Frontal sinus — communicates with the nasal sinus via frontonasal ducts, draining into the semilunaris hiatus at the level of the middle meatus; develops after 7 years of age. Lined with respiratory (pseudostratified columnar ciliated) epithelium. Receives sensory innervation from V1 (supraorbital), perfused via anterior ethmoidal arteries from the ophthalmic arteries

Supraorbital foramen — approximately 25 mm from midline glabella; exit point of supraorbital nerve (V1), artery, and vein

Supratrochlear foramen — 17 to 22 mm from midline glabella, variably present. When incomplete, it is present as a notch. Exit point of supratrochlear nerve (V1), artery, and vein.

Frontalis — thin quadrilateral muscle without distinct bony attachments, with fibers oriented in a vertical manner. Inferomedial fibers are contiguous with the
procerus and corrugator; inferiorly intermediate fibers blend with the orbicularis oculi and attach to the skin of the eyebrows. Superiorly, the muscle becomes contiguous with the galea below the level of the coronal suture and is innervated by the temporal branch of the facial nerve (CN VII).

Procerus — small vertically oriented muscle arising from fascia of the lower nasal bone, inserting on the skin of the lower forehead on either side of midline. Innervated by temporal and zygomatic branches of facial nerve (CN VII); contributes to transverse rhytids of the upper nose.

Corrugator supercilii — small pyramidal muscle arising from the medial edge of the supraciliary arch deep to the frontalis, with fibers passing superolaterally through the frontalis to insert on the skin above the midpoint of the orbital arch. Innervated by the temporal branch of the facial nerve (CN VII); contributes to vertical paramedian rhytids.

Supratrochlear artery — branch of ophthalmic artery, found 17 to 22 mm from midline glabella, exits via supratrochlear foramen or under superior orbital margin. Often used to supply paramedian forehead flap in nasal reconstruction.

Supraorbital artery — branch of ophthalmic artery, found approximately 25 mm from midline glabella; exits via supraorbital foramen.

Superficial temporal artery — branch of external carotid artery, passes superficially over the zygomatic arch; 5 cm superior to the arch divides into frontal and parietal branches. Anastomoses with posterior auricular and occipital arteries to supply scalp.

Sentinel vein — large perforating vessel 1 cm lateral to frontozygomatic suture, observed during open or endoscopic brow dissection. Serves as reliable landmark within 2 mm of temporal branch of facial nerve (VII).

Temporal branch of facial nerve (VII) — branches from main trunk of facial nerve within substance of parotid gland; crosses superiorly over zygomatic arch before separating into smaller branches with multiple interbranch anastomoses. The temporal branch becomes more superficial after crossing the zygoma, lying in the plane between the superficial temporal fascia (a continuation of the superficial musculoaponeurotic system [SMAS] and temporoparietal fascia) and the superficial layer of the deep temporal fascia. The facial nerve runs along a course from 0.5 cm below the tragus to 1.5 cm above the lateral eyebrow. Owing to the variation in brow position, another more reliable indicator for the location of nerve branches is the region overlying the zygomatic arch between a point 2 cm posterior to the lateral orbital rim and 0.8 cm anterior to the tragus (Figure 5.1).

Nasal bone — superior one-third of nose, bordered superiorly by the frontal bone and laterally by contributions from the maxilla

Naso-orbitoethmoid — lateral aspects of superior one-third of nasal bony architecture formed by extension of maxilla

Septum — the anterior portion of the septum is comprised of cartilage, approximately 2 mm thick on average. The inferior portion of the cartilaginous septum terminates at the maxillary crest. Posteriorly, the septum is comprised of the perpendicular plate of the ethmoid bone superiorly and the vomer inferiorly.

Upper lateral cartilage — support structure for the middle one-third of the nasal vault, superiorly originating posterior to the nasal bone and inferiorly lying posterior to the lower lateral cartilage to form the scroll region. Plays an important role in preventing external nasal valve collapse during inspiration.

Lower lateral cartilage — sometimes referred to as the alar cartilage, this paired cartilage forms a gull-wing shape, with a lesser wing extending along the inferior septum at the columella and the greater wing forming the structural underpinnings of the nasal tip before extending superolaterally to overlap the upper lateral cartilage in the scroll region. Despite the common misconception, the lower lateral cartilage plays little role in alar shape, which is primarily supported by fibrofatty tissue.