Membrane

Definition

A thin, pliable layer of tissue or cells that serves as a selective barrier or structural boundary. In arthropods, membranes occur at multiple scales: cellular membranes (lipid bilayers regulating molecular transport), cuticular membranes (flexible, unsclerotized regions of the exoskeleton allowing movement or expansion), and specialized sensory or acoustic membranes (tympana, tracheal air sacs, or wing bases). Membranes contrast with sclerotized, rigid cuticle in their compliance and permeability.

Etymology

Latin membrana, from membrum (limb, member)

Example

The tympanal membrane of a noctuid moth's ear is a thin, translucent cuticular membrane stretched over an air-filled tracheal sac, vibrating in response to bat echolocation calls and transducing sound to chordotonal sensilla.

Related Terms

• Cuticle
• Sclerite
• Tympanum
• Epidermis
• Basement membrane
• Hemolymph
• Trachea
• phragma

Usage Notes

In arthropod morphology, 'membrane' often specifically denotes flexible, unhardened cuticle between sclerites (intersegmental membranes, articular membranes) or specialized thin-walled structures (tympana, glandular ducts). This contrasts with general histological usage for any thin tissue layer. Specialists distinguish 'membranous' (flexible, thin, often transparent) from 'membrane' as a noun referring to the structure itself. The term is absolute in describing physical properties but relative in comparing degrees of sclerotization.