Mouth

:For the mouth of a river, see delta and estuary.

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The mouth, also known as the buccal cavity or the oral cavity, is the opening through which an animal or human takes in food. It is usually located in the head, but not always; the mouth of a planarium is in the middle of its belly.

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Most animals have a complete digestive system, with a mouth at one end and an anus at the other. Which end forms first in ontogeny is a criterion used to classify animals into protostome and deuterostome.

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Some animals, such as the cnidarians and the planaria, have no anus. They expel waste through the mouth, or as do brachiopods, which have very efficient digestive systems, roll it around in the stomach until it is finished.

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Some animals, such as the tapeworm, don't even have a mouth. The tapeworm lives inside the digestive system, so it doesn't need its own digestive system.

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In many animals, the mouth has mouthparts to chew food, hold food, or inject poison. In arthropods, they are external modified legs; in gnathostome vertebrates, they are internal.

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The horny structures covering the mouth of a bird compose its beak or bill.

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The human mouth is covered by an upper and lower lip. They play an important role in speech, facial expression, kissing, drinking (especially with a straw), sex, and smoking. Infants are born with a sucking reflex, by which they instinctively know to suck for nourishment using their lips and jaw. Lips are often adorned with lipstick or lip gloss. The philtrum is the vertical groove in the upper lip, formed where the nasomedial and maxillary processes meet during embryo development. When these processes fail to fuse fully, a hare lip and/or Cleft palate can result.

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According to etiquette the mouth is kept closed, especially when chewing.

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River: :For the Second World War frigate class, see River class frigate. For the state of Nigeria, see Rivers State....

Delta: Delta may refer to:...

Estuary: An estuary is a semi-enclosed coastal body of water which has a free connection with the open sea and within which sea water mixes with fresh water. The key feature of an estuary is that it is a mixing place for sea water and a significantly-sized river to supply fresh water. A tide is a necessary ...

Mouth related Images and Photos (experimental)

Mouth	Smart Mouth Game	Small Mouth Bass	Mouthy Mouth Puppet
Big Mouth 1967	Big Mouth 1967	Smash Mouth: All Star Smash Hits	Smash Mouth: All Star Smash Hits
Smash Mouth: All Star Smash Hits CD	Smash Mouth: All Star Smash Hits CD	Black Mouth Cur Caution Sign	Nil by Mouth