1 All Physician Training licenses expire on August 31, 2015, are good for three years, and can only renew once (for a total of six years). 2  All Physician Assistant licenses expire on January 31 of even-numbered years.  All Anesthesiologist Assistant licenses expire on January 31 of even-numbered years.
The epidermis is the uppermost or epithelial layer of the skin. It acts as a physical barrier, preventing loss of water from the body, and preventing entry of substances and organisms into the body. Its thickness varies according to body site. The epidermis consists of stratified squamous epithelium.
Langerhans cells of the skin. The epidermis is a stratified epithelium. In this location, specialised F4/80-positive macrophages called Langerhans cells (LC), can be seen spread specifically in the basal layer, in intimate contact with proliferating keratonocytes. LC have been of great interest because they can differentiate into specialised antigen-presenting dendritic cells. However, there is also considerable evidence that they regulate the function, differentiation and proliferation of epidermal keratinocytes.