Peritrophic membrane

Definition

A semipermeable, acellular sheath secreted by midgut epithelial cells that envelops the food bolus in the digestive tract of many arthropods and other invertebrates. The structure compartmentalizes digestion, protects the gut epithelium from mechanical abrasion and chemical damage, and reduces pathogen invasion while permitting nutrient absorption.

Etymology

Greek peri- (around) + trophikos (nourishment, feeding)

Example

In mosquitoes (Culicidae), the peritrophic membrane forms rapidly after a blood meal, creating a protective sleeve around the erythrocyte mass that allows proteolytic enzymes to penetrate and digest the blood while shielding the midgut epithelium from hemolytic damage and potential arbovirus infection.

Synonyms

• peritrophic matrix

Related Terms

• Midgut
• digestive tract
• peritrophic space
• Basement membrane
• Chitin

Usage Notes

The term 'peritrophic matrix' is increasingly preferred in modern literature, though 'membrane' remains common in entomology. Not a true cell membrane but a secreted extracellular layer; composition varies—Type I forms around food (as in most insects), while Type II forms continuously independent of feeding (as in some Diptera and Lepidoptera). Distinct from the basal lamina or other gut linings.