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
Read More Articles About: The Common Head Cold
( Originally Published Early 1900's )
The nose, as we use the term when speaking of its diseases, includes not only the external or visible portion, the nose proper, but also the cavities lying within, technically designated the nasal fossae. It is of course the latter that are important from a hygienic standpoint. They form a large wedge-shaped cavity, whose size, shape, and ex-tent can best be obtained from the front view of the skull, when no fleshy external nose obstructs the view. (Fig. 1.) It will be seen to extend from a large pear-shaped opening on the front of the skull, called the anterior nares, all the way to the throat, with which it communicates by an opening called the posterior nares.
Persons who have never examined the nasal fossae in the skull, often labour under a mistaken impression of the direction of the nasal passage. They imagine that these cavities run upward in-stead of backward in a generally horizontal direction as they do. (Fig. 5.) The error is due to the fact that the nostrils open in a horizontal plane which suggests that the direction of the nasal cavities is at right angles to this, that is, upward. It is essential that this false impression should not go uncorrected, for should one under this false belief have occasion to apply a probe in the nose, serious, even fatal result might follow. Instruments directed upward might impinge against the thin sieve-like layer of bone (cribriform plate) separating the nose from the brain, breaking through which they would unfailingly enter the cerebral cavity.
The nasal fossae are divided into like halves by a vertical partition or septum, (Fig. 1) which, beginning at the nostrils, extends backward to the posterior nares, the place of communication with the throat.
The septum is seldom perfectly straight but is usually deviated a little to one side or the other. When the deviation is very marked it will tend to close that side of the nose to which it is inclined. Often associated with this, there may be considerable ridges formed along the angle of deflection, which constitute the so-called "spurs" on the septum. These spurs themselves sometimes constitute considerable obstruction and have to be removed.
Again, taking up the skull, we see jutting from the outer wall of each side of the nasal fossae, three fragile scroll-like bony shelves, running (from before) backward and parallel with each other. (Figs. 1, 3 and 5.) These are spongy bones, and what are meant generally when we hear of "bones being removed from the nose." But covered, as they are in the living, with flesh and membrane, they should rather be spoken of as turbinated bodies, or simply turbinais. These structures are of great importance physiologically and should never be removed except for the most position indications.
Characteristic of these turbinals is the presence here of a special sort of tissue forming what are known as "swell bodies," or erectile tissue. The essential feature is a thick elastic network or plexus of veins which, according to need, will dilate and fill up with blood or completely col-lapse when contracted. This spongy or erectile tissue, which is necessary for the proper performance of the respiratory function of the nose, is found in greatest abundance on the lowest of the turbinai bodies, and less on the middle, while the uppermost one is practically free from it.
In looking into the nose of a healthy individual, only the inferior and middle turbinais are visible, and these not in their whole extent, for we view them as it were, "heads on," so that their "tails" are not visible from the front. But by introducing through the mouth a small mirror attached to a long shank it is possible with the aid of a good light to obtain an image of the posterior ends of all three turbinais.
A view of the transverse section of the head will show that surrounding the nasal fossae proper on all sides, and connected with them, are a number of other large air cavities, hollowed out of the adjacent bones of the face and skull. (Figs. 1, 3 and 15.) These are what are known as the sinuses or accessory nasal cavities which drain into the nose. They are very important because of their being the frequent seat of abcesses. These accessory sinuses are symmetrically disposed in pairs, those on each side being connected with their corresponding half of the nasal fossae by more or less constant and definitely located mouths of communication.
Just above the root of the nose, and extending upward, and outward to each side in the forehead are the two frontal sinuses. They are divided from each other by a septum into the left and right sinus. Back of the nasal fossae are also two cavities similarly disposed, called the sphenoid sinuses. On each side of the nasal cavities and lying between them and the eyes are a small series of cells which represent the ethmoid sinus, but because of the number and intricate disposition of the cells, called the ethmoidal labyrinth.
Of all the accessory sinuses the largest is the maxillary, called the antrum of Highmore. This capacious cavity occupies the hollow of the cheek. Its roof corresponds to the floor of the orbit of the eye, and its floor is in relation with the roots of the teeth, which often in fact penetrate into the cavity, and when diseased, may set up an abscess there.
The mucous membrane lining the interior of the nasal cavity extends through the little mouths of communication to line also the accessory sinuses, so that it is easy for disease to extend from the nasal fossae into the nasal sinuses or vice versa. The name "pituitary" meaning "phlegm producing," is applied to this membrane, because it is supplied with numerous minute glands which open on its free surface, some of which give origin to the secretions which are constantly present. The glands are of two kinds : mucous, whose secretion is of a viscoid mucilaginous character, and serous glands, which secrete a thin watery fluid.
The nasal mucous membrane is very richly sup-plied also with blood vessels and nerves. The nerves are of three kinds, (1) sensory, those which have to do with common sensation; (2) sympathetic, those which have control of the veins of the swell bodies, and (3) olfactory, the nerve which serves the function of the special sense of smell.
First, the extreme sensitiveness of the nose, its marked irritability as shown by a tendency "to run" and give rise to sneezing upon slight provocation, is due to the generous distribution of nerves of common sensation.
Second, a small ganglion of the sympathetic system, Meckel's Ganglion, is situated in the upper part of the nose, to give origin to the so-called vasomotor nerves which control the plexus of veins constituting the erectile tissue. Those veins are surrounded by unstriped muscular fibres that will be found wherever muscular action takes place automatically and independent of the will. Responding to certain stimuli therefore, the vasomotor nerves of the nose acting upon these vessels will cause them to contract and dilate according to physiological needs.
Third, we have the olfactory nerve or special nerve of smell. Just before entering the nose it breaks up into a number of threads which perforate the roof of the nose by little openings in the cribriform plate and pass downwards to supply the mucous membrane. The olfactory nerve is not supplied to the entire mucous membrane of the nose, as some suppose, but to a very limited area in the uppermost part, much smaller, than is generally taught in most text books. This smelling area has been found to extend only as far as the upper margin of the middle turbinai, and a corresponding surface on the septum.
The post-nasal space or nasopharynx is the upper part of the throat, lying just back of the nasal passages. (Fig. 5.) It is particularly interesting for the reason that in its dome-shaped roof, we have a little tonsil (tonsil of Luschka), normally present in young children but often abnormally enlarged, then constituting the growth known under the name of "'adenoids."
On the lateral walls of the nasopharynx are situated the mouths of the Eustachian tubes, right and left, (Fig. 5) these being the pharyngeal orifices of the narrow air channel connecting this region with the cavity of the middle ear.
As distinguished from the nasopharynx, the part of the throat which we see when we look directly in through the open mouth is called the pharynx, properly the oropharynx. (Fig. 4.)
Still lower we have the part just back of the larynx, called the laryngopharynx; which continues on down into the gullet or esophagus, while the continuation of the air tract is represented by the larynx and the trachea, lying just in front.
Let us make clear what is meant when we speak of the hard palate, soft palate, and uvula, for, from remarks made by patients, it is evident, that these parts are very frequently confused. As we look into the throat, (Fig. 4) we see a sort of curtain suspended from the roof of the mouth, the lower borders of which form two half arches meeting in the middle. This is the soft palate, and its central downward prolongation constitutes the uvula. Together they mark the boundary between the pharynx and the mouth, the pharynx, lying behind, while the term mouth may be applied to all that part of the cavity anterior. The soft palate is made up largely of muscle, as evidenced by the contracting action observed when the individual is instructed to utter the sound "ah," when the palate will become elevated and the uvula contract almost out of sight.
The name hard palate is applied to the entire arched roof of the mouth, which is of bony formation. It is limited by the gums (alveolar process) in front and on the side, and ends posteriorly by a free border to which the above described curtain-like soft palate is attached.
The soft palate, as it stretches out toward each side of the throat, becomes divided into folds, front and back called respectively the anterior and posterior pillars. (Fig. 4.) Between these folds or pillars lie two very important structures, the tonsils, sometimes spoken of as the faucial tonsils, to distinguish them from the tonsil of Luschka, or third tonsil already mentioned. These structures when normal are small almond-shaped bodies about an inch in length and a half inch in width and thickness. Normally they do not project beyond the two folds between which they are situated, but they are very frequently enlarged from repeated attacks of inflammation, when they may reach such size as to come into contact with one another, almost closing the throat.
It may be mentioned that there is still another tonsil in the throat of which we do not hear much, but which, nevertheless, may give rise to some very annoying symptoms when inflamed. The fourth tonsil is located at the base of the tongue, just in front of the epiglottis or lid of the larynx, and is known as the lingual tonsil. (Fig. 5.) It is of special interest to singers and others who use the voice habitually since when enlarged it may give rise to hoarseness and other voice symptoms.
That part of the respiratory tube which is especially modified to contain the organ of vocal production is known as the larynx or voice box. To get a general idea of its plan of construction, imagine the top of the trachea or windpipe to be surrounded by a ring of cartilage, which is widened out posteriorly, and so bears a general resemblance to a seal ring, called the cricoid cartilage. This ring forms the support or basis of the other cartillages of the larynx. (Fig. 9.)
The whole front and sides of this organ are constituted by the thyroid cartilages, so-called from their fancied resemblance to shields. They consist of two great square shaped wings which meet in the middle line in front but open posteriorly.
Situated backward in the opening between these wings, and resting on the broad posterior or signet portion of the cricoid ring are two little pyramidal shaped cartilages, known as the arytenoids. These cartilages are of great interest be-cause they are movable and, by their motion, effect the openings and closings of the vocal bands. Upon cross-section they are triangular, and the anterior end of the triangle is prolonged forward to form the so-called vocal process, to which the vocal cords are attached.
All the muscles of the larynx which move the vocal cords are attached to the arytenoids. Their action in opening and closing the cords will be described in the next chapter.
The epiglottis is the lid of the voice box. (Fig. 5.) It is a leaf-shaped plate of elastic cartilage, the stem of the leaf being attached in the upper part of the angle formed by the two plates of the thyroid.
The vocal cords are pearly white bands, composed of yellow elastic tissue, running from before backward, and parallel with each other when closed. They are attached in front at about the middle point of the angle formed by the two wings of the thyroid. From here they run backward to be inserted in the vocal processes of the arytenoid cartilages. Their length in the male is about % of an inch, and in the female slightly less.
Inasmuch as the anterior attachment is fixed, the openings of the cords can occur only by the movement of the arytenoids, to which they are attached posteriorly.
The slit formed by the separation of the vocal cords is called the glottis. It is of triangular form, the base of the triangle situated posteriorly being formed by the interarytenoid membrane (a membranous fold stretching from one arytenoid to the other), while the sides are formed by the vocal cords which come to an angle in front.
Lying above the vocal cords and to the outside, so as not to cover them, are two membraneous ligaments, to which the name "false cords" is given. (Fig. 7.) They have nothing to do ordinarily with phonation, though in cases of destruction of the true cords they can in some measure take their place.
The cartilages of the larynx are held together by ligaments and membranes, and the entire interior is lined by mucous membrane, which be-comes very thin over the vocal cords.
The epiglottis and the ligaments binding it to the tongue, inasmuch as they can be felt by the finger thrust into the back of the throat, have sometimes been mistaken by nervous individuals for foreign bodies such as fish-bones or some diseased growth. In some persons by depressing the tongue considerably, a yellow gristle-like object may be seen riding up over the posterior edge of its base. This is a part of the epiglottis and not some terrible tumor in the throat as the inexperienced may imagine. In the coloured race the epiglottis is nearly always directly visible upon depressing the tongue.
The location of the larynx is easily recognisable on the outside of the throat. The large prominence very marked in some individuals, always more so in men than in women, and popularly referred to as "Adam's apple" (pomum Adami), is formed by the thyroid cartilage. The upper borders of the thyroid dip decisively as they approach the middle line. They can be felt as a distinct notch from the outside.
The nerve supply of the larynx is derived from the pneumogastric nerve. There is one branch which supplies chiefly common sensation, and another which governs the muscles which act upon the vocal cords. Of the manner of the action of these muscles we will have something to say when discussing the physiology of these parts in the next chapter.