Nasal Septum

What Is the Nasal Septum?

The nasal septum is the vertical wall in the middle of the nose that separates the right nasal passage from the left one. Each face of the septum forms the medial (inner) wall of one half of the nasal cavity, while the curled nasal conchae project from the opposite, lateral wall. The name comes from the Latin saeptum, meaning a fence or partition.

The septum is a composite structure. Its front portion is a flexible plate of hyaline cartilage, its back portion is bone, and a short strip of skin and fibrous tissue at the very front sits between the nostrils. A mucous membrane covers both of its faces, so in life it is a soft, moist surface with a firm core. It belongs to the nose and is one of the first structures inhaled air meets in the upper respiratory tract.

Explained simply: think of the inside of your nose as two narrow hallways side by side. The nasal septum is the wall between them. It is bendy at the front, where you can wiggle the tip of your nose, and hard bone further back.

Where Is the Nasal Septum Located?

The nasal septum lies in the midline of the face, running from the nostrils at the front to the choanae at the back, where the nasal cavity opens into the throat. You can feel its front end as the column of tissue between your two nostrils, called the columella.

Borders of the nasal septum

• Front: the columella and the tip of the nose, where the septum meets the alar cartilages that shape the nostrils.
• Roof: the nasal bones and the nasal spine of the frontal bone in front, then the thin cribriform plate of the ethmoid bone, which separates the nose from the brain.
• Floor: the hard palate, formed by the maxillae and palatine bones, which is also the roof of the mouth.
• Back: the free rear edge of the vomer, which forms the inner border of each choana and faces the nasopharynx.

Most of the septum is hidden behind the bridge of the nose. Only the columella and the area just inside the nasal vestibule can be seen without instruments.

What Is the Nasal Septum Made Of?

The nasal septum is made of cartilage in front and bone behind, joined by fibrous tissue and covered on both sides by mucous membrane. Anatomists describe three parts: membranous, cartilaginous and bony.

Membranous and cartilaginous septum

The membranous septum is the short, skin-covered segment in the columella, between the inner limbs of the two major alar cartilages. Behind it lies the septal cartilage, also called the quadrangular cartilage because of its roughly four-sided shape. It is hyaline cartilage, the same glassy type found in the rings of the trachea, and it fills the angle between the two bones behind it. Its lower edge sits in a groove on the nasal crest of the maxilla, and a narrow strip called the vomeronasal cartilage lies along its lower border.

Bony septum

The bony septum has two main pieces. The perpendicular plate of the ethmoid bone forms the upper back part and hangs down from the cribriform plate. The vomer, a thin bone shaped like a plough blade, forms the lower back part and rests on the nasal crests of the maxillae and palatine bones. Small contributions come from the nasal bones, the frontal bone and the crest of the sphenoid bone at the back of the roof.

Nasal Septum vs Vomer: What Is the Difference?

The nasal septum is the whole dividing wall, while the vomer is only one bone inside it, forming the lower back part of that wall. People often mix the two up because the vomer is a whole bone in its own right, while the perpendicular plate is only one part of the ethmoid bone, so on a skull the vomer is the piece most easily named as the septum.

The difference shows clearly on skull models. On a dry skull the cartilage has usually decayed, so the septum looks short and the pear-shaped opening at the front of the nose, the piriform aperture, appears empty in the middle. In a living person the septal cartilage fills that gap and carries the wall forward to the tip of the nose.

The septum should also not be confused with the nasal cavity itself. The nasal cavity is the air space; the septum is the wall that splits it into two halves, each with its own conchae and nasal meatuses on the outer side.

Blood Supply and Nerves of the Nasal Septum

The nasal septum receives blood from branches of both the internal and the external carotid arteries, which meet in a dense network at the front of the septum. This network, called Kiesselbach's plexus or Little's area, lies in the lower front part of the septum just inside the nostril, where the lining is thin and exposed to drying air.

Because the vessels lie so close to the surface there, most nosebleeds start in Kiesselbach's plexus. Fewer nosebleeds start further back, from branches of the sphenopalatine artery. The veins follow the arteries and drain toward the facial vein, the pterygoid venous plexus and the ophthalmic veins.

Nerves of the septum

Touch and pain from the septum travel in branches of the trigeminal nerve. The nasopalatine nerve, from the maxillary division, runs forward and down across the vomer to the incisive canal in the roof of the mouth. The anterior ethmoidal nerve, from the ophthalmic division, supplies the upper front part. At the very top of the septum, olfactory nerve fibers pass through the cribriform plate to a small patch of smell-sensing lining, described on the sense of smell page.

What Is the Function of the Nasal Septum?

The nasal septum divides inhaled air into two streams, holds up the middle of the nose and adds a large moist surface that conditions air before it reaches the lungs.

• Structural support. The septal cartilage props up the bridge and tip of the nose and keeps the nostrils open. Without it, the lower nose would sag.
• Dividing airflow. Splitting the nose into two narrow passages keeps air close to the mucosa on both sides, where it is warmed, moistened and filtered.
• Air conditioning and cleaning. The lining is respiratory epithelium with mucus-making goblet cells and cilia, part of the mucociliary escalator that sweeps trapped dust toward the throat.
• Smell. The highest strip of the septum carries olfactory epithelium, which helps detect odors.
• The nasal cycle. Vascular tissue on the conchae and a thickened area of the septum, the septal swell body, fill and empty in turn, shifting more airflow to one side and then the other every few hours.

These jobs are why breathing through the nose differs from breathing through the mouth, as explained in nose breathing vs mouth breathing. Air that travels along the septum and conchae reaches the pharynx warmer, wetter and cleaner.

How Does the Nasal Septum Develop and Change With Age?

The nasal septum forms in the embryo from tissue in the middle of the developing face, the frontonasal prominence, and grows downward to meet the palate. When the two palatal shelves fuse with each other and with the lower edge of the septum, the nasal cavity is sealed off from the mouth and split into right and left halves. This stage is outlined on the development of the respiratory system page.

In newborns the septum is mostly cartilage. The vomer and the perpendicular plate of the ethmoid turn to bone gradually through childhood, and the septal cartilage acts as a growth center that helps push the middle of the face forward and down. In adults the septum is rarely perfectly straight: small bends and bony spurs, often where cartilage meets bone, are common and usually cause no trouble.

Common Conditions That Affect the Nasal Septum

The septum can be bent, injured or affected through its lining. The main conditions are listed here for education only; broader overviews are on the respiratory diseases page.

• Deviated septum: a septum that bends noticeably to one side, present from birth or caused by injury. A large bend can narrow one nasal passage. See deviated septum.
• Nosebleeds (epistaxis): most begin in Kiesselbach's plexus on the front of the septum, often when the lining is dry or irritated.
• Septal hematoma: blood collecting between the cartilage and its covering after a blow to the nose. The cartilage gets its nutrients from that covering, so doctors treat it as urgent.
• Septal perforation: a hole through the septum, which can follow injury, surgery, infection or irritating substances, and may cause crusting or a whistling sound when breathing.
• Nasal fracture: a break of the nasal bones that often also bends or shifts the septal cartilage.

Swelling of the lining during colds and allergies affects the septum along with the rest of the nose, and inflammation can spread to the paranasal sinuses, as in sinusitis. Anyone with lasting blockage, repeated nosebleeds or a nose injury should see a doctor.