Physiology of nose and pns

1. Physiology of Nose
And
Paranasal Sinuses
Dr Mohammed Nishad N

2. Physiological functions of the nose
• Respiration:
– Inspiration
– Expiration
• Air conditioning of inspired air:
– Heat exchange
– Filtration
– Humidification
• Protection of lower airway
• Vocal resonance
• Nasal reflex functions
• Olfaction

4. Heat exchange
• Inspired air
Vary from -50°c to 50°c
• Conduction, convection and radiation
• Conduction occurs without flow when heat
is transferred by increased molecular movement.
• A temperature gradient leads to convection
of currents that will affect airflow in the nose
causing turbulence.

5. • Gas in the nose and the arterial blood considered as
two fluids that are in thermal but not direct contact.
• Arterial blood flows forward from the sphenopalatine
artery.
• Airflow is counter-current during inspiration
and is more efficient.
• Efficiency is measured by comparing the temperature
difference of the two 'fluids‘ at one end, Tl with the
difference at the other end T2:

6. HUMIDIFICATION
• Vaporization cools the surface and 10 percent
of the body heat is lost.

7. INSPIRATION
• Saturation follows the temperature rise rapidly.
• Energy is required for two functions:
Raising the temperature of inspired air (1/5)
 The latent heat of evaporation (4/5)
• The amount of energy is dependent on ambient
temperature and relative humidity of inspired air.
• Ten percent of the body heat loss occurs through
the nose in humans.
• Air in the post-nasal space is approximately 31°C
and is 95 percent saturated.

8. EXPIRATION
• The temperature of the expired air at the back
of the nose is slightly below body core
temperature and is saturated.
• As the temperature drops along the nose,
some water condenses onto the mucosa.
• The temperature in the anterior nose at the
end of the expiration is 32°C and
approximately 30°C at the end of inspiration.

9. WATER PRODUCTION
• Water comes from the serous glands, which
are extensive throughout the nose.
• Additional water comes from the expired air,
the nasolacrimal duct and the oral cavity.

10. Filtration
• Nasal vibrissae at the entrance of nose acts as
filters to sniff larger particles.
• The front of nose can filter particles up to 3
micron, while nasal mucus traps particles 0.5 –
3 micron.
• Particles smaller than 0.5 micron seem to pass
through the nose into lower airways without
difficulty.

11. AIRFLOW
• The airflow and the sensation of it are very
different.
• Cold receptors sense airflow.
• Nasal flow is laminar as it enters the nasal vestibule,
flow passes throuh the nasal valve turbulent flow is
observed

12. • The following equations describe the flow:
Airflow: VA = constant,
Where V is mean velocity (m/s), A is cross
sectional area (m ),2
If cross-sectional area decreases, then
airflow increases.
Gases flow faster in anterior and posterior
choana.

13. Bernoulli’s equation: If there is change in velocity,
then pressure will also alter.
P + ½ DV 2
= Constant
Where D = density (g/m), P = pressure (N/m ), V
mean velocity (m/s),
2
is
• Nose has variable cross-section, so pressure and
velocity alter continuously.

14. Reynold’ number Re = dvD/n
Where D =density (g/m), v = average
velocity(m/s), d is diameter (m) and n is
viscosity (g/ms)
• Reynold’s number varies from 2000- 4000
(Laminar — Turbulent)

15. • Flow is turbulent in an irregular tube.
• The resistance is inversely proportional to the
square of the flow rate.
• Change from laminar to turbulent is important
as this reduce the velocity of the air and
allowing prolonged contact of inspired air with
nasal mucosa

16. • The characteristic of air flow were similar in
different noses regardless of variety of nasal shape
• The cross-sectional flow is maximal at the centre
and is zero at the edge.
• Bernoulli equation is not strictly applicable since
the energy overcoming the viscosity results in an
irreversible drop in pressure.

17. Inspiration
• Airflow passes upwards
and backwards initially
over anterior part of the
inferior turbinate• Splits into two – below
and over the middle
turbinate.
• Rejoining in the
posterior choanae.•
• The velocity at the
anterior valve is 12-18 m
sec¯1 during quiet
respiration.

18. Expiration
• Last longer than
inspiration.
• Initially airflow passes
upwards and
anteriorly at posterior
choanae.
• Due to resistance of
nasal valve and
turbinates, there will
be turbulent airflow in
the middle.

19. The anterior nasal valve
• narrowest part of the
nose
• Surrounded by :
 lower edge of the upper
lateral cartilages
 the anterior end of the
inferior turbinate
the adjacent nasal septum
together with the
surrounding soft tissues.
• Electromyography shows
contraction of the dilator
naris alone during
inspiration.
• Alar collapse occurs afterdenervation

20. NASAL RESISTANCE
• Nasal resistance differs between races
• The nose accounts for up to half of the total
airway resistance.
• Produced by two resistors
– fixed: bone, cartilage and muscle
– variable: mucosa
• High in infants (obligatory nose breathers)

21. • During expiration, the positive pressure is
transmitted to the alveoli.
• Removal of this resistance by tracheostomy
reduces the dead space but results in a degree
of alveolar collapse.
• Reduced alveolar ventilation gives a degree of
right to left shunting of the pulmonary blood.

22. • Changes in resistance to
airflow along the nasal
passage ( Based on the
results of the study of
Haight and Cole,1983)

24. Nasal cycle
• Each side of the nose alternates the phases of congestion
and decongestion .Vascular activity produces the changes,
Esp vol of blood in the capacitance vessals (venous
sinususoids)
• Cyclical &Occurs in every
4 – 12 hours. Constant for each person
• To control the airflow
through the nasal
chambers.
• Nasal secretions also more
in the side of greater
airflow.

25. FACTORS
• Allergy
• Infection
• Exercise
• Hormones
• Pregnancy
• Puberty
• Fear and emotions
• High co2 in inspired air
• Drugs: Noradrenalin blocker- nasal congestion

26. Rhinomanometry
• The study of nasal pressure and flow is termed
rhinomanometry.
• Nasal resistance to airflow is calculated by:
– R = P/V
– Where R= Resistance to airflow, in cmH O/litre/s2
– P = transnasal pressure in cmH O2
– V = nasal airflow in litre/s

27. Types of rhinomanometry
• Active rhinomanometry
– Involves the generation of nasal airflow and
pressure with normal breathing.
– It can be divided into anterior and posterior
methods according to location of the pressure
sensing tube.
• Passive rhinomanometry
– Involves the generation of nasal airflow and
pressure from an external source such as fan to
drive air into the nose.

28. Anterior rhinomanometry
• The pressure sensing tube
is normally taped to one
nasal passage.
• The sealed nasal passage
acts as extension of the
pressure sensing tube to
measure pressure in the
posterior nares.
• Nasal airflow is measured
from one nostril at a time
and the pressure sensing
tube is moved from one
side to the other.

29. Posterior rhinomanometry
•
The pressure sensing tube is
held in the mouth and detects
the posterior nares pressure
when the soft palate is relaxed
allowing an airway to the
mouth.
• Total nasal airflow can be
measured from both nasal
passages or by taping off one
nostril, the right and left nasal
airflow can be measured
separately.
Total nasal resistance can be
determined directly from the
total nasal air flow and trans
nasal pressure.

30. Acoustic rhinomanometry
This method consists of
generating an acoustic pulse from
a spark source or speaker and the
sound impulse is transmitted
along a tube into the nose.
• The sound pulse is reflected back
from inside the nose according to
changes in local acoustic
impedance which are related to
cross-sectional area of the nasal
cavity.
• The reflected sound is detected
by a microphone, which transmits
the sound signal to an amplifier
and computer system for
processing into an area distance
graph.

31. • It provides a measure of nasal cross-sectional
area along the length of the nasal passage.
• The normal value of nasal cross sectional area
is 0.7 cm2
with a range from 0.3 – 1.2 cm .2

32. • It provides a measure of nasal cross-sectional
area along the length of the nasal passage.
• The normal value of nasal cross sectional area
is 0.7 cm2
with a range from 0.3 – 1.2 cm .2

33. Protection of Lower Airway:
Mechanical and Chemical
• Removes particles - 30 μm
• Inspired air travels through 180 degree and velocity
drops markedly just after the nasal valve.
• Turbulence increases deposition of particles.
• Particles in motion - carry on in the same direction:
larger the mass the greater the tendency.
• Resistance to change in velocity is greater in irregular
particles because of larger surface area and the number
of facets.
• Vibrissae will only stop the largest particles

34. Nasal secretions
Composed of :–
– Mucus
– Water
• Glycoprotein – goblet cells, gandular mucus cells
• Water and ions –Serous glands &indirectly from
transduction from capillary network
• The anterior part of the nose contain serous
gland only in the vestibular region.
• Sinuses has fewer goblet cells and mixed glands.

36. Composition of mucus
• water and ions from transudation
• glycoproteins: sialomucins, fucomucins,
sulphomucins
• enzymes: lysozymes, lactoferrin
• circulatory proteins: complement, alpha 2
macroglobulin,C reactive protein
• immunoglobulins: IgA, IgE
• cells: surface epithelium, basophils, eosinophils,
leukocytes.

37. Proteins in nasal secretion
• 1. Lactoferrin
• Serous gland
• Bind divalent metal ions – like transferrin in the
circulation
• Prevent growth of certain bacteria, particularly
Staphylococcus and pseudomonas.
• 2. Lysozymes
• Comes from Serous glands and tears
• Also produced by leukocytes and macrophages
• Act only on non capsulated bacteria

38. 3. Antiproteases
• Produced by leukocytes
• Includes :
Alpha-antitrypsin
Alpha1-anti-chymotrypsin
Alpha 2 -macroglobulin
• Increase with infection
4. Complement
• C3 – produced by liver and locally by macrophages
• Functions: lysis of microorganism,enhancing neutrophil function (leukotaxis)
5. Hydroxy aminoacids
6. Ions and Water
7.Immunoglobulins

39. Cilia
Ultrastructure
• Found on the surface of cells in the
respiratory tract
• Function: to propel mucus backwards
• All cilia have the same ultrastructure
• Nasal cilia - relatively short at 5 μm, with up to
200 per cell

40. • 9 paired outer microtubules
surround a single inner pair
of microtubules.
• Outer paired microtubules
are linked together by
nexins and to the inner pair
by central spokes.
• Outer pairs also have inner
and outer dynein arms,
which consist of ATPase,
which is lost in kartagener’s
syndrome.

43. Mucociliary blanket
– Goblet cells in nasal
mucosa secrete a mucus
blanket.
– It consists of :
– Upper viscous or gel
layer
– Deep serous or sol layer
more watery & cilia move
freely

44. • Ciliary cycle
– Beat frequency is between 7 and 16 Hz.
– It remains constant between 32 and 40° C.
– It consists of a rapid propulsive stroke and a slow
recovery phase.

45. • During the propulsive
phase, the cilium is
straight and the tip
points into the viscous
layer of the mucus
blanket.
• In recovery phase, the
cilium is bent over in
the aqueous layer.

46. FACTORS AFFECTING CILIARY ACTION
• Drying stops the cilia
• Temperature below 10°C and above 45°C
• Solutions above 5 % and below 0.2%
• pH below 6.4 and above 8.5
• Upper respiratory tract infection – damage
the epithelium
• Ageing

47. DRUGS
• Acetylcholine - increases the rate
• Adrenaline - reduces the rate
• Propanolol – reduces the rate
• Cocaine hydrochloride (>10%) –causes
immediate paralysis

48. Protection of Lower Airway:
Immunological
• IgA
• IgE
• IgM
• IgG
• Certain bacterial allergens are neutralized
• The T and some B cells interact with macrophages, which
have specific and nonspecific immunological properties.
• Dendritic cells are important in the allergic response.
• cytokines act on CD4 + T cells and gives rise to two main
responses, the Thl response and the Th2 or allergic
response.

50. Nasal vasculature
• The nose is a rigid box devoid of a constricting
smooth muscle so changes in airway are
produced by alterations in blood flow and
pooling of blood in resistance and capacitance
vessels.
• The degree of development varies at different
sites within the nose.
• It is most complex over the turbinates and
part of the nasal septum.

51. • Arteries and arterioles
produce resistance and the
venules and sinusoids produce
capacitance.• Anastomotic arteries spiral
upward through the cavernous
plexus of veins.
• In diagram
• A- arteriole
• V- venule
• C- capillaries
• G- interstitial glands
• P- venous plexus
• S- venous sinusoids

52. • Arteries branch into arterioles and end in
capillaries which run parallel just below the
surface epithelium.
• Capillaries drain into the superficial venous
system.
• They are best developed just before the
superficial veins drain into venous sinusoids.
• Sinusoids receive both arterial and venous
blood.

53. Blood flow
• changes in colour
• photoelectric plethysmography
• temperature change (thermocouples)
• laser Doppler

54. Motor nerves
• Sympathetic nerve supply
– Derived from the lateral horn of the grey mater of
the spinal cord at the level of 1st
and 2nd
thoracic
vertebra.
Sympatheticfibers innervates smooth muscle in the
wall of arterioles and sinusoides
Primary NT is noradrenalin – VC of blood vessals

55. • Parasympathetic nerve supply
– The pons contain the superior salivatory nucleus
and pre-ganglionic fibres have their origin here.
– They proceed via the facial nerve to the
geniculate ganglion, then to greater superficial
petrosal nerve, deep petrosal nerve, the nerve of
the pterygoid canal into the sphenopalatine
ganglion.
– Post ganglionic fibres then pass into the nasal
mucosa.

57. SENSORY NERVE
Trigeminal (opthalmic and maxillary )nerve
supply sensory.
Temperature, pain, touch, irritation is
appreciated.
Nerve ending have H1 receptor.

58. Neurotransmitters
• Parasympathetic
– Acetylcholine(Ach) is the main parasympathetic
neurotransmitter.
– ACh produces widespread vasodilatation and
increased glandular activity& induce serous secretion.

59. • Sympathetic
– Noradrenaline is the main post-synaptic
transmitter with ACh acting at the postganglionic
synapses.

62. Drugs acting on the vascular tissue of
the nose
• Sympathomimetics and their antagonists
– Adrenaline and noradrenaline act mainly through
a receptors and cause vasoconstriction.1
– Antihypertensives, mainly B-blockers may cause
nasal obstruction.
• Parasympathomimetics and their antagonists
IV pilocarpine and carbachol cause nasal
congestion, vasodilation and watery secretions.

63. • Histamine and Antihistaminics
– Histamine vasodilates by relaxing vasculature
musculature and shrinks capillary endothelium.
– It irritates the sensory nerve endings and sneezing
results.
• Antihistaminics cause blockage of H1 receptors,
anticholinergic activity, local anaesthesia and
sedation.

64. Reflexes
• AXON REFLEXES:
Initiated by mechanical irritation or via histamine from mast cells.
Substance P liberate histamine from mast cells.
This amplifies the response.
• REFLEXES FROM NASAL STIMULI
Chemical irritation, temperature change and physical
stimuli may cause widespread cardiovascular and respiratory
responses.
• NASOPULMONARY REFLEXES
Increasing airflow through one side of the nose is
associated with increased ventilation of the homolateral
lung.

65. • REFLEXES ACTING ON THE NOSE
Exercise, emotion and stress may cause vasoconstriction.
Sympathetic nerves increase tone and stellate ganglion block abolishes
it.
Hyperventilation will cause nasal congestion.
• CUTANEOUS STIMULATION
Heating the skin of the feet, arm or neck will produce an increase in
nasal resistance.
Cooling results in vasoconstriction.
CENTRAL CONTROL
The hypothalamus controls cardiorespiratory responses.

66. The nose and the voice
• The nose adds quality by allowing some air to
escape through it.
• Voice is produced by modifying the vibrating
column of air from the larynx.
• If too little air escapes from the nose, then
rhinolalia clausa occurs.
• If too much air escapes, then rhinolalia aperta
ensues.

67. OLFACTION
• The olfactory
neuroepithelium lies
within a small region of
nasal mucosa
(approximately 2 cm2
)
in the upper recess of
nasal chamber lining
the cribiform plate and
sectors of superior
turbinate, middle
turbinate and septum.

68. • The olfactory area contains about 5 * 104
receptor cells/mm2
.
• The central processes of olfactory cells are
grouped into olfactory nerves which pass
through cribiform plate of ethmoid and end in
mitral cells of olfactory bulb.

69. Higher centres
– The anterior olfactory nucleus send impulses to
the opposite bulb and to the ipsilateral forebrain
through the anterior commissure.
– The primary olfactory cortex lies rostral to the
telencephalon and includes the olfactory tubercle,
the prepiriform and the pre-amygdaloid areas.

70. Olfactory area:
• inferior surface of cribriform plate , upper
septum , adjacent lateral wall , medial surface
of superior concha

71. • Olfactoy responses show marked adaptation
and thresholds increase with exposure
• Adaptation -2 components
– peripheral phenomenon –receptor level
– central phenomenon – post receptor
• Cross adaptations- A reduction in sensitivity to
an odour following adaptation to another odour

72. Olfactory neural pathway
– Olfactory receptor in nasal
mucosa- 20 olfactory nerve
bundles – synapse with
Mitral and tufted cells in
olfactory bulb – axon unite
to form olfactory tract-
flatten distally to form
olfactory trigone-
trifurcates into olfactory
striae- synapse with 1 and
2 olfactory cortex+
hypothalamus +
hippocampus + amygdala

73. Olfactory pathways
• Olfactory region (high up in nasal cavity)
• Olfactory cells and cillia
• Central process - olfactory nerves
• Pass through the cribriform plate
• Olfactory bulb
• Olfactory tract
• Prepyriform cortex
• Amygdaloid nucleus where it reaches
consciousness

74. Olfactory neural pathway

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77. Olfactory dysfunction:
• Anosmia:
– Absence of olfactory sensation.
– Causes: nasal polyp, enlarged turbinates, allergic and
vasomotor rhinitis, atrophic rhinitis, peripheral neuritis
• Hyposmia:
– Decrease of olfactory sensation.
– Causes: nasal polyp, enlarged turbinates.
• Parosmia/ cachosmia:
– Perversion of smell.
– Perception of a pleasant odor as unpleasant one.

78. • Phantosmia:
– Perception of odor in absence of olfactory stimulus
• Hyperosmia:
– increased olfactory sensation
• Olfactory agnosia:
– unable to identify odor

79. Olfactory function tests
• Supra-threshold test: only identifies odor
Smell bottles
Smell Identification Test (S.I.T.)
• Threshold Olfactometry: measures weakest
perceptible odor with help of serial dilution
Manual
Dynamic (automatic)

80. University of Pennysylvania Smell
Identification Test
– U P S I T consists of 4 test booklets, each
containing 10 stimuli for smell.
– All 40 stimuli are presented in rectangular
areas.
– Subjects scratch and then sniff them.
– They are required to pick 1 from 5 multiple
choices present for each stimuli.

81. • 36-40: Normal
• 16-35: Partial anosmia
• 6-15: Total anosmia
• 0-5: Malingering

82. Saccharin test
• Evaluates ciliary
function by measuring
time taken for a drop of
saccharin to be tasted
in throat when applied
to inferior turbinate
(anterior tip)• Normal speed = 5-10
mm/ min
• Normal time = 10-20
min

83. THE PARANASAL SINUSES
• The physiological role of paranasal sinuses is
uncertain.
• They are continuation of the respiratory cavity
and are lined by a respiratory mucosa.
• They have relatively poorly developed
vasculature and nerve supply.

84. • Functions of paranasal sinuses:
– Vocal resonance
– Air conditioning
– Pressure damper
– Reduction of skull weight
– Increasing of the olfactory area
– Thermal insulator

85. Ventilation of paranasal sinus
• Inspiration:
– negative pressure created in nasal
cavity sucks out air from
paranasal sinuses via their ostium
• Expiration:
– eddies within nasal cavity create
positive pressure ventilates
paranasal sinuses via their ostium

86. Mucosa
• Respiratory mucosa runs in continuity from
the nose.
• Goblet cells and cilia are less numerous.
• Since the nerve supply is less well developed,
the sinus mucosa is able to give only a basic
vasomotor response and increase mucus
production with parasympathetic stimulation.

87. Oxygen tension
• The po2 is lower in the maxillary sinuses than
in the nose.
• If the ostium is blocked, the oxygen tension
drops further.
• If the blood supply is impaired, ciliary activity
is reduced and stasis of secretion results.

88. Ostium size
• Blockage of natural sinus ostium results in a
reduction of ventilation and stasis of
secretions.
• An ostium below 2.5 mm predisposes to
disease.

89. Drainage of PNS
– Mucociliary clearance in the maxillary sinus is
spiral and towards the natural ostium.
– Drainage of frontal and sphenoidal sinuses is
downwards and is aided by gravity.

92. Comments
• The volume of the largest sinus is under 50 ml
and so contributes little to air conditioning.
• A damper has to have a large volume to be
effective.
• The reduction of skull weight is small
compared to the overall weight.
• Most of the cranial activity is away from the
sinuses so they play little part in insulating the
brain.

93. • Apart from the mucus production and some
strengthening of facial bones, the paranasal
sinuses have little physiological function.

94. THANK YOU