The Common Head Cold:
Colds In General
Nose And Throat Functions
Highways For The Invasion Of Disease
Colds And Micro-organisms
Symptoms, Complications And Sequelae
Principles Of Prevention
Methods Of Prevention
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Nose And Throat Functions
( Originally Published Early 1900's )
Nature, in its exercise of the hygienic function of protecting the organism against hostile and injurious elements, is nowhere so beautifully and so profusely illustrated as in the upper air passages.
The nose is usually regarded as an organ for breathing and smell, (respiration and olfaction). These are, indeed, the main positive functions. In addition, the nose performs important contributory duties to the functions of taste, speech, and hearing.
But let us contemplate for a moment its less conspicuous, though no less valuable, duties as a protector.
In the first place, the threshold of the nasal passages is supplied with. a number of coarse hairs called the vibrissae. Their purpose is to catch the dust and larger particles floating in the atmosphere in order to save the more delicate mucous membranes beyond from being injured.
Next, observe with regard to the mucous membrane itself, the peculiar features of its protective character. Its acute sensitiveness is necessary in order that it may quickly become aware of injurious foreign bodies. The irritation of the latter produces attacks of sneezing, the purpose of which is to dislodge them. At the same time more or less copious secretions are stimulated, which bathe the membrane, and tend to wash away the offending substance.
Recent studies, moreover, have shown that these secretions possess bactericidal properties; they overcome and destroy the micro-organisms which have gained entrance to the nasal cavities. Again, the surface of the nasal mucous membrane is provided with myriads of fine hairs too small to be seen except under the microscope, and known as cilia. These keep up a constantly waving motion, which has the effect of sweeping out particles of dust and other foreign agents which may have gained entrance to the nasal fossae.
Both the olfactory and the respiratory functions, when analysed, will be seen to be designed in a great measure to protect the organism. The sense of smell has its esthetic side, and may often be the source of delectable sensations, but primarily its purpose must be acknowledged to be, to detect elements that might be deleterious to the organism, and warn against their ingestion or inspiration. In the lower animals this function is of paramount importance.
The rôle that the nasal organ has in the process of respiration is largely one of protecting the delicate air cells of the lungs from the known injurious effects of the air ordinarily found in nature. Unless this be warmed and moistened, as well as freed from impurities, it is unfit for the sacred precincts of the pulmonary or lung cells. The construction of the nasal organ is such that under normal conditions these tasks are well and properly done, and the lungs safely protected. In the throat and mouth cavities also, we may observe provisions essentially or incidentally protective. Taste is analogous with smell in enabling the individual to distinguish the beneficial from the harmful. The tongue, in addition to its customary function, is probably the most sensitive organ of the body to the sensations of touch and temperature, and is naturally of extreme importance in safe-guarding the digestive tract.
The palate with its uvular prolongation exercises a most useful, protective function in the act of swallowing. (Fig. 6-B.) By applying themselves tightly to the posterior wall of the pharynx, during the swallowing act, they close the upper, or nasopharynx cavity completely from the region below, and thus prevent food and water from passing upward and getting into the nasal cavity, and possibly also the Eustachian tubes. The value of this function may be appreciated when the palate, from diphtheria or other causes, becomes paralysed and the patient suffers with each act a regurgitation of food or liquid which may enter the nose and pass forward, and even out through the nasal cavities.
Very little is known of the function of the tonsils, but the one most generally ascribed is that of protecting the organism by way of phagocytosis, that is to say the power of its cells to swallow and destroy the numerous pathogenic organisms which are found in the oral cavity.
At the larynx, the last gateway which must be passed before entering the lungs, Nature, not to take any chances, has placed several special guards to protect against the entrance of unwelcome guests. If the latter have succeeded in getting by the foreposts stationed above, here they will meet new and more effective barriers.
First, the larynx is provided with a lid, the epiglottis, which aids in keeping food from getting into the respiratory tract, and in directing it back into the proper channel, the esophagus. If however, through mishap any particles get into the vestibule of the larynx, immediately such a violent contraction is set up, first in the false cords which are above, and then in the true cords, which are just below, that further intrusion is usually impossible. (Figs. 6-B and 8.)
The choking and suffocation which most of us have suffered at times, as a result of "swallowing the wrong way," is due to tight closure of the chink of the glottis from this spasmodic, persistent contraction of the cords. Finally, if particles get below the glottis, the irritation will produce mucous secretions, and a forcible expulsive cough, which are generally effective in dislodging them.
The olfactory function is, as we have indicated, of far less importance in man than it is in some of the lower animals, in which it is highly developed, and plays an essential rôle in the struggle for existence.
Since the filaments of the olfactory nerves, are distributed only to the uppermost part of the nasal fossa, called the olfactory fissure or chink, it is necessary for the air-borne, odoriferous particles to impinge upon the mucous membrane in this locality if they are to be smelled. This is done by the production of eddies in the current of the inspired air. The air does not pass through the olfactory slit in its passage outward. This fortunate provision explains why odours which originate in the throat arising from decomposition or digestive disturbances are not ordinarly perceived by the patient.
The act of sniffing, with which we are familiar in the attempt to obtain an odour, as when we would enjoy the fragrance of a flower, is readily understood in the above given description of the process of olfaction. Sniffing is an attempt to bring the odoriferous air quickly into the upper region of the nose, in the region of the olfactory nerve.
As distinguished from the olfactory, all the remaining part of the nasal cavity is sometimes called the respiratory fissure ,or cleft. The course of the air current through the nose will be influenced to a certain extent by the position of the nostrils and the general conformation of the nasal cavities, and by the effort in breathing, but it follows in general a very regular tract. The in-spired air does not pass directly backward along the floor of the nose, but describes an upward curve and passes more or less over the middle turbinai, and then gradually downward to enter the throat through the posterior nares.
The work that the nose performs as an organ of respiration is of the most vital importance to the organism. The popularly prevailing conception of the nose is that it is an organ intended chiefly by nature for the purpose of olfaction (or smelling). It is thought of as being useful to smell with, not to breathe through, the latter function not being looked upon as at all peculiar to the nose, or at least of but secondary consideration. To this erroneous conception may be traced a lamentable indifference to certain of the most vitally important ordinances of nature. If through accident or diseased condition, congenital or acquired, the nose has become obstructed or disabled, it is sup-posed, in conformity with such restricted view of its physiology, that the consequence is nothing more than a certain inconvenience, and that, too, pertaining rather to the esthetic than the practical environments. On the contrary, we ought really to consider the olfactory function as subsidiary to the respiratory, in the sense that thereby we are apprised of the state of the atmosphere about us and warned as to what air we may or may not breathe.
The nose is eminently adapted, by reason of its structure to take a certain part in the great process of respiration, and a failure to so use it will entail upon the system irreparable damage. If an individual breathes constantly through the mouth instead of the nose he is guilty of a hygienic transgression for which he will have to pay a heavy penalty.
As an evil practice upheld by popular belief, though more difficult to correct, more imperatively demands correcting, and as physiology is the helpful handmaid of Hygiene let us now consider in particular the respiratory functions of the nose.
The nose has three important duties to perform, all of which are necessary as preliminary and prerequisite steps in the preparation of the outside air before it enters the lungs. These are to warm, to moisten, and to filter.
For this work it is especially qualified by the great expanse of its Interior lining and by the fact that the latter is provided with a kind of tissue suitable to the purpose and capable of con-forming to the varying conditions of the atmosphere. This is the cavernous or erectile tissue known as "swell bodies" (German, Schwellnetze) on account of its property of contraction and expansion to a marked degree as explained in the last chapter. It consists of a rich network of blood-vessels, interlacing in every direction. Under a nervous control extremely sensitive to the temperature environment, the nose is thus enabled to bring the air which passes through it in inspiration up to a nearly uniform standard of temperature, whatever may be that of the external atmosphere; and so the colder the air outside, the greater the work that is done by the nose. When the air is very cold, the membrane containing the cavernous tissue is stimulated, swelling follows due to the filling up of the blood-vessels, and thus an increasing amount of heat is given off to the air passing through.
Moisture taken up by the inspired air, like the heat, comes in great part from the nose, given off by the rich blood-supply here present. Before reaching the lungs, the air normally has almost reached the point of saturation, so that it is required to make no additional demands upon these organs. It has been estimated that in the course of twenty-four hours no less than 500 grams, or one pint of serum is given up to the air from the nasal mucous membrane.
The function of filtration is not the least important of the duties performed by the nose. Not only are particles of dust, noxious vapours, effluvia, and all sorts of inorganic substances arrested in their progress and prevented from entering the lungs, but so also, as recent research has proved, are the -organic inhabitants of the air, the germs, the hostile bacteria, the disease producing cocci and bacilli, innumerable hordes of which surround us on all sides. While the grosser particles are caught either in the vibrissae (or coarse hairs) at the vestibule of the nose, or are taken up and thrown off by the glandular secretions, the other, the invisible elements, are combated in the nose by a bactericidal serum. Although we may find living germs in the vestibule in great number, upon microscopical examination they will be missed. from the secretion taken from other parts of the interior of the nose.
Thus, standing at the threshold of the respiratory tract, the nose, rightly used, performs a guard duty of the most vital importance. It has a responsible protective rôle to play, failure of which means incalculable damage to the whole system. It is its place to act as a special barrier to the entrance into the lungs of all agents which may prove directly injurious to these organs, or, escaping thence into the circulation of the blood, give rise to manifold disturbances of health, including often perhaps the infectious fevers. Truly then, it cannot be considered extravagant to claim that it is the nose that gives to the inspired air the best right to the title of the "Breath of Life." Man may go for weeks without food, for days without water, but the limit of time that he can go without breathing is about four minutes.
In the Biblical account of the creation of man it is written, "into his nostrils God breathed the breath of life." Let modern hygienic science take note that it was not said "into his mouth," and in this instance admit it has no quarrel with revealed religion.
We can best appreciate what nasal respiration means to the health and life of man, when we know the damage done by its loss. This we must post-pone until we take up the subject of mouth-breathing.
In addition to these direct principal functions, the nasal organ also plays a not unimportant rôle contributary to three other functions whose chief seats are elsewhere.
We refer to taste, hearing, and voice production. The nose through its olfactory function con-tributes a large and important part of the sense of taste. We usually think of taste as being wholly located in the tongue and palate. As a matter of fact, all that these organs can do is to appreciate the gustatory impressions produced by what is sour, bitter, salty or sweet.
All the other elements of taste, those in fact which may be called the refinements of this sense, and which make it a source of pleasure in the consumption of food and drink, take their origin in the function of olfaction. Without the nose we should wholely fail to recognise the subtle bouquet of the various wines; without the nose the delicate aroma of the coffee would fail to exist; without the nose there could be no appreciation of the delicious flavours of the various triumphs of the culinary art. Without the nose we would drink without zest, and eat without relish and though we had appetite, nothing would be palatable or savoury.
The word savoury illustrates the close relationship between taste and smell. It is derived from the Latin "sapere," meaning to taste, yet we apply it more frequently to what pleasantly affects the sense of smell. The savoury property of what is set before us is appreciated before we take it into the mouth, and it probably adds to the success of digestion as well as to our pleasure. For what is savoury stimulates the digestive juices, and promotes the digestive processes.
The nose plays a rôle contributory to the function of phonation or speech, which may be compared to its part in the function of taste. Phonation pure and simple takes place in the larynx, but if we could hear the sound produced by the vibration of the vocal cords, without the modification which is given it by the resonating chambers of the nose and throat, we should turn in disgust from its harsh, strident, unmusical, inharmonious tones. The quality of the voice, that which makes it resonant and pleasing, is due in a very great measure to the resonating chambers constituted by the nasal cavities and its accessory sinuses. It is from the supplementary vibrations in these spacious pneumatic cavities of the head that are produced those musical overtones which give the indescribable charm of both the singing and the speaking voice.
The nose is contributory to the function of hearing, only in the sense that it furnishes to the Eustachian tube the air which the latter in its turn conveys to the middle ear. A. certain supply of the air thus furnished is necessary to the health and normal activity of this organ. How essential a free or open passage is to the auditory function may be readily inferred from the degree in which it suffers when the nose becomes, from any cause, obstructed. Nasal obstruction is regarded as a prolific factor in the causation of auditory disease. The simple experiment of swallowing with the nostrils held closed is sufficient to give any-one a personal illustration of the effect upon the ears of even a temporary nasal obstruction. An unpleasant sensation is immediately felt in the ear, due to the aspiration of the air from the tympanic cavity when the tubes are opened in the act of swallowing.
The part of the pharynx which we see when looking directly into the throat through the open mouth, the oropharynx, is peculiar in the fact that it belongs equally to and forms a part of both the respiratory and the digestive tracts, and must therefore perform the function of each. The oropharynx is, so to speak, the cross-road of these two tracts in the throat, (Frontispiece) and we ought not to be surprised that it frequently be-comes diseased when we consider that it is exposed at the same time to the dangers and burdens incident to the respiratory and digestive functions.
The air tract begins with the nose, continues in the nasopharynx, then, intersecting the digestive tract in the oropharynx, passes forward to continue again in the larynx, trachea, and bronchi.
The digestive tube begins in the mouth, and intersecting the respiratory tract in the oropharynx, passes back and downward to continue in the laryngopharynx, and then in the esophagus to the stomach.
We have referred to the fact that the mucous membrane in that part of the nose which is designated as the respiratory fissure is covered with epithilial cells. Each of these cells contains minute waving hairs which are for the purpose of sweeping out dust that has collected on the membrane from the inspired air.
These ciliated, epithilial cells are peculiar to the respiratory mucous membrane. They are found also in the nasopharynx, which justly be-longs to the respiratory tract. But, as we reach the oropharynx a modification appears, in order that this section of the throat may accommodate itself to its double function of digestion and respiration. Here the ciliated epithelia become replaced by flat epithelia of the pavement kind, the ciliated variety not being found again until we reach the larynx.
As the nose is the organ which stands guard at the head of the respiratory tract, protecting it from evil influences and preparing the air for entering the lungs, the mouth may be said to occupy an analogous position with regard to the digestive tract. The exquisitely sensitive tongue is quick to detect whatever is too hot or too cold, or what might be otherwise harmful to the stomach and by its manifold muscular contractions mixing the food with the secretions of the salivary glands, it prepares it for entering this organ.
When food or liquid is swallowed, the pharynx is automatically closed both above and below from its connection with the respiratory tract, to become at that moment a part of the digestive tract alone. (Fig. 6-B.) Above, the closure is, as remarked, effected by the simultaneous contraction of the muscles of the upper part of its posterior wall with the muscles of the soft palate.
The closure at the lower end is brought about chiefly by the depression of the epiglottis, acting as a lid for the larynx, assisted by a backward movement of the root of the tongue. Failure at this point may occur as a result of a severe ulcerative disease of the epiglottis and be manifested by a distressing paroxysm of coughing and strangling due to entrance of food into the windpipe.
The pharynx is continued downward by two separate tubes having different functions : be-hind, the esophagus or gullet for the passage of food to the stomach, in front, the larynx for the transmission of air to the lungs.
The larynx has, however, in addition to the breathing function, another very important duty, namely the production of sound for purpose of speech. (Figs. 7 and 8.) This is accomplished by the interposition of two little whitish bands, stretched across the interior of the larynx from front to back, and giving rise to tones by the vibrations produced by the current of air impinging on their free edges.
Variation in the pitch of the sound produced is accomplished by a group of muscles attached to and surrounding the cords, which by their con-traction not only effect a closer approximation of the cords, but also a varying degree of the tension of their free edges.
As the congestion due to cold, spreading to the larynx, can easily involve these delicate structures and produce hoarseness and other voice troubles, it is interesting for voice users to have an intelligent understanding of the mechanism.
The muscles which act upon the vocal cords may be divided into openers, closers, and tensors. Nearly all of them have an attachment to the movable arytenoid cartilages, whose form and situation we have elsewhere described. These two cartilages, the elongated internal borders of which form the small posterior part of the glottis, are capable of two kinds of movement ; a sliding movement of the cartilages in tote toward each other, and a rotary movement upon a vertical axis.
The rotary movement is effected by muscles attached to the so-called muscular process of the arytenoid cartilage which is the outer angle of its base. One pair of muscles have as their fixed point of attachment the broad posterior expanded or seal part of the seal ring (cricoid cartilage).
The effect of the contraction of this pair of muscles is to swing the anterior angle,—that part of the arytenoid to which the vocal cords are attached,—directly outward and thus to open the glottis. (Fig. 9-C.) This muscle which is known as the crico-arytenoideus posticus, or simply the posticus, is the only opener of the glottis. Directly antagonistic to this in action, is the crico-arytenoideus lateralis. Its fixed attachment is on the side of the ring of cartilage from which it runs up-ward and backward to be inserted into the muscular process of the arytenoid. The effect of its action is to cause its anterior angles or vocal process to swing inward toward each other and therefore to close the glottis. (Fig. 9-B.) To help close the posterior part of the cord, we have a little muscle running from one posterior surface of the arytenoid to its fellow, which upon contracting tends to cause these cartilages to slide bodily toward each other. (Fig. 9-D.) It is called the interarytenoid muscle. A muscle that is very intricate in its connection and whose action is not yet fully under-stood is one that runs from the thyroid to the arytenoid cartilages along the border of the vocal cords. It is exceedingly important in the function of vocalisation, and the general opinion is that it acts as a tensor of the cords. According to some authorities, certain filaments which are attached to the outer edge of the cord are for the purpose of modifying its elasticity. Acting according to this theory, now upon one part and now upon another part of the cord they can relax or tighten certain sections separately and thus have much the same effect as the stop action of the finger on the violin strings.
It remains to mention only one other muscle, the cricoid thyroid which is attached below to the front and sides of the ring cartilages and above to the lower border of the thyroid. The effect of its contraction is to increase the distance between the anterior and posterior attachments of the vocal cords and to act therefore as tensors.