The nose (Latin: Nasus) is an organ composed of bone and cartilage and covered by muscle and skin. It plays a crucial role as the first organ of the respiratory system. Its shape resembles a triangular pyramid, though its size and shape vary greatly depending on race and individual. This pyramid is situated in front of a pear-shaped opening (apertura piriformis) located at the front of the facial skeleton.
When we look at the structure of the nose from the outside, we can generally divide it into several sections. The nasal bridge is formed by the front junction of both nasal sides, and the part where it joins the forehead is called the nasal root. The parts of the lateral sides surrounding the nostrils are called the nasal wings, and of course, the openings that allow airflow are the nostrils.
The most important structures forming the nasal roof are the nasal bones (nasal bones), which form the upper part of the nasal bridge and connect to the frontal bone above, and the nasal septum, a cartilaginous partition that divides the nasal cavity into two. In addition, the upper nasal cartilages, which attach to the nasal bones and the septum, and the lower nasal cartilages (alar cartilages), which give shape to and support the tip and wings of the nose, help support this framework.
When we examine the structures within the nasal cavity, we see the nasal septum, which divides the cavity into two, and three nasal turbinates (nasal conchae) on each outer wall. This cavity opens into the nasopharynx at the back through two openings called the choanae. The floor of the nasal cavity is formed by the hard palate, while the roof is formed by the air-filled spaces known as sinuses and the skull base. The anterior two-thirds of the septum is cartilaginous.
The structures inside the nose have very important functions. These include:
- Serving as an air passage
- Detecting odors
- Humidifying the air
- Warming the air
- Filtering the air
In addition to being the first organ of the respiratory system, the nose also performs the important function of smell. The sense of smell is provided by olfactory cells located in the mucosa of the nasal roof, where the middle turbinate meets the septum. The mucosa and secretions lining the inner surface of the nose and the turbinates trap particles from the air. These particles are transported by ciliated cells on the mucosa to the nasopharynx and from there to the throat, where they are swallowed. Additionally, the mucosal secretions contain antimicrobial substances. The turbinates expand and contract due to the dilation and constriction of the blood vessels within them, thereby increasing and decreasing blood flow. As a result, air passing through the nasal cavity is warmed by the swollen, blood-filled turbinates before entering the trachea and lungs. These functions of the nose also help protect the lower respiratory tract.