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					Physiology of Nose &
  Paranasal Sinuses
Physiology of Nose
     FUNCTIONS OF NOSE
• RESPIRATION
• AIR CONDITIONING
   – FILTERATION
   – TEMPERATURE CONTROL
   – HUMIDIFICATION
• PROTECTION OF AIRWAY
   – MUCOCILIARY MECHANISIM
   – IMMUNOGLOBULINS & ENZYMES
   – SNEEZING
• VOCAL RESOSANCE
• NASAL REFLEX FUNCTIONS
• OLFACTION
Respiration

• Natural instinct

•Allows breathing and eating simultaneously


•Bypassed during exercise
 Respiration
• During quite respiration
  • Inspiratory current ----- middle part of nose and
    little air through inferior
    meatus or olfactory region
  • So weak odorous substances
    are sniffed
 Respiration
• During expiration

  • Same coarse

  • But all air current is not
    expelled

  • Limen nasi converts it into eddies under cover of
    inferior and middle turbinates to ventilate ostia.
 Respiration
• Nasal cycle

  • Mucosal cyclic congestion and decongestion

  • Controls air flow

  • Varies every 2 ½ - 4 hr

  • Individual variations
     Air conditioning of inspired air
• Filteration and Purification

  • Nasal vibrissae act as filters for large particles

  • Small particles adhere to mucus sheet

  • Front of nose can catch particles of 3 micro m

  • Mucin can trap particles from 0.5 to 3 micro m

  • Smaller than 0.5 micro m can easily pass
     Air conditioning of inspired air
• Temperature control

  • Highly vascular mucous membrane
    esp on middle and inferior turbinate



  • Sinusoids control blood flow ,
    increasing or decreasing size of
    turbinates
     Air conditioning of inspired air
• Temperature control

  • Air at – 50 to +50 C regulated to 37 C in 1/4th of a second
    Air conditioning of inspired air
• Humidification

  • Dry air in winter and moist in
    summer
  • Mucous membrane adjusts humidity
    of inspired air to 75% or more
  • Serous and mucous secreting glands
  • 1000 ml water evaporated from nasal
    mucosa in 24 hrs
Air conditioning of inspired air
• Humidification
  • Decrease in moisture      decrease ciliary function
       stasis of secretions     respiratory infections
 Protection of airway
• Mucociliary mechanism
• Goblet Cells
  – Glycoproteins—viscosity and elasticity
  – Innervation (para=thick, symp=thin)

• Basement membrane
   – Submucosal glands
Microscopic Anatomy




                      15
    Protection of airway
• Mucous blanket
• Two layers
   – Superficial layer --- mucus
   – Deep layer --- serous
   – both float on cilia
• Function
   – Superficial layer traps bacteria and particulate
     matter.
   – Enzymes, antibodies, immune cells
    Protection of airway
• Mucous blanket
• conveyer belt ----- towards nasopharynx

   – 5 -10 mm / min
   – Complete clearance in 10 – 20 mins
   – 600 – 700 ml secretions produced / day
   Protection of airway
• Ciliary movements

  • effective and recovery strokes
  • immotile cilia syndrome           stagnation of mucous
             chronic sinusitis and bronchiectasis
  • Drying, adrenaline, excessive heat and cold, infections &
    fumes e.g., sulphur dioxide decrease movements
   Protection of airway
• Enzymes and immunoglobulins
  • Muramidase ( lysozyme ) ----- pH 7.0 is maintained

  • Ig A and IgE

  • Interferon
   Protection of airway
• Sneezing
  • Protective reflex

  • FB, noxious substances
    washed out
 500 CF AIR IN 24 HRS IS FILTERED,
    HUMIDIFIED, ADJUSTED TO
TEMPERATURE, CLEARED OF DUST,
   BACTERIA & VIRUSES BEFORE
      REACHING THE LUNGS
   Vocal Resonance
• Resonating chamber

• M/N/NG --- sound passed
through nose

•B/D/G --- denasal
   Olfaction
• Pleasure and enjoying taste

•Ammonia via trigeminal ----- irritates nasal
mucosa
Olfaction
     Olfaction
•Abnormalities of olfaction
• anosmia (absence of the sense of smell);

• hyposmia (diminished olfactory sensitivity);

• dysosmia (distorted sense of smell);

• phantosmia (perception of an odorant when none is present);

• agnosia (inability to classify, contrast, or identify odor
sensations verbally, even though the ability to distinguish between
odorants may be normal).
Physiology of PNS
 The lateral nasal wall:
1. Inferior meatus:
   nasolacrimal duct
2. Middle meatus:
   •   Maxillary sinus
   •   Frontal sinus
   •   Anterior ethmoid
3. Superior meatus:
   posterior ethmoid
4. Sphenoethmoidal
   recess: sphenoid sinus
Ostiomeatal complex : OMC


                               Frontal ostium



                                HSI

    Maxillary ostium   Infundibulum

                                            R
     Mucosa
• respiratory mucosa

• globlet cell and cilia less frequent but more near ostia

• no sinosoids ----- so pale mucosa

• less developed nerve supply ---- basic vasomotor response

• increased mucous production with parasympathetic stimulation
     Drainage
• clearance is spiral and towards
natural ostia

•frontal and sphenoid clearance is
downwards

• Secretions join the nasal mucous in
middle meatus

•
     Oxygen tension and ostia size
• lower in maxillary and frontal sinus than nose

• If ostia is blocked       O2 tension further falls   decrease
ciliary action        stasis of fluid

• N2O levels are high

• ostia below 2.5 mm predisposes to disease
     Pressure changes
• Pressure in maxillary sinus changes with respiration but lacks
behind 0.2 sec

• When nose patent variation of + / - 4 pascals

• pressure changes reach 17 – 20 m pascal in exercise

• more marked with nasal obstruction
Purpose of sinuses

Resonating chamber for voice
Diminution of auditory feedback
Air conditioning
Decrease weight of skull
Flotation of skull in water
Shock absorbers
Heat insulation
Mechanical rigidity
Immune system
THANKS

				
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