Buccal pouch

Cheek pouches are pockets on both sides of the head of some mammals between the jaw and the cheek. They can be found on mammals including the platypus, some rodents, and most monkeys, as well as the marsupial koala. The cheek pouches of chipmunks can reach the size of their body when full.

Cheek pouches are located in the thickness of the flange on both sides of the mouth of some mammals. Monkeys have open cheek pouches within the oral cavity, but they open out in some rodents of America. Hence the name "diplostomes" is associated with them, which means "two mouths." In some rodents, such as hamsters, the cheek pouches are remarkably developed; they form two bags ranging from the mouth to the front of the shoulders.Étienne Geoffroy Saint-Hilaire described that some bats of the genus Nycteris have an amazing form of cheek pouches, as they have a narrow opening, through which the bat can introduce air, closing the nasal canal through a special mechanism and pushing air under the skin, so they expire in the tissue, which unites the very loose skin to the underlying muscles.

Cheek pouches have several roles; they allow the rapid collection of food, but also serve as temporary storage and transport. In monkeys of the subfamily of Cercopithecinae, they allow for more predigested food. Cheek pouches contribute to the protection of animals by allowing them to carry their food in the pouches to shelter, allowing them to transport their food to safer locations, as they are pressing these pouches to the back of the mouth with the back of the leg, or moving the jaw. The females of some species of hamster are known to hide their young in their cheek pouches to carry them away when they fear danger. Other species of hamsters are known to fill their pouches with air, allowing them to float better while they swim.

The cheek pouches can become infected as a result of an injury caused by a sharp object inserted into them or a fight. An abscess can form, which can be confused with protuberance with stored food. If the abscess bursts and the pus contained therein is absorbed by the animal, it can be a victim of sepsis and die of the poisonous toxins. The cheek pouches can also turn outwards.

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Wikipedia