The nose contains the human olfactory system, which is responsible for the sense of smell. The paranasal sinuses are a group of air-filled structures within the frontal bone and the facial skeleton. Together, they fulfill the following functions:
- The nose contains the , which is responsible for transmission of olfactory signals from the olfactory epithelium to the brain.
- Paranasal sinuses are air-filled cavities within the bones of the skull (, , ) and face ().
- The nose and paranasal sinuses aid help provide resonance to the voice.
- The nose and paranasal sinuses warm and humidify air that is inhaled.
- The nose and paranasal sinuses are part of the mucosal immune system
|Frontal sinus|| || |
|Ethmoidal sinus|| |
|Sphenoid sinus|| || |
|Maxillary sinus|| || |
- Frontal, , , nasal, palatine,
- Roof: composed of the nasal, frontal, ( ), and
Floor: composed of the (palatine process) and the (horizontal plate).
- Transmits branches of the sphenopalatine artery and the nasopalatine nerve through the incisive foramen
- Medial wall (nasal septum): composed of septal cartilage, the vomer, and the perpendicular plate of the ethmoid bone
- Lateral wall: composed of the , , medial pterygoid plate of the , perpendicular plate of the , frontal process of the , nasal surface of the , and the inferior, middle, and superior meatus
|Inferior meatus|| |
|Sphenopalatine recess|| |
- Lateral nasal branches of the anterior and posterior ethmoidal arteries
- Posterolateral and posteroseptal branches of the sphenopalatine arteries
- Greater palatine branch of the descending palatine artery
- Superior labial artery
- Lateral nasal branch
- Via the (cranial nerve I)
- Other sensation
- Anterior and posterior ethmoidal branch of the ophthalmic nerve
- Anterior-superior alveolar branch of the infraorbital nerve
- Nasopalatine branch
- Posterior-superior branch
- Posterior-inferior branch
Kiesselbach plexus: Formed by the anterior ethmoidal artery, sphenopalatine artery, greater palatine artery, and the septal branch of the superior labial artery.
- Formed by the lower two thirds of the nasal cavity
- The anterior part of the vestibule in the nasal cavity is lined with keratinized, stratified, squamous epithelium.
- Posterior to the vestibule, the epithelium becomes pseudostratified, with (respiratory epithelium).
- Contains vibrissae, short and thick hair that filter large particles from inspired air.
- The lamina propria is abundantly vascularized.
- Serves to warm, humidify, and clean air that is inhaled.
- Found on the roof of the nasal cavity, in the superior nasal meatus, on both sides of the nasal septum
Lined by tall, pseudostratified, ciliated, columnar epithelium
- Olfactory cells
- Sustentacular and microvillar (supporting) cells
- Basal cells
- The lamina propria contains Bowman cells, fibroblasts, blood vessels, and unmyelinated fibers from the olfactory neurons.
Olfactory glands (Bowman glands)
- Tubulo-alveolar glands in the olfactory mucosa that secrete odorant-binding proteins, , ,
- Moistens the nasal mucosa and acts as a solvent for odor molecules
- Olfactory glands (Bowman glands)
- 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, in which lies the olfactory bulb.
- 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 receptor cells:
- Sustentacular cells: contain microvilli and secretory granules
- Basal cells: stem cells of the olfactory epithelium
- Mucus is produced by Bowman cells.
- Odorants react with olfactory receptor cells via diffusion or odorant-binding proteins.
- Olfactory glomerulus: neurons with identical olfactory receptors form glomeruli in the olfactory bulb.
- Second neurons
- Periglomerular cell: inhibit mitral cells and tufted cells laterally → sharper contrast between different smells
- Granule cells
|Olfactory tract|| |
|Primary olfactory cortex|| |
|Secondary olfactory cortex|| |
|Olfactory nuclei|| |
Development of the nose and paranasal sinuses