The epidermis is a hardened, stratified, squamous epithelium. Its density varies from 0.5 to 3mm. depending on its location. Being the most external layer of the skin, it is obviously an important place for microbial colonization.

The most common cell of the epidermis (comprising approximately 90% of all the cells of the skin) is the keratinocyte. New keratinocytes are continually being created in the stratum basale. When they are moved towards the surface, they experience a process called keratinization.

This implies the synthesis of a unique protein called keratin, and the eventual death of the cell. The dead keratinized cells (called squames) comprise the external layers of the epidermis with lipids that occupy the intercellular spaces and are gradually sloughed off - a process called desquamation. It has been calculated that the skin surface of the average adult is composed of approximately 2 x 10 (9) squames. It takes between 14 and 28 days for the passage of a cell from the basal layer to the external layer of the skin, and as a consequence of this process, it has been calculated that the stratum corneum is completely renewed every 15 days.

The keratin contained by cells defends the underlying tissues from heat, chemicals, and microbes. Melanocytes are the next most typical cells of the epidermis. These have long thin projections that produce a dark pigment termed melanin. This pigment is then moved to the keratonicytes where it absorbs ultraviolet rays, thus protecting the skin from its harmful effects, stopping the development of further actinic keratosis symptoms. The only other cells present in the epidermis are Langerhans cells (which are involved in the defensive response to microbial intruders) and Merkel cells (which are linked with sensory neurons and are involved in the sense of touch).

Your skin and the production of acne

The dermis has a highly complex structure that consists of:

1) Connective tissue including collagen and elastin fibers giving the skin elasticity; 2) Tiny finger-like projections (papillae) which reach into the epidermis and contain nerve endings sensitive to touch, heat and pain; 3) Hair follicles; 4) Arrector pili muscles for controlling hair movement; 5) Sebaceous glands; 6) Sudoriferous glands; 7) Nerves; 8) Adipose tissue; and 9) Capillaries and veins.

It is essential to know how and why acne issues occur within your skin's anatomy. On the keratin lined follicle canal, where the sebaceous glands are found, Proprionibacterium bactaria exists in symbiosis, feasting on and transforming the sebum secreted from the sebocytes cells before it submerges on the surface of the skin. The nascent sebum is largely lipid in structure and also has DNA, RNA, proteins, and other cell components that result from the breakdown of sebocytes themselves. Proprionibacterium acne is observed only in sebaceous rich areas.

If the substrates in the follicular canals augment due to an active and large sebaceous system and sebum does not evacuate adequately out of the canals, then colonization and high reproduction rates of Proprionibacterium acne will form. The resident bacterial flora creates biologically active molecules such as histamine, extracellular enzymes and peptides, which may trigger the inflammatory reaction that characterizes acne breakouts.