Nose and sinuses

Abstract

Gross anatomy

Overview

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 olfactory nerve, 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 (frontal, ethmoid, sphenoid) and face (maxilla).
    • They reduce the weight of the skull, especially of the frontal and facial bones, to facilitate maintenance of the upright head position.
  • 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

Paranasal sinuses

Sinuses Location Structures
Frontal sinus
  • Connects with the middle nasal meatus
    • Via the frontonasal duct, which drains into the semilunar hiatus
Ethmoidal sinus
  • Ethmoidal labyrinth
  • Between the orbits and the nasal cavity
Sphenoid sinus
Maxillary sinus
  • Only the paranasal sinus is present at birth.
  • Drains into the middle nasal meatus

The nose

Bones

Boundaries

Meatus

Meatus Drainage
Superior meatus
Middle meatus
Inferior meatus
Sphenoethmoidal recess
Sphenopalatine recess

Vasculature

  • Ophthalmic artery
    • Lateral nasal branches of the anterior and posterior ethmoidal arteries
  • Maxillary artery
    • Posterolateral and posteroseptal branches of the sphenopalatine arteries
    • Greater palatine branch of the descending palatine artery
  • Facial artery
    • Superior labial artery
    • Lateral nasal branch

Innervation

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

Microscopic anatomy

Respiratory epithelium

  • 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, ciliated columnar epithelium with goblet cells (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.

Olfactory epithelium

  • 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, IgA, amylase, lysozyme
      • Moistens the nasal mucosa and acts as a solvent for odor molecules

Olfaction (smell)

Overview

  • 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 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.

Structure Characteristics
Olfactory tract
Primary olfactory cortex
Secondary olfactory cortex
Olfactory nuclei

Embryology

Development of the nose and paranasal sinuses

Clinical significance

last updated 12/13/2018
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