Anatomy

• Functions of the nasal cavity:

  • Process inspired air - humidify, warm and filter
  • Smell
• External nose:

  • Anterior naris (nostril) - opening into the nose
  • Ala nasi (the nares) - wings of the nostril
  • Vestibule - areas just inside nostril that leads into the nasal cavity - lined with short coarse hairs that filter
  • Columella - fleshy external end of nasal septum
  • Nasal septum - provides structural support to nasal cavity - helps conduct odorants to the olfactory nasal mucosa
• The nasal cavity consists of:

  • 3 regions - vestibule, respiratory, and olfactory
  • Turbinates/concha
  • There is also an important pouch in the bone posterior to the nasal cavity - Sella turcica - where pituitary gland sits
• Regions of the nasal cavity:

  • 2 nasal cavities separated by the septum
  • Open anteriorly via the nares and posteriorly connect to the nasopharynx
  • The vestibule region - opening of nasal cavity which has has hair follicles
  • Respiratory region - lined with respiratory mucosa
  • Olfactory region - lined with olfactory mucosa
• Turbinates/concha:

  • 3 long thin curved bones covered in tissue each forming a channel/meatus behind them
  • Inferior, middle and superior turbinate
  • Function = increase surface area within the nose helping to warm and moisturise as much air as possible that flows through the nose
• Olfaction:

  • Air and odour molecules enter the nose through the nostrils
  • The olfactory nerve (CN I) forms the olfactory bulb (bundle of nerve fibres)
  • Nerve projections of olfactory bulb project through cribriform plate (part of the ethmoid bone that forms the roof of the nasal cavity)
  • Odour molecule that enter nasal cavity bind to the receptors and send signals to the brain
  • Each olfactory sensory cell responds to a different type of odour molecule - send signal to a specific glomerulus in the olfactory bulb responsible for that smell
• Openings into nasal cavity:

  • Paranasal sinuses
  • Eustachian tube - connects the middle ear with the back of the nose
  • Nasolacrimal duct - carries tears from lacrimal sac of the eye into the nasal cavity - if blocked patients will have a watery irritated eye
• Paranasal sinuses:

  • Air filled cavities in the skull named after the bones of the skull they sit within:
  • Frontal sinus (frontal bone)
  • Ethmoidal sinus (ethmoid bone)
  • Maxillary sinus (maxilla)
  • Sphenoidal sinus (sphenoid)
• Paranasal sinus openings into nasal cavity:

  • Enter via holes called ostia (ostium singular)
  • Sphenoidal sinus - into superior meatus behind superior turbinate
  • Frontal sinus - into middle meatus behind middle turbinate
  • Maxillary sinus - into middle meatus
  • Ethmoidal sinus - sits medial to orbit, opens into superior and middle meatus
• Function of sinuses:

  • Decrease weight of skull
  • Increase resonance of voice
  • Humidify and heat inspired air
  • Support immune defence of nasal cavity