ANATOMY OF THE PHARYNX

ANATOMY, PHYSIOLOGY AND EXAMINATION OF THE PHARYNX, LARYNX, TRACHEA AND BRONCHUS

The pharynx is the expanded portion of the alimentary tract lying between the oral cavity and the esophagus. It is also part of the respiratory tract, as it connects the nasal cavity with the larynx. The upper part of the phar­ynx, called the epipharynx, communicates with the nasal cavity through the choanae and is known as the nasopha­rynx.

The openings of the Eustachian tubes lying on a level with the posterior ends of the inferior nasal turbinates are to be found on the lateral walls of the nasopharynx. An accumulation of lymphadenoid tissue in the top part of the posterior wall of the nasopharynx forms the pharyngeal or third tonsil, consisting of 5-6 lobes, and diverging from a common centre. In children aged two or three years this tonsil is often hypertrophied, as they grow older it decreas­es in size and by the age of puberty consists of diffuse lymp­hadenoid tissue scarcely emerging over the surface of the mucous membrane covering the nasopharyngeal roof. A plane which is a backward extension of the hard palate separ­ates the nasopharynx from the middle part of the pharynx, known as the mesopharynx or, more commonly, as the oropharynx (Fig.  67).

The oropharynx is bounded by the posterior and lateral walls continuous with the corresponding walls of the naso­pharynx, and anteriorly it communicates with the oral cav­ity through the fauces. The fauces are bounded by the soft palate above, by the base of the tongue below and by the anterior and posterior palatine arches, otherwise called faucial pillars, on the sides.

Oropharynx: (7) posterior wall of pharynx, (1) uvula, (3) palatine tonsil, (4) anterior faucial pillar, (2) posterior faucial pillar, (7) soft palate

 

 

The pharynx contains well-developed lymphadenoid tis­sue which forms fairly large masses embedded on both sides between the faucial pillars, which are known as the first and second palatine or faucial tonsils. The letter’s free surface facing the pharynx contains numerous pit-like de­pressions, or crypts, running through the entire body of the tonsil (Fig. 68). The squamous epithelium which lines the free surface of the tonsil also lines the crypts. A similar accumulation of lymphadenoid tissue at the base of the tongue forms the lingual, or fourth, tonsil. The ring-like chain of lymphoid tissue made up of these four tonsils and the lymphatic follicles in the mucous membrane is known as the lymphoid ring of the pharynx.

The plane that extends backwards from the base of the tongue divides the oropharynx from the laryngopharynx, or hypopharynx, which lies below and directly opens into the esophagus. The lower portion of the pharynx opens into the larynx. The mucous membrane of the nasopharynx consists of a stratified, columnar, ciliated epithelium, while its other two departments are lined with a stratified squamous epithelium. The pharyngeal mucosa contains numerous mucous glands.

 

Fig. 68. Horizontal  Midline Section, of Tonsil Showing Deep, Branched Crypts Surrounded by Isolated Follicles

 

The constrictor muscles lie under the pharyngeal mucosa and serve to contract the middle and lower portions of the pharynx and push food into the esophagus.

PHYSIOLOGY OF THE PHARYNX

The pharynx serves as a passage for air and food, and also as a resonating chamber for the voice. Because the digestive and respiratory tracts cross each other at the pharynx it has reflex mechanisms to regulate the passage of food and air. At rest, the nasopharynx is open to the oral cavity, whereas in swallowing and in the articulation of certain vowels and consonants the soft palate is pulled up against the posterior pharyngeal wall and firmly shuts off the nasopharynx from the oropharynx, so preventing food from getting into the nasopharynx and nose, which sometimes happens in paralysis of the soft palate, for exam­ple,  following  diphtheria.

The passage of the alimentary bolus is accompanied by closure of the larynx, which moves up slightly under the base of the tongue, whose pressure compressed the epig­lottis against the narrow entrance to the larynx, whereupon the bolus is passed into the esophagus.

The pharynx which is studded with gustatory nerve end­ings on the soft palate and at the base of the tongue, also functions as the organ of taste and performs the protective function of reflex muscular contraction in response to sharp thermic and chemical irritation or to the entry of foreign bodies.

As to the exact function of the pharyngeal lymphoid ring, this is still a matter for discussion. Most authors ad­here to the “protective theory”, that is, regard the tonsils and the other lymphadenoid structures as a protective bar­rier against bacterial infection. In pathological conditions, the tonsils with their crypts which always harbour mi­crobes prove, on the contrary, to be an entryway for infec­tion and so account for the causal relationship between in­flammations of the tonsils and constitutional diseases. In essence, the function of the lymphadenoid structures of the pharynx cannot be separated from the function of sim­ilar follicular structures in other organs, like Peyer’s patches of the small intestine, which produce lymphocytes and presumably neutralize infectious toxins entering the blood. For this reason, the removal of pathologically al­tered tonsils, corroborated by everyday practice, should not lead to any substantial damage from the viewpoint of their functional value for the body as a whole.

The other parts of the lymphoid ring and the lymphade­noid structures of the digestive tract will compensate for the defective function of pathological tonsils as well as for their complete removal.

The functional examination of the oral cavity and naso­pharynx, the process of chewing and deglutition excluded, essentially consists in a gustatory test by using sugar, quinine, common salt and vinegar solutions to determine the taste for sweet, bitter, salty and sour substances respecti­vely. The solution is applied on a glass stick to either side of the tongue in turn, with the nose being firmly closed to shut off the sence of smell.

In view of their different nerve-supply systems, the an­terior and posterior parts of the tongue should be examined separately. The residue of the earlier used solution must be washed out of the mouth before any further examination is made.

 

METHODS OF EXAMINING THE PHARYNX

 

The oral cavity and oropharynx may be examined by means of artificial and natural lighting.

The patient and the source of light are placed in the same position as for examination of the nose; the head mirror is used similarly. Examination of the oral cavity which is a necessary prelude to examination of the pharynx commences with inspection of the lips and vestibule of the mouth. A spatula, or tongue depressor, is used to re­tract, in turn, the corners of the mouth and to avert with a gentle tug the upper and lower lips in order to note the colour of the mucosa, detect scratches, ulcers or fistulas and to inspect the gums and teeth. The tongue, as well as the hard and soft palates, should also be inspected. The floor of the oral cavity is examined by using the spatula to push up the tip of the tongue. The parts which are exam­ined next are the faucial tonsils and the posterior pharyn­geal wall. Here, the spatula is used gently to push down the dorsum of the tongue. The spatula must not be insert­ed too far into the mouth, or else the gag reflex will be brought into play. The patient should not put out his tongue or hold his breath, as this will interfere with the examination.

A stubborn child who resists examination by clenching its teeth must be firmly fixed in the same position as in adenoidectomy (see Fig. 71). If it does not open its mouth for breathing when its nose is pinched, the spatula is in­serted in the mouth corner, behind the posterior molar, and pushed as far as the base of the tongue. This will cause the child to gag and open its mouth, which enables the doctor to depress its tongue with the spatula in order to examine the pharynx.

  

Attention is paid to the soft palate with its axches, the mobility of the soft palate as well as to possible fistulas, scars or fissures in the roof of the mouth. The normal col­our of the pharyngeal mucosa is pink-red or pink, whereas the uvula and the faucial pillars often have a deeper hue.

In examination of the faucial tonsils, attention is given to the colour of their mucous membranes as well as to their size, possible adhesions to the faucial pillars, and the contents of the tonsillar crypts.

For inspection of the free surface of the tonsils hidden between the faucial pillars, as well as of the contents of the crypts, the anterior pillar is pulled outwards with a spatula or a blunt hook, and the spatula is gently pressed on the anterior pillar to shift the tonsil from its bed and to express the contents of its deep depressions. When the laryngeal part of the pharynx is being inspected the tongue is firmly pressed down and outwards, preferably with a curved spatula or a postnasal mirror, as in laryn­goscopy.

  

 

In examination of the oral cavity and pharynx, it is essential to note simultaneously the condition of the sub­maxillary region and the lateral parts of the neck to de­tect enlarged lymph nodes metastases or tumour outgrowths, phlegmons, etc.

 

ANATOMY OF THE  LARYNX

 

The larynx is a part of the wind-pipe, the upper end of which opens into the pharynx, through which it communi­cates with the oral and nasal cavities, while its lower end continues as the lumen of the trachea. The larynx lies in the anterior portion of the neck on a level with the fourth and sixth cervical vertebrae. A broad ligament connects the larynx with the hyoid bone above.

The laryngeal skeleton is made of cartilage (Figs. 84 and 85). The basic cartilage is the cricoid which resem­bles a signet ring in shape. Its narrow part faces outwards, while its broad, so-called signet portion looks backwards. Above it lies the thyroid cartilage which consists of two * wings or alae joined together at an angle and forming a notch at their junction. As this portion of the thyroid car­tilage is covered with skin alone, it may be easily felt with the fingers, and in men it protrudes at the front of the neck, and is known as “Adam’s apple”. On the upper surface of the posterior part of the cricoid there are two arytenoid cartilages with two processes at their base, namely, the muscular and the vocal. The vocal muscle is attached to the latter. In addition, the laryngeal aperture is covered by a special cartilage, known as the epiglottis, which is attached by ligaments to the upper margin of the notch in the thyroid cartilage. All the laryngeal cartilages are bound together by numerous ligaments as well as by their   joints.

The true vocal cords comprising the paired vocal, or thyroarytenoid,   muscle   are   prominent   in   the   laryngeal space. The vocal cords are stretched between the inner surface of the thyroid cartilage and the vocal process of the arytenoid cartilage on the appropriate side. In respi­ration, the vocal cords form a triangular opening for the passage of air known as the rima glottidis or the glottis (Fig. 86). In phonation the vocal cords draw nearer toge­ther.

 

Above the true vocal cords lie the false vocal cords which are simply two folds of mucosa. Between the true and the false cords, on the sides, there are two slit-like pockets, the so-called Morgagni’s ventricles whose mucosa has nu­merous  glands which  moisten  the  vocal cords.

 

Fig. 84. Ligaments and Joints of Larynx  (Front View)

 

(1) epiglottis; (2) lesser comu of hyoid bone; (3) greater cornu of hyoid bone, (4) opening in thyrohyoid membrane for passage of superior laryngeal nerve; (5) thyroid cartilage; (6) tracheal cartilages; (7) cricotra-cheal ligament; (8) cricoid cartilage; (9) conus elasticus; (10) middle thyrohyoid ligament; (11) corpus adiposum; (12) thyrohyoid membrane

(2) Fig. 87. Laryngeal Muscles posterior cricoarytenoid muscle; transverse interarytenoid muscle; (3)      oblique  interarytenoid muscles

 

Fig. 86. Larynx in Vertical Section

(1) epiglottis;  (2)  extrinsic thyroarytenoid muscle;  (3) Morgagni‘s ventricle, (4) true vocal cord; (5) cricoid cartilage; (6) false ligament; (7) thyroid cartilage;(8)  glottis;  (9)  subglottic  region;   (10)  trachea

 

 

The laryngeal muscles. These may be divided into the extrinsic and the intrinsic muscles. The former connect¹ the larynx with other parts of the skeleton. They lift and lower the larynx, or fix it in a certain position.

Fig. 88. Laryngeal Muscles

(1)posterior cricoarytenoid muscle;  (2)      lateral cricoarytenoid ‘muscle; (3) Intrinsic   thyroarytenoid   muscle

 

The intrinsic muscles are attached to the inner and out­er surfaces of the larynx and do not extend beyond its li­mits. It is these muscles that perform the laryngeal func­tions of respiration and voice production. In accordance with these functions, the intrinsic laryngeal muscles di­vide into the constrictors and the dilators of the glottis. The basic, respiratory function of the larynx is performed by one paired muscle, namely, the posterior cricoaryte­noid muscle, or simply the posterior muscle (Fig. 87), the only muscle which dilates the glottis; all the other muscles directly or indirectly serve to close the glottis. The antagonist of the posterior cricoarytenoid muscle is the lateral cricoarytenoid muscle (Fig. 88) which draws the  vocal cords together and,  consequently,  narrows the glottis. The interarytenoid muscles, the transverse and the oblique, bring the arytenoid cartilages together and close the posterior part of the glottis. The vocal cords are kept in tension by the above-mentioned vocal, or thyroary­tenoid muscle. The anterior cricothyroid muscle tenses the vocal cords, since it is attached to the cricoid and thy­roid cartilages and in contraction lengthens the larynx in the anteroposterior aspect. The laryngeal mucosa is composed of elastic fibres and covered with a ciliated co­lumnar epithelium, excluding the true vocal cords, arytenoepiglottic ligaments, laryngeal surface of the aryte­noid cartilages and interarytenoid space covered with a stratified  squamous  epithelium.

 

The larynx is innervated by two branches of the vagus nerve,     namely,     the    superior and      the     inferior     laryngeal; nerves.  The    former   is   prima-1 rily   a   sensory     nerve    which! supplies  sensation to the entire! laryngeal   mucosa.    This   nerve I also   has  one  motor  branch ex- tending to the anterior cricoary-1 tenoid muscle.   The   nerve sup-! ply to all   other  laryngeal mu­scles is through branches of the inferior laryngeal  nerve.

The   larynx    is  not   only  an organ   for   the   passage    of   air but also   for   voice   production. The   sound is produced   by  the vibration   of   tense   vocal cords during   the   passage   of   air   in I expiration   through   the   glottis 8 closed to a narrow chink.

 

METHODS OF EXAMINING THE LARYNX

 

Examination    of   the   larynx is conducted   by   means  of dired visual   inspection or mirrorlaryngoscopy with a laryngeal mirror attached to the handle of another laryngeal instrument (Fig. 89).

In laryngeal examination the patient is asked to lean slightly forward and to put out his tongue which is then held in position with a square gauze throughout the re­mainder of the examination. The mirror is slightly warmed, glass side down, in the flame of an alcohol lamp or in hot water, so that it will not fog on the patient’s breath when inserted in the mouth.

 

                                                                                    

 

The laryngeal mirror is placed in the mouth, mirror side down, at an angle of 45° to the horizontal, with its back surface pushing the uvula and soft palate backwards and upwards, care being takeot to touch the posterior pharyngeal wall to avoid the gagging reflex. At the same time, the patient is told to breathe quietly and drawl the sound “e-e-e-e-e-e”. This raises the epiglottis and the la­rynx can be viewed reflected in the mirror.

 

The epiglottis is the first organ visible and by changing the position of the mirror a thorough exami­nation of all its parts can be made, after which the vocal cords and interarytenoid region are subjected to the same scrutiny. Examination of the larynx can be considered successful only when all of its parts have been inspected, and mobility of the vocal cords in quiet breathing and phonation (voice production) has been ascertained (Fig. 90). It should be remembered that in mirror laryngoscopy all anterior parts of the larynx will appear as if being above, and all the rear parts will be seen as if below. The la­teral parts will not change their positions in mirror re­flection  (Fig.   91a,   b).

 

 

 

The larynx can also be examined by means of direct la­ryngoscopy, in which inspection is made without a mirror. An angular spatula is firmly pressed against the back of the tongue to push it forward. The patient’s head is grad­ually tilted backwards to bring the oral cavity_r pharynx and larynx in one straight line. In this position, the epi­glottis, arytenoid cartilages and vocal cords may be exa­mined in turn with the aid of an appropriate light. In mo­dern practice, the angular spatula has been supplanted by a more convenient instrument called the laryngoscope. Laryngeal mirrors marked with the letter “K” on the re­verse side may be kept in boiling water. Other types of mirror cannot resist boiling and are sterilized in antisep­tic solutions of lysol or carbolic acid, washed in boiled water and wiped dry with a square of gauze.