Chapter 26: Sinonasal Development and Anatomy

Nasal Cavity

1. Nasal embryology

   • The embryologic precursors of the nasal turbinates arise in the eighth week of gestation as ridges along the lateral nasal wall.

   • Maxilloturbinal: originates inferiorly from the maxillary process and gives rise to inferior turbinate.

   • Ethmoturbinals: arise superiorly from ethmoid bone, five arise with only four persisting throughout development.

     1. First ethmoturbinal:

        • Ascending portion gives rise to agger nasi

        • Descending portion gives rise to uncinate process (UP)

        • Regresses during development

     2. Second ethmoturbinal: gives rise to middle turbinate

     3. Third ethmoturbinal: gives rise to superior turbinate

     4. Fourth and fifth ethmoturbinals: gives rise to supreme turbinate (when present)

   • Primary furrows: form the recesses separating the ethmoturbinals and gives rise to meati

     1. First primary furrow: separates first and second ethmoturbinals; gives rise to middle meatus

     2. Second primary furrow: gives rise to superior meatus

     3. Third primary furrow: gives rise to supreme meatus

2. External nasal anatomy

   • Subcutaneous layers of the nose

     Mnemonic = “Subcutaneous Fat DeeP

     1. S = Superficial fatty layer (connected to dermis)

     2. F = Fibromuscular layer (nasal superficial musculoaponeurotic system [SMAS])

     3. D = Deep fatty layers (contains neurovascular system)

     4. P = Periosteum/perichondrium

        • Optimal plane of dissection is located between D and P as it is avascular and heals with minimal fibrosis

   • External nasal landmarks

     1. Nasion: corresponds to nasofrontal suture

     2. Radix: nasal root; centered at nasion, extends inferiorly to the level of the lateral canthus and superiorly by equivalent distance

     3. Rhinion: corresponds to bony-cartilaginous junction along nasal dorsum

     4. Supratip break: a break in the nasal profile separating the nasal dorsum and lobule located immediately superior to the tip defining point

     5. Supratip lobule: portion of lobule located superior to tip-defining point

     6. Tip defining point: two points located at the highest, medial, and cephalic portion of the lateral crus; corresponds to light reflex externally

     7. Infratip lobule: portion of lobule located inferior to tip-defining point and superior to infratip break

     8. Infratip break: lobule-columella junction

     9. Nasal sill: nostril rim located between columella and alar facial attachment

   • Nasal tip support

     1. Major tip supports

        • Medial and lateral crura

        • Attachment of medial crura to caudal edge of quadrangular cartilage

        • Attachment of upper lateral cartilage to lower lateral cartilage (“scroll area”)

     2. Minor tip supports

        • Skin-soft tissue envelope (attachment of lower lateral cartilage to overlying skin and musculature)

        • Sesamoid complex (located between lateral crura and pyriform aperture)

        • Interdomal ligament (located between lower lateral cartilages)

        • Anterior nasal spine

        • Cartilaginous septal dorsum

        • Membranous nasal septum

   • Nasal osteology

     1. Two nasal bones fuse in the midline to form a pyramidal shape

     2. Nasal bones are thicker superiorly than inferiorly

     3. Nasal bone attachments =

        • Superior: nasal process of frontal bone

        • Lateral: frontal process of maxilla

     4. Pyriform aperture = bony opening into the nasal cavity bounded by

        • Superior: caudal margin of nasal bones

        • Inferior: alveolar process of maxilla

        • Lateral: frontal process of maxilla

        • Medial: nasal septum

   • Nasal cartilages

     1. Upper lateral cartilage (ULC)

        • Attached superiorly to nasal bones

        • Articulates inferiorly with the ...