Sentence:  <WSD>Squames</WSD> begin life as normal cells in the lower layers of the epidermis but, as they travel towards the surface, they progressively lose all recognizable contents, becoming plates of mainly keratin protein, based on a progressive deposition of protein on the intermediate filaments of the cytoskeleton. 
Meaning of the word marked with <WSD> tags:  A flake of dead skin tissue.