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382793715 nasal anatomy

382793715 nasal anatomy

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Nasal Anatomy

Embryology

The developmental precursors of the nose are the neural crest cells, which commence their

caudad migration toward the midface around the fourth week of gestation. Two nasal placodes

develop inferiorly in a symmetrical fashion. Nasal pits divide the placodes into medial and lateral

nasal processes. The medial processes become the septum, philtrum, and premaxilla of the nose,

whereas the lateral processes form the sides of the nose. Inferior to the nasal complex, the

stomodeum, or future mouth, forms. (See the image below.)

Nasal embryology.

A nasobuccal membrane separates the oral cavity inferiorly from the nasal cavity superiorly. As

the olfactory pits deepen, the choanae are formed. Primitive choanae form initially, but with

continued posterior development, the secondary, or permanent, choanae develop. By 10 weeks,

differentiation into muscle, cartilage, and bony elements occurs. Failure of these carefully

orchestrated events in early facial embryogenesis may result in multiple potential anomalies,

including choanal atresia, medial or lateral nasal clefts, nasal aplasia, and polyrrhinia.

[1]

Neonates

are obligate nasal breathers for the first 6 weeks. When bilateral choanal atresia is present in a

neonate, emergency action is needed.

Skin and Soft Tissues

Like the underlying bony-cartilaginous framework of the nose, the overlying skin may also be

divided into vertical thirds. The skin of the upper third is fairly thick but tapers into a thinner,

mid-dorsal region. The inferior third regains the thickness of the upper third owing to the more

sebaceous nature of the skin in the nasal tip. The dorsal skin is usually the thinnest of the 3

sections of the nose. The difference in the skin thickness must be appreciated during dorsal

reduction.

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The nasal muscles are encountered deep to the skin and consist of 4 principal groups: the

elevators, the depressors, the compressor, and the dilators. The elevators include the procerus

and levator labii superioris alaeque nasi. The depressors are made up of the alar nasalis and

depressor septi nasi. The compressor of the nose is the transverse nasalis, whereas the dilators

are the dilator naris anterior and posterior. The muscles are interconnected by an aponeurosis

termed the nasal superficial musculoaponeurotic system (SMAS).

The internal nasal lining consists of squamous epithelium in the vestibule. This transitions to

pseudostratified ciliated columnar respiratory epithelium with abundant seromucinous glands

within the nose.

Subunit principal

The external soft tissue of the nose can be divided into subunits. The purpose of subunits is to

divide the nasal anatomy into segments useful forreconstruction. If more than 50% of the subunit

is lost, one would strive to replace the whole unit with regional tissue or tissue from a donor site.

The subunits include the dorsal nasal segment, lateral nasal wall segments, the hemilobule

segment, soft tissue triangle segments, the alar segments and the columellar segment. (See the

image below.)

Nasal subunits include the dorsum, sidewalls, lobule, soft triangles, alae,

and columella.

Blood Supply and Lymphatics

The nose, like the rest of the face, has an abundant blood supply. The arterial supply to the nose

may be principally divided into (1) branches from the internal carotid, namely the branches of

the anterior and posterior ethmoid arteries from the ophthalmic artery, and (2) branches from the

external carotid, namely the sphenopalatine, greater palatine, superior labial, and angular arteries.

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Nasal Anatomy Embryology The developmental precursors of the nose are the neural crest cells, which commence their caudad migration toward the midface around the fourth week of gestation. Two nasal placodes develop inferiorly in a symmetrical fashion. Nasal pits divide the placodes into medial and lateral nasal processes. The medial processes become the septum, philtrum, and premaxilla of the nose, whereas the lateral processes form the sides of the nose. Inferior to the nasal complex, the stomodeum, or future mouth, forms. (See the image below.) Nasal embryology. A nasobuccal membrane separates the oral cavity inferiorly from the nasal cavity superiorly. As the olfactory pits deepen, the choanae are formed. Primitive choanae form initially, but with continued posterior development, the secondary, or permanent, choanae develop. By 10 weeks, differentiation into muscle, cartilage, and bony elements occurs. Failure of these carefully orchestrated events in early facial embryogenesis may result in multiple potential anomalies, including choanal atresia, medial or lateral nasal clefts, nasal aplasia, and polyrrhinia.[1] Neonates are obligate nasal breathers for the first 6 weeks. When bilateral choanal atresia is present in a neonate, emergency action is needed. Skin and Soft Tissues Like the underlying bony-cartilaginous framework of the nose, the overlying skin may also be divided into vertical thirds. The skin of the upper third is fairly thick but tapers into a thinner, mid- ...
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