Atlas Musculature: Deglutition Action
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Atlas Musculature: Deglutition Action |
Erhard Thiele 025a-e |
| Atlas Musculature Inventory | MYONET.TOTAL PROGR CONTENTS |
I.3.5 The Physiological Act of Deglutition
Thiele,E. :The Action Chain of the Swallow Reflex: Activities and Assignments, Page 369 f.f. in: Hanson, Marvin, L. : Orofacial Myology international perspectives (2.Edition) by: Charles C. Thomas-Publishers Ltd., Springfield, Illinois 2003.
The Action Chain Of The Swallow Reflex.
and its Activities / Assignment.
(Lips, Vestibulum, Tongue Segments, lateral Vestibulum and Cheeks, Velum.)
1. Complete Description of the Links of the Reflex Chain
The Swallow Mechanism
We may compare this mechanism with a chain with a defined number of links. If it is a chain which transmits the power of a machine, a broken link will halt the power transmission and with it the system efficiency. If we are to repair a mechanism we first of all have to get acquainted to it, identify its parts and perceive them. As in the swallow reflex the fluent action of processing taken up food can indeed be seen as a stepwise operation. We can easily match the steps as links in a chain. Let us unroll this biomechanical process from the very beginning.
To start with, we climb back down the ontogenetic ladder to our very early ancestors. As you know, quite a lot of software from the long ascend of development has been kept in the chromosomes and still influences our actions and reactions. For our therapy concept the history becomes most interesting with our entering the worm stage . The dominant form is a muscle tube and this is, what we essentially still are. A most vital function of these muscle tubes was and is the peristaltic wave moving trough the tube - moving the food through the tube and moving the tube through the food. And this is, what still runs trough our digestion tract - right from the tip of one hole to the edge of the other.
As we are presumably interested in "the one hole" ( which actually is the hole number two in development), we will fix our vision on that muscular wave from its very beginning at the front edge of the lips till its cross-over into the pharyngeal swallow .
Further on we will discuss that swallow is not like swallow by its different ways of being performed. For a process as complex and elaborate as this it is indisputable that there will be a biomechanical adaptation to the slightest variation in the material taken up. Just to get started let us join the worm in a mash of tiny crumbs all around me. The intake of the food has to be initiated. This takes place without "instrumentarium", no equipment as cutlery or dishes. The worm feels with the outmost, frontmost margin of the muscle tube the crumb, engulfs it and moves it inward.
For a human the foremost rim of the tube means the medial of the three rings of the Orbicularis covered with a special sort of epithelium being a transition from mucous to skin. This part is delicately attuned in its sensitivity and motility to this task. For example: If my mouth feels a sand corn or a hair this sets to work a mechanism of (peristaltic) movements in an outward direction to push the material as far as possible forward in front of the lips to, then, be wiped of or grasped by the fingers (or spit out, if accidentally nobody is looking).
By the way, fellows who masterly control the actions of this muscle region are the flautists regulating the air stream on to the mouthpiece of their instrument. The counteracting movement is displayed in our case. Just let me put in here the unique biomechanical feature of skin muscles not forming a layer beyond the surface but branching into it directly which gives the inner as well as the outer cover of our orofacial system this cunning motility. By this we are notably well capable of for example nipping a rice grain from the table – and move it inwards via Vestibulum.
( This is printed on a new line to demonstrate:
FIRST STEP, first link in the swallow .)
The Orbicularis opened just as wide as to allow the material to penetrate, respectively be grasped, shuts behind it and opens in front of it, performing a muscular wave. (There it is! The Peristalsis.) Mind: this is almost artistic and requires several unique qualifications:
The tactile sensitivity of the lip surface to locate a tiny object.
The ability of the lip slot to be opened and closed fine-motorically.
The unharmed lip surface to feel and grasp.
The fine motility to move bits of surface in the right direction.
(SECOND STEP) This first step is immediately followed by a brief sip holding and sucking further inward the material, bridging the gap of the Vestibulum and simultaneously emptying it. Mind: This sip requires the air tight seal of the lip slot, the air tight seal of the Oral Cavity at its back (Velum Palatinum) and the ability of the mouth bottom musculature to make a sinking movement to enlarge the Oral Cavity. Permit my transforming the one little grain into something more substantial, a Bolus, as physicians like to call a lump of certain size of well chewed and moistened material ready to be swallowed. Not that we would / should not be fit to swallow a single grain. And let us assume that we had been well capable of chewing! As this action (Chewing) is not truly a link of our chain (swallow) I will just mention this complex and complicated mechanism here in a marginal note. I myself, as a dentist, am deeply involved in the mechanisms of chewing and its bouquet of deficiencies including possible failures in the morphology of the surface of each single tooth, the posture of opposing teeth, the posture of adjacent teeth in the teeth bow/ jaw bow, the movement of the jaws against each other ( the Mandible against the Maxilla, exactly), the movement of the Temporo-Mandibular Joints and finally the action of the masticatory muscles.
I am sparing you those details but I should mention one detail, namely in respect of existing exercises. So among the multitude of feed-back loops running throughout the whole organism there also are those in our cervico-cranial system steering conscious and subconscious neuromuscular processes being intensively linked with the mastication activities This applies to preparative visual and olfactory stimulations; here, an anticipative tone regulation is triggered. Gustatory stimuli will also add to this through hypomnesic balancing. A tactile-esthetical evaluation is gained through the superficial sensory system evaluating the grain size while the bathyesthesia within the parodont measures the firmness of the foodstuff. This is going on continually during mastication to define the end quality oft the mastication load. This feed-back circuit has its special meaning in the running chewing process to safeguard the parodontium against direct pressure overstrain: When the food bolus is crushed a pressure absorption takes place through the "crush-collapsible matter" ingestant as the muscular pressure is converted into energy for chopping up the material. As soon, as there will be an direct tooth-to-tooth antagonistic contact it will cause an immediate alteration from closing to opening movement within the fraction of a second. This alteration gets a bit out of control if there is e.g. a stone fragment among soft material getting between the occlusal surface. Here the pressure exertion is far higher and more abrupt but will be compensated through a lightning-fast turnaround. This compensation will be missing in the loop as with hyposensitivity for example through a raised stimulus threshold owing to dysfunctions as grinding or bruxing. This must be considered when prescribing muscle exercises which may contribute to sensitivity changes by nonphysiological burdening of the teeth.
Prescribing work-outs (JAW EXERCISES) you should just remember that all the factors mentioned have to work correctly and correctly together to gain this "Bolus". By the way, the salivatory glands should equally be functioning sufficiently to moisten the an aspect stuff (which requires perfectly working gustatory nerves, too.).
Within that procedure is involved fitting into our field: The balancing of the material to load the masticatory surfaces of the teeth during the up and down of the jaw. You may well see this activity as your holding a nail against the wall while your partner swings the big hammer. With all its regulatory consequences.). This, by the way, again affords the special branching in of the tiny muscular fibres into the skin/ gum surface - to keep the food on the teeth, the whole row along and all at the same time.
In connection with the setting together of opposing teeth, the Occluding, I would like to place an interjection.
In my opinion it should be widely avoided or at least closely watched with exercising. Too many cases show a hypertonic action leading to grinding or clenching causing the early loss of teeth. The cases of hypotone Mandibula adductors are very view. (further remarks about this matter see below).
As we now have to form that Bolus we decide (trough the signalling of our sensors) to have chewed well enough ( also a delicate tactile kinesthetic mechanism). We perform that little frontal sip (SECOND STEP). This specifically empties the front Vestibulum. It has to be accompanied (or rather followed fractions of a second later, which is to be the THIRD STEP.) by a similar sip laterally. This mechanism now has emptied the complete Vestibulum (cheek pockets and font behind the lips) but as well the interdental spaces at the outside of the teeth(We take that as FOURTH STEP, the Sweep Clean). At the inside the tongue surface and papillae are sweeping clean as well as swept clean and concurrently forming this ball, the Bolus. Mind: This affords quite some tactile kinesthetic qualities and coordination again partly in the micro range. The whole performance aims to the positioning of the Bolus,
(our FITH STEP) likewise in a micromotoric range. For this positioning a bowl of small finger nail size forms on the surface of the frontal third of the tongue (SIXTH STEP). This bowl takes up the material to be swallowed. From now on back to the throat we are confronted with a construction -based difficulty. As our by and by developing brain had to be especially shielded, we grew a bony skull, the brain skull, which the physicians see divided from the face skull (not literally). Our therapeutic engagement makes it necessary to add a third skull, the masticatory skull. So that we have three skulls at the end ( equally not literally, we only may distinguish). This confronts us with the hard palate, the roof of the Cavum (oris).As for the Peristaltic we have to substitute one muscular tube wall because it has become bony and rigid, the Palate. Nature found out an exquisite fill-in through the specified motility and mobility of the tongue and especially its surface. Our colleagues discerned a micro movement of the tongue, more precisely its surface, that resembles in appearance and functioning the small device in the base plate of a sewing machine; little hooks in rows are moved down and back, then up and forth, again down and back and on and on.
This maintains the functioning of the Peristaltic even with one tube wall being solid. So, while the muscle wave laterally runs through the cheek muscles and the tongue margin, against the Palate roof it goes sewing machine with the surface papillae as hooks (SEVENTH STEP).
This mechanism naturally ends with the hard palate and simultaneously the rear end of the lateral Vestibulum. STEP EIGHTH sets to action. The tongue ground / rear end heaves up to contact the transition line from hard to soft palate (called a-line by the dentist), to the Velum Palatinum, which is sealing the pharynx against the nasal cavity (which, if you like may be seen as STEP NINE –).Here a specialty should be mentioned; the Raphe pterygomandibularis links the M. buccinator with the M. constrictor pharyngis. At this site the M. palatoglossus demonstrates intelligibly the advancing peristalsis wave as it is forming a muscle ring together with the transversal tongue muscles. At this point I feel obliged to work in an annotation:
I do not differentiate up to nine steps by sheer pleasure. The exercises existing are thus differentiated and we should get them into a perceptible grouping.
From there on, after step 9, the gullet (Esophagus) advances the muscle wave via stomach. Quite interesting, that all this procedure commonly passes off involuntarily but may be influenced by will; the influencing getting more and more difficult the further backwards the action develops. This is quite important for a therapeutic access.
And, so, these nine links of the chain are our goal for therapy? No, but they are the basis:
At the beginning we used a rice grain, then assumed “ something more substantial” as our Bolus, may be a piece of well chewed bread. But there are so many more possibilities and situations for swallowing hard and soft, liquid and solid, single and repeatedly. We should try to put all that into a logical order, let us say, from easy going to heavy duty. Each single type will possess its own and typical picture of more and less accented links of the nine fold chain. Let us list up ......
At the beginning we might put the types of a statistically most frequent succession of single actions.
Among the distinguishable swallow sequences the least elaborate surely is what we are unconsciously practicing round the clock, the Saliva Swallow. Being surely effective it takes the least strain and accuracy, not, for example, depending on Bolus collecting or a cleansweep effect. We furthermore may categorize two groups within it, the Daytime and the Nighttime Saliva Swallowing, the latter being our Number One on the list as the easiest version. Next in the row could be the Continuous Swallow, again with a differentiation, here taking into account the posture of the head .The Continuous Drinking, A: from a cup, B: with a straw. In situation A taking up the liquid is comparably easy, the passage trough the Cavum promoted by gravitation.
The greater stress will be put on the action of the tongue back and the Velum to avoid choking. Drinking with a straw implies almost the opposite. The necessity to pump or suck up the liquid will involve the mouth bottom and a good sealing of the lips. Drinking from a fountain is surely a carry out, which stands steps higher in our list affording an elaborate technique. A subclass might be drinking from a puddle. A further method would be to take in the liquid from a spoon. This belongs to the category of handling any kind of cutlery and affords stressed acting with the lips.
To get on to higher degrees of Swallowing we are going to modify the consistency of the material toward more solid modifications changing to mushy as with mashed potatoes which now enters upon forming a bolus to be put into the tongue front bowl. Further we get to rohkost porridge or as well to chewed bread, the latter now involving salivation and chewing. If it comes to dry toast an increased strain will be put on the whole program. It gets really laborious with not so tasty things, becomes hard work for some people with swallowing pills. In these advanced cases the consciousness intervenes helping, the neuromuscular actions are equally carried out on a high tone. And at the highest rank I would see the gulp of terror with a dry mouth (meeting a ghost at midnight).
These examples may show us, that there is not the one correct swallow. We will have to deal with a bunch of them and we will have to decide about the degree of pathological or physiological carry out of the swallow.
We will have to determine the broken links in the chain.
We will have to decide about the path of therapy.
It therefore is quite helpful to picture, what is to be understood as physiological. As we have just seen, there is quite a wide frame covering the “normal”. It is known under the name:
The Physiological Frame (Jigsaw Puzzle)