Nose and sinuses

Last updated: January 27, 2022

Summarytoggle arrow icon

The nose is the protruding structure at the center of the face that serves as the organ of smell and entrance of the respiratory system. The paranasal sinuses (maxillary, frontal, ethmoidal, sphenoid) are air-filled cavities within the bones of the skull that surround the nasal cavity. The nose and the paranasal sinuses provide resonance to the voice and humidify and warm inhaled air. The nasal cavity consists of a respiratory region, which is lined with ciliated pseudostratified columnar epithelium interspersed with goblet cells, and an olfactory region, which is lined with pseudostratified ciliated columnar epithelium interspersed with olfactory receptor neurons. Olfactory information is communicated to the brain via the olfactory nerve (CN I), which arises from the respiratory epithelium. The olfactory receptor neurons in the respiratory epithelium react with odorants via diffusion of odorant-binding proteins. The signal is carried by olfactory receptor neurons, whose axons bundle in fascicles. These fascicles then pass through the cribriform plate of the ethmoid bone and form the olfactory bulb within the forebrain. From there the signal is transmitted on to the target regions in the brain via the olfactory tract. Unlike other sensory tracts, the olfactory tract bypasses the thalamic nuclei and projects directly into the primary olfactory cortex. Diseases affecting the nose and the paranasal sinuses include nasal polyps, epistaxis, choanal atresia, and sinusitis.

Gross anatomytoggle arrow icon


Paranasal sinuses

Characteristics of paranasal sinuses
Sinuses Location Structures
Frontal sinus
Ethmoidal sinus
  • Ethmoidal labyrinth
  • Between the orbits and the nasal cavity
Sphenoid sinus
Maxillary sinus

The nose




Nasal meatuses and recesses
Meatus Drainage
Superior meatus
Middle meatus
Inferior meatus
Sphenoethmoidal recess
Sphenopalatine recess


Kiesselbach plexus is formed by the anterior ethmoidal artery, sphenopalatine artery, greater palatine artery, and the septal branch of the superior labial artery.


Microscopic anatomytoggle arrow icon

Respiratory epithelium

Olfactory epithelium

Olfaction (smell)toggle arrow icon


  • Molecules are inspired and absorbed by the respiratory region of the nose before reaching the olfactory epithelium.
  • Smell is the sensation produced when the olfactory epithelium reacts with dissolved odorant substances.
  • Mucus secretion is required for odorant molecules to interact with the olfactory epithelium (aids in dissolving odorants).
  • The conscious and unconscious perception of smell takes place in different areas of the brain.
  • Smell plays an important role in the formation of memory and emotions.
  • Smell aids in gustation (sense of taste).

Anatomy of smell

  • The olfactory neurons are primarily located in the superior part of the nasal cavity.
  • Odorants travel through the superior nasal meatus to reach the olfactory bulb.
  • The olfactory system is characterized by direct projections that connect directly to the cortex, bypassing the thalamic nuclei (unlike other sensory systems).

Olfactory epithelium

Olfactory bulb

Smell pathways

Several areas of the brain are associated with the sense of smell, including: the anterior olfactory nucleus, amygdala, piriform cortex, entorhinal cortex, and olfactory tubercle.

Overview of smell pathways
Structure Characteristics
Olfactory tract
Primary olfactory cortex
Secondary olfactory cortex
Olfactory nuclei

Embryologytoggle arrow icon

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