Nasal Septum

Introduction

Introduction to the Nasal Septum and Nasal Cavity

The nasal cavity is a critical component of the respiratory system, serving as the primary passage for air intake and filtration. It is divided into two halves by the nasal septum, a structure composed of both bony and cartilaginous elements. The nasal cavity plays essential roles in humidifying, warming, and filtering inspired air, as well as housing the olfactory epithelium for the sense of smell.

Anatomical Boundaries and Functions

The nasal cavity is bounded superiorly by the cribriform plate of the ethmoid bone, laterally by the maxilla and ethmoid bone, and inferiorly by the hard and soft palates. Its anterior opening is the nares, while the posterior opening, the choanae, leads into the nasopharynx. The nasal septum, typically midline, ensures balanced airflow and structural support.

Study

Composition of the Nasal Septum

The nasal septum is formed by three primary components: the perpendicular plate of the ethmoid bone, the vomer, and the septal cartilage. The perpendicular plate of the ethmoid bone descends from the cribriform plate and contributes to the superior-posterior portion of the septum. The vomer, a thin, flat bone, forms the posteroinferior part, while the septal cartilage provides flexibility and completes the anterior portion. Deviations in the septum can result from trauma or congenital factors, potentially leading to airflow obstruction.

Lateral Wall of the Nasal Cavity and Nasal Conchae

The lateral wall of the nasal cavity is characterized by three curved bony projections known as the nasal conchae or turbinates: the superior, middle, and inferior conchae. These structures increase the surface area of the nasal cavity, enhancing its ability to warm, humidify, and filter air. The spaces beneath each concha are called meatuses, which serve as drainage pathways for the paranasal sinuses. The superior meatus drains the posterior ethmoid sinuses, the middle meatus drains the frontal, maxillary, and anterior ethmoid sinuses, and the inferior meatus receives the nasolacrimal duct.

Blood Supply and Innervation of the Nasal Cavity

The nasal cavity receives a rich blood supply from branches of both the internal and external carotid arteries. Key contributors include the sphenopalatine artery (from the maxillary artery), the anterior and posterior ethmoidal arteries (from the ophthalmic artery), and the superior labial artery (from the facial artery). Venous drainage follows the arterial supply, with blood ultimately draining into the pterygoid plexus and facial vein. Innervation is provided by the olfactory nerve (CN I) for smell, and branches of the trigeminal nerve (CN V), specifically the ophthalmic (V1) and maxillary (V2) divisions, for general sensation.

Paranasal Sinuses and Their Clinical Significance

The paranasal sinuses are air-filled cavities within the bones surrounding the nasal cavity, including the frontal, ethmoid, maxillary, and sphenoid sinuses. These sinuses lighten the weight of the skull, resonate the voice, and produce mucus that drains into the nasal cavity. The maxillary sinus, located within the maxilla, is particularly clinically significant due to its proximity to the roots of the maxillary teeth, which can lead to odontogenic sinusitis. The ethmoid sinuses are divided into anterior, middle, and posterior groups, with the anterior and middle groups draining into the middle meatus and the posterior group into the superior meatus.

Common Pathologies and Clinical Correlations

Deviated nasal septum, often resulting from trauma or congenital factors, can cause nasal obstruction, recurrent sinusitis, and sleep disturbances. Septal perforations may occur due to trauma, infection, or iatrogenic causes, leading to crusting, epistaxis, and whistling sounds during respiration. Sinusitis, inflammation of the paranasal sinuses, is frequently caused by viral or bacterial infections and can present with facial pain, nasal congestion, and purulent discharge. Understanding the anatomical relationships of the nasal cavity is crucial for diagnosing and managing these conditions.

Summary

Key Takeaways

The nasal cavity is divided by the nasal septum, composed of the perpendicular plate of the ethmoid, vomer, and septal cartilage. The lateral wall features the superior, middle, and inferior nasal conchae, which create meatuses for sinus drainage. Blood supply arises from branches of the internal and external carotid arteries, while innervation is provided by CN I and CN V. The paranasal sinuses play roles in respiration, voice resonance, and skull weight reduction.

Clinical Correlate

Deviations of the nasal septum or pathologies such as sinusitis can significantly impact respiratory function and quality of life. Knowledge of the anatomical relationships within the nasal cavity is essential for performing procedures like nasal endoscopy, septoplasty, or sinus surgery. Additionally, understanding the drainage pathways of the paranasal sinuses aids in diagnosing and treating sinus infections and obstructions.