Nasal Septum

The nasal septum is a vertical partition made up of bone and cartilage that separates the left and right nasal cavities. It provides structural support to the nose and forms a central barrier within the nasal passages. The nasal septum is composed of both bony and cartilaginous components and is lined by mucous membrane. It plays an essential role in maintaining the structure and airflow within the nasal cavity.

Location

The nasal septum is located in the midline of the nasal cavity, running vertically from the external nasal opening (nares) at the front of the nose to the back of the nasal cavity, where it connects with the nasopharynx. It separates the nasal cavity into two halves and attaches to surrounding bones, including the ethmoid and vomer, as well as the nasal cartilage.

Structure and Anatomy

The nasal septum is a complex structure composed of bone and cartilage that divides the nasal cavity into two equal parts. It provides structural support to the nose and plays a key role in directing airflow through the nasal passages. Below is a detailed description of the anatomy of the nasal septum.

Components of the Nasal Septum

The nasal septum is made up of both bony and cartilaginous structures, which together form the vertical partition that separates the nasal cavities.

• Cartilaginous Part: The anterior portion of the nasal septum is composed of flexible septal cartilage. This part is positioned at the front of the nose and provides shape and flexibility to the nasal structure. The septal cartilage extends from the bony part of the septum toward the external opening of the nose (nares).
• Bony Part: The posterior part of the nasal septum is formed by two bones:
• • Perpendicular Plate of the Ethmoid Bone: This thin, vertical plate of the ethmoid bone forms the upper posterior portion of the nasal septum. It descends from the cribriform plate of the ethmoid bone and contributes to the superior part of the nasal septum.
  • Vomer Bone: The vomer is a plow-shaped bone that forms the lower and posterior portion of the septum. It extends upward from the floor of the nasal cavity and meets the perpendicular plate of the ethmoid bone to complete the bony portion of the septum.

Cartilaginous Part

The cartilaginous part of the nasal septum is primarily composed of the septal cartilage (also known as the quadrangular cartilage). It makes up the front, flexible portion of the septum.

Septal Cartilage: This large piece of hyaline cartilage is triangular in shape and lies between the nasal bones and the hard palate. It provides structural support to the tip of the nose and contributes to the flexibility of the nasal septum. The septal cartilage connects posteriorly to the bony portion of the septum and anteriorly to the external nasal structures.

Bony Part

The bony portion of the nasal septum is primarily made up of the perpendicular plate of the ethmoid bone and the vomer, with contributions from other smaller bones.

• Perpendicular Plate of the Ethmoid Bone: This is a thin, flat bone that forms the superior part of the bony septum. It extends downward from the ethmoid bone, which is part of the skull base, and plays a crucial role in supporting the nasal cavity’s structure.
• Vomer Bone: The vomer is a flat, plow-shaped bone that forms the inferior and posterior portion of the bony septum. It sits on top of the nasal crest of the maxilla and palatine bones, providing a stable base for the septum.
• Maxillary Crest: The nasal crest of the maxilla is a ridge located along the floor of the nasal cavity. The vomer bone fits into this crest, helping to anchor the septum in place.
• Palatine Bone: The horizontal plate of the palatine bone also contributes to the floor of the nasal cavity and provides structural support for the septum’s posterior portion.

Mucosal Lining

The nasal septum is covered by a mucous membrane that plays a protective and functional role.

• Respiratory Epithelium: The mucosa covering the nasal septum is composed of pseudostratified ciliated columnar epithelium, also known as respiratory epithelium. This lining contains goblet cells, which produce mucus to trap dust, pathogens, and other foreign particles.
• Blood Supply: The mucosal surface of the nasal septum is richly supplied by blood vessels, including branches from the sphenopalatine artery, greater palatine artery, superior labial artery, and anterior and posterior ethmoidal arteries. The rich blood supply helps warm and humidify inhaled air and plays a role in the body’s immune defense mechanisms.

Nerve Supply

The nasal septum receives sensory and autonomic innervation from branches of the trigeminal nerve (cranial nerve V) and the autonomic nervous system.

• Ophthalmic Division of the Trigeminal Nerve (V1): The anterior part of the nasal septum is innervated by the anterior ethmoidal nerve, a branch of the ophthalmic division of the trigeminal nerve.
• Maxillary Division of the Trigeminal Nerve (V2): The posterior part of the septum receives sensory input from the nasopalatine nerve, a branch of the maxillary division of the trigeminal nerve.
• Autonomic Innervation: Sympathetic and parasympathetic fibers supply the nasal mucosa. Sympathetic fibers regulate blood flow by controlling vasoconstriction, while parasympathetic fibers are involved in mucus secretion.

Blood Supply

The nasal septum has a rich blood supply that helps to humidify and warm the air as it passes through the nasal cavity. The blood supply comes from several arteries, forming an anastomotic network.

Kiesselbach’s Plexus: Also known as Little’s Area, this is a region located on the anterior part of the nasal septum where several arteries converge. It is a common site for epistaxis (nosebleeds). The arteries that supply the septum include:

• • Sphenopalatine Artery: A branch of the maxillary artery, this is the main artery supplying the posterior nasal septum.
  • Greater Palatine Artery: This artery contributes to the blood supply of the septum and also supplies the hard palate.
  • Superior Labial Artery: A branch of the facial artery, this artery supplies the anterior portion of the septum.
  • Anterior and Posterior Ethmoidal Arteries: These are branches of the ophthalmic artery and supply the upper part of the nasal septum.

Adjacent Structures

The nasal septum interacts with several other anatomical structures, including:

• Nasal Bones: The nasal bones form the bony upper portion of the external nose and support the septum.
• Lateral Nasal Wall: The lateral walls of the nasal cavity contain the turbinates (conchae), which project into the nasal passages. The septum divides the space between these structures.
• Nasal Cavity: The nasal septum separates the nasal cavity into left and right halves, ensuring that airflow is directed symmetrically through the nose.

Function

The nasal septum plays a key role in maintaining the structure of the nasal cavity and ensuring proper airflow and respiratory function. Its primary functions include separating the nasal cavities, supporting the nose, regulating airflow, and contributing to filtration, humidification, and olfaction. Below is a detailed explanation of these functions.

Separation of the Nasal Cavities

The nasal septum divides the nasal cavity into two distinct left and right nasal passages, providing symmetry within the nasal structure.

• Structural Division: By forming a partition between the two nasal cavities, the septum ensures that each nostril and corresponding nasal passage remains distinct. This separation is essential for balanced airflow distribution through both sides of the nose.
• Protection Against Cross-Infections: The separation provided by the septum helps minimize the risk of cross-contamination between the two nasal cavities. In cases of infection or irritation in one side, the other side may remain unaffected, helping to reduce the spread of nasal infections.

Support of the External Nose

The nasal septum provides structural support to the external nose, particularly to its central portion.

• Maintaining Nasal Shape: The cartilaginous part of the septum plays a critical role in supporting the midline of the nose and ensuring that the nasal structure remains upright. This support prevents the collapse of the external nose and helps maintain the aesthetic and functional integrity of the nasal framework.
• Stabilization of Surrounding Structures: The septum anchors various nasal bones and cartilage, stabilizing the overall nasal structure. It connects to the nasal bones, ethmoid bone, and vomer, ensuring that these structures remain aligned and stable.

Regulation of Airflow

The nasal septum plays a crucial role in regulating airflow through the nasal cavities, ensuring that inhaled air passes smoothly and efficiently through each nostril.

• Even Air Distribution: By dividing the nasal cavity into two channels, the septum ensures that air is evenly distributed through both the left and right nasal passages. This balance is essential for efficient breathing, as it prevents one side of the nasal cavity from being overburdened with airflow.
• Flow Modulation: The septum works in conjunction with the turbinates (or conchae) on the lateral walls of the nasal cavity to modulate airflow. This regulation optimizes the speed and volume of air entering the lungs during both quiet breathing and exertion.
• Assisting in Breathing Efficiency: An intact and properly aligned septum allows for unobstructed airflow through both nostrils. If the septum is deviated, it can lead to uneven or obstructed airflow, resulting in difficulty breathing through one or both nostrils.

Filtration of Inhaled Air

The nasal septum plays a key role in the filtration of airborne particles by helping trap dust, pollutants, and pathogens.

• Mucus Production: The nasal septum is lined with a mucous membrane containing goblet cells, which secrete mucus. This mucus traps dust, allergens, and other foreign particles, preventing them from reaching the lower respiratory tract.
• Ciliary Action: The surface of the nasal septum is covered with pseudostratified ciliated columnar epithelium, which is responsible for moving trapped particles toward the pharynx, where they can be swallowed or expelled. This ciliary action ensures that the nasal passages remain clean and free of harmful materials.
• Immune Defense: The rich vascular supply to the nasal septum also plays a role in immune defense, providing nutrients and immune cells that help fight off pathogens in the inhaled air.

Humidification and Warming of Air

The nasal septum aids in humidifying and warming the air before it enters the lungs, making it more suitable for gas exchange.

• Rich Vascular Supply: The nasal septum contains numerous blood vessels, particularly in Kiesselbach’s plexus (Little’s area). These blood vessels help warm the air as it passes through the nasal cavity, bringing it closer to body temperature. This warming prevents cold, dry air from reaching the sensitive tissues of the lower respiratory tract, reducing the risk of irritation and injury.
• Mucosal Humidification: The mucosal lining of the septum also helps humidify the inhaled air by adding moisture from the mucus. Humidified air is essential for maintaining the health of the respiratory tract, as dry air can irritate the lungs and hinder efficient gas exchange.

Contribution to Olfaction (Sense of Smell)

The nasal septum indirectly contributes to the sense of smell by directing airflow to the olfactory region at the top of the nasal cavity.

• Airflow Direction: The septum helps direct inhaled air toward the olfactory epithelium, located on the superior part of the nasal cavity. This area contains olfactory receptors responsible for detecting odors. Proper airflow through the nasal passages ensures that these receptors can interact with odor molecules, enabling the sense of smell.
• Maximizing Olfactory Exposure: By ensuring that air passes evenly through both sides of the nasal cavity, the septum helps expose the olfactory receptors to a consistent volume of air, optimizing the detection of smells.

Facilitation of Nasal Drainage

The nasal septum plays a role in facilitating mucus drainage from the nasal cavity, ensuring that the nasal passages remain clear and free from obstructions.

• Drainage Pathway: The septum helps guide mucus produced in the nasal cavity toward the pharynx, where it can be swallowed or expelled. This function is important for maintaining the health and cleanliness of the nasal cavity.
• Prevention of Mucus Accumulation: By providing a structure that supports proper airflow and ciliary action, the septum prevents mucus from accumulating within the nasal passages. This prevents blockages that could lead to sinus infections or breathing difficulties.

Clinical Significance

The nasal septum plays a critical role in maintaining normal nasal function, and any abnormalities in its structure can lead to various clinical conditions. Deviated nasal septum (DNS) is one of the most common conditions associated with the septum, where the septum is displaced to one side, leading to nasal obstruction, breathing difficulties, and chronic sinus infections. A deviated septum can also contribute to snoring and sleep apnea due to airflow obstruction.

Nasal septum perforation occurs when there is a hole in the septum, often caused by trauma, infection, or overuse of nasal sprays. This can lead to symptoms like nasal congestion, bleeding, and whistling sounds during breathing. Additionally, the septum is a common site for epistaxis (nosebleeds), especially in Kiesselbach’s plexus, which is richly supplied with blood vessels. These conditions can affect overall nasal function and may require medical or surgical intervention to restore normal airflow and nasal health.