Learning Objective: By the end of this session, the learner will be able to describe the divisions, structures, openings, vasculature, innervation, and clinical relevance of the nasal cavity, and apply this knowledge to conditions such as epistaxis, spread of infection, and cribriform plate fractures.

The nose functions as both an olfactory and a respiratory organ. It consists of a nasal skeleton that houses the nasal cavity, a space essential for filtering, warming, humidifying, and sensing air.

Functions of the Nasal Cavity

The nasal cavity:

Warms and humidifies inspired air
Traps pathogens and particulate matter
Provides the sense of smell
Drains the paranasal sinuses and lacrimal ducts

Divisions of the Nasal Cavity

The nasal cavity is the most superior part of the respiratory tract, extending from the vestibule to the nasopharynx, and consists of:

Vestibule

Immediately inside the anterior opening
Contains coarse hairs that trap large particles

Respiratory Region

Largest area
Lined by ciliated pseudostratified epithelium with goblet cells
Humidifies and filters air

Olfactory Region

Located on the roof and apex
Contains olfactory receptors for smell

Nasal Conchae and Meatuses

The conchae (turbinates)—inferior, middle, and superior—are curved bony shelves projecting from the lateral walls. They create four airflow pathways:

Inferior meatus
Middle meatus
Superior meatus
Spheno-ethmoidal recess (posterior and superior to the superior concha)

Function:

Conchae increase surface area and create turbulent airflow, allowing more time for air conditioning.

Openings Into the Nasal Cavity

Paranasal Sinus Drainage

Frontal, maxillary, anterior ethmoidal sinuses → Middle meatus via semilunar hiatus
Middle ethmoidal sinuses → Ethmoidal bulla
Posterior ethmoidal sinuses → Superior meatus
Sphenoid sinus → Posterior roof (spheno-ethmoidal recess)

Other Openings

Nasolacrimal duct → Inferior meatus
Auditory (Eustachian) tube → Nasopharynx, equalizing middle ear pressure

Clinical Relevance – Spread of Infection

Because the auditory tube connects the nasopharynx and middle ear, upper respiratory infections can spread, leading to:

Otitis media
Blocked Eustachian tube
Conductive hearing loss

Gateways to the Nasal Cavity

Cribriform plate (ethmoid bone): Passage for olfactory nerve fibers
Sphenopalatine foramen: Entry of the sphenopalatine artery and nasopalatine/superior nasal nerves
Incisive canal: Transmits nasopalatine nerve and greater palatine artery

Vasculature of the Nasal Cavity

The nasal cavity is highly vascularized to regulate temperature and humidity.

Internal Carotid Artery Branches

Anterior ethmoidal artery
Posterior ethmoidal artery

External Carotid Artery Branches

Sphenopalatine artery (major supply)
Greater palatine artery
Superior labial artery
Lateral nasal arteries

The anterior septum (Kiesselbach area) has extensive anastomoses → a common site for epistaxis. Venous drainage follows arteries and may drain into: