. Author manuscript; available in PMC: 2014 May 1.

Published in final edited form as: Wiley Interdiscip Rev Nanomed Nanobiotechnol. 2013 Feb 5;5(3):205–218. doi: 10.1002/wnan.1211

Table 1.

Nature of skin strata: cellular and molecular components and associated functions

	Anatomical feature	Cellular components		Molecular components	Function
Epidermis
*Stratum Corneum*	A cornified layer possessing a “bricks and mortar” structure	Corneocytes, the dead cells lacking nuclei and organelles		Intercellular lamellar lipid bilayers	Contributes significantly to the permeation barrier properties of skin
*Stratum Lucidum*	A thin and clear/translucent layer found only in certain areas of thick skin	The major cells of the viable epidermis are keratinocytes (90–95%). As the keratinocytes in the basal layer of epidermis proliferate, the daughter cells migrate superficially and differentiate, forming the shallower layers	Flattered and dead keratinocytes filled with eleiden, an intermediate form of keratin	Oily lamellar bodies containing lipids and proteins	Water proof barrier preventing fluid loss
*Stratum Granulosum*	A highly differentiated granular layer		Keratinocytes becoming granular cells that contain keratohyalin granules	Oily lamellar bodies containing lipids and proteins	Water proof barrier preventing fluid loss
*Stratum Spinosum*	A spinous layer where keratinization begins		Adjacent keratinocytes are joined together by desmosomes; Langerhans cells (the dendritic cells)	Cytokeratins, the intermediate filaments of keratin, and desmosomes	Cytokeratin-desmosome networks provide structural support, helping the skin resist abrasion. Langerhans cells contribute to the immunological response of the skin
*Stratum Basale*	The deepest layer of epidermis		Melanocytes produce melanin that contributes to skin pigmentation and protects the skin from harmful ultraviolet radiation; Merkel-Ranvier cells (the oval receptor cells) contribute to sensory reception).		This is where the epidermal (keratinocytes) differentiation initiates
Dermis
*Papillary Dermis*	A layer intertwined with the overlaying epidermis, forming rete pegs and rete ridges along the dermal-epidermal junction	Fibroblasts, macrophages, and adipocytes		Collagen, elastin, glycos-aminoglycans and glycoproteins	Provides tight contact between epidermis and dermis
*Reticular Dermis*	A layer of dense collagen and elastic fiber matrix	Fibroblasts, macrophages, and adipocytes		Collagen, elastin, glycos-aminoglycans and glycoproteins	Main source of the strength, flexibility and elasticity of the skin.