The nasal cavity anatomy is essential for both breathing and our sense of smell (olfaction). But did you know that 80% of taste actually comes from what we smell? That is why food is almost tasteless when our nose is clogged.
The nose is the most prominent part of the human face. It has internal and external parts. If you’re in show business, the appearance of the external part is certainly very important. However besides esthetics, the external nose also functions to protect the inner nose and allows the entry of air. The internal part of the nose is termed the nasal cavity. It is involved in respiration, olfaction, speech and taste. In this page, we are going to study the nose anatomy, with a special focus on the anatomical importance of the nasal cavity structure.
The external nasal anatomy is quite simple. It is a pyramidal structure, with its root located superiorly and apex sitting inferiorly. The root is continuous with the anterior surface of the head and the part between the root and the apex is called the dorsum of the nose. Inferior to the apex are the two nares (nostrils), which are the openings to the nasal cavity. The nares are separated by the nasal septum and are laterally bounded by the ala nasi (wings of the nostrils) which are the lateral processes of the septum.
The external nose is comprised of both bony and cartilaginous components. The bony part shapes the nose root, formed by the nasal, maxillae and frontal bones. The cartilaginous part is located inferiorly and is comprised of several alar, two lateral, and one septal cartilage:
- Alar cartilages; major alar cartilage forms the apex of the nose, minor alar cartilages support the ala nasi
- Lateral processes of the alar cartilage; form the dorsum of the nose
- Septal cartilage; bounds the nares medially
Note that the septal cartilage is attached to both the bony nasal septum (which is actually the perpendicular plate of the ethmoid bone) and the vomer bone. Both nasal septum and vomer are bony parts of the internal nose.
To learn more about the external nose and see how it fits in the picture of the respiratory system, check out this article and video tutorial!
The internal part of the nose is the nasal cavity. The two nasal cavities sit within the external nose and the adjacent skull. The cavities open anteriorly to the face through the two nares. Posteriorly the cavities communicate with the nasopharynx by two apertures called choanae.
Besides the anterior and posterior apertures, each nasal cavity has a roof, floor, and lateral and medial walls. There are 12 cranial bones in total that contribute to the nasal cavity structure, which include the paired nasal, maxilla, palatine and lacrimal bones, as well as the unpaired ethmoid, sphenoid, frontal and vomer bones.
Among all of them, the ethmoid bone is the most important element, for two reasons: first, it makes the greatest portion of the nasal skeletal framework by forming the roof and walls of the nasal cavities; and second, it contains ethmoidal cells which, as a group, are one of the four paranasal sinuses. Want to know everything about the ethmoid bone? We got you covered with this article, video tutorial and quiz.
Three bony shelves called the inferior, middle and superior nasal conchae are attached to the lateral walls and by projecting into the cavities, they divide both nasal cavities into four air channels:
- Inferior nasal meatus; between the floor and inferior concha
- Middle nasal meatus; between the inferior and middle concha
- Superior nasal meatus; between the middle and superior concha
- Sphenoethmoidal recess; between the superior concha and the nasal cavity roof
The nasal cavity is divided into three regions, aligned as if a three floor building. The vestibule is located just inside the anterior external opening of the nose (1st floor) and it contains hair follicles. The largest region is the respiratory region, which is lined with respiratory epithelium (2nd floor). Finally, there is the olfactory region, a small area located inside the skull at the superior apex of the cavity, which is lined with olfactory cells and receptors (3rd floor).
The two nasal cavities communicate with four bony recesses called the paranasal sinuses. They are named according to the bones they are placed within, as the: sphenoidal, maxillary, and frontal sinuses, and the ethmoidal cells. All of the sinuses are covered by respiratory mucosa and innervated by the trigeminal nerve (CN V). To learn everything about the nasal cavity in a fun and engaging way, check out these articles, video tutorials and clinical case.
The nose is supplied by branches of both the external and internal carotid arteries. The external carotid artery sends the sphenopalatine, greater palatine, superior labial and lateral nasal arteries which mostly supply the vestibule and respiratory portions of the nasal cavity, as well as the surrounding parts of the external nose (apex and dorsum).
The internal carotid artery gives off the anterior and posterior ethmoidal arteries which mostly supply the apex of the nasal cavity and the surrounding part of the external nose. Many of the external and internal carotid arterial branches anastomose at the anterior part of the medial wall. This particular spot is the place from where the most nosebleeds occur. Learn more about the blood supply of the nose, and which part of the nose each branch supplies, from this video, article and quiz.
The nose is innervated by three cranial nerves:
- Olfaction is provided by the olfactory nerve (CN I)
- General sensation is carried by the trigeminal nerve (CN V)
- Serous glands in the nasal mucosa which produce fluid that constantly lubricates the nose walls are innervated by the parasympathetic fibers of the facial nerve (CN VII). Sympathetic innervation comes from T1 level of spinal cord and is intended for regulation of blood flow through mucosa
To learn everything about the nerves that supply the nose, and their branches, check out the following articles, video tutorials and quizzes:
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.