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

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

This involves the production of a unique protein known as keratin, and the subsequent death of the cell. The dead keratinized cells (known as squames) populate the external layers of the epidermis with lipids that fill 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 made 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 outermost layer of the skin, and as a result of this process, it has been calculated that the stratum corneum is completely renewed every 2 weeks.

The keratin contained by cells defends the underlying tissues against heat, chemicals, and microbes. Melanocytes are the next most common cells of the epidermis. These have long slender projections that produce a brown-black pigment termed melanin. This pigment is then transferred to the keratonicytes where it blocks ultraviolet rays, thus defending the skin against its damaging effects, stopping the development of further actinic keratosis symptoms. The only other cells present in the epidermis are Langerhans cells (which are part of the defensive response to microbial invaders) and Merkel cells (which are linked with sensory neurons and are involved in the sense of touch).

Getting to know skin anatomy

The dermis has a highly intricate structure that consists of:

1) Connective tissue including collagen and elastin fibers giving the skin elasticity; 2) Small 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 coordinating 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 invested follicle canal, where the sebaceous glands reside, Proprionibacterium bactaria exists in symbiosis, feasting on and changing the sebum produced by the sebocytes cells before it submerges on the exterior of the skin. The nascent sebum is largely lipid in composition and also contains DNA, RNA, proteins, and other cell components that result from the rupture of sebocytes themselves. Proprionibacterium acne is found 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 properly out of the ducts, then colonization and high reproduction rates of Proprionibacterium acne will appear. The resident microbial flora creates biologically active molecules like histamine, extracellular enzymes and peptides, which can trigger the inflammatory response that characterizes acne breakouts.