Mouth

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This article is about the body part in many animals. For the human body part, see Human mouth. For the landform, see River mouth. For other uses, see Mouth (disambiguation).
Mouth
Basel Zoo in Switzerland
Details
Identifiers
Latinos, oris[1]
MeSHD009055
TA98A05.1.00.001
TA2119, 2774
FMA49184
Anatomical terminology]

The mouth is the

teeth in their mouths,[4] although some fish species have pharyngeal teeth
instead of oral teeth.

Most

gut tube with a mouth at one end and an anus at the other. Which end forms first in ontogeny is a criterion used to classify bilaterian animals into protostomes and deuterostomes
.

Development

Main articles: Protostome and Deuterostome
Development of the mouth and anus in protostomes and deuterostomes

In the first

sponges which, despite their large size, have no mouth or gut and capture their food by endocytosis.[5]

However,

diploblastic animals probably consisted of a mouth and a one-way gut. Some modern invertebrates still have such a system: food being ingested through the mouth, partially broken down by enzymes secreted in the gut, and the resulting particles engulfed by the other cells in the gut lining. Indigestible waste is ejected through the mouth.[5]

In animals at least as complex as an

gut. In deuterostomes, the blastopore becomes the anus while the gut eventually tunnels through to make another opening, which forms the mouth. In the protostomes, it used to be thought that the blastopore formed the mouth (proto– meaning "first") while the anus formed later as an opening made by the other end of the gut. More recent research, however, shows that in protostomes the edges of the slit-like blastopore close up in the middle, leaving openings at both ends that become the mouth and anus.[6]

Anatomy

Invertebrates

Butterfly tongue

Apart from sponges and

Annelids have simple tube-like guts, and the possession of an anus allows them to separate the digestion of their foodstuffs from the absorption of the nutrients.[8]
Many molluscs have a
Aristotle's lantern.[12]

Vertebrates

In vertebrates, the first part of the digestive system is the

gill arches.[13]

Litoria chloris
calling

Nearly all amphibians are carnivorous as adults. Many catch their prey by flicking out an elongated tongue with a sticky tip and drawing it back into the mouth, where they hold the prey with their jaws. They then swallow their food whole without much chewing.

vomerine teeth attached to the bone in the roof of the mouth.[15]

The mouths of reptiles are largely similar to those of mammals. The

sockets in their jaws.[16] They are able to replace each of their approximately 80 teeth up to 50 times during their lives.[17] Most reptiles are either carnivorous or insectivorous, but turtles are often herbivorous. Lacking teeth that are suitable for efficiently chewing of their food, turtles often have gastroliths in their stomach to further grind the plant material.[18] Snakes have a very flexible lower jaw, the two halves of which are not rigidly attached, and numerous other joints in their skull. These modifications allow them to open their mouths wide enough to swallow their prey whole, even if it is wider than they are.[19]

Birds do not have teeth, relying instead on other means of gripping and macerating their food. Their beaks have a range of sizes and shapes according to their diet and are composed of elongated mandibles. The upper mandible may have a nasofrontal hinge allowing the beak to open wider than would otherwise be possible. The exterior surface of beaks is composed of a thin, horny sheath of keratin.[20] Nectar feeders such as hummingbirds have specially adapted brushy tongues for sucking up nectar from flowers.[21]

In mammals, the buccal cavity is typically roofed by the

oesophagus.[22]

Other functions of the mouth

Crocodilians living in the tropics can gape with their mouths to provide cooling by evaporation from the mouth lining.[23] Some mammals rely on panting for thermoregulation as it increases evaporation of water across the moist surfaces of the lungs, the tongue and mouth. Birds also avoid overheating by gular fluttering, flapping the wings near the gular (throat) skin, similar to panting in mammals.[24]

Tasmanian devil in defensive stance

Various animals use their mouths in threat displays. They may gape widely, exhibit their teeth prominently, or flash the startling colours of the mouth lining. This display allows each potential combatant an opportunity to assess the weapons of their opponent and lessens the likelihood of actual combat being necessary.[25]

A number of species of bird use a gaping, open beak in their fear and threat displays. Some augment the display by hissing or breathing heavily, while others clap their beaks.[26]

Mouths are also used as part of the mechanism for producing sounds for communication. To produce sounds, air is forced from the lungs over

trachea, the syrinx. For each burst of song, the bird opens its beak and closes it again afterwards. The beak may move slightly and may contribute to the resonance but the song originates elsewhere.[29]

See also

References

  1. ISBN 978-3-03019-898-5
    . Retrieved December 24, 2023.
  2. ^ Gray, Henry (1918). "2a. The Mouth". Gray's Anatomy. Archived from the original on Oct 10, 2022.
  3. ^ "Buccal definition". Dictionary Reference. The Free Dictionary. Retrieved 18 July 2013.
  4. ^ "Mouth definition". Dictionary Reference. The Free Dictionary. Archived from the original on Sep 30, 2013. Retrieved 18 July 2013.
  5. ^
    ISBN 978-0-03-030504-7
    .
  6. S2CID 4406268
    .
  7. ISBN 978-81-315-0104-7.{{cite book}}: CS1 maint: multiple names: authors list (link
    )
  8. ISBN 978-81-315-0104-7.{{cite book}}: CS1 maint: multiple names: authors list (link
    )
  9. ISBN 978-81-315-0104-7.{{cite book}}: CS1 maint: multiple names: authors list (link
    )
  10. ISBN 978-81-315-0104-7.{{cite book}}: CS1 maint: multiple names: authors list (link
    )
  11. ISBN 978-81-315-0104-7.{{cite book}}: CS1 maint: multiple names: authors list (link
    )
  12. ISBN 978-81-315-0104-7.{{cite book}}: CS1 maint: multiple names: authors list (link
    )
  13. ISBN 978-0-03-030504-7
    .
  14. ISBN 978-0-03-030504-7
    .
  15. ISBN 978-0-691-03281-8
    .
  16. PMID 24023957
    .
  17. ^ Nuwer, Rachel (13 May 2013). "Solving an alligator mystery may help humans regrow lost teeth". Smithsonian.com. Archived from the original on Jun 12, 2013. Retrieved 4 November 2013.
  18. ISBN 0412461102
    .
  19. ISBN 0-394-50824-6
    .
  20. ISBN 0-7167-2415-4
    .
  21. doi:10.1111/j.1442-9993.1989.tb01457.x
    .
  22. ^ Pourtauborde, Aniza. "What is the buccal cavity?". WiseGeek. Conjecture Corporation. Retrieved 2013-11-30.
  23. ISBN 978-1-85391-092-0
    .
  24. PMID 16675613
    .
  25. ^ "Showing Off Your Weapons In The Animal Kingdom: Threat Displays May Prevent Serious Physical Harm". ScienceDaily. 2006-06-21. Retrieved 2013-11-30.
  26. ISBN 0-674-00827-8
    .
  27. ^ "The production of speech sounds: Articulators above the larynx". personal.rdg.ac.uk. Retrieved 2013-11-30.
  28. ISBN 978-0-691-03281-8
    .
  29. ^ Ehrlich, Paul R.; Dobkin, David S.; Wheye, Darryl (1998). "Bird voices". web.stanford.edu. Retrieved 2013-11-30.

External links

  • The dictionary definition of mouth at Wiktionary
  • Quotations related to Mouths at Wikiquote
  • Media related to Mouths at Wikimedia Commons
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