Dr. Sigrid Graumann-Brunt
Chewing, speaking and the pterygoidei muscles
Chewing, speaking and the pterygoidei muscles
© Dr.Sigrid Graumann-Brunt
In the practice of speech therapy one quite often encounters patients that have a problem
chewing solid food. It is no coincidence to find such patients in the speech therapy room
because speech motor problems often go hand in hand with difficulty chewing. And not without
good reason, as it has been known for some time that elements of the chewing pattern are
to be found in speech-related movements ( see Fröschels: in addition to the opening and
closing of the mouth, the forward and backward motion of the lower jaw are common to both
However, the movements common to both speech and chewing are by no means identical; there
are differences, e.g. the angle at which the jaws are opened for the purpose of speaking
differs from that required for the act of chewing and the teeth are set further apart;
moreover, the mouth is generally closed when chewing. We can, nevertheless, still assume
a certain degree of similarity and it is therefore worth taking a closer look at the act
of chewing while bearing in mind the movements observed in the act of speaking.
The temporomandibular joint is a minor technical miracle because it enables us to open our
mouth wide, close it, but also to move the lower jaw forwards and back again. The opening
and forward motions combined give rise to a shovel-like movement. Perhaps it was this that
first gave us the idea for the shovel excavator.
The muscles involved in the act of chewing can be quite clearly seen. They are
- the musculus temporalis (1) ( provides the necessary pressure for chewing and
pulls back the lower jaw.) and
- the musculus masseter (2) ( provides the necessary pressure for chewing),
- the musculus pterygoideus lateralis (3) (pulls the lower jaw forward) and
- the musculus pterygoideus mediales (4) (contributes to the pressure necessary
taken from Lippert: Anatomie. Text und Atlas, 10th edition 2017 copyright Elsevier
GmbH, Urban & Fischer, Munich (We cannot accept any liability for any claims
lodged by third parties)
The first three above-mentioned muscles are particularly strong; they all play a part
in closing the mouth and in providing the pressure necessary for chewing.
The functional mechanics of chewing will be readily understood by those who
tinkering with mechanical devices, but everyone else will need to acquire a certain
"feeling" for it.
Beginning with the musculus temporalis, where one needs to distinguish between its twin
functions: the anterior parts perform the same function as the musculus masseter
(exerting pressure for the act of chewing) whereas its posterior sections perform
something quite different in that they pull the lower jaw back. Its opposite number
in this respect, the muscle that pulls the lower jaw forward, is the musculus
The mouth is opened by the action of the musculus pterygoideus lateralis pulling the condyle
of the lower jaw out of the mandibular fossae in a forward movement. A number of further
ligaments, omitted here for the sake of simplicity, hold the lower jaw firm as they pull
The lower jaw is pushed forward by the pulling action of the musculus pterygoideus lateralis
while the masseter and the musculus pterygoideus medialis prevent the jaw from opening.
The retraction of the lower jaw is performed by the lower sections of the musculus temporalis;
this, however, requires restraining the action of the musculus pterygoideus lateralis.
So far, so good; but the grinding action of chewing is not, unfortunately, a synchronous
parallel pattern of movement; on the contrary, it is a counterdirectional one (comparable
perhaps to the act of locomotion, which, once fully developed, necessitates a cross-pattern
movement). This means that, during the grinding action of chewing, the lower jaw swings back
and forth alternately to the left and right. This action is produced by the temporomandibular
joint being pulled forward on one side and backwards on the other.
Earlier and later patterns
This cannot be achieved unless earlier patterns of movement in which the left and right
parts of the mouth move synchronously in parallel fashion cease to dominate. If the suck
reflex still persists and becomes active, it will cause "interference". In such
cases work will need to be done to mitigate the persisting suck reflex (with eyes closed!).
When one considers the complexity of these patterns of movement, it is hardly surprising
that they are prone to impairment and that complaints of insufficient chewing become
audible in the therapy room. The lower jaw may not have grown sufficiently in size
and strength (at birth it is very small by comparison and does not need to acquire
more "mass" until sucking is superseded by chewing).
The angle to which the jaw opens may not be wide enough, the lower jaw may have insufficient
or no forward thrust, etc. (see also Angermann´s convincing observations from the behavioural
biologist´s point of view that suggest that the lower jaw.can and may only be thrust forward
and interpreted as a social gesture from a certain age or stage of development). If one takes
conditions in the cranial muscles into account, which one is well advised to do as far as
possible, it becomes clear that the complex function of the musculus temporalis in particular
may be severely impaired by a general tenseness in the cranial region. A psychological aspect
may also, of course, play a part in the problem: everyone knows of the need to "clench
one´s teeth" in critical situations – a tensing of all muscles.
Asymmetry factors are often found among the complex of symptoms, as they tend to be particularly
evident in the temporomandibular joint, and then it is not only the forward thrust which
It is often accompanied by a persisting tonic labyrinthine reflex which hinders manoeuvring
of the lower jaw.(see the diagrams illustrating the position of the lower jaw in the lecture
on stuttering). Whatever the genesis of these asymmetry factors may be, they indirectly impair
the act of chewing and speaking, do damage to the joints and muscles and may result in a
rejection of coarser forms of nutrition. Work on asymmetry of this kind is therefore
fundamentally beneficial; to put it more precisely, it is one of the cornerstones of
therapeutic treatment. There are, however, one or two very simple but useful tips that
Massage the musculus temporalis and practise tensing and relaxing it (front and rear
region of the musculus temporalis. It is usually quite easy to locate and touch with
Massage all head muscles to relax them (like any good hairdresser is capable of doing),
a treatment generally much appreciated by all.
You can have the child feel for what is called the head joint ( located the width of one
finger above the wing of sphenoid bone, adjacent to the temporal bone, a region where
tension is often present, and allow the child to gently massage the spot.
The musculi pterygoidei are frequently tense to the point of causing pain. Children are
quite able to relieve tension in these muscles by applying their index finger to the inside
of the mouth (another finger applied to the same place on the outside of the face in the
vicinity of the ear can aid orientation).
Problems concerning the structural equilibrium of the body as a whole and the posture of
the head have been omitted here for the sake of simplicity. The same applies to some
further aspects, including the fact that, despite its bony constitution, the mandible
is not merely functional, but should, from a genetic perspective, be assigned to the
digestive system (see claims made by embryologists as to their developing from a
common somite) and that there may be a connection between digestive disorders and
dysfunctions in the mandible´s movement patterns. The production of speech sounds
has likewise been omitted, although it would be interesting to investigate evidence
of the "grinding" action playing a part in speech motor patterns (when forming
the sch sound in German maybe?). This would be taking matters too far here.
I should like to thank the publishers, Elsevier, very much for granting me permission
to use illustrations from Lippert´s book (which I can sincerely recommend to everyone)