The nasal cavity is an irregular air-filled space located above the roof of the oral cavity. It is positioned between the nares and external environment anteriorly and the choanae and nasopharynx posteriorly. The nasal cavity is the inner part of the nose, and the nose leads to it.

The nasal cavity is divided into two parts - the nasal vestibule and the nasal cavity proper.

The nasal vestibule is the anterior portion of the nasal cavity. It begins from the inside of the nares and the external opening of the nose and continues till the limen nasi, which is a mucosal ridge. The vestibular part of the nasal cavity is covered by hair. This part is bounded by the lateral crus of the major alar cartilage and fibrofatty tissue laterally and the medial crus of the major alar cartilage and nasal septal cartilage medially.
The nasal cavity proper is the posterior portion of the nasal cavity. It extends from the limen nasi to the choanae and nasopharynx. Functionally, this part is subdivided into two regions (olfactory region and respiratory region). The middle nasal conchae mark the border between both of them.
- Respiratory part - positioned below the middle nasal concha; it contains glands, and secretions produced by these glands moisturize the surface of the mucous membrane and trap dust parts and microbes, expelling them to the external environment; this part also contains a venous plexus that warms the inhaled air and releases heat.
- Olfactory part - situated above the middle nasal concha; it contains glands and olfactory receptors from which the olfactory nerve fibers (CN I) arise.

The nasal cavity is a part of the upper airways. It communicates with the paranasal sinuses, nasopharynx, orbit, infratemporal fossa and pterygopalatine fossa, and cranial cavity.

Bony framework of nasal cavity

The nasal cavity is formed by several paired and unpaired bones of the skull.

The paired bones include the following:

The unpaired bones forming the nasal cavity are as follows:

Anteriorly, the nasal cavity opens onto the face with the anterior nasal opening that is known as the pyriform (piriform) aperture. Posteriorly, the nasal cavity opens into the nasopharynx through a pair of oval openings called the choanae.

Walls

The nasal cavity is divided into two compartments by a nasal septum. Each division has four walls - roof, floor, medial and lateral walls.

The roof of the nasal cavity is formed by the cribriform plate of the ethmoid and the anterior aspect of the body of the sphenoid posteriorly. In addition, the nasal spine of the frontal bone and the nasal bones participate in forming the anterior aspect of the roof.
The floor of the nasal cavity is broader than the roof, and it is formed by the palatine process of the maxilla anteriorly and the horizontal plate of the palatine bone posteriorly.
The medial wall of the nasal cavity corresponds to the nasal septum. The anterior part of the septum is made of cartilages, while the posterior of bones. The cartilaginous part of the nasal septum is mostly formed by the quadrangular-shaped septal nasal cartilage. The bony part of the nasal septum is composed of the vomer, the perpendicular plate of the ethmoid, and the nasal crests of the maxilla and palatine bone.
The lateral wall of the nasal cavity is formed by the nasal surface of the maxilla, perpendicular plate of the palatine bone, labyrinth of the ethmoid, inferior nasal concha, nasal surface of the lacrimal bone, and the medial plate of the pterygoid process of the sphenoid. Most of the lateral wall is formed by three inferiorly curved bone plates called conchae. They project medially into the nasal cavity.

Nasal conchae

The lateral wall of the nasal cavity presents with several long, narrow, and paired formations called the nasal conchae or conchas. They are shaped like curved shelves of bones that curl medially and downward. Overall, conchae increase the surface of the nasal cavity and provide rapid humidification and warming of the inhaled air, as well as its filtration. The airflow through conchae is turbulent and slower because of their shape.

Each lateral wall of the nasal cavity presents with three nasal conchae:

Superior nasal concha - the smallest one;
Middle nasal concha - larger than the superior nasal concha;
Inferior nasal concha (Read more!) - the longest, broadest and largest.

Sometimes, the nasal cavity has one more concha called the supreme nasal concha. If present, it is located above the superior nasal concha and arises from the medial wall of the ethmoidal labyrinth. Overall, the supreme nasal concha is very variable and small.

The superior nasal conchae and the middle nasal conchae are parts of the ethmoidal labyrinth, while the inferior nasal conchae are separate bones of the skull. Nasal conchae covered by the mucosal membrane are referred to as turbinates.

Nasal meatuses

The nasal conchae project into the nasal cavity, creating several pathways between them. They are called the nasal meatuses.

Superior nasal meatus - located between the middle and superior nasal conchae;
Middle nasal meatus - situated between the inferior and middle nasal conchae;
Inferior nasal meatus - located between the floor of the nasal cavity and the inferior nasal concha;
Supreme nasal meatus (if the supreme nasal concha is present) - between the supreme and superior nasal conchae;
Common nasal meatus - between the nasal septum and the medial aspects of the conchae.

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Nasal cavity