drying of the nasal mucosa.
Complete exclusion of the nose from breathing leads in the long term to
deep-seated mucosal changes. Mechanical obstruction within the nose, e.g., due
to septal deviation, hypertrophy of the turbinates, cicatricial stenoses, etc.,
can lead to mouth breathing and its damaging consequences and can also cause
mucosal diseases of the nose and nasal sinuses.
The nasal patency can be influenced by many different factors, including
temperature and humidity of the surrounding air, the position of the body,
bodily activity, changes of body temperature, the influence of cold on different
parts of the body, e.g., the feet, hyperventilation, and psychological stimuli.
The state of the pulmonary function, of the heart, and of the circulation,
endocrinologic disorders such as pregnancy, hyper- or hypofunction of the
thyroid gland, and some local, oral, or parenteral drugs may have considerable
influence on the patency of the nose.
Protective function of the Nose
During normal nasal respiration, the inspired air is warmed, moistened, and
purified during its passage through the nose.
The warming of the inspired air through the nose is very effective, and the
constancy of the temperature in the lower airways is remarkably stable. The
nasal mucosa humidifies and warms the air. The temperature in the nasopharynx
during normal (exclusively nasal) respiration is constant at 31° to 34°C
independent of the external temperature. The heat output of the nose increases
as the external temperature falls so that the lower airways and the lungs can
function at the correct physiologic temperature.
The optimal relative humidity of room air for subjective well-being and function
of the nasal mucosa lies between 50% and 60%. The water vapor saturation of the
inspired air in the nasopharynx lies between 80% and 85%, and in the lower
airway is fairly constant between 95% and 100%, independent of the relative
humidity of the environmental air. The water vapor secreted by the entire
respiratory tract per 1000 liters of air can reach 30 g. Most of this is
supplied by the nose. On the other hand, the mucosal blanket renders the nasal
mucosa watertight and prevents release of too much water into the air, which
would cause drying of the mucosa.
The cleaning function of the nose includes: first, cleaning of the inspired air
from foreign bodies, bacteria, dust, etc., and second, cleaning of the nose
itself. About 85% of particles larger than 4,5 mm are filtered out by the nose,
but only about 5% of particles less than 1 mm in size are removed.
Foreign bodies entering the nose come into contact with the moist mucosal
surface and the mucosal blanket, which continually carries away the foreign
bodies.
The Nasal Mucosa as a Protective Organ
In addition to warming, humidifying, and cleaning the inspired air, the nose
also has a protective function consisting of a highly differentiated, efficient,
and polyvalent resistance potential against environmental influences on the
body. A basic element of this defensive system is the mucociliary apparatus.
This is the functional combination of the secretory film and the cilia of the
respiratory epithelium by which the colloidal secretory film is transported
continuously from the nasal introitus toward the choana. A foreign body is
carried from the head of the inferior turbinate to the choana in about 10 to 20
min. The efficiency of this cleansing system depends on several factors such as
pH, temperature, condition of the colloids, humidity, width of the nose, toxic
gases, etc. Disturbances in the composition or in the physical characteristics
of the mucosal blanket or of the ciliary activity can have marked influences on
the physiology of the nasal cavity.
The nasal mucosa protects the entire body by making contact with and providing
resistance against animate and inanimate foreign material in the environment.
Two defence zones can be distinguished in the nasal mucosa: first, the mucosal
blanket and the epithelium, and second, the vascular connective tissue of the
lamina propria.
Resistance factors of the first defensive zone include: (1) physical cleaning by
the mucociliary apparatus; (2) nonspecific protective factors in the secretions
such as lysozymes, interferon, secretory protease inhibitors, complement system,
and secretory glucosidases; and (3) specific protective factors such as
immunoglobulin A (IgA), immunoglobulin M (IgM), and immunoglobulin G (IgG).
Resistance factors of the second defensive zone include: (1) nonspecific
protective factors and structures such as the ground substance and fibrils,
micro- and macrophages, mast cells, vessels, the autonomic nervous system,
hormones, interferon, protease inhibitors, complement, etc.; and (2) specific
defensive factors such as sensitized B- and T-lymphocytes, eosinophil
granulocytes, immunoglobulin IgG, IgM, and IgE.
The Nose as a Reflex Organ
Specific nasal reflex mechanisms may arise: - Within the nose and affect the
nose itself - From other parts of the body or organs and affect the nose - In
the nose and affect other parts of the body. A reflex system which is obviously
confined to the nose is the nasal cycle. One cycle lasts between 2 and 6 h.
Provided that both halves of the nasal cavity are of normal patency, the lumen
widens and narrows alternately, lowering or increasing the respiratory
resistance in each half of the nose. However, the resistance of the entire nose
remains constant in the ideal case. This reflex phenomenon is controlled by the
action of the autonomic nervous system on the cavernous spaces of the vascular
system of the nasal mucosa.
Nasopetal reflexes arise, e.g., from cooling of the extremities, which changes
the respiratory resistance. They may also arise from the lungs and bronchi and
from other autonomic control points.
Important nasofugal communications exist between the nose and the lung, the
heart and circulation, the metabolic organs, and the genitals.
In addition, there are sneezing, lacrimal, and cough reflexes, and under certain
emergency situations, reflex respiratory arrest.
Influence of the Nose on Speech
The nose influences the sound of speech. During the formation of the resonants
"m", "n", and "ng", e.g., the air streams passes through the open nose, whereas
during the formation of the vowels the nose and the nasopharynx are more or less
closed off by the soft palate from the resonating cavity of the mouth.
Function of the Paranasal Sinuses
The biologic purpose of the nasal sinuses is largely speculative. The main
function of the paranasal sinuses is the protection of the cranial cavity. It
is obvious that the pneumatized cavities of the bone of the skull reduce the
weight, at the same time increasing the superficial extent of the bones of the
skull.
The existence of the ostia causes particular pathophysiologic problems affecting
ventilation and drainage.
Ostial obstruction interrupts the self-cleaning mechanism of the affected sinus:
therefore, the secretions stagnate and change in composition. The retained
secretions form an ideal medium for saprophytic bacteria which are often present
in normal sinuses.
The causes of closure of the ostium include:
1. Environmental factors such as relative dryness of the nose, toxic gases, or
agents in the air.
2. Local congenital or acquired anomalies, including: deviation of the septum,
scars, lesions of the turbinates, infections of the nose or nasal cavities,
dental diseases, allergic diseases of the nose or nasal sinuses (particularly in
children), vasomotor dysfunctions with a neurogenic or hormonal basis, metabolic
diseases such as avitaminoses, diabetes, disordered electrolytes, mechanical
obstruction due to crusts, polypi, foreign bodies, prolonged use of a
nasogastric tube or prolonged nasal tracheal intubation, and benign and
malignant tumors.
The vicious circle of ostial occlusion can only be broken in the long term by
dealing with the causal factors by appropriate medical or surgical measures.
The nasal sinuses are only minimally involved in the respiratory phases of the
nasal cavity.
The change in pressure which can be recorded in the sinuses during respiration
is relatively slight.
ANATOMY OF THE PHARYNX
The pharynx extends from the base of the skull to the level of sixth cervical
vertebrae. This is a 12 to 13 cm long muscular tube in the adult; it narrows
from above downward, is covered with mucosa, and is divided into three
compartments each of which has an anterior opening (Fig. 26).
The nasopharynx is limited superiorly by the base of the skull, inferiorly by an
imaginary plane through the soft palate, and it opens into the nasal cavity. The
most important anatomic structures are as follows: anteriorly the choanae,
posterosuperiorly the adenoid, laterally the pharyngeal ostium of the eustachian
tube and the cartilaginous torus tubarius immediately posterior to which is
Rosenmueller's fossa and the tubal tonsil, and anteriorly and inferiorly the
soft palate (Fig. 28). The embryonic pharyngeal bursa may persist in the
posterior wall of the nasopharynx causing chronic inflammation and retention of
secretions. The posterior wall of the nasopharynx is separated from the spinal
column by the tough prevertebral fascia which lies on the longus capitis
muscles, the deep muscles of the neck, and the arch of the first cervical
vertebra.
The shape and width of the nasopharynx show marked individual variation. The
epithelial lining is respiratory ciliated and stratified squamous epithelium,
with transitional epithelium at the junction with the oropharynx.
The oropharynx extends from the horizontal plane through the soft palate
described above to the superior edge of the epiglottis and is continuous with
the oral cavity through the faucial isthmus. It contains the following important
structures: the posterior wall consisting of the prevertebral fascia and the
bodies of the second and third cervical vertebrae, the lateral wall containing
the palatine tonsil with the anterior (palatoglossal) and posterior
(palatopharyngeal) faucial pillars, and the supratonsillar fossa lying above the
tonsil between the anterior and posterior faucial arches. The anterior surface
of the soft palate with the uvula are the parts of the oropharynx (Fig. 27).
The epithelial lining consists of nonkeratinizing stratified squamous
epithelium.
The hypopharynx extends from the upper edge of the epiglottis superiorly to the
inferior edge of the cricoid cartilage. It opens anteriorly into the larynx. On
each side of the larynx lie the funnel-shaped pyriform sinuses. The valleculae,
the base of the tongue, and the lingual surface of the epiglottis are usually
described as being the part of the hypopharynx.
Important anatomic structures and relations include: on the anterior wall the
marginal structures of the laryngeal inlet and the posterior surface of the
larynx; on the lateral wall the inferior constrictor muscle and the pyriform
sinus, the latter being bounded medially by the aryepiglottic fold and laterally
by the internal surface of the thyroid cartilage and the thyrohyoid membrane.
Immediate relationships of the hypopharynx at the level of the larynx include
the common carotid artery, the internal jugular vein, and the vagus nerve.
Relations of the posterior wall, apart from the pharyngeal constrictor muscle,
include the prevertebral fascia and the bodies of the third to the sixth
cervical vertebrae. Inferiorly the hypopharynx opens into the esophagus, the
boundary being the superior sphincter of the esophagus. The epithelial lining
consists of nonkeratinized stratified squamous epithelium.
The muscular tube of the entire pharynx consists of two layers with different
functions (Fig. 25):
1. A circular muscle layer consisting of the three pharyngeal constrictor
muscles: the superior constrictor inserted into the base of the skull, the
middle constrictor inserted into the hyoid bone, and the inferior constrictor
inserted into the cricoid cartilage. Each of these funnel-shaped muscular
segments is overlapped at its lower end by the segment below. All segments are
inserted posteriorly into a tendinous median raphe.
The inferior constrictor muscle is of particular clinical importance. It is
divided into a superior thyropharyngeal part and an inferior cricopharyngeal
part. The triangular dehiscence (Killian's triangle) is from the posterior wall
of the hypopharynx between the superior oblique and the inferior horizontal
fibres.
2. The raising and lowering of the pharynx is also achieved by three paired
muscled radiating into the pharyngeal wall from outside. These are the
stylopharyngeus, the salpingopharyngeus, and the palatopharyngeus muscles. The
stylohyoid and styloglossus muscles are also responsible for elevation. A true
longitudinal muscle does not occur in the pharynx and only begins at the mouth
of the esophagus. The ability of the pharynx to slide over a distance of several
centimetres is due to the existence of fascial spaces (parapharyngeal and
retropharyngeal) filled with loose connective tissue.
Vascular supply of the pharynx. The arterial supply is provided by the ascending
pharyngeal artery, the ascending palatine artery(facial artery), the tonsillar
branches of the facial artery, the descending palatine artery(maxillary artery),
and branches of the lingual artery. All these arise from the external carotid
artery. The venous drainage is via the facial vein and the pterygoid plexus to
the internal jugular vein.
The lymphatic drainage is either via an inconstant retropharyngeal lymph node
and then to the deep jugular lymph nodes or directly to the latter group. The
inferior part of the pharynx also drains to the paratracheal lymhph nodes, and
thus gains a connection to the lymphatic system of the thorax.
Nerve supply of the pharynx. The individual pharyngeal muscles gain their motor
supply from the glossopharyngeal, vagus, hypoglossal, and facial nerves. The
nasopharynx derives its sensory nerve supply from the maxillary division of the
trigeminal nerve, the oropharynx from the glossopharyngeal nerve, and the
hypopharynx from the vagus nerve.
Lymphoepithelial System of the Pharynx
A very pronounced collection of lymphoepithelial tissue, Waldeyer's ring, lies
at the opening of the upper aerodigestive tracts. These lymphoepithelial organs
are called tonsils. From above downward, the following may be distinguished:
1. The pharyngeal tonsil, the adenoids, which is single and lies on the roof and
posterior wall of the nasopharynx.
2. The tubal tonsil, which is paired and lies around the ostium of the
eustachian tube in Rosenmueller's fossa.
3. The paired palatine tonsil, lying between the anterior and posterior faucial
pillars.
4. The lingual tonsil, which is single and lies in the base of the tongue.
Less constant and obvious are:
5. The tubopharyngeal plicae, lateral bands, which run almost vertically at the
junction of the lateral and posterior walls of the oro- and nasopharynx.
6. Lymphoepithelial collections in the laryngeal ventricle. Unlike lymph nodes,
lymphoepithelial organs possess only efferent lymph vessels and do not have
afferent vessels. The difference in pathology and physiology of the individual
collection of lymphoid tissue rests on their different structure.
The fine structure of a tonsil is in principle as follows: the soft tissue
lamellae or septae arise from a basal connective tissue capsule. These serve as
a supporting framework in which blood vessels, lymphatics, and nerves run. This
fan-shaped supporting framework considerable increases the active surface of the
tonsil since it carries the actual lymphoepithelial parenchyma. It is estimated
that the epithelial surface of one palatine tonsil amounts to 300 cm2. In the
palatine tonsil the active surface is sunk within the mucosa, whereas in the
adenoids it projects above the surface. The broad flat niches opening into the
oral cavity caused by enfolding are called lacunae; the branching clefts running
throughout the entire substance of the tonsil are called crypts. The actual
tonsil tissue consists of a collection of a very large number of the
lymphoepithelial units. The crypts usually contain cell debris and round cells,
but may also contain bacteria and colonies of fungi, collections of pus, and
encapsulated microabscesses.
The tonsils of Waldeyer's ring are present at the embryonal stage, but they only
acquire their typical structure with secondary nodes in the postnatal period,
i.e., after direct contact with environmental pathogens. They begin increasing
rapidly in size between the 1-st and the 3-rd year of life, with peaks in the
3-rd and 7-th year. They involute slowly as of early puberty. Like the rest of
the lymphatic system, they atrophy with increasing age.
The arterial blood supply of the tonsils is provided by various branches of the
external carotid artery including the ascending pharyngeal artery, the
descending pharyngeal artery (maxillary a.), the ascending palatine artery
(facial a.), the lingual artery, and also possibly direct tonsillar branches.
The veins of the pharyngeal tonsil usually drain via the palatal vein and from
there to the jugulofacial venous angle of the internal jugular vein. There is
also drainage via the pterygoid venous plexus to the internal jugular vein.
PHYSYOLOGY OF THE PHARYNX
Several functional systems are collected in the pharynx including the swallowing
apparatus, the lymphoepithelial ring, and articulation. Furthermore, the
respiratory and digestive tracts cross in this area.
The function of the tonsils is:
1. The tonsils ensure controlled and protected contact of the organism with the
pathogenic and antigenic environment serving the purpose of immunologic
surveillance. This allows adaptation to the environment, especially in children.
2. The tonsil produce lymphocytes.
3. The tonsils expose B- and T-lymphocytes to current antigens and are
instrumental in the production of specific messenger lymphocytes and memory
lymphocytes.
4. The tonsils produce specific antibodies after the production of the
appropriate plasma cells. All types of immunoglobulins occur in tonsillar
tissue.
5. The tonsils shed topical immune-stimulated lymphocytes for both humoral and
cell-mediated immunity into the oral cavity and the digestive tract.
6. The tonsils are instrumental in the production and discharge of immunoactive
lymphocytes into the blood and lymphatic circulation.
Part 3
ANATOMY AND PHYSIOLOGY OF THE LARYNX,
TRACHEOBRONCHIAL TREE AND ESOPHAGUS
LARYNX
Anatomy
The larynx extends from the level of C4 to the level of C6 in adults and from
the level of C3 to the level of C4 in children.
The laryngeal skeleton consists of the thyroid, cricoid, and arytenoid
cartilages (Fig. 31), which are hyaline cartilage, the epiglottis, which is
fibrous cartilage, and the fibroelastic accessory cartilages of Santorini
(corniculate) and Wrisburg (cuneiform), which have no function.
The unpaired cartilages. The epiglottis is a leaf-shaped piece of cartilage
which is attached both to the base of the tongue and to the upper part of the
thyroid cartilage. The thyroid cartilage (the largest cartilage of the larynx)
is that which makes the prominence upon the front of the neck known as “Adam’s
apple” (Fig. 30). It consist of two wings or alae which are joined together in
the midline anteriorly and extend backwards. In the front, at the junction of
the alae, is a notch which is called the “thyroid notch”. On the posterior edge
of the alae, above and below, there are two processes or horns – superior and
inferior. Below the thyroid cartilage, and articulating with it posteriorly, is
the cricoid cartilage. In front it is joined to the thyroid cartilage by the
cricothyroid membrane. The cricoid cartilage (Fig. 29) is a closed ring of
cartilage in the form of a signet ring, of which the signet or large portion of
the cartilage is the posterior part.
The paired cartilages. First and most important are the arytenoid cartilages.
They can rotate and also slide on the cricoid and thus play an important part in
the movement of the vocal cords. Each arytenoid has the shape of a three-sided
pyramid. The anterior process is spoken of as the vocal process; the lateral
process as the muscular process. To the vocal process, in front, are attached
the vocal cords, while the muscular processes form the main attachment for whose
muscles activating the vocal cords in phonation and respiration. The
aryepiglottic fold connects the arytenoid with the base of the epiglottis and
forms the upper edge of the laryngeal inlet.
Ossification of the thyroid cartilage begins at the time of puberty.
Ossification of the cricoid and arytenoid cartilage follows somewhat later. The
female larynx calcifies considerably later than that of the male.
The cartilaginous framework is bound together by ligaments and covered with
muscle and mucous membrane.
Internal and external ligaments and membranes unite the cartilages and stabilise
the soft tissue covering. The thyroid cartilage is united by a joints to the
cricoid cartilage. Rocking and slight gliding movements occur at this joints.
The cricoid cartilage is united by a joints to arytenoid cartilages.
The muscles, ligaments, and membranes between the cartilage allow the
functionally important movements between different parts of the larynx.
The external ligaments and connective tissue membranes anchor the larynx to the
surrounding structures.
The most important membranes include (Fig. 32):
The thyrohyoid membrane has the opening for the superior laryngeal artery and
vein and for the internal branch of the superior laryngeal nerve which supplies
sensation to the larynx above the vocal cords.
The cricothyroid (conical) membrane is the point where the airway comes closest
to the skin: it is the site of laryngotomy.
The cricotracheal ligament provides attachment to the trachea.
The internal ligaments and connective tissue membranes, e.g., the conus
elasticus, the thyroepiglottic ligament, the aryepiglottic ligament connect the
cartilaginous parts of the larynx to each other.
The external muscles of the larynx:
- sternohyoid muscle;
- sternothyroid muscle;
- thyrohyoid muscle.
The internal muscles act synergistically and antagonistically to control the
functions of the larynx (Fig. 33, 34). They open and close the glottis and put
the vocal cords under tension.
This interplay explains the different positions of the vocal cords in paralysis
of the recurrent laryngeal nerve or of the external branch of the superior
laryngeal nerve.
Functions of the Laryngeal Musculature
Opening of the glottis, abduction of the vocal cordsPosterior
cricoarytenoid muscle (posticus muscle)
Closure of the glottis, adduction of the vocal cordsLateral cricoarytenoid
muscle (lateralis muscle)
Transverse arytenoid muscle (transversus muscle)
Oblique arytenoid muscle
Thyroarytenoid muscle, lateral part
Tension of the vocal cords
Cricothyroid muscle (anticus muscle)
Thyroarytenoid muscle, medial part (vocalis muscle)
Movement of the
epiglottis Aryepiglottic muscle
Thyroepiglottic muscle
There is only one muscle which opens the glottis, the "posticus". The muscles
that close it are clearly in the majority. The ratio of their relative power is
1:3. Only the arytenoid muscle (pars transversa) is unpaired; all other muscles
are paired.
Laryngeal cavity (Fig. 35, 37). In the interior of the larynx two folds of
mucous membrane are stretched from front to back. They are rounded and pink in
colour, and are called the false cords (vestibular cords). Under the vestibular
cords there are vocal cords (true cords). The vocal cords are attached
anteriorly in the midline to the posterior surface of the thyroid cartilage.
Posteriorly they are attached to the arytenoid cartilages. The vocal cord
includes the vocal ligament, the vocalis muscle, and the mucosal covering. The
length of the vocal cord is 0,7 cm in the newborn, 1,6 to 2 cm in women, and 2
to 2,4 cm in men.
The laryngeal ventricle is the site of the primitive air sac and lies between
the vocal cord and vestibular cord.
The laryngeal cavity is divided for clinical purposes into three compartments:
Supraglottis, Glottis, Subglottis. The glottis is formed by the edges of the
true vocal cords, it is divided into an intermembranous part which lies between
the paired vocal ligaments and an intercartilaginous part which lies between the
arytenoid cartilages of each side.
Superiorly, the larynx is limited by the free edge of the epiglottis, the
aryepiglottic fold, and the interarytenoid notch. Inferiorly, the lower edge of
the cricoid cartilage marks the junction with the trachea.
The nerve supply of the laryngeal musculature is provided by the external branch
of the superior laryngeal nerve and by the recurrent laryngeal nerves that arise
from the vagus nerve.
The superior laryngeal nerve divides into a sensory internal branch, which
supplies the interior of the larynx down into the glottis, and an external
brunch, which provides the motor supply to the cricothyroid muscle.
The recurrent laryngeal nerve provides motor supply to the entire ipsilateral
internal laryngeal musculature. In addition, it provides sensation to the
laryngeal mucosa inferior to the glottic cleft.
The left recurrent laryngeal nerve passes around the aortic arch to reach the
larynx in the groove between the trachea and the esophagus. The right recurrent
laryngeal nerve passes around the subclavian artery and then runs superiorly in
a groove between the trachea and the esophagus.
Both recurrent laryngeal nerves enter the larynx at the inferior cornu of the
thyroid cartilage. The relations of this nerve to the inferior thyroid artery
and thyroid gland are important in surgical anatomy.
The blood supply of the larynx is divided by the glottis into two areas.
The supraglottic blood supply from the superior laryngeal artery, originates
from the external carotid artery, whereas the subglottic vessels, the inferior
laryngeal artery, derive from the thyrocervical trunk of the subclavian artery.
The venous drainage passes superiorly via the superior thyroid vein to the
internal jugular vein and inferiorly via the inferior thyroid vein to the
brachiocephalic vein.
The lymphatic drainage of the larynx is of great clinical importance. Here again
the glottis forms the embryologic barrier between the superior and inferior
lymphatic streams.
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