Nasal Anatomy
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Direct answer
The nose is an air-conditioning and drainage architecture whose exam value lies in three maps: the septum, the lateral wall and the blood supply. The septum is quadrangular cartilage in front with the perpendicular plate of ethmoid above and vomer below-posterior; its anteroinferior Little's area carries Kiesselbach's plexus, the anastomosis of sphenopalatine, anterior ethmoidal, greater palatine and superior labial vessels responsible for most nosebleeds. On the lateral wall, the turbinates (conchae) overhang meatuses that name the drainage: middle meatus receives the maxillary, frontal and anterior ethmoidal sinuses through the hiatus semilunaris — the ostiomeatal complex whose blockage explains most sinus disease — while the posterior ethmoids drain to the superior meatus and the sphenoid to the sphenoethmoidal recess. The sphenopalatine artery, the terminal of the maxillary, is the posterior feeder whose ligation ends refractory posterior epistaxis.
What you must remember
- Septum components: quadrangular (septal) cartilage, perpendicular plate of ethmoid, vomer and maxillary crest; deviation is commonest at the vomer-cartilage junction, and dislocation of the cartilage from the crest causes caudal dislocation.
- Kiesselbach's plexus (Little's area): on the anteroinferior septum, where sphenopalatine, anterior ethmoidal, greater palatine and septal branches of the superior labial anastomose — over 90 per cent of epistaxis arises here; Woodruff's plexus, posteroinferiorly, is the venous source of posterior bleeds.
- Lateral wall drainage: maxillary, frontal and anterior ethmoidal sinuses open in the middle meatus (ostiomeatal unit — uncinate process, hiatus semilunaris, ethmoidal bulla); posterior ethmoids open in the superior meatus; the sphenoid sinus opens in the sphenoethmoidal recess above the superior turbinate.
- Turbinates: the inferior turbinate has its own independent bone and hypertrophies in allergic rhinitis — the turbinate surgery target; the nasolacrimal duct opens into the inferior meatus (valve of Hasner).
- Arterial supply triangle: branches of the external carotid (sphenopalatine, greater palatine via maxillary) plus the internal carotid (ethmoidal via ophthalmic); anterior ethmoidal ligation suits bleeds above the middle turbinate.
- Danger areas: the olfactory neuroepithelium (roof, upper septum, superior turbinate) abuts the cribriform plate, and the sphenopalatine foramen is the endoscopic ligation landmark.
- Paranasal sinus development: maxillary and ethmoid sinuses are present at birth; the sphenoid pneumatises around 5-7 years and the frontal around 7 years, reaching adult size after puberty — hence frontal sinusitis is a disease of older children.
- Nasal cycle: the turbinate cavernous plexus alternates congestion every few hours in about 80 per cent of people — a normal phenomenon mistaken for disease.
How the anatomy explains three operations
Follow the corridors surgeons use. For refractory anterior epistaxis in a young man, the scene is Little's area: cautery of the four-vessel anastomosis settles most, with endoscopic sphenopalatine artery ligation reserved for failed cautery and packing. For a posterior bleed in the hypertensive elderly, blood streams behind the soft palate from the sphenopalatine artery emerging at the posterior end of the middle meatus — the exact target when packing fails.
Now walk into the ostiomeatal complex, the funnel between the uncinate process and the ethmoidal bulla. Every sinus draining into the middle meatus depends on this millimetre-scale gate: a deviated septum pressing the middle turbinate, or allergic mucosal swelling, locks it; secretions stagnate in the maxillary antrum and become sinusitis or polyps. Functional endoscopic sinus surgery is nothing but restoration of this anatomy — uncinectomy, bulla opening, natural ostium enlargement — because drainage, not the infection per se, is what broke. A stem offering frontal sinusitis in a child under seven is answered by anatomy: the frontal sinus is not yet pneumatised, so look elsewhere.
Where students slip
Drainage-site mixing is the commonest error: posterior ethmoids go to the superior meatus (not the middle), and the sphenoid to the sphenoethmoidal recess. The second slip is naming Little's area supply as anterior ethmoidal only — it is a four-vessel anastomosis, which is why single-point cautery sometimes fails. The nasolacrimal duct opening in the inferior meatus is forgotten during turbinate surgery, and the olfactory neuroepithelium's distribution (roof, upper septum, superior turbinate) matters because biopsies there risk cerebrospinal fluid leak through the cribriform plate.
Frequently asked questions
Which vessels form Kiesselbach's plexus and where?
The sphenopalatine, anterior ethmoidal, greater palatine and septal branches of the superior labial arteries anastomose on the anteroinferior septum (Little's area), the source of most epistaxis.
Where do the maxillary, frontal and anterior ethmoidal sinuses drain?
Into the middle meatus through the hiatus semilunaris of the ostiomeatal complex, between the uncinate process and the ethmoidal bulla — the region targeted in functional endoscopic sinus surgery.
Which turbinate is independent and which surgery targets it?
The inferior turbinate has its own bone (not part of the ethmoid) and hypertrophies in allergic rhinitis, making it the target of submucosal diathermy or partial turbinoplasty.
Where does the sphenoid sinus open?
Into the sphenoethmoidal recess above and medial to the superior turbinate.
At what ages do the frontal and sphenoid sinuses pneumatise?
The sphenoid around 5-7 years and the frontal around 7 years — so frontal sinusitis is unusual in young children.