Gizzard

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Duck gizzards

The gizzard is a specially-adapted stomach that is found in birds, reptiles, earthworms, some insects, mollusks, and other creatures that is used for grinding up food. It has a thick, muscular wall in many invertebrate animals, enabling a powerful crushing and pulverizing action. In certain insects and mollusks, the gizzard features chitinous plates or teeth.

The gizzard is also known as a ventriculus, a gastric mill, or a gigerium.

[edit] Name

The word "gizzard" comes from the Middle English giser, which derives from a similar word in Old French, and earlier from the Vulgar Latin "*gicerium", which follows from the Latin word "gigeria", meaning cooked entrails of poultry. The Latin word "gigeria" probably is derived from the Persian word for liver, which is "jigar".

[edit] Structure

The bird first softens up food in its glandular stomach, or crop, which is in the lower part of its esophagus and then crushes and grinds up the food in its lower, true stomach, the gizzard.

Bird gizzards are lined with a tough layer constructed of the protein keratin, to protect the muscles in the gizzard.

[edit] Gizzard stones

Some animals that lack teeth will swallow stones or grit to aid in digestion. All birds have gizzards, but not all will swallow stones or grit. However, the birds that do, employ the following method of 'mastication':

"A bird swallows small bits of gravel that act as 'teeth' in the gizzard, breaking down hard food such as seeds and thus helping digestion." (Solomon et. al, 2002).

These stones are called gizzard stones or gastroliths and are usually smooth and round from the polishing action in the animal's stomach. When too smooth to do their required work, they may be passed or regurgitated.

[edit] Animals with gizzards

Emus, turkeys and chickens, like all birds, have gizzards.

Lough Melvin in County Fermanagh, Ireland, is home to the Gillaroo (Salmo stomachius), a species of trout which eats mostly snails. The gillaroo is a distinct species, characterised by a rich coloration and a "gizzard", which is used to aid the digestion of hard food items such as water snails.

The gizzard shad, or mud shad, is a fish with a gizzard. It is found in freshwater coastal areas, in streams and lakes, from New York to Mexico.

Dinosaurs are also known to have used gizzard stones. This has been discovered by finding groups of polished stones within the area occupied by a dinosaur skeleton.

[edit] Dinosaurs with Gizzards

Dinosaurs who are suspected to have gizzards because of gizzard stones found near their fossils include:

• Claosaurus
• Psittacosaurus
• Massospondylus
• Sellosaurus
• Omeisaurus
• Apatosaurus
• Barosaurus
• Dicraeosaurus
• Seismosaurus

[edit] Eating gizzards

The gizzards of poultry are a popular food the world over. Grilled chicken gizzards are sold as street food in China, Taiwan, Japan, Philippines, Haiti and the rest of Southeast Asia. Stewed gizzards are eaten as a snack in Portugal, while pickled turkey gizzards are a traditional food in some parts of the Midwestern United States. In the Southern United States, the gizzard is typically served fried, sometimes eaten with hot or honey mustard sauce.

Giblets consist of the heart, liver and gizzard of a bird, and are often eaten.

[edit] Sources

• Solomon, E.P., Berg L.P., and Martin D.W., 2002. Biology Sixth Edition. Thomson Learning Inc., Australia, Canada, Mexico, Singapore, Spain, United Kingdom, United States pp. 664

• A description of the gizzard shad