The nose is the most prominent structure of the face and plays an important role in breathing and the sensation of smell.
The nasal passages serve as an entrance to the respiratory tract. These passages are lined by a moist mucous membrane with hair-like projections known as cilia which help collect dust, debris, and bacteria. The nose thus acts like an air conditioner, warming, moistening and filtering the air we breathe in, while olfactory organs within the nose provide the sensation of smell. The nose consists of an intricate network of bones, cartilage, blood vessels and nerves. It is mainly divided into two parts - the external and internal nose.
- The external nose is the outer part of the nose that protrudes from the face and is shaped like a pyramid. The ridge that continues from the forehead to the tip of the nose is known as the bridge or dorsum.
- The nares or nostrils are the two openings that lead into the nasal cavity. The initial part of the nasal cavity is called the vestibule.
- The top one-third of the nose is made up of bone and the lower two-thirds are made up of cartilage. The bone and cartilage are covered by the skin on the outside and a mucous membrane on the inside.
- The nasal bones are paired, rectangular structures attached to the skull bone above and the cartilage below. The distal ends of these bones are thinner and wider, making them susceptible to fractures during an injury.
- The cartilage of the nose includes the septal cartilage and the upper and lower lateral cartilages. Together the nasal bones, cartilage, and connective tissue give shape to the nose.
- The internal nose or nasal cavity is a passage 6-7 cm long, running above the roof of the mouth. The palate separates the nasal cavity from the oral cavity. The back of the nasal passage communicates with the throat and is called the nasopharynx. The palate presses upwards while swallowing to prevent food from entering the nasopharynx.
- The internal nose consists of the nasal septum, the conchae, and the sinuses.
- The nasal septum is a wall of cartilage and bone that separates the two nasal passages.
- The conchae are shelf-like projections from the bony side wall of the nasal cavity. The space or channel underneath a concha is referred to as a meatus.
- The superior concha is the smallest of the conchae and located high up in the nasal cavity. The space underneath it is called the superior meatus. The middle concha is present below the superior concha. The space it encloses is called the middle meatus. The inferior concha is the largest of the conchae and envelops the inferior meatus.
- Sinuses are air-filled cavities inside the face, near the nasal passages. They are hollow areas within the bones of the skull that are lined with mucous membrane. Sinuses help cushion the eyes and brain during severe injuries to the face. They provide warmth and humidify the air that enters the nasal passages. Sinuses also give resonance to the voice. There are four major pairs of sinuses. These include the ethmoidal sinuses, the maxillary sinuses, the frontal sinuses, and the sphenoidal sinuses.
- The ethmoidal sinuses are paired sinuses located between the eyes and nasal cavity. Each sinus consists of 4-18 air containing cavities called ethmoidal air cells. The air cells in front communicate with the middle meatus and the air cells behind communicate with the superior meatus.
- The maxillary sinuses are large paired sinuses located within the cheekbones. They open into the middle meatus.
- The frontal sinuses are located within the bones of the forehead at the region of the brow near the midline. They open into the middle meatus.
- The sphenoid sinuses are located deep within the face behind the nose. They communicate through a small recess or depression present behind the superior meatus.
- The nasolacrimal duct that drains tears from the eyes into the nasal passage opens into the inferior meatus.
Blood and Nerve Supply
The nose and sinuses mainly receive their blood supply through the internal and external carotid arteries. The superior part of the nose is supplied by the ethmoid branches of the internal carotid artery. The rest of the nose and sinuses are supplied by branches of the external carotid artery.
The branches of the external and internal carotid artery combine together to form a plexus in the front part of the nasal septum known as Little’s area or Kiesselbach’s plexus. This area is significant as it is a common site of nasal bleeding.
The olfactory organs which provide the sensation of smell are situated beside and above the superior concha. They consist of nerve cells in the lining of the mucous membrane. Moisture on the nerve fibers helps dissolve odor-producing chemicals in the air which then stimulate the nerve cells to produce the sensation of smell.