The nasal cavity is an essential region of the body for three main reasons:
- it assists the human body to inhale and exhale air via special respiratory epithelia
- it governs one of the five human senses which is the sense of smell using olfactory cells
- its bony borders including the nasal bones and their adjacent alar cartilage make up the centre of the face and are responsible for the esthetic contours of a person's individual characteristics.
In this article the nasal cavity will be discussed in detail, including its borders, conchae, nerve and vascular supply and the most common pathological findings.
Anteriorly, the outer nose including the nasal bones and the attached cartilage and skin can be seen, with the two nostrils creating constant communication with the external environment. Inferiorly the palatine process of the maxilla and the horizontal plate of the maxilla form a solid base lined with respiratory epithelium.
The choanae of the skull are situated posteriorly. Laterally as with superiorly, a range of cranial bones surround the cavity including the maxilla, the ethmoid bone, the palatine bone, the sphenoid bone, the inferior nasal concha and the lacrimal bone.
The septum separates the nasal cavity into two symmetrical spaces and is made up of the perpendicular plate of the ethmoid bone, the vomer and the septal cartilage.
There are three nasal conchae situated on each side of the nasal septum. They act as drains for certain regions and structures within the nasal cavity. They cascade caudally in an anterior direction.
The superior nasal concha is the smallest of the three and is mostly located superior to the superior meatus. It drains the sphenoethmoidal recess and the sphenoidal sinus. The part of it that is located inferior to the superior meatus drains the superior meatus and the posterior ethmoidal sinus.
The middle nasal concha and the concha below it are all below the superior meatus and it drains the middle meatus as well as the anterior and middle ethmoidal sinuses, the frontal sinus and the maxillary sinus.
The inferior nasal concha is the last of the three and the largest. It drains the inferior meatus and the nasolacrimal duct.
The arterial supply of the nasal cavity is shared between three arteries which include:
The following branches correspond to this trio and include:
- the anterior ethmoid artery
- the posterior ethmoid artery
- the sphenopalatine artery
- the greater palatine artery
- the superior labial artery
As far as venous drainage goes, an intricate cavernous plexus runs under the epithelium and drains into either the emissary vein, the sphenopalatine vein or one of the ethmoidal branches.
Two types of nervous tissue help innervate the nasal cavity. The first is that which aids olfaction and its fibers contain special visceral afferent fibers, while the second is that of general sensation or general somatic afferent fibers as they are more commonly known.
Branches that participate in the general somatic innervation of the nasal cavity include:
- the ophthalmic nerve
- the ethmoid nerve
- the maxillary nerve
- the infraorbital nerve
- the nasopalatine nerve
- the posterior inferior branch of the greater palatine nerve
- the posterior superior nasal nerve
- the posterior lateral superior nasal nerve
- the posterior medial superior nasal nerve
Finally, several conditions that one is likely to come across in relation to the nasal cavity, include nosebleeds, nasal infections and sometimes even a deviated septum.
Epistaxis, which is the clinical term for a nosebleed, is usually caused by:
- a trauma
- sinus infection
- an arid environment
- hematologic disorders
The most common form is anterior epistaxis which occurs along the septum and arises from kiesselbach's plexus. Posterior epistaxis is usually due to the maxillary artery. Depending on the area of the bleed, various treatments are available since the blood will either run out of the nose in an anterior case or down the throat in a posterior case.
Rhinitis is another clinical term and its simple name is a stuffy nose. An inflammation causes nasal congestion, sneezing, rhinorrhea or a runny nose and nasal itching. The most common cause is allergic rhinitis more commonly known as hay fever. This is systematically treated with decongestants, antihistamines and steroids.
A deviated septum means that the bony midline of the nasal cavity is off centre, either due to a trauma or birth defects and this results in partial or total occlusion of one side of the cavity. The treatment is surgical and a septoplasty is usually performed.