The nasal cavity is a large, air-filled space located behind the external nose and above the oral cavity. It serves as the initial segment of the respiratory tract.
Roof
Formed by the nasal bones, frontal bone, cribriform plate of the ethmoid, and sphenoid body.
Separates the nasal cavity from the cranial cavity.
Floor
Formed by the hard palate (palatine process of maxilla and horizontal plate of palatine bone).
Separates it from the oral cavity.
Medial Wall
The nasal septum, made up of:
Septal cartilage
Perpendicular plate of the ethmoid
Vomer
Lateral Walls
Contain turbinates (conchae): superior, middle, inferior.
Beneath each turbinate is a meatus (superior, middle, inferior) where paranasal sinuses and nasolacrimal duct drain.
Vestibule – just inside the nostrils, lined with skin and coarse hairs (vibrissae).
Respiratory region – main central portion, lined with ciliated pseudostratified columnar epithelium with goblet cells.
Olfactory region – upper portion near the roof, containing olfactory epithelium for smell.
Frontal sinus
Maxillary sinus
Ethmoidal air cells
Sphenoidal sinus
Rich vascular supply from both the internal carotid (ophthalmic branch) and external carotid (maxillary and facial branches) arteries.
Notably, Kiesselbach’s plexus on the anterior septum is a common site of epistaxis (nosebleeds).
Sensory: Trigeminal nerve (ophthalmic V1 and maxillary V2 divisions).
Olfaction: Olfactory nerve (Cranial Nerve I).
Autonomic: Parasympathetic (via facial nerve CN VII) controls glandular secretion.
The nasal cavity plays key roles in respiration, filtration, smell, and resonance.
Turbinates create turbulence, ensuring air contacts the mucosa.
Air is warmed by rich vascular supply.
Air is humidified by mucous and serous secretions.
Air is filtered by vibrissae (hairs) in the vestibule and mucus trapping particles; cilia transport mucus posteriorly toward the pharynx (“mucociliary escalator”).
Olfactory receptors in the olfactory epithelium detect odorants.
Signals are transmitted through the cribriform plate to the olfactory bulb, then to the brain.
The nasal cavity and paranasal sinuses act as resonating chambers, affecting vocal quality.
Nasal-associated lymphoid tissue (NALT) and mucosal secretions (IgA, lysozyme) provide immune defense against pathogens.
Sinuses drain into meatuses, maintaining pressure balance and voice resonance.
The nasolacrimal duct drains tears into the inferior meatus.
✅ In summary:
The nasal cavity is not just a passageway for air but a multifunctional structure that conditions inhaled air, enables smell, contributes to speech, and protects against pathogens.