Physiology of NOSE

1. PHYSIOLOGY OF NOSE
Dr. Ankit Choudhary

2. The nose contains organ of smell and respiration
It warms, cleans and humidifies the inspired air,
cools and remove the water from the expired air
It adds quality to speech production
ENT surgeons should distinguish normal nasal
fuction from pathological symptoms to prevent
unnecessary surgery
Although the nose is a paired structure divided
coronally into two chambers, it act as a functional
unit

3. Physiological functions of Nose
1. Respiration.
2. Air conditioning.
3. Protection of lower airway.
4. Ventilation and Drainage of PNS.
5. Vocal resonance.
6. Olfaction.

4. Respiration
Nose is the natural pathway for breathing.
Mouth breathing is acquired through
learning
Nose permits breathing and eating to go on
simultaneously
Air passage through Nose during
respiration allows for Humidification, Heat
transfer and Filtration of it

5. • Expiration lasts longer than
inspiration and is more
turbulent
• Friction offered at limen
nasi converts it into eddies
under cover of inferior and
middle turbinates and this
ventilates the sinuses
through the ostia
• Airflow is directed upwards
and backwards from the
nasal valve initially, mainly
over the anterior part of the
inferior turbinate
• It then splits into two,
below and over the middle
turbinate, rejoining into
posterior choana

6. Nasal Cycle
Under control of autonomic nervous system Nasal
mucosa undergoes rhythmic cyclical congestion
and decongestion, thus controlling the air flow
through nasal chambers.
When one nasal chamber is working, total nasal
respiration, equal to that of both nasal chambers,
is carried out by it.
Cycle changes 4-12 hours.
Antihistamine has Anticholinergic effects  block
the parasympathetic activity  increase the
sympathetic tone  improve airway

7. Air Conditioning
•Nose adjusts temperature and humidity of inspired air
before it passes it on to the lungs.
•Air in post nasal space is approximately at 31oC and is 95%
saturated.
Heat Exchange:
Temperature control of the inspired air is by large surface
of nasal mucosa, particularly in the region of middle and
inferior turbinates and adjacent parts of the septum ( highly
vascular with cavernous venous spaces)
Time taken is almost one fourth of a sec.

8. Humidification
10% of body heat loss occurs through the nose in humans
Energy is required for:
Raising the temperature of inspired air (1/5)
Latent heat of evaporation (4/5)
Humidification of Inspired air done by nasal mucosa is due to
Secretions by the serous glands.
One third of water comes from Expired air which is
saturated and condenses onto the mucosa.
Additionally water comes from Nasolacrimal duct and Oral
cavity.

9. Protection of lower airway
Mechanical
The nose protects the lower airway by removing particles
down to approximately 30 μm, including the most pollens
from the inspired air.
The shape and roughness of smaller particles may cause
them to be deposited in the nose.
Inspired air travels through 180o and velocity drops
markedly just after the nasal valve.
Turbulence increases deposition of particles.
Vibrissae will stop the larger particles.

10. Chemical
Nasal secretions
Composed of two elements – mucus and water
Water and ions – produced mainly from the serous glands
Mucus composed of
•Glycoprotein: Sialomucins, fucomucins, sulphomucins
•Enzymes: Lactoferrin, Lysozymes, α-antirypsin, α1-
antichemotrypsin, α2-antimicroglobulin
•Circulatory proteins: complement, α2-macroglobulin, C
reactive protein
•Immunoglobulins: IgA, IgE, IgG, IgM, IgD
•Cells: surface epithelium, basophils, eosinophils, leukocytes

11. Mucociliary Clearance
Cilia is found on the surface of cells in the respiratory tract
Function is to propel mucus backwards in the nose
towards the nasopharynx.
Nasal cilia are relatively short(5 μm), with up to 200 per
cell.
Nasal mucus film is in two layers, one upper more viscous
layer and a lower more watery layer in which cilia can move
freely.
Metachronous movement
of cilia consists of a rapid
propulsive stroke and a slow
recovery phase.

12. Immunological
Nasal Immune System
Surface properties
Mechanical
Physical characteristics of mucus
Innate immunity
Bacteriocidal activity in the mucus
Proteins: lactoferrins, lysozymes
α2 macroglobulins, C reactive protein, complement
system
Cellular: polymorphs and macrophages
Acquired immunity
Surface IgA, IgM, IgE and IgG
Primed macrophages
Submucosa macrophage IgM, IgG, T and B
Lymphocytes: mucosal associated lymphoid tissue
Distant sites Adenoids, lymph nodes and spleen

13. Sneezing
Protective reflex.
Foreign particles which irritate nasal mucosa are
expelled by sneezing
Copious flow of nasal secretions that follows
irritation by noxious substance helps to wash them
out.

14. Ventilation and Drainage of PNS
Inspiration creates negative pressure in nasal
cavity thus sucks the air out from paranasal sinuses
via their ostium.
Expiration creates positive pressure in nasal
cavity thus ventilates the para nasal sinuses via
there ostium.
Eddies formed during expiration and Uncinate
process aids in ventilation of PNS.
Mucociliary action helps in drainage of PNS
through their respective ostia.

15. Vocal resonance
•Nose form resonating chamber for certain
consonants in speech
•Phonating nasal consonants (M/N/NG) – sound
passes through the nasopharyngeal isthmus and is
emitted through the nose
•When nasopharynx is blocked, speech becomes
denasal, i.e. M/N/NG are uttered as B/D/G
respectively
•Rhinolalia clausa – too little air escapes from nose
•Rhinolalia aperta – too much air escapes from nose
•The sinuses have no effect on modifying voice

16. Olfaction
•Olfactory solute in mucus needs high water and lipid
solubility.
•Olfactory area is 200-400mm2 with a density of
approximately 5x104 receptor cells/mm2
•Odours  react with lipid bilayer of the receptor cells
at specific sites  causes outflow of K+ and Cl-  Cell
depolarization.
•It is a G-protein coupled receptors which interact
with a specific adenyl cyclase within neuroepithelium.
•Adrenergic and muscarinic antagonists – blocks some
odour.

17. Threshold of olfaction depends on :-
•The chemical nature of the stimuli.
•Level of inhibitory activity generated by higher centre.
•Changes in nasal mucus and its pH.
•Age – decreases the threshold .
•Hormones (sex hormones) – increases the threshold.
Adaptation :-
•Olfactory response shows marked adaptation and thresholds
increase with exposure.
•Adaptation is both peripheral and central phenomenon.
•Cross adaptation occurs between odours at high concentration.
Olfaction has role in – Food recognition, initiate digestion- lat &
ventromedial hypothalamus, ↑ salivation & output of enzymes
- Reproduction
- Communication

18. Olfactory pathways
•Smell is perceived in the olfactory
region (high up in nasal cavity)
•Peripheral process of each olfactory
cells reaches the mucosal surface
with several cilia on it
•Central process are grouped into
olfactory nerves which pass through
the cribriform plate of ethmoid and
end in the mitral cells of the
olfactory bulb
•Axons of mitral cells forms olfactory
tract Olfactory trigone Olfactory
Striae Prepyriform cortex,
amygdaloid nucleus, hypothalamus,
hippocampus

19. Disorders of smell
Anosmia: Total loss of sensation of smell
Hyposmia: Partial loss of sensation of smell
Parosmia: Perversion of smell i.e, interprets the odour
incorrectly
Seen in recovery phase of post influenzal anosmia,
intracranial tumour
Cachosmia: Perception of pleasant odour as unpleasant
Phantosmia: Perception of odour in absence of olfactory
stimulus
Olfactory agnosia: Unable to identify previously known odour

20. Thank You