Gizzard

Definition

A muscular, grinding chamber of the foregut in many invertebrates and some vertebrates, located posterior to the crop and anterior to the midgut. In arthropods, the gizzard (also called the proventriculus in some groups) uses thickened cuticular plates, teeth, or muscular contractions to mechanically break down food, often assisted by ingested grit or mineral particles. It serves as a specialized stomach for physical digestion before enzymatic processing begins in the midgut.

Etymology

From Middle English giser, derived from Old French gésier, of uncertain origin; unrelated to the anatomically distinct ventriculus of birds.

Example

In grasshoppers (Orthoptera), the gizzard contains six sclerotized plates arranged as opposing teeth that grind plant material against embedded sand grains; in some decapod crustaceans, chitinous ossicles within the gastric mill perform analogous trituration of food.

Synonyms

• Ventriculus
• gastric mill
• Proventriculus

Related Terms

• crop
• Foregut
• Midgut
• Proventriculus
• peritrophic matrix
• sclerotized plate
• gastric mill
• bolus

Usage Notes

In entomology, 'gizzard' and 'proventriculus' are sometimes used interchangeably, though proventriculus more precisely denotes the muscular, cuticularized region immediately preceding the midgut, while gizzard emphasizes the grinding function. The term is less commonly applied to arachnids, which typically lack a discrete grinding chamber. In vertebrate anatomy, gizzard refers specifically to the muscular stomach of birds and archosaurs, a convergent structure unrelated by homology to the arthropod gizzard.