Nboost Doctor brochure - Flipbook - Page 12
Reassessing the epidermis
What is the epidermis?
The epidermis is the outermost layer of the skin composed of multiple layers and several cell types.
Sublayers
Cell types
Stratum
corneum
Corneocytes
Functions
(dead keratinocytes)
Stratum lucidum
(found only in thick skin)
Stratum
granulosum
Keratinocytes
Dendritic cell
Stratum
spinosum
Lanherans
Merkel cell
Stem cell
Stratum
basale
Melanocyte
1. MAINTENANCE OF HOMEOSTASIS 1
2. PROTECTION FROM INFECTION, PHYSICAL
DAMAGE AND CHEMICAL INJURY VIA TWO
IMPORTANT BARRIERS 2
▶ Corneocytes (Stratum Corneum) – prevent the
entry of foreign substances, microorganisms and
loss of water
▶ Keratinocytes (Subjacent Layers) – seal the cells
and produce protective biomolecules
3. THERMOREGULATION AND HYDRATION 3
4. UV PROTECTION AND SKIN PIGMENTATION 4
Dermis
How does the epidermis change as we age?
The visible effects of ageing
on the epidermis
Hydration & Transepidermal Water Loss (TEWL)
▶ Thin skin
▶ Appearance of wrinkles
▶ Skin dryness
▶ Uneven pigmentation
▶ Increased vulnerability to injury
▶ Enlarged pores and rough texture
Young
Old
Epithelium
Basement
membrane
Papillary
dermis
Reduced expression of aquaporins (AQP), water channels in the
membrane,5 together with changes in the main component of the
skin’s natural moisturising factor, decreases the binding capacity of
water.6
Structure & thickness
Keratinocytes, become shorter and fatter as skin ages, while
corneocytes become larger as a result of decreased epidermal
turnover. The loss of dermal papillae and reduced interdigitation
between layers results in less resistance to shearing forces.7
Keratinocyte proliferation & differentiation
Largely due to the keratin cytoskeleton acquired throughout the
epidermal cell differentiation process, keratinocytes have a high
deformation resistance, contributing to their protective action.
This protection is reduced with age.8
Melanin & erythema
Reticular
dermis
© 2008 Mine et al.
Uneven distribution of pigment cells, local loss of melanocytes
(decreasing at a rate ranging from 8 to 20% per decade), and
changes in their interaction with keratinocytes causes a heterogeneity
in skin color.9
