näsa

Näsa is the Swedish term for the nose. The nose is the organ on the face that serves as the entry to the respiratory system and the sense organ for smell. It includes both the external visible structure and the internal airways that lead to the pharynx.

Anatomy: The external nose is supported by nasal bones and cartilage, with a visible tip and two nostrils. The internal nasal cavity is lined with mucous membrane and divided by the nasal septum, a cartilage and bone partition. The lateral walls contain turbinates, or conchae, which create turbulence that helps warm, humidify, and filter inspired air.

Function and physiology: The nose filters particles, humidifies and heats inhaled air, and houses receptors for the sense of smell in the olfactory epithelium at the roof of the nasal cavity. Olfactory information is transmitted by the olfactory nerve (CN I) to the brain, while other nasal sensations are carried by branches of the trigeminal nerve. The nasal mucosa also plays a role in immune defense and drainage of the paranasal sinuses.

Clinical notes: Common conditions include allergic rhinitis, nonallergic rhinitis, sinusitis, nasal polyps, and deviated septum. Trauma can cause nasal fractures or epistaxis (nosebleeds). Treatments range from saline irrigation and medications to surgical procedures for persistent obstruction or structural issues.