cuticules

Cuticle, sometimes spelled cuticules, is a term used in biology to describe protective outer layers that surround or cover exposed surfaces in a variety of organisms. Although the specific structure and composition differ, cuticles generally function as barriers against desiccation, mechanical damage, and microbial invasion.

In humans, the cuticle refers to a thin layer of dead skin at the base of the nail plate. The proximal skin that overlaps the nail is called the eponychium, while the skin at the underside of the nail is the hyponychium. The cuticle helps protect the nail matrix and the nail bed from infection. Care typically involves gentle grooming and hydration; aggressive cutting or picking can lead to irritation or infection.

In botany, the plant cuticle is a waxy, hydrophobic layer covering the epidermis of leaves, fruits, and stems. It is composed mainly of cutin and embedded waxes. The cuticle minimizes water loss and provides a barrier to pathogens, while its thickness and chemical composition vary with environmental conditions and plant species. Stomata in the leaf surface regulate gas exchange through pores that traverse the cuticle.

In arthropods, the cuticle is the exoskeleton external to the body, secreted by the epidermis. It consists of layers such as the epicuticle and the procuticle (including the exocuticle and endocuticle) and is primarily made of chitin and associated proteins. The cuticle provides structural support, protection against physical damage and parasites, and a barrier to water loss. Growth requires molting and remodeling of the cuticle, followed by sclerotization to harden the new exoskeleton.