Nose

The nose is a central feature of the face that serves as the entry point to the respiratory tract and house of the olfactory system. It consists of an external visible portion and internal air passages that connect to the nasopharynx. The external nose is formed by nasal bones and cartilage, covered by skin, and includes the two nostrils (nares). Inside, the nasal cavity is divided by the midline nasal septum and lined with mucous membrane. The lateral walls bear scroll-like bony projections called nasal turbinates or conchae, which increase surface area and help regulate airflow.

The superior part of the nasal cavity houses the olfactory region, where specialized receptor cells detect scent molecules. Olfactory nerves transmit these signals to the brain. The remainder of the nasal mucosa contains ciliated epithelial cells and mucous glands that trap and remove particles from inspired air.

Functions of the nose include conditioning inspired air by warming, humidifying, and filtering it; protecting the lower airways through mucociliary clearance and immune defenses; and enabling the sense of smell, which contributes to flavor perception and environmental awareness. The nose also contributes to voice resonance and can influence speech quality.

Nerve and blood supply are distributed to the nose via branches of the trigeminal nerve for sensation and the facial and maxillary arteries for circulation. The mucous membranes are richly innervated and vascularized, which supports rapid warming and humidification of air but also makes the area susceptible to bleeding in some conditions.

Common clinical aspects involve nasal obstruction from allergic rhinitis or deviated septum; chronic sinusitis; nasal polyps; and epistaxis (nosebleeds). Treatments range from medications, such as antihistamines and nasal sprays, to surgical interventions in cases of structural abnormalities.