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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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290 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 25
Drawing showing ossification of the otic
capsule at 18 wk. Source: After Anson
and Donaldson (4).
Figure 26
Drawing showing ossification of the otic
capsule at 21 wk. Source: After Anson
and Donaldson (4).
CHAPTER 9: PHYLOGENY AND EMBRYOLOGY ■ 291
Serial Embryologic Sections
The following photomicrographs (Figs. 27–62) show four developmental
stages of the human ear. The first three series are from fetuses of approximately 8, 12, and 16 weeks of gestation, respectively. The ages of the fetal
specimens were determined by crown-rump length correlated with gestational ages. These figures are compiled from averages and serve as approximations; therefore there may be individual variations. The fourth series is
from an infant of approximately five months of age with retarded postnatal
development caused by cerebrohepatorenal (Zellweger’s) syndrome.
The first photomicrograph in each of the fetal series is a cranial
overview, placing the ear perspective with the rest of the head. Then five
horizontal serial sections of the temporal bone are presented, progressing
from superior to inferior levels. To the extent possible, sections are presented
at comparable levels. The higher power photomicrographs show in
sequence the cochleae, utricles and saccules, and cristae ampullares.
292 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
FETUS A (8 WEEKS)
Figure 27
This photomicrograph is an overview
of a horizontal section of the head. The
outlined area indicates the regions
shown in Figures 28 to 32, passing
sequentially from superior to inferior.
CHAPTER 9: PHYLOGENY AND EMBRYOLOGY ■ 293
Figure 28
The future middle ear cavity contains
mesenchyme. The facial and vestibular
nerves are seen passing from the brain
stem to the internal auditory canal.
Figure 29
This view shows the developing cartilaginous otic capsule and membranous
labyrinth. The primitive cochlear duct
and spiral ganglion are visible.
294 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 30
The cochlear duct has its full two and
one-half turns. The perilymphatic
space of the vestibule is developing as
reticulum is resorbed. (See Fig. 33.)
Figure 31
The malleus and incus are seen. The
normally massive cartilaginous footplate rests in the oval window.
Figure 32
The tubotympanic recess is invading
the mesenchyme of the middle ear. The
ectoderm of the first branchial groove
is approaching the mesodermal condensation of the future tympanic
membrane.
CHAPTER 9: PHYLOGENY AND EMBRYOLOGY ■ 295
Figure 33
This photomicrograph is a higher magnification of the cochlea appearing in
Figure 31.
Figure 34
The utricle is seen in high magnification. The sensory epithelium, otolithic
membrane, and vestibular nerve bundles are visualized.
296 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 35
This high magnification of the saccule
shows an already well-formed sensory
epithelium.
Figure 36
The sensory epithelium and the cupula
of the lateral canal are well developed.
The endolymphatic space is fully
developed and the perilymphatic space
is forming by dissolution of reticulum.
CHAPTER 9: PHYLOGENY AND EMBRYOLOGY ■ 297
Figure 37
Shown here is an overview of a horizontal section of the head. The outlined
area indicates the regions included in
Figures 38 to 42.
Figure 38
The internal auditory canal is well developed. Ossification has not yet begun.
Facial nerve fibers are located in a sulcus
in the middle ear.
FETUS B (12 WEEKS)
298 ■ ANATOMY OF THE TEMPORAL BONE WITH SURGICAL IMPLICATIONS
Figure 39
The cochlear scalae are developing and
the cochlear duct has assumed its characteristic triangular shape in the basal
turn. The outlined area is magnified in
Figure 43.
Figure 40
The spiral ganglion is visible in the
basal turn of the cochlea. The vestibule
has expanded.
CHAPTER 9: PHYLOGENY AND EMBRYOLOGY ■ 299
Figure 41
Note that the cochlear duct in the basal
turn already is nearly triangular in outline while the cochlear duct in the apex
still possesses the more immature oval
configuration.
Figure 42
The primitive cochlear aqueduct is
seen extending from the scala tympani
of the basal turn to the posterior cranial
fossa near the inferior petrosal sinus.
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