Physiology of Nose & P.N.S.

1. Physiology of Nose & P.N.S. Dr. Vishal Sharma

2. Functions of nose • Respiration • Air conditioning of inspired air • Protection of lower airway • Ventilation & drainage of P.N.S. • Olfaction: increased on sniffing • Nasal resistance • Vocal resonance • Nasal reflexes

3. Functions of P.N.S. (?) • Air conditioning of inspired air • Vocal resonance • Thermal insulators for orbit & cranium from fluctuating nasal temperature • Lightens weight of skull

4. Respiration Inspiration: air current passes along mid-portion of nasal cavity in lamellar flow. Expiration:resistance of nasal valve & turbinates leads to formation of eddy current in expired air. This results in awareness of breathing & ventilation of paranasal sinus.

5. Respiration

6. Air conditioning Filtration: particles > 3 μm in inspired air are trapped by nasal vibrissae Temperature control:Heat exchange b/w blood in cavernous venous sinusoids of turbinates & inspired air, by radiation Humidification: by secretions of nasal & P.N.S. mucosa; for better ciliary function

7. Protection of lower airway 1. Muco-ciliary blanket:traps pathogens in inspired air > 0.5 μm & transports them to nasopharynx for swallowing 2. Sneezing: protects against irritants 3. Lysozyme:kills bacteria & viruses 4. Immunoglobulins A & E: for bacteria 5. Interferon:for protection against virus

8. Muco-ciliary blanket • Goblet cells in nasal mucosa secrete a mucous blanket; moved backwards like a conveyer belt into nasopharynx. • Consists of:  Superficial mucous or gel layer  Deep serous or sol layer

9. Muco-ciliary blanket

10. Muco-ciliary blanket

11. Ciliary cycle

12. Factors decreasing mucociliary function • Dry atmosphere (absence of humidity) • Smoking, air pollutants & nasal irritants • Infection • Extremes of temperature • Hypoxia • Drugs: anaesthetics, sedatives, topical nasal decongestants, beta blockers

14. Ventilation of P.N.S. • 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.

15. Ventilation of P.N.S.

16. Drainage of sinuses

17. Drainage of sinuses • Anterior sinuses drain in lateral pharyngeal gutter • Posterior sinuses drain over posterior pharyngeal wall

18. Drainage of sinuses

19. Nasal resistance Nasal resistance to expired air keeps positive pressure in respiratory tract & prevents alveolar collapse

20. Nasal Resistance • Nose provides 50-60 % of total airway resistance • Nasal resistance is provided by 3 areas: • Nasal vestibule • Nasal valve (maximum contribution) • Nasal turbinates

21. Nasal valve Anterior nasal valve (ostium internum)is located at limen nasi, 1.5 cm posterior to anterior nares.Consists of inferior margin of upper lateral nasal cartilage + anterior end of inferior turbinate + adjacent nasal septum.Cross-section of airway here is 20-40 mm2 on each side.It is narrowest part of upper respiratory tract. Cottle’s test checks valve patency.

26. Vocal resonance • Nasal cavity & paranasal sinus cavity provide vocal resonance for nasal consonants M, N & nG • De-nasal voice is seen in nose block. Nasal consonants M, N & nG are uttered as B, D & G respectively

27. Nasal reflexes 1. Smell reflex: increasessecretions of saliva & gastric juice 2. Naso-pulmonary reflex:Chronic, severe nasal obstruction increased pulmonary resistance  pulmonary hypertension 3. Sneeze reflex: protection against F.B.

28. Nasal Cycle

29. Nasal Cycle • Reflex, periodic alternation in nasal airflow resistance b/w two nasal cavities • Regulated by autonomic nervous system • Due to congestion & decongestion of venous sinusoids of inferior turbinates & anterior nasal septum • Each cycle lasts for 2-12 hrs (average 2-4 hrs)

31. Factors modifying nasal cycle  Temperature & humidity of surrounding air • Head position • Body temperature • Physical activity • Emotional & psychological status • Hypothyroidism & hyperthyroidism • Nasal decongestants & anti-hypertensives

32. Olfactory area of nose

33. Olfactory neural pathway Olfactory receptorson nasal mucosa  20 Olfactory nerve bundles  synapse with Mitral & Tufted cells in Olfactory bulb  Axons unite to form Olfactory tract  flattens distally to form Olfactory trigone  trifurcates into Olfactory striae  synapse with 10 & 20 Olfactory cortex + hypothalamus + hippocampus + amygdala.

34. Olfactory neural pathway

35. Olfactory neural pathway

36. Olfactory neural pathway • Olfaction is the only sensation to reach cerebral cortex directly without first relaying at thalamus • Olfactory pathway incorporates limbic system & is concerned with emotional behaviour, mood & recent memory

37. Olfactory dysfunction causes 1. Upper respiratory viral infection (30 %) 2. Idiopathic (25 %) 3. Head trauma (20 %) 4. Obstructive sino-nasal disease (15 %)  Rhino-sinusitis  Nasal polyp / neoplasm 5. Neurologic & Psychiatric diseases 6. Intra-cranial neoplasm 7. Toxic chemicals & surgical trauma

38. Classification • Conductive loss: obstruction of nasal passages • chronic nasal inflammation, polyposis • Sensorineural loss: damage to neuroepithelium • viral infection, airborne toxin • Central olfactory neural loss: C.N.S. damage • tumors, neurodegenerative disorders

39. Olfactory dysfunction types 1. Anosmia: absence of olfactory sensation 2. Hyposmia:decreased olfactory sensation 3. Parosmia / cachosmia: perception of a pleasant odour as unpleasant odour 4. Phantosmia:perception of odour in absence of olfactory stimulus 5. Hyperosmia: increased olfactory sensation 6. Olfactory agnosia:unable to identify odour

40. Tests for olfactory disorders 1. Tests for nasal airflow a. Simple Rhino-manometry:anterior & posterior b. Acoustic Rhino-manometry: uses sound waves 2. Tests for ciliary function a. Saccharine test 3. Tests for olfaction 4. CT scan & MRI of PNS & brain

41. Rhino-manometry • Test of nasal function, measures air pressure & rate of nasal airflow during respiration. These are used to calculate nasal airway resistance. • anterior rhino-manometry: pressure sensor placed at tip of each nostril in turn. • posterior rhino-manometry:pressure sensor (small plastic tube) placed behind nasal cavity.

43. Anterior Rhino-manometry

44. Posterior Rhino-manometry

45. Rhinogram

46. Acoustic rhino-manometry

47. 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.

48. Olfactory function tests 1. Supra-threshold test: only identifies odour  Smell bottles  Smell Identification Test (S.I.T.) 2. Threshold Olfactometry: measures weakest perceptible odour with help of serial dilution  Manual  Dynamic (automatic)

49. University of Pennsylvania 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 & then sniff them. They are required to pick 1 from 5 multiple choices present for each stimuli.

50. 36 - 40 normal; 16 - 35 partial anosmia 6 - 15 total anosmia; 0 - 5 malingering