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The Digestion of a Duck
1. THE ENTRANCE Food, such as seeds, roots, insects, snails, fish, and so on, enters the duck's body through its mouth. Ducks also take in little bits of stone, called grit (which comes in handy later). Unlike humans, ducks don't have teeth or strong chewing muscles to break down food. With a tilt of the duck's head, food is swallowed whole. It then heads into the elevator.
2. THE ELEVATOR The esophagus (eh-SOF-uh-gus) is a tube-like organ with strong muscles that squeeze food down toward the stomach. Before food reaches the stomach, though, it goes into storage.
3. THE STORAGE ROOM The crop stores extra food until it's ready to be digested. The crop is part of the esophagus that widens out to form a sac. Ducks often eat more than their bodies can digest right away. When the food needs to be digested, it is sent into the next part of the food factory.
4. THE CHEMISTRY ROOM Food moves from the crop into the first part of the stomach, called the proventriculus (pro-ven-TRIK-yuh-lus). This is where digestion actually begins. Digestive juices are mixed with the food here. The juices contain chemicals that dissolve, or break down, food.
5. THE GRINDING ROOM Next, the food passes into the gizzard, which is the second part of the stomach. Digestion continues here, through the action of muscles instead of chemicals. The muscles that make up the gizzard's walls are very strong. The walls have lots of ridges. As the muscles squeeze, food is ground between the ridges. Grit also helps the gizzard's grinding action. As the sharp stones are squeezed together with the food, they break it down even more. Still, the gizzard can't grind down everything a duck eats. Some hard-coated seeds will pass through the factory completely whole. You can think of the gizzard as a duck's "teeth". The gizzard chews up food just as your teeth do.
6. THE SHIPPING ROOM Food moves on to the intestine (in-TES-tin). More digestive juices mix with the food here to finish breaking it down. These juices come from other parts of the body, called the liver and the pancreas (PAN-kree-us). The food also passes into a special section of the intestine that contains tiny life-forms called bacteria. The bacteria break down certain materials the digestive juices cannot. The intestine
is also where tiny blood vessels absorb, or take in, needed materials from the digested food. Then larger blood vessels carry the materials to the rest of the body's blood stream. Water is also absorbed into the body.
7. THE EXIT The last part of the duck food factory is the cloaca (klo-AY-kuh). Any solid material that's not digested passes through here and out of the duck's body.
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