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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4450_Библиотеки_им_академика_М_И_Перельмана
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Medial crus
Intermediate part (not always identifiable)
Dome
Lateral crus
Medial Crus
The medial crus is the slightly bent medial part of the
lobular cartilage. It supports the columella, nares, and tip.
Its length and width vary greatly. As the medial crura run
into the columella, they become closely associated and
form a support for the septal cartilage. Their free ends
protrude slightly into the vestibules, broadening the
columellar base (▶ Fig. 1.28). The space between the medial
crura is filled with loose connective tissue. There are no
crossing fibers between the two crura. See also ▶ Fig. 1.101
and ▶ Fig. 1.102; ▶ Intercrural Area.
Fig. 1.28Lobular cartilages in relation to the tip, alae, and columella.
Intermediate Part
The intermediate part may be defined as the transitional
segment between the medial crus and the dome. It cannot
always be clearly identified as a separate part of the
lobular cartilage. Many authors therefore do not recognize
it as a separate structure.
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Dome
The dome is the strongly bent part of the lobular cartilage
between the medial and lateral crura. Its curvature varies
greatly from 80° (ballooning type) to 10° (narrow type). Its
cranial border is often notched. The two domes together
make the nasal tip. It has been suggested that the two
domes are connected by a bundle of midline crossing
fibers, an interdomal ligament, or Pitanguy ligament. In a
histological study ([340]), we were unable to confirm the
presence of horizontal, midline-crossing fibers, and
certainly not a ligament (see ▶ Fig. 1.98, ▶ Fig. 1.99, and ▶ Fig.
1.100).
Although a true ligament characterized by highly organized
fiber directions is not present, the connecting tissue
between the domes and adjacent intermediate parts of the
lobular cartilages is biomechanically important.
Lateral Crus
The lateral crus is the lateral extension of the lobular
cartilage supporting the ala. Its shape may be convex,
convex–concave, concave–convex, concave, or flat (▶ Fig.
1.29). The convex type is the most frequent. Its length
(mediolateral dimension) varies from 16 to 30 mm, its
maximal height (craniocaudal dimension) from 6 to 16 mm.
The distance of its caudal margin to the alar rim increases
in the ventrodorsal direction.
Fig. 1.29Most common shapes of the lateral crus of the lobular cartilage.
Soft-Tissue Areas
The external nasal pyramid has four soft-tissue areas.
Unfortunately, there is considerable confusion about their
terminology in the literature. We suggest using the
following nomenclature (▶ Fig. 1.30):
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Fig. 1.30The four soft-tissue areas.
Paraseptal cleft or paraseptal soft-tissue area
Lateral soft-tissue area or hinge area
Caudal lobular notch
Alar soft-tissue area
The paraseptal cleft (paraseptal soft-tissue area) is a
narrow triangular opening between the cartilaginous
septum and the lower third of the medial margin of the
triangular cartilage, filled with loose connective tissue. It
allows the outward and inward movement of the lower part
of the triangular cartilage during respiration.
The lateral soft-tissue area (hinge area) is a more or less
triangular soft-tissue area between the lateral margin of
the triangular cartilage and the lateral wall of the piriform
aperture. It consists of relatively dense connective tissue
fibers with two to three accessory cartilages. It allows
outward and inward movements of the triangular cartilages
(and valve) and alae. It is therefore also called the hinge
area.
The caudal lobular notch is found medially at the lower
margin of the lateral crus. It does not seem to have any
special functional significance. It deserves special attention
and needs to be carefully preserved during lobular surgery.
The alar soft-tissue area is the most dorsal and caudal part
of the ala inferior to the lateral crus of the lobular
cartilage. The ala is not completely occupied by the lobular
cartilage.
Skin and Connective, Muscular, and Fatty Tissues
Overlying the External Nose
The external nasal pyramid is covered from outside to
inside by:
An epidermis of varying thickness and a dermis with
sebaceous glands and hair follicles
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A connective tissue layer of varying thickness
containing the vascular and nerve supply, and a
variable amount of fatty tissue
A muscle layer
A thin, loose connective tissue layer permitting gliding
movements of the overlying tissues
A periosteal or perichondrial layer that is attached to
the bone or cartilage
Nowadays, some authors like to speak of a superficial
musculoaponeurotic system (SMAS), consisting of a
superficial fatty layer, a fibromuscular layer, a deep fatty
layer, a longitudinal fibrous layer, and an intercrural
ligament ([187]). However, we prefer to reserve the term
SMAS for a connective tissue layer containing a variable
number of muscle fibers that extends cranially from the
platysma, covers the parotid gland and facial nerve
branches, and stops at the level of the zygomatic arch.
Anteriorly, the SMAS is continuous with the orbicularis
oculi and zygomaticus major muscles. Because this layer is
in the same level as the facial muscles, it can best be
regarded as the vestige of the facial muscle layer in a
region where such muscles are not needed anymore (i.e.,
the parotid region). Indeed, in primates, the cranial border
of the platysma runs as high as the zygomatic arch ([159]).
Therefore, we do not follow the distinction between the
various layers as described by [187]; moreover these layers
show considerable differences in the various parts of the
external nasal pyramid. See also ▶ Fig. 1.95, ▶ Fig. 1.96, and
▶ Fig. 1.97; ▶ Septolateral Cartilage: Cartilaginous Septum and
Triangular Cartilages.
The bony pyramid is covered in its upper part by relatively
thick skin with a considerable amount of subcutaneous
connective tissue and muscle fibers (procerus). In its lower
part, the nasal bones are covered by a rather thin skin, a
thin layer of loose connective tissue, and some transverse
muscle fibers (transverse part of nasalis) (▶ Fig. 1.31).
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Fig. 1.31Thickness of the skin and subcutaneous tissues overlying the external
pyramid.
The loose subcutaneous layer allows movement of the skin
over the bone while offering protection against trauma and
pain from pressure. This is illustrated by patients in whom
this layer has not been preserved during surgery; they
often complain of tenderness in this region.
The cartilaginous pyramid is covered by a somewhat
thicker layer of soft tissue. The skin has a larger number of
sebaceous glands and hair follicles. The muscle fiber layer
is also thicker. See also ▶ Fig. 1.95 and ▶ Fig. 1.96; ▶
Septolateral Cartilage: Cartilaginous Septum and Triangular
Cartilages.
The lobule has a thick covering consisting of epidermis,
dermis with hair follicles and numerous sebaceous glands,
fat, connective tissue with the vascular supply, lymph
vessels and nerves, muscle fibers, and areolar tissue.
The thickness and quality of the skin depend on a great
number of factors, including gender, age, and
climatological influences. The subcutaneous connective
tissue layer is relatively thick, especially between the
cartilages. A variable amount of fatty tissue can be found in
the midline just above the interdomal area and laterally.
See also ▶ Fig. 1.104 and ▶ Fig. 1.105; ▶ Alae.
Four different muscles can be distinguished. The fibers run
from the lobular cartilage into the skin, adding to the
rigidity of the lateral lobular wall or ala. As a result, the
lobular skin is not freely movable over the lobular cartilage.
Musculature
The external nasal pyramid is almost completely covered by
a thin layer of musculature. There is no consensus on the
number of muscles that can be distinguished and no
agreement on their names.
[70] recognizes five nasal muscles. Most anatomical and
rhinosurgical textbooks, however, mention seven or nine.
All nasal muscles have a mimic function. Some of them also
play a role in breathing and provide stability for the lateral
nasal wall. In this section we follow the work of [22], who
recognized seven different nasal muscles (▶ Fig. 1.32).
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