The nasal cavities extend from the vestibule in front to the nasopharynx behind. The nasal septum (made of cartilage and bone) separates the nose into two nasal cavities. The soft cartilaginous septum can be distorted during birth or in later life as a result of injury. A deviated nasal septum is common and can sometimes cause a blocked nose and can be treated surgically if required (see Chapter 17).

The rich blood supply to the nasal cavities is derived from both the internal and external carotid artery systems (see Chapter 16). Venous drainage is through valveless veins that follow the arterial pattern and have direct communication with the cavernous sinuses. This has a bearing on spread of infection to the intracranial cavity.

The nasal vestibule is lined with squamous epithelium. The nasal cavity itself is covered with pseudo-stratified ciliated columnar respiratory epithelium, rich in seromucinous glands. Figure 15.1 outlines the anatomy of the lateral nasal wall, where the paranasal sinuses and the lacrimal duct drain.

Paranasal Sinuses

The paranasal sinuses are a network of air-filled spaces lined with respiratory mucosa (pseudo-stratified columnar squamous epithelium). They extend from the nasal cavities and occupy part of the skeleton of the mid-face and the skull (Figure 15.2). The mucosa is rich with mucous-producing goblet cells. Infection or inflammation in the nose can occur in these sinuses resulting in sinusitis (see Chapters 19 and 20).

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