From the Guidelines
The epidermis is a complex, multi-layered structure composed primarily of keratinocytes, with its main function being to serve as the body's primary protective barrier against the external environment. The epidermis is subdivided into four stratums: basale, spinosum, granulosum, and corneum, with each stratum having distinct features and functions 19. Keratinocytes, the main cell-type present in the epidermis, are created in the stratum basale and migrate progressively to the next layers, giving rise to a permanent cellular renewal process 19.
Key Features of the Epidermis
- The epidermis is avascular, meaning it contains no blood vessels, and receives nutrients through diffusion from the underlying dermis 1.
- The stratum corneum is the most superficial layer of the epidermis and is composed of dead cells, known as corneocytes, which provide a barrier against water loss and external pathogens 20.
- The epidermis also contains other cell types, such as melanocytes, Langerhans cells, and Merkel cells, which play important roles in skin function and immune response.
Importance of the Epidermis
- The epidermis plays a crucial role in protecting the body against physical trauma, pathogens, and UV radiation 1.
- It also helps to regulate body temperature and prevent water loss 29.
- The epidermis is an important site for the delivery of topical and transdermal therapies, with the stratum corneum being the primary barrier to drug diffusion 21.
Clinical Relevance
- Understanding the structure and function of the epidermis is essential for the development of effective topical and transdermal therapies, such as lipid vesicles 37.
- The epidermis is also an important consideration in the treatment of skin conditions, such as aged skin, burns, and wounds, where the cellular composition and function of the skin are altered 39, 40.
From the Research
Epidermis Structure and Function
- The epidermis is one of the two main layers of the skin, the other being the dermis 2
- It is the outermost epithelial tissue that protects the body from the external environment 3
Epidermal Thickness and Atrophy
- Topical corticosteroids can cause skin atrophy and telangiectasia, including a decrease in epidermal thickness 4
- A study found that treatment with hydrocortisone 1% cream led to a significant decrease in epidermal thickness after 2 weeks, while pimecrolimus 1% cream caused a less pronounced decrease 4
Treatment of Skin Conditions
- Pimecrolimus 1% cream is an effective topical treatment for facial seborrheic dermatitis, with considerable control of symptoms and lower recurrence rates 5
- Pimecrolimus cream 1% has a favourable safety profile when used to treat adult patients with moderate to severe atopic dermatitis for up to 1 year 6
Barrier Function
- The skin epidermis plays a crucial role in barrier function, protecting the body from the external environment 3