Nasal cavity

The nasal cavity, also known as the nasal fossa, forms part of the upper respiratory tract.

Terminology

Somewhat confusingly, the nasal cavity may refer to either the space either side of the nasal septum or the two spaces combined. So for the same individual one can correctly refer to their single nasal cavity and their left and right nasal cavities.

The definition of the nasal fossae is used by most as a synonym for the nasal cavity. However, in a well-known medical dictionary, the fossa is defined as that part of the nasal cavity lying anterior to the middle meatus ¹¹.

Gross anatomy

The nasal cavity is formed by ¹:

• anteriorly: anterior nares
• laterally: inferior, middle and superior nasal conchae (turbinates)
• superiorly: cribriform plate of the ethmoid bone
• inferiorly: palatal processes of the maxilla and horizontal portion of the palatine bone forming the hard palate
• posteriorly: posterior nasal aperture (a.k.a. choanae or posterior nares) at the posterior margin of the bony nasal septum

In the midline, the nasal cavity is divided into right and left halves by the nasal septum composed of fibrocartilage anteriorly and the vomer and the perpendicular plate of the ethmoid bone posteriorly and inferiorly. 

Anterior most, lies a small dilated portion, the nasal vestibule, which lies between the nasal aperture and the anterior nares, and posteriorly it is continuous with the nasopharynx via the posterior choanae. Laterally, the three nasal conchae form the three nasal meati.

Connections

• superior meatus
  • posterior ethmoidal air cells and sphenoid sinuses via the sphenoethmoidal recess ²
• middle meatus
  • frontal sinus via frontal recess
  • anterior ethmoidal air cells and maxillary sinuses via ostiomeatal complex
• inferior meatus
  • nasolacrimal duct ³

Arterial supply

The arterial supply of the nasal cavity is rich and derives from both the internal and external carotid arteries ^4,5,10:

• lateral nasal wall
  • superior lateral nasal wall: anterior and posterior ethmoidal arteries
  • inferior and middle turbinates: posterior lateral nasal artery (sphenopalatine artery)
  • posterior lateral nasal wall: pharyngeal artery
• nasal septum
  • anteriorly: greater palatine artery
  • posteroinferiorly: posterior septal artery (sphenopalatine artery)
  • superiorly: anterior and posterior ethmoidal arteries
• floor
  • greater palatine and superior labial arteries

Rich arterial supply results in two anastomotic areas, which are common sites of epistaxis ⁴:

• Woodruff area: anastomosis of sphenopalatine and pharyngeal arteries in the inferior lateral nasal wall, posterior to the inferior turbinate
• Kiesselbach plexus: anastomosis of the anterior ethmoid, greater palatine, sphenopalatine and superior labial arteries in the anteroinferior nasal septum (see article on Kiesselbach plexus)

Venous drainage

A rich submucosal venous network is formed by veins that accompany arteries. It should be noted that the posterior ethmoid veins anastomose with veins of the dura mater and orbit, making this a potential route of spread of infection. There is also an anastomosis with veins of the external nose ⁶.

Lymphatic drainage

• anterior drainage: to the external nose ⁶
• posterior drainage: via separate pathways to the lateral pharyngeal lymph nodes or deep cervical chain ⁶

Innervation

The olfactory nerve (CN I) supplies the special sensation of smell to the olfactory epithelium in the roof of the nasal cavity, with fibres passing upwards through the cribriform plate to the olfactory bulb.

Mucosal somatic sensation of the nasal cavity is derived from numerous nerves, but in general terms the branches of the ophthalmic division of the trigeminal nerve (CN Va) supply the anterosuperior half whereas branches of the maxillary division of the trigeminal nerve (CN Vb) supply the posteroinferior half. More specifically:

• the nasal septum is innervated by:
  • anterior: anterior ethmoidal nerve
  • posterosuperior: medial branch of the posterior superior nasal nerve
  • posteroinferior: nasopalatine nerve
• the lateral nasal wall is innervated by:
  • anterosuperior: anterior ethmoidal nerve
  • anteroinferior: anterior superior alveolar nerve
  • posterosuperior: lateral branch of the posterior superior nasal nerve
  • posteroinferior: lateral posterior inferior nasal nerve from the greater palatine nerve