Anatomy Of Larynx Trachea Bronchi And Esophagus Endoscopically Considered


Categories: ANATOMY OF LARYNX, TRACHEA, BRONCHI AND ESOPHAGUS, ENDOSCOPICALLY CONSIDERED
Sources: A Manual Of Peroral Endoscopy And Laryngeal Surgery

The larynx is a cartilaginous box, triangular in cross-section, with

the apex of the triangle directed anteriorly. It is readily felt in

the neck and is a landmark for the operation of tracheotomy. We are

concerned endoscopically with four of its cartilaginous structures:

the epiglottis, the two arytenoid cartilages, and the cricoid

cartilage. The epiglottis, the first landmark in direct

laryngoscopy, is a leaf-like projection springing from the

anterointernal surface of the larynx and having for its function the

directing of the bolus of food into the pyriform sinuses. It does not

close the larynx in the trap-door manner formerly taught; a fact

easily demonstrated by the simple insertion of the direct laryngoscope

and further demonstrated by the absence of dysphagia when the

epiglottis is surgically removed, or is destroyed by ulceration.

Closure of the larynx is accomplished by the approximation of the

ventricular bands, arytenoids and aryepiglottic folds, the latter

having a sphincter-like action, and by the raising and tilting of the

larynx. The arytenoids form the upper posterior boundary of the

larynx and our particular interest in them is directed toward their

motility, for the rotation of the arytenoids at the cricoarytenoid

articulations determines the movements of the cords and the production

of voice. Approximation of the arytenoids is a part of the mechanism

of closure of the larynx.



The cricoid cartilage was regarded by esophagoscopists as the chief

obstruction encountered on the introduction of the esophagoscope. As

shown by the author, it is the cricopharyngeal fold, and the

inconceivably powerful pull of the cricopharyngeal muscle on the

cricoid cartilage, that causes the difficulty. The cricoid is pulled

so powerfully back against the cervical spine, that it is hard to

believe that this muscles is inserted into the median raphe and not

into the spine itself (Fig. 68).



The ventricular bands or false vocal cords vicariously phonate in

the absence of the true cords, and assist in the protective function

of the larynx. They form the floor of the ventricles of the larynx,

which are recesses on either side, between the false and true cords,

and contain numerous mucous glands the secretion from which lubricates

the cords. The ventricles are not visible by mirror laryngoscopy, but

are readily exposed in their depths by lifting the respective

ventricular bands with the tip of the laryngoscope. The vocal cords,

which appear white, flat, and ribbon-like in the mirror, when viewed

directly assume a reddish color, and reveal their true shelf-like

formation. In the subglottic area the tissues are vascular, and, in

children especially, they are prone to swell when traumatized, a fact

which should be always in mind to emphasize the importance of

gentleness in bronchoscopy, and furthermore, the necessity of avoiding

this region in tracheotomy because of the danger of producing chronic

laryngeal stenosis by the reaction of these tissues to the presence of

the tracheotomic cannula.



The trachea just below its entrance into the thorax deviates

slightly to the right, to allow room for the aorta. At the level of

the second costal cartilage, the third in children, it bifurcates into

the right and left main bronchi. Posteriorly the bifurcation

corresponds to about the fourth or fifth thoracic vertebra, the

trachea being elastic, and displaced by various movements. The

endoscopic appearance of the trachea is that of a tube flattened on

its posterior wall. In two locations it normally often assumes a more

or less oval outline; in the cervical region, due to pressure of the

thyroid gland; and in the intrathoracic portion just above the

bifurcation where it is crossed by the aorta. This latter flattening

is rhythmically increased with each pulsation. Under pathological

conditions, the tracheal outline may be variously altered, even to

obliteration of the lumen. The mucosa of the trachea and bronchi is

moist and glistening, whitish in circular ridges corresponding to the

cartilaginous rings, and reddish in the intervening grooves.



The right bronchus is shorter, wider, and more nearly vertical than

its fellow of the opposite side, and is practically the continuation

of the trachea, while the left bronchus might be considered as a

branch. The deviation of the right main bronchus is about 25 degrees,

and its length unbranched in the adult is about 2.5 cm. The deviation

of the left main bronchus is about 75 degrees and its adult length is

about 5 cm. The right bronchus considered as a stem, may be said to

give off three branches, the epiarterial, upper- or superior-lobe

bronchus; the middle-lobe bronchus; and the continuation downward,

called the lower- or inferior-lobe bronchus, which gives off dorsal,

ventral and lateral branches. The left main bronchus gives off first

the upper-or superior-lobe bronchus, the continuation being the

lower-or inferior-lobe bronchus, consisting of a stem with dorsal,

ventral and lateral branches.



[FIG. 44.--Tracheo-bronchial tree. LM, Left main bronchus; SL,

superior lobe bronchus; ML, middle lobe bronchus; IL, inferior lobe

bronchus.]



The septum between the right and left main bronchi, termed the carina,

is situated to the left of the midtracheal line. It is recognized

endoscopically as a short, shining ridge running sagitally, or, as the

patient lies in the recumbent position, we speak of it as being

vertical. On either side are seen the openings of the right and left

main bronchi. In Fig. 44, it will be seen that the lower border of the

carina is on a level with the upper portion of the orifice of the

right superior-lobe bronchus; with the carina as a landmark and by

displacing with the bronchoscope the lateral wall of the right main

bronchus, a second, smaller, vertical spur appears, and a view of the

orifice of the right upper-lobe bronchus is obtained, though a lumen

image cannot be presented. On passing down the right stem bronchus

(patient recumbent) a horizontal partition or spur is found with the

lumen of the middle-lobe bronchus extending toward the ventral surface

of the body. All below this opening of the right middle-lobe bronchus

constitutes the lower-lobe bronchus and its branches.



[FIG. 45.--Bronchoscopic views.

S; Superior lobe bronchus; SL, superior lobe bronchus; I, inferior

lobe bronchus; M, middle lobe bronchus.]



[56] Coming back to the carina and passing down the left bronchus, the

relatively great distance from the carina to the upper-lobe bronchus

is noted. The spur dividing the orifices of the left upper- and

lower-lobe bronchi is oblique in direction, and it is possible to see

more of the lumen of the left upper-lobe bronchus than of its

homologue on the right. Below this are seen the lower-lobe bronchus

and its divisions (Fig. 45).





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