The Epidermis

The epidermis is incredibly thin - about as thin as a piece of paper - especially when compared to total skin thickness. The epidermis is a layered epithelium made up of five distinct cell layers.

• Stratum Corneum (Horny Cell Layer)
• Stratum Lucidum (Clear Cell Layer)
• Stratum Granulosum (Granular Cell Layer)
• Stratum Spinosum (Prickle Cell Layer or Spinous Cell layer)
• Stratum Germinativum (Basal Cell Layer)

The skin is in a continuous process of self-renewal, and each epidermal layer corresponds to a specific stage in this process, which is called keratinization.

The process is called keratinization because the stratum corneum is mainly keratin, the tough protein that is also the major component of hair, hoof, horn, and nails.

Normal keratinization and desquamation depend on timing and balance. A healthy stratum corneum is produced when cells are manufactured at a normal rate, when cells are shed at a normal rate, and when these two processes are in sync with each other.

If keratinocytes are produced faster than they can possibly be sloughed off, as is the case in psoriasis, scaly plaques form. If desquamation takes place too early, the skin isn’t an effective protective barrier.

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