integuments

Integuments are natural outer coverings that encase and protect an organism or its parts. The term is used across biology to describe coverings in both animals and plants, and it often denotes layers that act as barriers, sensors, or protective envelopes.

In animals, the integumentary system includes the skin and its derivatives, such as hair, nails, feathers, scales, and glands. In vertebrates, the skin comprises two main layers: the epidermis (epithelial tissue) and the dermis (connective tissue), sometimes with a subcutaneous hypodermis. Functions include protection against mechanical injury and pathogens, prevention of water loss, temperature regulation, and sensory perception. Glands (sebaceous and sweat glands) and appendages (hair, nails) contribute to thermoregulation, communication, and defense. In arthropods, the integument consists of an external protective cuticle secreted by an underlying epidermis; it often becomes hardened through sclerotization and tanning and is periodically shed in a process called molting.

In botany, integuments refer to the protective outer layers of an ovule. Most angiosperms have one or two integuments that surround the nucellus and are typically fused to form the seed coat, or testa, after fertilization. The integumentary layers protect the developing embryo and contribute to seed dispersal traits.

Across kingdoms, integuments thus serve as critical interfaces between the organism and its environment, balancing protection, water balance, sensory input, and, in reproductive contexts, seed formation.