Nose and PNS physiology

1. Prepared by- Bisrat G. / ORL-HNS (R1)
Moderator - Dr. Mesele / ORL - HNS Surgeon
March 2018 GC

2. Outline
Revision of the embryology
Nasal Physiology
Air conditioning
Humidification
Measurements Nasal function
Protection
Vocal resonances
Nasal reflexes
Physiology of PNS
Bibliography

3. Embryology
 Nose During 4th – 8th GW
 Nasal placodes Nasal Pits (5th ) Nasal sac
 Bilateral Maxillary process & median FNP
 Septum = Fusion of MXP and FNP
 MNP + MXP = upper maxilla and Philtrum
 10 & 20 palatal shelves
 PNS 25 wk – 3 medial projections from lateral wall of nose Diverticula
 Maxillary sinus – 10th wk – invagination of the middle meatus

4. Nasal Physiology
 The major functions of the nose are
Humidification
 Respiration /Air Conditioning/ Heat Transfer
Filtration
 Protection
 Olfaction
 Vocal resonance
 Nasal Reflex functions
These functions are aided by the convoluted anatomy of the nasal cavity; which creates a
large surface area.

5. Air Conditioning
 Nose is the natural pathway for breathing
 The nose acts as an air conditioning unit and performs three
functions: humidification, heat transfer and fitration.

6. Humidification
 This function goes on simultaneously with the temperature control of inspired air.
Inspiration
 Energy is required for two functions: raising the temperature of inspired air (1/5), and
the latent heat of evaporation (4/5).
Expiration
 T0 of expired air (back of nose) < Body core T0
 As the temperature drops along the nose, some water condenses onto the mucosa.
 Appx 1/3rd of water required for humidify recovered.
Independent of the environmental humidity, the sinonasal system can raise the humidity of inspired air
to approximately 85%

7. AIRFLOW
 Cold receptors sense airflow.
 The flow is turbulent, but is considered laminar at rest.
 The equations below describe flow, two for laminar and one for the transition to
turbulent flow:
 Gases flow faster through the choana.

8. Cont…
 Because flow is turbulent in an irregular tube, the resistance is
inversely proportional to the square of the flow rate.
Inspiration
 The airflow is directed upwards and backwards from the nasal
valve initially, mainly over the anterior part of the inferior
turbinate.
 It then splits into to, below and over the middle turbinate,
rejoining into the posterior choana.
 The velocity at the anterior valve is 12-18 m sec - 1 during quiet
respiration.

9. Cont…
Expiration
 Expiration lasts longer than inspiration and is more turbulent.
 Extra pulmonary airflow is turbulent because the direction
changes, the caliber varies markedly and the walls are not
smooth.

10. Cont…
Nasal resistance
 The nose accounts for up to half the total airway resistance.
 The resistance is made up of two elements; one essentially fixed
comprising the bone, cartilage and attached muscles, and the other
variable, the mucosa.
The nasal resistance is high in infants who initially are obligatory
nose breathers.

11. The anterior nasal valve/ostium internum
/liminal chink
 It is formed by the lower edge of the upper lateral cartilages, the
anterior end of the inferior turbinate and the adjacent nasal septum.
 This is the narrowest part of the nose and is less well defined
physiologically than anatomically.
 Narrowest Part = Greatest resistor = Turbulent flow

12. Nasal cycle
 The nasal cycle refers to spontaneous congestion and decongestion alternating
between the two nasal passages.
 The changes are produced by vascular activity, particularly the volume of blood on
the venous sinusoids (capacitance vessels).
 The physiological significance is uncertain but, in addition to a resistance and flow
cycle, nasal secretions are also cyclical with an increase in secretions in the side
with the greatest airflow.
 Various factors may modify the nasal cycle and include allergy, infection, exercise,
hormones, pregnancy, fear and emotions, including sexual activity.

13. Rhinomanometry
 Rhinomanometry is the simultaneous measurement of transnasal pressure and
airflow.
 Rhinorheomanometry, Rhinomanometry, and Rhinomanography are names that
have been applied to these measurements.

14. Acoustic Rhinometry
 Noninvasive way to measure cross-sectional area of the nasal cavity by analyzing
reflected sound waves within the nasal cavity. /vascular supply indirectly/
 The area of maximal narrowing corresponding to the nasal valve usually lies within
the first 2 cm of the nasal vestibule
 The next downward deflection in the acoustic rhinometry curve usually
corresponds to the narrowing caused by the head of the inferior turbinate at the
piriform aperture.
 According to Poiseuille's law, nasal airflow is directly proportional to the radius to
the fourth power.
Complementary information: Rhinomanometry determines resistance or how hard it is to breathe,
whereas Acoustic Rhinometry allows localization of abnormalities.

16. Rhinostereometry
 Rhinostereometry involves the use of a microscope for assessing
changes in nasal congestion.
 Rhinostereometry has been shown to be useful for the detection of the nasal
cycle; however, a good correlation of results with those of acoustic rhinometry is
not observed when the two are directly compared.
 This method has been used for research into the effects of medication on nasal
mucosal blood flow.

17. Cont…
Manometric rhinometry is a technique in which
the volume of air in the nose is assessed by closing off the nose, removing a
volume of air, and then recording the resultant pressure change.

18. PROTECTION OF THE LOWER AIRWAY:
MECHANICAL AND CHEMICAL
 Normal sinonasal mucosa is made of an epithelial layer, lamina propria,
submucosa, and periosteum.
 The nasal epithelial cells are ciliated, pseudo-stratified, columnar cells
with a variable number of goblet cells.
 Coarse nasal hairs, vibrissae, located at the nasal orifice filter out large
particles entering the nose.
 Particles smaller than 0.5 μm pass through the nasal filter to the lower
airways.
 Mucociliary clearance serves to transport trapped particles including
pathogens out of the sinuses and nose.

19. Cont…
Nasal secretions
 Nasal secretions are composed of two elements, mucus and water.
 Glycoproteins are produced by the mucus glands and the water and ions are produced
mainly from the serous glands and indirectly from transudation from the capillary
network.
 Glycoproteins are classified a acidic or neutral
 The acid is either sialic acid (sialomucins) or form a sulphate group (sulphomucins).
 Neutral glycoproteins contain fucose (fucomucins).
 Sinuses have fewer goblet cells and mixed glands.

20. Cont…
 The mucous blanket is divided into the inner sol layer and outer gel layer.
 Goblet cell-produced glycoproteins give the gel layer of nasal mucus its viscosity
and elasticity.
 The gel layer lies on top of the nasal cilia, whereas the sol layer surrounds
the cilia.
 The sol layer of mucus is considerably less viscous so that ciliary movement can
propel the overlying layer of mucus and any trapped particles.
20 - 40 mL of mucus/ 24 hr
160 cm2 of Nasal Mucosa

21. Cont…
Composition of mucus
 Water and ions from transudation;
 Glycoproteins: sialomucins, fucomucins, sulphomucins
 Enzymes: lysozymes, lactoferrin
 Circulatory proteins: complement, α-2-macroglobulin, C reactive
 Immunoglobulins: IgA, IgE, IgG, IgM, IgD
 Cells: surface epithelium, basophils, eosinophils, leukocytes.

22. Rheology of mucus
 Glycoproteins give mucus its two most commonly measured properties, viscosity
and elasticity.
 Viscosity and elasticity are easier to measure, but adhesiveness and fluidity may be
more important.
Proteins in nasal secretion
 These are derived either from the circulation or are produced by the mucosa.
 Some compounds, such as lactoferrin, are present only in nasal secretions.

23. Cont…
LACTOFERRIN
 Lactoferrin is produced by the glandular epithelium, mainly the serous cells. Its
action is to bind divalent metal ions - like transferrin in the circulation.
 By removing heavy metal ions, it prevents growth of certain bacteria, particularly
staphylococcus and pseudomonas.
LYSOZYMES
 Lysozymes come from the serous glands and tears.
 They are also produced from leukocytes and macrophages.
 Their actions are nonspecific and act only on bacteria without capsules.

24. Cont..
ANTIPROTEASES
 A number of different antiproteases have been demonstrated and they increase
with infection; their role remains uncertain.
COMPLEMENT
 Its functions include the lysis of microorganisms and enhancing neutrophil function
as well as leukotaxis.
LIPIDS
 Phospholipids and triglycerides are present; their exact function is unknown.

25. Cont…
IONS AND WATER
 Na + and Cl - are hyperosmolar in mucus.
 Evaporation may account for some of the hyperosmolarity but active ion transport
also exists.
IMMUNOGLOBULINS
 All classes of immunoglobulins have been found in nasal
secretions.
 Two immunoglobulins involved with mucosa defense, IgA2 and IgE, are present in
greater quantities than serum.

26. Cilia
 Found on the surface of cells in the respiratory tract.
 their function here is to propel mucus backwards in the nose towards the
nasopharynx.
 Outer : Inner ( 9:1 ) 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 an ATPase, which is lost in Kartagener's syndrome.

27. CILIARY ACTION
 Beat frequency is between 7 and 16 Hz at body temperature.
 The beat consists of a rapid propulsive stroke and a slow recovery phase.
 During the propulsive phase, the cilium is straight and the tip points into the
viscous layer of the mucus blanket; whereas in recovery the cilium is bent over in
the aqueous layer.
 Energy is produced by conversion of ATP to ADP by the ATPase of the dynein arms
and the reaction is dependent of Mg2 + ions.

28. Factors affecting ciliary action
 Drying stops the cilia
 Movement will cease below 10°C and above 45°C.
 Isotonic saline will preserve activity, but solutions above 5 percent and below 0.2
percent will cause paralysis.
 Cilia will beat above pH 6.4 and will function in slightly alkaline fluids of pH 8.5 for
long periods.
 Upper respiratory tract infection
 Ciliary function may deteriorate with age
 DRUGs
 Acetylcholine increases the rate and adrenaline decreases
the rate.

29. Cont…
 Mucociliary transit time is measured by the saccharin test.
 A saccharin pellet is placed in the anterior part of the nasal cavity, dissolves, and is
transported by the mucociliary system into the nasopharynx, and then the
oropharynx where the sweet taste is detected.
 Normal transport times are less than 20 minutes, with most subjects detecting the
taste within 10 minutes. Other methods are also available

30. Correlates
 Recurrent sinus infections resulting from increased mucociliary transit time are most
commonly associated with primary or secondary ciliary dysfunction.
Primary ciliary dyskinesia (PCD)
 autosomal recessive disorder resulting from defective ciliary structure and function.
 50 % of patients with PCD have Kartagener syndrome with bronchiectasis, sinusitis, and
situs inversus.
SCD usually occurs during or after a respiratory infection and is often reversible.

31. PROTECTION OF THE LOWER AIRWAY:
IMMUNOLOGICAL
 IgA and IgE are mainly present on the surface, and IgM and IgG act if the mucosa is
breached.
Nonspecific/Innate/ immunity
 The innate immune system refers to any inborn resistance that is already present
the first time a pathogen is encountered. The innate immune response is modified
only in quantitative rather than qualitative terms following repetitive exposure.
 Lactoferrin, lysozymes, complement, antiproteases and other macromolecules
interact with a number of bacteria, particularly those without capsules, to give an
innate nonspecific immunity.

32. Cont…
Acquired immunity
 IgG (except IgG4 subgroup) activates complement resulting in cell lysis and
phagocytosis. Viruses and mycobacteria initiate cell-mediated immunity.
 The acquired immune response across the sinonasal tract is mediated by dendritic
cells (DCs), which are phagocytic antigen-presenting cells present in substantial
numbers in the nasal mucosa.

33. Cont…
IgE
 This is the main immunoglobulin involved in allergic reactions.
 IgE does not activate complement.
SURFACE CELLS
 Mucus contains epithelial cells, leukocytes, basophils, eosinophils, mast cells and
macrophages.
 Leucocytes and macrophages are important in phagocytosis and may help prevent
bacterial or via invasion.

35. NASAL VASCULTURE AND NERVE SUPPLY
 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.
Blood flow
 Measurement of nasal blood flow is difficult because instruments introduced into
the nose will alter nasal resistance if the mucosa is touched.
 Blood flow may be inferred by
• changes in color;
• photoelectric plethysmography;
• temperature change (thermocouples);
• laser Doppler.

36. Cont…
 A number of combinations of blood flow may exist depending on the balance
between arterial flow, arteriovenous shunting and venous pooling.
 Three main variations are seen clinically:
1. Hyperemia with both shunting and venous congestion.
2. Reduced arterial perfusion with no shunting giving rise to venous
congestion.
3. Ischemia

37. Vocal Resonances
 The nose adds quality by allowing some air to escape through it.
 Sound resonates within the nose and mouth, if too little air escapes from the
nose then Rhinolalia clausa occurs, if too much then Rhinolalia aperta ensue.
 In phonating nasal consonants (M/N/NG), sound passes through the
nasopharyngeal isthmus and is emitted through the nose.
 The sinuses have no effect on modifying voice. They may help with auditory
feedback as transmission of sound though the facial skeleton helps monitor
voice quality.

38. Nasal Reflexes
 Nose is endowed with various reflexes. These reflexes are aimed at
protecting the lower airway from insults.
Nasonasal reflex:
 This reflex is also known as sneezing. This is purely a protective reflex
aiming to protect the lower airways from the deleterious effects of
substances mixed with the inspired air.
 This reflex is mediated by the trigeminal and vagal nerves.
 This reflex is caused by deep inspiration followed by forced expiration
against closed glottis.

39. Cont…
Nasobronchial reflex:
 This reflex is also known as nasopulmonary reflex / nasolaryngeal reflex.
 This is an ipsilateral reflex again mediated by trigeminal and vagal nerves.
 This is caused due to constriction of bronchioles and laryngeal inlet.
 This reflex was demonstrated by increased levels of carbon dioxide in
blood following packing of nasal cavities.
 This reflex is more predominant in elderly.
=> Pulmonary hypertension or corpulmonale

40. Cont…
Corporonasal reflex:
 This reflex is also known as the classic diving reflex.
 This reflex is caused when face or upper part of the body comes into
contact with cold water. This causes cessation of respiration.
 This reflex also causes bradycardia and contraction of sub mucosal blood
vessels under the nasal mucosa.

41. Cont…
Nasocardiac reflex:
 In this reflex strong stimulation of nasal mucosa causes bradycardia and
reduction in cardiac output and lowering of blood pressure.
Nasovascular reflex:
 In this reflex stimulation of nasal mucosa causes peripheral
vasoconstriction.

42. Cont…
Genitonasal reflex:
 Sexual arousal / orgasm causes swelling of nasal mucosa, especially the
turbinates.
Gastronasal reflex:
 Strong gastric stimulation causes increased nasal secretion and congestion
of nasal mucosa.

43. Cont…
Crutch Reflex
 Axillary pressure leads to unilateral and systemic changes in sympathetic reflexes
(crutch reflex).
 Five minutes of unilateral axillary pressure decreased the ipsilateral minimum nasal
cross sectional area (median change = 0.09 cm2, P < 0.01)
 The contralateral nasal minimum cross-sectional area was significantly increased
(median change = 0.35 cm2, P = 0.01) (median change = 0.35 cm2, P = 0.01)
suggesting a contralateral increase in sympathetic vasoconstriction.

44. THE PARANASAL SINUSES
 The physiological role of the paranasal sinuses is uncertain.
Drainage
 In all the sinuses, mucus moves toward the natural ostia.
 Maxillary sinus mucociliary clearance begins at the floor and flows against gravity
toward the maxillary infundibulum.
 The anterior ethmoids drain into the middle meatus and the posterior ethmoid
cells drain into the superior meatus.
 Mucus in the frontal sinus drains toward the ostium only from the lateral side.

45. Cont…
 Like the maxillary sinus, the sphenoid sinus flows against gravity toward its ostium
that drains into the sphenoethmoidal recess.
 The P02 is lower in the maxillary sinuses than in the nose and it is lower still in the
frontal sinuses.
 If the blood supply is impaired, ciliary activity is reduced and stasis of secretions
results.
 Levels of nitrous oxide are higher in the sinuses than in the nasal cavity.
Pressure changes
 Pressures in the maxillary sinus vary with respiration but lag behind by 0.2 s.

47. Cont…
Physiological functions of the sinuses
 The functions of the sinuses are listed below:
 Vocal resonance
 Diminution of auditory feedback
 Air conditioning
 Reduction of skull weight
 Floatation of skull in water
 Mechanical rigidity
 Heat insulation
 Pressure damper

48. Bibliography
 Scott brown ORL – HNS 7thed. Vol 2, Chap 106, Physiology of the nose and
paranasal Sinuses, P. 1355 - 1369
 Cummings Otorhinolaryngology 5thed, Vol 2, Part 4, Chapter 42 P.341 - 359
 Bailey’s HNS – ORL 5thed Vol I, Section II, Part 23, Sinonasal Anatomy and
Physiology P.359- 370
 Diseases of Ear Nose and Throat 6thed, Chapter 24, Physiology of the Nose, P. 140 -
143
 Online references