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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4501_Библиотеки_им_академика_М_И_Перельмана
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100 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 103
This section of the eustachian tube,
taken at its isthmus, shows its lumen
and cartilage as well as adjacent structures. Source: Courtesy of Dr. Sando,
University of Pittsburgh.
CHAPTER 3: THE MIDDLE EAR ■ 101
Figure 104
The relationship of the cartilaginous
part of the eustachian tube to the tensor
and levator veli palatini muscles is
shown. Source: Courtesy of Dr. Sando,
University of Pittsburgh.
102 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 105
The pharyngeal orifice of the
eustachian tube is seen in this view.
Also shown are Rosenmüller’s fossa
and the levator veli palatini muscle.
Source: Courtesy of Dr. Sando,
University of Pittsburgh.
CHAPTER 3: THE MIDDLE EAR ■ 103
Figure 106
This photomicrograph and the following two magnified views from the outlined areas Aand B are from horizontal
sections of a newborn infant.
Figure 107
This magnified view of area A in Figure
106 shows the respiratory epithelium of
the fibrocartilaginous part of the
eustachian tube.
104 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
The Palatal Muscles
The tensor veli palatini muscle arises from the spine of the sphenoid bone,
the scaphoid fossa, the lateral lamina of the tubal cartilage, and the salpingopharyngeal fascia (47) to run a course nearly parallel to the slit-like lumen
of the tube. Anteroinferiorly, it forms a tendon that sweeps around the
hamulus of the medial pterygoid plate and inserts medially into the soft
palate. Its crucial role in tubal opening is to draw the lateral lamella of the
tubal cartilage inferiorly. Some of its fibers are thought to be continuous with
those of the tensor tympani muscle (see p. 82 and Fig. 78 on p. 83) (22). Its
innervation is derived from the mandibular division of the trigeminal nerve.
The levator veli palatini muscle arises from the inferior aspect of the
petrous bone anterior to the carotid canal, as well as from the medial
cartilaginous lamina of the eustachian tube. The belly of this muscle
descends parallel to the tube to insert into the soft palate. Upon stimulation
through the pharyngeal plexus of the vagus, the levator veli palatini muscle
shortens and thickens, thus elevating the eustachian tube and widening its
lumen (Fig. 100).
The salpingopharyngeus muscle originates from the inferior aspect of
the medial cartilaginous lamella of the eustachian tube and divides inferiorly to insert into the posterior wall of the pharynx and onto the superior
horn of the thyroid cartilage. It also is innervated by the vagus nerve.
In its resting position, the eustachian tube is closed due to a combination of passive mechanisms including the elasticity of the cartilage, pressure
from surrounding tissues, and the capillary force of apposed moist mucous
membranes (46). With deglutition or yawning, the tensor veli palatini, the
levator veli palatini, and the salpingopharyngeus muscles act in concert to
open the tube (42, 43, 46).
Dysfunctions of the mechanisms controlling tubal function cause: (1)
serous otitis (otitis media with effusion) when the tube fails to open on swallowing and (2) the patulous tube syndrome (autophony) when it fails to
close. Another dysfunction of this mechanism is palatal myoclonus in which
Figure 108
This magnified view of area B in Figure
106 shows the mucous glands and
lymphoid tissue at the nasopharyngeal
orifice of the eustachian tube.
CHAPTER 3: THE MIDDLE EAR ■ 105
clonic spasms of the levator palatini and/or tensor tympani muscles cause
an annoying clicking sensation in the ear. The function of the eustachian tube
is affected by the amount of peritubal adiposity [fat pad of Ostmann (48);
Fig. 109]. Obesity may lead to eustachian tube obstruction, while loss of
body weight may cause tubal patency.
Figure 109
This photo shows the mid-portion of
the eustachian tube and adjacent
anatomic structures. Source: Courtesy
of Sando et al. (336).
106 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 110
This schematic drawing illustrates the
cell types in the middle ear mucosa.
Abbreviations: BM, basement membrane; CAP, capillary. Source: Courtesy
of Lim (44).
THE MIDDLE EAR MUCOSA
Histology
A knowledge of the structure of the normal mucosa of the human middle
ear, mastoid, and eustachian tube will help in understanding the
mechanisms involved in otitis media and middle ear effusions (Fig. 110).
In electron microscopic observations, Hentzer (49) distinguished five
types of cells in the middle ear mucosa: (1) nonciliated without secretory granules, (2) nonciliated with secretory granules, (3) ciliated, (4) intermediate, and
(5) basal. He analyzed the distribution of these five types of cells within the
middle ear, mastoid, and eustachian tube and divided them into seven
regions: (1) The mastoid contained ciliated cells and nonciliated cells without
secretory granules. (2) The posterior part of the middle ear had a thicker
epithelium with two additional types of cells—nonciliated cells with secretory
granules and basal cells. Simple squamous epithelium without cilia could
also be found. (3) The epitympanic recess was lined with epithelium similar to
CHAPTER 3: THE MIDDLE EAR ■ 107
that of the posterior part of the middle ear; however, simple nonciliated squamous epithelium could also be found. (4) In the area of the promontory, pseudostratified ciliated columnar epithelium predominated over ciliated cuboidal
epithelium. Goblet cells as well as intraepithelial and submucosal glands were
seen. Simple nonciliated squamous epithelium no longer appeared. (5) At the
tympanic orifice of the eustachian tube, the epithelium was similar to that of
the promontory, save for less frequent glands and more nonciliated cells with
secretory granules. (6) The pars flaccida possessed a simple nonciliated epithelium. (7) The epithelium of the pars tensa varied in height from pseudostratified, ciliated columnar to simple, nonciliated cuboidal. Mature goblet cells
were not found on the tympanic membrane.
Hentzer (49) concluded that the mucosa of the middle ear represents a
modified respiratory mucosa. He proposed that the nonciliated cell was its
sole secretory structure which, in its most active secretory phase, resembled
a goblet cell.
The Mucociliary Transport System
The secretions produced by the glands and goblet cells produce a mucous
blanket and the ciliated cells mobilize this blanket to create the mucociliary
transport system. Studies by Shimada and Lim (50), Lim et al. (51), and Lim
(44, 52) have demonstrated that the distribution of the ciliated cells corresponds
to that of the secretory cells. Metachronal motion (coordinated beating) of the
cilia is responsible for propelling the mucous blanket. By using six power or
higher magnification, ciliary activity can frequently be observed in the anterior
part of the hypotympanum through a perforation of the tympanic membrane.
Light reflections in the mucous sheath will be observed to be shimmering.
Lim (52) describes three distinct mucociliary tracts in the tympanic
cavity: (1) a hypotympanic tract commencing in the hypotympanum and
leading into the eustachian tube, (2) an epitympanic tract from the epitympanum to the eustachian tube, and (3) a promontory tract leading from the
promontory to the eustachian tube (52). The eustachian tube likewise
possesses a mucociliary transport system; its lining cells are believed to
secrete a surface-active agent (like a surfactant) which reduces surface
tension, thus facilitating tubal opening (53). The mastoid air cells do not
appear to have a mucociliary transport system.
Blockage of the eustachian tube in children characteristically results in
a seromucinous fluid in the tympanomastoid compartment, whereas in
adults the fluid is serous. The difference is probably related to an associated
inflammatory reaction in children, causing hyperactivity of the mucous producing goblet cells and glands.
A perforation of the tympanic membrane in association with a blocked
eustachian tube may cause a mucoid otorrhea, especially in children.
108 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
THE IMMUNE SYSTEM OF THE MIDDLE EAR
Another defense mechanism in the middle ear involves the secretion of
immunoglobulin-A (IgA) and the antibacterial enzyme, lysozyme, by the
mucosal epithelium (54). Tissue macrophages are also seen in normal human
middle ear mucosa (44). Acid phosphatase, a cytochemical marker for
lysosomes (55), has been found in the epithelium of normal mucosa,
although its exact cellular location is undetermined (56, 57). Possibly some
of the lysosomal enzymes are integrated into the enzymatic defense of the
middle ear by the mucosal secretory cells. Tracer studies (58) have
documented pinocytosis of tracer particles by the surface epithelium; these
particles then either enter the blood or lymphatic circulation or are acted
upon by the tissue macrophages of the submucosa.
Thus, the submucosa also participates in middle ear defense. This thin
connective tissue layer consists of fibroblasts and fibrocytes with their associated collagen fibers. Scattered wandering tissue phagocytes, occasional
plasma cells and lymphocytes, as well as sporadic clumps of mast cells are
also present in the submucosa; it is permeated by a multitude of blood and
lymph capillaries, and there is an abundance of nerve fibers. Plasma cells
producing immunoglobulins A, E, G, and M have been detected in the submucosa by immunohistochemical methods; in contrast, only IgA staining
has been observed in the epithelial cells of the mucosa [by immunofluorescence techniques (59)]. These immunoglobulins are believed to play a role in
local immunocompetency (60).
The Mucosal Folds
The middle ear is completely lined by a mucous membrane that is continuous with the mucosa of the eustachian tube and the mastoid antrum (see the
section on Histology, see p. 106). It also extends from the walls of the
tympanic cavity to envelop the middle ear structures such as the ossicles
with their various ligaments and the tendons of the intratympanic muscles.
In doing so, the mucosa forms several folds and pouches. As the mucosa
drapes over the anterior process and anterior ligament of the malleus, as
well as the closely associated chorda tympani nerve, it forms the anterior mal-
leal fold. This fold extends from the notch of Rivinus to the head and neck of
the malleus and, in conjunction with the anterior tympanic stria (see the section on Tympanic Membrane, p. 41), encloses a blind pouch, the anterior
pouch of von Tröltsch. The posterior malleal fold envelops the posterior segment of the chorda tympani nerve as the latter stretches from the pretympanic spine to the neck of the malleus. The posterior pouch of von Tröltsch
lies between the posterior malleal fold and the posterior tympanic stria. In
Figure 111, Prussak’s space communicates with the posterior pouch of von
Tröltsch. As the mucosa descends from the roof of the tympanic cavity to
cover the body and short process of the incus, it forms the incudal fold. The
stapes, including the obturator foramen, is sheathed by an extension of
mucosa from the posterior tympanic wall referred to as the stapedial fold.
Proctor (61) produced an exhaustive description of the genesis of these
folds as well as detailed diagrams of their anatomy. Their constancy is
related to the development of the tubotympanic recess as an outpouching of
the nasopharynx (see chap. 9). By approximately 28 weeks’ gestation, four
CHAPTER 3: THE MIDDLE EAR ■ 109
Figure 111
This view shows the tympanic membrane and ossicular anatomy at the
level of the lateral process of the
malleus. The posterior pouch of von
Tröltsch is bounded medially by the
posterior malleal fold (male, age 63yr).
buds known as primary sacs or pouches invade the middle ear cavity: (1)
The saccus anticus, the smallest of the four, forms the anterior pouch of von
Tröltsch as it extends superiorly, anterior to the tendon of the tensor tympani
muscle. (2) The saccus medius also reaches superiorly, forming the attic; it
then sprouts three saccules. The anterior saccule gives rise to the anterior
compartment of the attic, while the medial saccule develops into the
superior incudal recess. The posterior saccule is responsible for the pneumatization of the petrous part of the mastoid air cell system. (3) The saccus
superioris forms the posterior pouch of von Tröltsch and the inferior incudal
recess as it expands posterolaterally between the manubrium and the distal
aspect of the long process of the incus. With continued posterior expansion,
the saccus superioris also extends medially, entering the antrum and eventually pneumatizing the pars squamosa of the temporal bone. (4) The saccus
posticus courses in the hypotympanum and forms the round window niche,
the sinus tympani, and the majority of the oval window niche. Mucosal
folds, carrying the vessels which supply the ossicles (much like the abdominal mesentery), develop where these four major sacs come into contact with
each other.
According to Proctor (61), the various compartments of the ear defined
by these folds limit, at least in early stages, the extent of disease processes
such as cholesteatoma, and also designate probable routes of extension of
disease. Proctor believes that as long as the mucosal folds are intact, it is possible to remove a cholesteatoma and its lining epithelium and still preserve
the integrity of the particular middle ear compartment involved and the
blood supply of the ossicles. Clinical observations indicate, however, that
these folds have minimal influence on the location or magnitude of
advanced disease in the tympanomastoid compartment.
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