Presentation on theme: "Physiology of Nose & P.N.S. Dr. Vishal Sharma. Functions of nose 1.Respiration 2.Air conditioning of inspired air 3.Protection of lower airway 4.Ventilation."— Presentation transcript:
Physiology of Nose & P.N.S. Dr. Vishal Sharma
Functions of nose 1.Respiration 2.Air conditioning of inspired air 3.Protection of lower airway 4.Ventilation & drainage of P.N.S. 5.Olfaction: increased on sniffing 6.Nasal resistance 7.Vocal resonance 8.Nasal reflexes
Functions of P.N.S. (?) 1.Air conditioning of inspired air 2.Vocal resonance 3.Thermal insulators for orbit & cranium from fluctuating nasal temperature 4.Lightens weight of skull
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.
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
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
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
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
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.
Ventilation of P.N.S.
Drainage of sinuses
Anterior sinuses drain in lateral pharyngeal gutter Posterior sinuses drain over posterior pharyngeal wall
Drainage of sinuses
Nasal resistance Nasal resistance to expired air keeps positive pressure in respiratory tract & prevents alveolar collapse
Nasal Resistance Nose provides % of total airway resistance Nasal resistance is provided by 3 areas: Nasal vestibule Nasal valve (maximum contribution) Nasal turbinates
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 mm 2 on each side. It is narrowest part of upper respiratory tract. Cottle’s test checks valve patency.
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
Nasal reflexes 1. Smell reflex: increases secretions of saliva & gastric juice 2. Naso-pulmonary reflex: Chronic, severe nasal obstruction increased pulmonary resistance pulmonary hypertension 3. Sneeze reflex: protection against F.B.
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)
Factors modifying nasal cycle Temperature & humidity of surrounding air Head position Body temperature Physical activity Emotional & psychological status Hypothyroidism & hyperthyroidism Nasal decongestants & anti-hypertensives
Olfactory area of nose
Olfactory neural pathway Olfactory receptors on 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 1 0 & 2 0 Olfactory cortex + hypothalamus + hippocampus + amygdala.
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
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
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
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.
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 = min.
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)
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.