These impart negative charge to the skin surface, which results in trapping of
any cationic substances.
15
"Delivery system Handbook for personal care and cosmetic products", Meyer R. Rosen, William Andrew Publishing, NY. USA, 2005 edition, Skin
physiology and penetration pathway- Stratum corneum.

16. THANK YOU!
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