Midgut

Definition

The middle section of the alimentary canal in arthropods and other invertebrates, lying between the foregut (stomodeum) and hindgut (proctodeum), where the majority of enzymatic digestion and nutrient absorption occurs. In insects, the midgut is typically a tubular or sac-like region lined with a protective peritrophic matrix and columnar epithelial cells that secrete digestive enzymes and absorb nutrients; it is the only portion of the gut derived from endoderm, lacking cuticular lining. The midgut often includes anterior extensions (caeca) that increase surface area and may harbor symbiotic microorganisms.

Etymology

From English 'mid-' (middle) + 'gut' (digestive tract)

Example

In caterpillars, the midgut is highly alkaline (pH 9–11) and produces powerful proteinases that break down plant leaf tissues; disruption of midgut ion transport by Bacillus thuringiensis toxins causes lethal osmotic swelling.

Synonyms

• mesenteron
• Ventriculus

Related Terms

• Foregut
• Hindgut
• peritrophic matrix
• Malpighian tubules
• gastric caeca
• digestive enzyme
• enterocyte
• Stomodeum
• Proctodeum

Usage Notes

In entomology, 'midgut' and 'mesenteron' are often used interchangeably, though 'mesenteron' emphasizes the embryonic (endodermal) origin. Contrast with 'ventriculus' in some older literature, which can refer specifically to the midgut's expanded region. The midgut is the primary target for many insecticidal proteins (e.g., Bt toxins) and is a key site for host–pathogen and host–symbiont interactions. In vertebrate embryology, 'midgut' refers to a specific developmental region of the intestine; this usage is distinct from the arthropod anatomical term.