There are a number of routes by which nerves and vessels enter and leave the soft tissues lining each nasal cavity (Fig. 8.242), and these include the cribriform plate, sphenopalatine foramen, incisive canal, and small foramina in the lateral wall, and around the margin of the nares.
The fibers of the olfactory nerve [I] exit the nasal cavity and enter the cranial cavity through perforations in the cribriform plate. In addition, small foramina between the cribriform plate and surrounding bone allow the anterior ethmoidal nerve, a branch of the ophthalmic nerve [V1], and accompanying vessels to pass from the orbit into the cranial cavity and then down into the nasal cavity.
In addition, there is a connection in some individuals between nasal veins and the superior sagittal sinus of the cranial cavity through a prominent foramen (the foramen cecum) in the midline between the crista galli and frontal bone.
One of the most important routes by which nerves and vessels enter and leave the nasal cavity is the sphenopalatine foramen in the posterolateral wall of the superior nasal meatus. This foramen is just superior to the attachment of the posterior end of the middle nasal concha and is formed by the sphenopalatine notch in the palatine bone and the body of the sphenoid bone.
The sphenopalatine foramen is a route of communication between the nasal cavity and the pterygopalatine fossa. Major structures passing through the foramen are: the sphenopalatine branch of the maxillary artery, the nasopalatine branch of the maxillary nerve [V2], and superior nasal branches of the maxillary nerve [V2].
Another route by which structures enter and leave the nasal cavities is through the incisive canal in the floor of each nasal cavity. This canal is immediately lateral to the nasal septum and just posterosuperior to the root of the central incisor in the maxilla. The two incisive canals, one on each side, both open into the single unpaired incisive fossa in the roof of the oral cavity and transmit: the nasopalatine nerve from the nasal cavity into the oral cavity, and the terminal end of the greater palatine artery from the oral cavity into the nasal cavity.
Small foramina in the lateral wall
Other routes by which vessels and nerves get into and out of the nasal cavity include the nares and small foramina in the lateral wall:
Internal nasal branches of the infra-orbital nerve of the maxillary nerve [V2] and alar branches of the nasal artery from the facial artery loop around the margin of the naris to gain entry to the lateral wall of the nasal cavity from the face.
Inferior nasal branches from the greater palatine branch of the maxillary nerve [V2] enter the lateral wall of the nasal cavity from the palatine canal by passing through small foramina on the lateral wall.
The nasal cavities have a rich vascular supply for altering the humidity and temperature of respired air. In fact, the submucosa of the respiratory region, particularly that related to the conchae and septum, is often described as “erectile” or “cavernous” because the tissue enlarges or shrinks depending on the amount of blood flowing into the system.
Arteries that supply the nasal cavity include vessels that originate from both the internal and external carotid arteries (Fig. 8.243):
Vessels that originate from branches of the external carotid artery include the sphenopalatine, greater palatine, superior labial, and lateral nasal arteries.
Vessels that originate from branches of the internal carotid artery are the anterior and posterior ethmoidal arteries.