Psoriasis

Psoriasis is a non-contagious, chronic autoimmune disease that causes skin inflammation, and is linked to other autoimmune deficiencies such as psoriatic arthritis.

It can be incredibly itchy and form silver plaques on the skin that can be embarrassing, and have both physical and psychological effects.

Afflicted reality TV star Kim Kardashian, and singer Cyndi Lauper have each spoken out on how psoriasis can have a significantly negative impact on the quality of life.

Normally, the skin is divided into three layers--the epidermis, dermis, and hypodermis.

The hypodermis is made of fat and connective tissue that anchors the skin to the underlying muscle.

Just above the hypodermis is the dermis, which contains nerves, sweat glands, lymph and blood vessels.

Just above the dermis is the epidermis.

The epidermis itself has multiple cell layers that are composed of developing keratinocytes - which are named for the keratin protein that they’re filled with.

Keratin is a strong, fibrous protein that allows keratinocytes to protect themselves from getting destroyed when you rub your hands through the sand at the beach.

Keratinocytes start their life at the lowest layer of the epidermis called the stratum basale, or basal layer, which is made of a single layer of small, cuboidal to low columnar stem cells that continually divide and produce new keratinocytes.

These new keratinocytes migrate upwards, forming the other layers of the epidermis.

As keratinocytes in the stratum basale begin to mature and lose the ability to divide, they migrate into the next layer, called the stratum spinosum which is about 8 to 10 cell layers thick.

The stratum spinosum also has dendritic cells lurking around, which are star-shaped immune cells constantly patrolling for invading microbes as part of the body’s immune defense system.

The next layer up is the stratum granulosum which is 3 to 5 cell layers thick.

Keratinocytes in this layer begin the process of keratinization, which is the process where the keratinocytes flatten out, and get rid of their intracellular structures and die, and in the process they create the epidermal skin barrier.

Keratinization leads to development of the stratum lucidum layer which is 2 to 3 cell layers thick of translucent, dead keratinocytes that have shed nuclei.

The stratum lucidum is only found in thick skin like on the palms and soles of the feet, because those are the areas that need extra protection.