2 Functions of nose Respiration Air conditioning of inspired air Protection of lower airwayVentilation & drainage of P.N.S.Olfaction: increased on sniffingNasal resistanceVocal resonanceNasal reflexes
3 Functions of P.N.S. (?) Air conditioning of inspired air Vocal resonanceThermal insulators for orbit & cranium from fluctuating nasal temperatureLightens weight of skull
4 RespirationInspiration: 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.
6 Air conditioningFiltration: particles > 3 μm in inspired air are trapped by nasal vibrissaeTemperature control: Heat exchange b/w blood in cavernous venous sinusoids of turbinates & inspired air, by radiationHumidification: by secretions of nasal & P.N.S. mucosa; for better ciliary function
7 Protection of lower airway 1. Muco-ciliary blanket: traps pathogens ininspired air > 0.5 μm & transports them tonasopharynx for swallowing2. Sneezing: protects against irritants3. Lysozyme: kills bacteria & viruses4. Immunoglobulins A & E: for bacteria5. Interferon: for protection against virus
8 Muco-ciliary blanketGoblet 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
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.
19 Nasal resistanceNasal 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 vestibuleNasal valve (maximum contribution)Nasal turbinates
21 Nasal valveAnterior 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 mm2 on each side. It is narrowest part of upper respiratory tract. Cottle’s test checks valve patency.
26 Vocal resonanceNasal cavity & paranasal sinus cavity provide vocal resonance for nasal consonants M, N & nGDe-nasal voice is seen in nose block. Nasal consonants M, N & nG are uttered as B, D & G respectively
36 Olfactory neural pathway Olfaction is the only sensation to reach cerebral cortex directly without first relaying at thalamusOlfactory pathway incorporates limbic system & is concerned with emotional behaviour, mood & recent memory
39 Olfactory dysfunction types 1. Anosmia: absence of olfactory sensation2. Hyposmia: decreased olfactory sensation3. Parosmia / cachosmia: perception of apleasant odour as unpleasant odour4. Phantosmia: perception of odour inabsence of olfactory stimulus5. Hyperosmia: increased olfactory sensation6. Olfactory agnosia: unable to identify odour
40 Tests for olfactory disorders 1. Tests for nasal airflowa. Simple Rhino-manometry: anterior & posteriorb. Acoustic Rhino-manometry: uses sound waves2. Tests for ciliary functiona. Saccharine test3. Tests for olfaction4. CT scan & MRI of PNS & brain
41 Rhino-manometryTest 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.
47 Saccharin Test Evaluates ciliary function by measuring time taken for adrop of saccharin to be tastedin throat when applied toinferior turbinate (anterior tip).Normal speed = 5-10 mm / min.Normal time = 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, eachcontaining 10 stimuli for smell. All 40 stimuli arepresented in rectangular areas. Subjects scratch& then sniff them. They are required to pick 1from 5 multiple choices present for each stimuli.
53 Counseling & Precautions 1. Beware of the following:Spoiled foodExplosive gases: use electric stovesSmoke & fire: use detectors with visual alarmsSocially unacceptable odors2. Food enjoyment: flavor additives