näshålan

Näshålan, or the nasal cavity, is the air-filled space inside the skull and facial bones that conducts air from the nostrils to the choanae, the openings at the back that lead to the nasopharynx. It is divided into two halves by the nasal septum and bordered laterally by the maxillary, ethmoid, sphenoid, and palatine bones.

Anatomy and layout

The cavity is divided by the superior, middle, and inferior conchae (turbinates) into corresponding meatuses. The superior part contains the olfactory region, where the olfactory epithelium detects smells. The rest of the cavity is lined by respiratory epithelium with goblet cells that produce mucus. The vestibule at the entrance contains coarse hairs (vibrissae) that help filter large particles.

Function and physiology

The näshålan conditions inhaled air by warming and humidifying it and by trapping dust and microbes in mucus. Cilia on the epithelium help move mucus toward the pharynx for swallowing. The olfactory region provides the sense of smell, while the larger portion supports respiration and conditioning of inspired air.

Connections and innervation

The nasal cavity communicates with the paranasal sinuses and the nasopharynx. The nasolacrimal duct drains tears into the inferior meatus. Blood supply primarily comes from branches of the maxillary artery (notably the sphenopalatine artery), and venous drainage parallels the arterial supply. Sensory innervation includes the olfactory nerve for smell (CN I) and branches of the trigeminal nerve for general sensation.

Clinical relevance

Common issues include allergic rhinitis, sinusitis, nasal polyps, and septal deviation, all of which can affect breathing and the sense of smell. Trauma or infection of the näshålan can influence airflow, mucous production, and olfactory function.