cuticular

Cuticular is an adjective relating to the cuticle, the protective outer covering found on many organisms and to structures derived from it. The term is used across biology to describe features of plants, animals, and human anatomy that involve this outer layer.

In plants, the cuticle is a thin, waxy film secreted by epidermal cells on aerial surfaces, notably leaves and fruits. It is primarily composed of cutin, a polyester of fatty acids, reinforced by cuticular waxes. The cuticle forms a hydrophobic barrier that limits water loss and helps protect against pathogens and UV radiation. Its thickness and composition vary with species, tissue type, and environmental conditions; stomata, pores for gas exchange, are gaps in the barrier. Some plants also have suberin-rich layers in the periderm beneath the cuticle.

In arthropods and other invertebrates, the cuticle is the chitinous exoskeleton secreted by epidermal cells. It consists of layers: the epicuticle on the surface, and the procuticle divided into exocuticle and endocuticle. The cuticle provides structural support, protection, and a barrier to water loss; its mechanical properties are adjusted by sclerotization, a crosslinking of proteins and other components. Cuticular hydrocarbons and waxes also play roles in desiccation resistance and chemical communication.

In humans and other vertebrates, the term cuticular is used for structures derived from the cuticle, such as the hair cuticle, the outermost layer of the hair consisting of overlapping cells that protect the cortex; damage to the cuticle yields dullness and split ends. The nail cuticle, or eponychium, is a fold of skin at the base of the nail plate.