Anatomy of the Nose

The nose performs functions that are easy to underestimate: it warms, humidifies, and filters inspired air; it houses the olfactory neuroepithelium; it provides resonance to the voice; and it drains the paranasal sinuses and lacrimal apparatus. Its anatomy explains why a septal deviation causes unilateral obstruction, why nosebleeds occur almost always at the same spot, and why a posterior epistaxis can be life-threatening when an anterior one is not. This article builds the nasal anatomy from outside to inside.

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External Nose — Framework

The external nose is a three-dimensional structure supported by a framework of bone superiorly and cartilage inferiorly.

Bony Framework

The upper third of the external nose is supported by the paired nasal bones, which articulate with the nasal spine of the frontal bone superiorly and the frontal processes of the maxillae laterally. The nasion is the midline junction of the nasal bones and frontal bone — the root of the nose. Nasal bone fractures in trauma most commonly occur at or just below the nasion, where the bones are thinnest.

Cartilaginous Framework

The middle and lower thirds of the nose are cartilaginous:

Upper lateral cartilages (ULCs): Paired cartilages that support the middle third. They abut the nasal bones superiorly (the keystone area — an important surgical zone in rhinoplasty, where disrupting the ULC-nasal bone articulation can cause a saddle deformity). Inferiorly, they articulate with the lower lateral cartilages. The ULC forms the lateral wall of the internal nasal valve — the narrowest point of the nasal airway (see below).

Lower lateral cartilages (LLCs, alar cartilages): Paired, C-shaped cartilages forming the tip and alae. Each LLC has a medial crus (forming the columella), an intermediate crus (the dome — the most projected part of the tip), and a lateral crus (the alar lobule). The tip of the nose is therefore a four-layered structure: skin, dome of the LLC, opposite dome of the LLC, skin.

Septal cartilage (quadrangular cartilage): Forms the anteroinferior septum (see below).

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Nasal Septum

The nasal septum divides the nasal cavity into right and left halves. It is composite:

• Perpendicular plate of the ethmoid — the bony posterior-superior portion, articulating with the cribriform plate above
• Vomer — the bony posterior-inferior portion, articulating with the palatine and maxillary bones at the choanae
• Quadrangular cartilage (septal cartilage) — the anterior portion; articulatse with the perpendicular plate posteriorly, the vomer inferoposteriorly, the nasal bones and ULCs anterosuperiorly, and rests on the maxillary crest inferiorly

The junction of cartilage and bone is the site of most septal deviations — forces applied to the nose during childhood trauma or birth cause buckling at these junctions. A deviated septum may cause unilateral nasal obstruction; if the deviation causes a spur that contacts the lateral nasal wall, it can obstruct drainage of the paranasal sinuses and cause recurrent sinusitis.

The columella is the central pillar of tissue between the two nostrils, housing the medial crura of the lower lateral cartilages and the anterior septal cartilage.

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Nasal Valves — The Airflow Bottlenecks

The nasal airway has two critical narrow points:

Internal nasal valve: The angle between the lower border of the upper lateral cartilage and the septum, at the level of the nasal bones — the narrowest part of the nasal airway in most adults. Normal angle is approximately 10–15°. Collapse of the ULC (as in ageing or post-rhinoplasty disruption) narrows this angle and is the most common cause of nasal airway obstruction after septal deviation.

External nasal valve (nasal vestibule): The aperture of the nostril, bounded by the columella medially, the alar lobule (lateral crus of LLC) laterally, and the sill inferiorly. Dynamic collapse on inspiration (when negative pressure narrows the nostril) is detectable on clinical examination by the Cottle manoeuvre — gentle lateral cheek traction that opens the external valve; if this improves airflow, external valve collapse is a component of the obstruction.

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Nasal Cavity — Walls and Openings

Lateral Wall

The lateral wall of each nasal cavity carries the turbinates (conchae) — scroll-like bony projections covered by vascular, ciliated respiratory mucosa. There are three (occasionally four):

• Inferior turbinate: A separate bone (the inferior nasal concha), not part of the ethmoid. The largest turbinate; the most important for humidifying and warming inspired air because of its large mucosal surface area and capacious submucosal vascular plexus. Hypertrophy of the inferior turbinate is the most common cause of bilateral nasal obstruction.

• Middle turbinate: Part of the ethmoid bone. The space below the middle turbinate (middle meatus) is the drainage pathway for the anterior paranasal sinuses — the frontal, anterior ethmoid, and maxillary sinuses drain here via the ostiomeatal complex.

• Superior turbinate: Small; the space above it (superior meatus) drains the posterior ethmoid cells. The olfactory cleft lies medial to the superior turbinate, adjacent to the septum.

The sphenoethmoidal recess — the space above and medial to the superior turbinate — is where the sphenoid sinus opens.

Key Openings in the Lateral Wall

• Inferior meatus: The nasolacrimal duct opens here (just inside the anterior end of the inferior turbinate). This explains why crying causes a runny nose — tears drain via the nasolacrimal system into the inferior meatus.
• Middle meatus / ostiomeatal complex: The maxillary sinus (via the maxillary ostium and infundibulum), the anterior ethmoid cells (via the ethmoid bulla), and the frontal sinus (via the frontonasal recess/agger nasi cells) all drain here. The ostiomeatal complex (OMC) is the functional unit of anterior sinusitis — obstruction here produces maxillary, anterior ethmoid, and frontal sinusitis simultaneously.
• Superior meatus: Posterior ethmoid cells
• Sphenoethmoidal recess: Sphenoid sinus

Choana

The posterior nasal apertures — the choanae — are the openings connecting each nasal cavity to the nasopharynx. In neonates, choanal atresia (bony or membranous occlusion of the choana, unilateral in 60–70%) presents as respiratory distress at birth that improves with crying (mouth breathing). Bilateral choanal atresia is a neonatal emergency.

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Blood Supply — Kiesselbach’s Plexus (Little’s Area)

The nasal cavity has a rich, anastomotic blood supply from both the internal carotid artery (ICA) system and the external carotid artery (ECA) system — which is why posterior epistaxis can be life-threatening (it is ECA territory but near the ICA).

Arterial Supply

ICA territory:

• Anterior ethmoidal artery (branch of ophthalmic artery → ICA) → supplies the anterosuperior nasal cavity, septum, and the roof
• Posterior ethmoidal artery (branch of ophthalmic artery → ICA) → posterior septum and roof

ECA territory:

• Sphenopalatine artery (terminal branch of maxillary artery → ECA) → the dominant blood supply to the nasal cavity; supplies the posteroinferior septum, lateral wall, and inferior turbinate. Enters through the sphenopalatine foramen just posterior to the posterior end of the middle turbinate. The sphenopalatine artery is the most important vessel in epistaxis management — it is the target of sphenopalatine artery ligation or endoscopic cauterisation for posterior epistaxis.
• Greater palatine artery (branch of maxillary artery → ECA) → enters through the incisive foramen to supply the anteroinferior septum
• Superior labial artery (branch of facial artery → ECA) → supplies the anterior nasal floor and vestibule

Kiesselbach’s Plexus (Little’s Area)

The anteroinferior septum — specifically, the junction of the four arteries listed above — forms the Kiesselbach’s plexus (also called Little’s area). This dense anastomotic network is the source of >90% of all nosebleeds (epistaxis). It is the most accessible part of the nasal septum, lying just inside the nostril on the septal surface, and the thin overlying mucosa makes the vessels vulnerable to trauma (nose picking, dry air, minor abrasion).

Treatment of anterior epistaxis targets Little’s area: direct pinching pressure, silver nitrate cauterisation, or nasal packing is applied here.

Posterior Epistaxis

Posterior epistaxis — bleeding from the posterior nasal cavity, usually from the sphenopalatine artery or Woodruff’s plexus (a venous plexus on the posterior lateral nasal wall below the posterior end of the inferior turbinate) — is less common but more serious. It cannot be controlled by pinching the nose, may present with blood flowing down the pharynx rather than through the nostril, and may require posterior packing, sphenopalatine artery ligation, or interventional radiology embolisation.

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Nerve Supply

Olfactory nerve (CN I): Bipolar olfactory receptor neurons in the superior nasal septum and roof (the olfactory cleft) project axons through the cribriform plate of the ethmoid to the olfactory bulb. These unmyelinated axons are the only part of the CNS directly exposed to the environment; they are easily damaged by head trauma (shearing at the cribriform plate), viral infection, and toxic inhalation. The cribriform plate is also the route of intracranial spread for nasal tumours and a site of CSF leak after skull base fractures.

Ophthalmic division (CN V1):

• Anterior and posterior ethmoidal branches of the nasociliary nerve → anterosuperior septum and lateral wall, nasal tip skin (external nasal nerve — the sole branch of V1 that supplies external skin)

Maxillary division (CN V2):

• Sphenopalatine (pterygopalatine) ganglion branches → posteroinferior septum (nasopalatine nerve) and posterolateral wall (posterior nasal nerves)
• Greater palatine nerve → floor and lower septum
• Infraorbital nerve → vestibule and alar skin

Autonomic:

• Parasympathetic (from pterygopalatine ganglion via vidian nerve): secretomotor to nasal glands and vasodilator to nasal mucosa — responsible for rhinorrhoea and congestion in allergic rhinitis and vasomotor rhinitis
• Sympathetic (from superior cervical ganglion via deep petrosal nerve → vidian nerve): vasoconstrictor — decongestion; explains why nasal decongestant sprays and oral sympathomimetics work

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Key Numbers

Parameter	Value
Internal nasal valve angle	~10–15°
Site of anterior epistaxis	Little’s area / Kiesselbach’s plexus
Arteries forming Kiesselbach’s plexus	5 (ant. ethmoidal, post. ethmoidal, sphenopalatine, greater palatine, superior labial)
Dominant blood supply to nasal cavity	Sphenopalatine artery (ECA)
Percentage of epistaxis from anterior septum	>90%
Nasolacrimal duct opens into	Inferior meatus
Maxillary sinus drains into	Middle meatus (ostiomeatal complex)
Sphenoid sinus opens into	Sphenoethmoidal recess
External nasal skin — only V1 branch	External nasal nerve (from anterior ethmoidal)

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Frequently Asked Questions

Why does almost every nosebleed come from the same spot? Kiesselbach’s plexus on the anteroinferior septum is an anastomotic convergence of five arteries — it is therefore the most vascular spot in the nose. The overlying mucosa is thin, poorly supported, and directly exposed to inspired air (drying it further). It is the part of the nasal cavity that fingers can reach. These anatomical factors combine to make it the overwhelming site of anterior epistaxis — self-resolving with 5 minutes of pinching in the vast majority of cases.

What is the ostiomeatal complex and why is it important in sinusitis? The ostiomeatal complex (OMC) is the functional drainage unit in the middle meatus — a narrow space bounded by the uncinate process medially, the ethmoid bulla laterally, and the hiatus semilunaris between them. The maxillary sinus, anterior ethmoid cells, and frontal sinus all drain through or adjacent to this space. When it becomes oedematous (as in allergic or infective rhinitis), mucociliary clearance from all three sinuses is impaired simultaneously — explaining why sinusitis affects multiple sinuses at once. Functional endoscopic sinus surgery (FESS) targets the OMC to restore drainage.

Where does the olfactory nerve pass and why is it vulnerable to trauma? The olfactory nerve fibres (CN I) pass as a series of fine, unmyelinated axons through the multiple foramina of the cribriform plate of the ethmoid bone. This thin, perforated bony plate forms the roof of the nasal cavity and the floor of the anterior cranial fossa. In head trauma, frontal impact causes anterior–posterior shearing forces across the cribriform plate — the delicate olfactory nerve fibres are torn, producing anosmia (loss of smell). This is one of the most common neurological sequelae of mild-to-moderate head injury and is frequently missed because patients are not specifically asked about smell.