Reply #7: Gizzards [View All]

The gizzard, also referred to as the ventriculus, gastric mill, and gigerium, is an organ found in the digestive tract of some animals, including birds, reptiles, earthworms and some fish. This specialized stomach constructed of thick, muscular walls is used for grinding up food; often rocks are also instrumental in this process. In certain insects and mollusks, the gizzard features chitinous plates or teeth.

Birds swallow food and store it in their crop if necessary. Then the food passes into their glandular stomach, also called the proventriculus, which is also sometimes referred to as the true stomach. This is the secretory part of the stomach. Then the food passes into the ventriculus (also known as the muscular stomach or gizzard). The gizzard can grind the food with previously-swallowed stones and pass it back to the true stomach, and vice versa. Bird gizzards are lined with a tough layer made of the carbohydrate-protein complex koilin, to protect the muscles in the gizzard and to aid in digestion.

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. 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 round and smooth from the polishing action in the animal's stomach. When too smooth to do their required work, they may be passed or regurgitated.

http://en.wikipedia.org/wiki/Gizzard

Sorry, I couldn't bring myself to post the photo. :puke: