The nose has two main regions: an external structure you can see and touch, and an internal nasal cavity that does most of the work. Together, these parts filter, warm, and humidify every breath before it reaches your lungs, while also giving you your sense of smell. Here’s a breakdown of each part and what it does.
The External Nose
The visible portion of your nose is built from a combination of bone and cartilage. The upper third, called the bridge, is the firm, bony section formed by two small nasal bones and extensions of the upper jaw. Below the bridge, the structure transitions to flexible cartilage, which shapes the lower two-thirds of the nose, including the tip (or apex) and the soft, rounded sides called the alae. The alae flare outward to frame the two nostrils, which are the entry points for air into the nasal cavity.
This mix of rigid bone and flexible cartilage is what lets your nose hold its shape while still giving slightly under pressure. It also creates two narrow passages, the nasal valves, that play a surprisingly important role in breathing.
The Nasal Valves
Just inside each nostril, two valve-like structures regulate how much air flows into your nose. The external nasal valve sits at the nostril opening, bordered by the septum, the lower cartilage, and the soft tissue of the nostril wall. Slightly deeper, the internal nasal valve is the narrowest point in the entire airway, bounded by the septum, the upper cartilage, and the front end of the lowest turbinate (more on those below).
Because the internal valve is so narrow, even small changes in its shape can noticeably affect breathing. Nasal valve dysfunction is one of the most common causes of chronic nasal obstruction. If you’ve ever pulled your nostrils open with your fingers and felt dramatically better airflow, the valve area is likely what’s involved.
The Nasal Septum
Running down the center of the nasal cavity, the septum divides the nose into right and left sides. Its front portion is cartilage, while the back is bone, contributed by three separate bones of the skull. The septum is often slightly crooked or off-center, a condition called a deviated septum, which can narrow one or both sides of the nasal cavity and make breathing feel uneven.
The Turbinates
Along the outer wall of each nasal passage, three shelf-like structures called turbinates project inward. Each one has a thin bony core wrapped in soft tissue and a moist lining. Their job is to increase the surface area inside the nose so that air contacts more tissue on its way through. This extra contact is what allows the nose to warm, humidify, and filter air so efficiently.
The inferior turbinate is the largest, running the full length of the nasal cavity along the floor. It handles most of the air conditioning work. The middle turbinate sits above it and extends into the central nasal cavity, positioned near the openings where the sinuses drain. The superior turbinate is the smallest, tucked high and toward the back of the nasal cavity, close to the area responsible for smell.
Below each turbinate is a groove called a meatus. These grooves serve as drainage channels for the sinuses and are the spaces that tend to get blocked during sinus infections.
The Nasal Lining
Almost the entire nasal cavity is lined with a moist tissue called respiratory mucosa. This lining contains several types of cells working together. Ciliated cells cover the surface with tiny hair-like projections that beat in coordinated waves, roughly 1,000 beats per minute. Each beat has a rapid forward stroke followed by a slow return, creating a current that moves mucus toward the throat like a slow conveyor belt.
Scattered among these ciliated cells are goblet cells, which produce mucus. Additional glands beneath the surface contribute to the mucus layer as well. This thin coating traps dust, pollen, bacteria, and other particles before they can reach the lungs. The mucus also contains enzymes that break down some pathogens on contact.
Beyond filtration, this mucus layer is essential for conditioning air. As you inhale, water evaporates from the mucus surface into the passing airstream, humidifying it. At the same time, the blood-rich tissue beneath the lining radiates heat, warming incoming air. The nose can handle ambient temperatures ranging from well below freezing to over 100°F and still deliver air to the lungs at near-body temperature and close to full humidity.
The Smell Region
High in the nasal cavity, near the roof, a small patch of specialized tissue called the olfactory epithelium is responsible for your sense of smell. Odor molecules dissolve in the mucus coating this region and interact with receptor cells embedded in the tissue. Each receptor cell sends a thin nerve fiber upward through tiny holes in the bone above (the cribriform plate of the ethmoid bone). These fibers bundle together into 15 to 20 groups that connect to the olfactory bulb, a structure sitting on the underside of the brain’s frontal lobe. From there, signals travel deeper into the brain for processing.
This is why congestion can dull your sense of smell. When swollen tissue or excess mucus blocks airflow to the upper nasal cavity, fewer odor molecules reach the receptors.
The Paranasal Sinuses
Though technically not inside the nose itself, four pairs of air-filled cavities in the surrounding facial bones connect directly to the nasal cavity and function as part of the same system. They are lined with the same type of mucus-producing tissue and drain into the nose through small openings in the meatus grooves beneath the turbinates.
- Maxillary sinuses: the largest pair, located in the cheekbones on either side of the nose.
- Frontal sinuses: in the forehead area, just above the eyebrows.
- Ethmoid sinuses: a cluster of small air cells between the eyes.
- Sphenoid sinuses: set deep in the skull, behind the eyes.
These sinuses produce mucus that drains into the nasal cavity continuously. When the drainage openings swell shut during a cold or allergic reaction, mucus backs up inside the sinus, creating the pressure and pain of a sinus infection.
Blood Supply and Nosebleeds
The nasal cavity has an unusually rich blood supply, which is part of why it’s so effective at warming air, and also why nosebleeds are so common. Five named arteries send terminal branches into the nasal lining. At the front of the septum, several of these branches converge into a dense network of tiny vessels called Kiesselbach’s plexus. This is where the vast majority of nosebleeds originate, because the blood vessels here sit close to the surface and are easily irritated by dry air, nose-picking, or minor trauma.
Less commonly, bleeding can start from a second network of vessels toward the back of the nasal cavity, called the Woodruff plexus, fed by arteries deeper in the skull. Posterior nosebleeds like these are harder to control and more often require medical attention.