# Keratinocytes --- **Keratinocytes** are the cells that make up the majority of the [[epidermis]], and also play roles in other [[integumentary system#Accessory Structures|accessory structures]] of the integumentary system, such as the [[hair]] and [[nails]]. Keratinocytes produce a fibrous protein called **keratin** which is what gives our [[hair]], [[nails]] and [[epidermis|skin]] their hardness and water-resistance. Keratin actually kills the cells as it accumulates, I imagine it a little like cement. When keratinocytes differentiate they start out cuboidal, but they are continiously squished out onto a more superficial layer of [[epidermis]], in a deeper column of a [[hair|hair root]], or a distal part of the [[nails|nail plate]]. Along the way they dry out and became squamous. The keritin they produce gives their dead flat bodies a hardness that persists long after they have died. ![[epidermis.png]] ___