TSM21: NOSE AND PARANASAL SINUSES 1
09/10/08
LEARNING OUTCOMES
Describe the structure of the nose
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The external nose extends from the nasal bones and surrounding parts of the maxilla and frontal bone
o It is mainly supported by the central septal cartilage and its lateral processes
o Anteriorly at the apex there are two major alar cartilages
o Posteriorly near the maxilla there are a number of smaller minor alar cartilages
The internal nose comprises two paired nasal cavities which extend and expand supero-posteriorly
from the openings of the external nose (nostrils or anterior nares)
o The nasal septum separates the left and right cavities in the midline composed of the:
 Septal cartilage anteriorly
 Perpendicular plate of ethmoid bone superiorly
 Vomer infero-posteriorly
o The hard palate makes up the floor of the cavities and separates them from the oral cavity
o The choanae or posterior nares open from each cavity posteriorly into the nasopharynx
There are three general regions of the internal nose:
o Vestibular – the skin-lined space just within the nostrils
o Respiratory – ciliated epithelium making up the bulk of the cavity walls
o Olfactory – specialised olfactory epithelium on the roofs of the cavities
The lateral wall of each nasal cavity has three curved bones that project medially and inferiorly
o These are the superior, middle and inferior conchae
 The superior and middle conchae arise from the ethmoid bone
 The inferior conchae are processes of the maxilla
o The narrow air passages formed by these conchae constitute the superior, middle and
inferior meatus
o The sphenopalatine foramen is a major route of entry for nerves and vessels into the nasal
cavities and is found on the postero-lateral wall of the superior meatus
o The superior-most space formed above the superior concha is called the spheno-ethmoidal
recess
Describe the anatomy of the paranasal sinuses
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There are four separate, paired paranasal sinuses:
o Ethmoidal
 Collection of specialised ethmoidal air cells in the respiratory region
 Openings in the bulla ethmoidalis on the lateral wall of the middle meatus
 Cells between medial and lateral plates of the ethmoid labyrinths
o Sphenoidal
 Posterior to the nasal cavity within the sphenoid bone
 Openings in posterior wall of spheno-ethmoidal recess
 Immediately antero-inferior to the pituitary fossa
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Maxillary – the largest of the sinuses
 Beyond the lateral walls of the nasal cavity within the maxillae
 Openings in the hiatus semilunaris floor on the lateral wall of the middle meatus
 Drain at the apex – prone to filling with fluids that are then difficult to drain
o Frontal
 Superior to the nasal cavities within the frontal bone
 Openings in the hiatus semilunaris ‘roof’ on the lateral wall of the middle meatus
 Drains through the frontonasal duct to the ethmoidal infundibulum
The nasolacrimal duct carries tears from the corner of the eye and opens in the inferior meatus
infero-anterior to the hiatus semilunaris
Describe the blood supply of the nose
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The nasal cavities are supplied by various branches of the internal and external carotid arteries:
o Sphenopalatine artery
 Terminal branch of maxillary artery – branch of external carotid
 Enters the nasal cavity through the sphenopalatine foramen
 Gives lateral branches supplying most of the lateral wall
 Gives septal branches supplying most of the medial wall
o Greater palatine artery
 Branch of maxillary artery – branch of external carotid
 Enters the anterior floor of the nasal cavity through the incisive canal
 Supplies the anterior septum and floor
 Anastomoses with septal branches of the sphenopalatine artery
o Anterior and posterior ethmoidal arteries
 Both branches of the ophthalmic artery – branch of internal carotid
 Both descend into the nasal cavity through the cribriform plate
 Both give lateral and septal branches
 Anterior division has anastomoses with branches of the sphenopalatine artery and
terminates as the external nasal artery supplying skin of the external nose
 Posterior division supplies the upper lateral and medial walls
Describe the nerve supply of the nose
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General sensory innervation to the nose is through the ophthalmic and maxillary divisions of the
trigeminal cranial nerve –and V2 respectively
o Ophthalmic nerve (V1) gives two key branches, the ethmoidal nerves:
 Anterior branch travels with the anterior ethmoidal artery and supplies the anterior
medial and lateral walls before terminating as the external nasal nerve
 Posterior branch supplies the ethmoidal air cells and does not enter the nasal cavity
o Maxillary nerve (V2) gives various branches, the majority of which pass through the
sphenopalatine foramen:
 Lateral branches supply the lateral wall
 Nasopalatine nerve supplies the medial wall before terminating in the oral mucosa
The associated mucous glands are innervated by parasympathetic fibres of the facial nerve
o Post-ganglionic fibres arise from the pterygopalatine ganglion and run with V2 fibres