15' Mouth, teeth, pharynx

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15. Mouth, teeth, pharynx/
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In Deuterostomes, mouth forms where the
archenteron meets the stomodeum (a fold in
ectoderm).
The pharynx forms just posterior to that point.
Early in ontogeny and phylogeny it has associated
gill structures.
Fig. 16.1
Liem, Bemis, Walker Grande.
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Pharynx performs respiratory and digestive
system functions
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The pharynx is the major respiratory structure in
early vertebrates.
Water high in O2 and low in CO2 enters pharynx
via mouth and / or spiracle
This water is forced across gills and out
external gill slits
Blood low in O2 and high in CO2 is pumped into
gills where gas exchange takes place
What mechanism makes gases move from water
to blood or blood to water?
Diffusion gradient
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The pharynx is highly vacularized To allow it to
function in respiration.
Walker and Homberger
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a short secondary palate is present in Some
turtles
Crocodilians evolve A long secondary Palate, as
in Alligator
a primary palate Still present in Dermochelys
Synapsids evolve A long secondary Palate, as in
Homo and Canis
Surrounds Internal nares
a primary palate primitive condition for
Choanata
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13 hard palate
8 esophagus
33 trachea
28 soft palate
24 oral cavity
21 vomero- nasal opening
27 nasal cavity
palate separates respiration from ingestion
but systems cross paths in the pharynx
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Muscles of the pharyngeal region
Walker and Homberger
Fig. 7-20
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(thyroid cartilage)
Walker and Homberger
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Fig. 10-20 Walker and Homberger The larynx of
the cat
A. Longitudinal section
B. Lateral view of the laryngeal and tracheal
cartilages
C. Lateral view of the laryngeal muscles
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Tongue modified hypobranchial muscle anchored
by hyoid apparatus
Tongue function
1- food handling
2- taste buds
3- move scent to vomeronasal organ
4- prey capture
5- grooming
6- speech
Lingual or glossal refers to tongue
Genio refers to chin
Adams apple
Marieb
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Seven openings into pharynx
1 oral cavity
23 paired internal nares
4 esophagus
5 trachea
67 paired eustachian tubes
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Superior esophageal sphincter
Superior esophageal sphincter
Function of epiglottis
Marieb
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Basic Terms Used for Feeding Mechanisms of
Vertebrates 1. Suspension-feeding (
filter-feeding) - filter small particles (alive
or dead, depending on species) out of water
column 2. Suction-feeding - open mouth, suck in
food 3. Ram-feeding - open mouth, swim over
food Ram-Suction Index - compares movement of
food relative to movement of feeder 4.
Inertial-feeding - inertia of food is used to
move it in oral cavity 5. Transport - movement
of food within oral cavity (by water currents in
aquatic vertebrates or tongue in tetrapods) 6.
Mastication - physical reduction of food size by
chewing
Liem, Bemis, Walker Grande.
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Mastication requires teeth
Primitively homodont, and non-occlusal
With a variety of tooth attachment types
and tooth replacement modes
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Some Important Terms for Teeth Polyphyodont -
multiple generations of tooth replacement (most
vertebrates) Diphyodont - two sets of teeth
milk and permanent (most mammals incisor, canine
and premolar teeth are replaced) Monophyodont -
a single set of teeth (e.g., cetaceans) Homodont
- teeth of similar shape along jaw Heterodont -
teeth of different shape along the jaw Tooth
plate or Toothplate - at least two uses are
common 1. Many individual teeth fused together
at their bases separate cusps are still visible
(e.g., in pharynx of fishes) 2. Fusion of
individual teeth during ontogeny separate cusps
may not still be visible (e.g., lungfishes,
chimaeras)
Liem, Bemis, Walker Grande.
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Heterodonty has produced four tooth types
Types of Mammalian Teeth and Dental
Formulae Incisor teeth (I), typically these are
replaced Canine teeth (C), typically these are
replaced Premolar teeth (P), typically these are
replaced Molar teeth (M), typically these are
not replaced Formulae are expressed as type in
upper jaw/ in lower jaw I 5/4, C 1/1, P 2/2, M
4/4 opossum I 2/2, C 1/1, P 2/2, M 3/3
humans
Liem, Bemis, Walker Grande.
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Montre moi vos dents, et je vous dit que vous
est
Carnassial Pair P4-M1
Fig. 16.6
Liem, Bemis, Walker Grande.
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Cleft Palate
A cleft palate is a fairly common congenital
disorder (a problem occurring during gestation -
in this case during the fourth or tenth week)
when the medial, lateral, and maxillary nasal
processes on either left, right or both sides of
the forming craniofacial complex do not fuse
completely. This creates a fissure in the mouth
that affects about 1 in 700 people every year.

• The problems created by a cleft palate can
  extend from a simple fissure in the soft palate
  to a fissure into the hard palate, creating an
  opening between the nasal cavity and the mouth.
  This disorder has many variations and may be
  unilateral, bilateral, lip only, palate only, or
  both lip and palate. The septum (dividing wall)
  between the nostrils may be absent, and the teeth
  at the cleft site may be malformed or absent.
• Suspected causes include environmental factors
  such as maternal diseases, chemotherapy,
  radiation, alcohol, excess retinoic acid,
  anticonvulsant medications and other teratogens,
  and genetic factors. There are greater chances of
  congenital malformations in teenage pregnancies
  and in pregnancies in women over age 35.
• A cleft palate can limit a childs sucking
  ability which may lead to malnutrition. The child
  may also require oral or maxillofacial surgery,
  speech and language therapy, plastic surgery,
  dental surgery, and orthodontic treatment.

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Andrew cleft palate