physiology of nose

1. Dr. Anunya Reddy
Dept of E.N.T

2.  Nose contains organ of smell and respiration.
 It warms ,cleans and humidifies the inspired
air, cools and remove water from the expired
air.
 Also add quality to speech production.
 Although nose is a paired structure divided
coronally in to two chambers, it act as a
functional unit.

3.  Breathing
 Air conditioning of inspired air
 Protection of lower airway
 Ventilation and drainage of p.n.s
 Olfaction
 Nasal resistance
 Vocal resonance
 Nasal reflexes

4.  Nose is the natural pathway for breathing ,mouth
breathing is acquired through learning.
 Newborn infant with choanal atresia may
asphyxiate to death if urgent measures are not
taken to relieve it.
 Nose also permits breathing and eating to go on
simultaneously.
 Inspired air passes upward in a narrow stream
medial to middle turbinate and then downwards
and backwards in the form of an arc, and thus
respiratory air currents are restricted to the
central part of nasal cavity

5.  During expiration ,air currents follows the
same course as inspiration but the entire
current is not expelled directly through the
nares.
 Friction offered at limen nasi converts in to
eddies under cover of inferior and middle
turbinates and this ventilates the sinuses
through the ostia.

6.  Under autonomic nervous system nasal
mucosa undergoes rhythmic cyclical
congestion and decongestion, thus controlling
the air flow through nasal chambers.
 The changes are produced by vascular activity,
particularly the volume of blood on the venous
sinusoids (capacitance vessels).
 When one nasal chamber is working, total
nasal respiration, equal to that of both nasal
chambers is carried out by it.

7.  In modern western literature it was first
described by German physician Richard Kayser
in 1895.
 Cycle lasts 2-12 hours(average 2.5-4 hours).
 FACTORS AFFECTING:
 Allergy, infection, exercise, hormones,
pregnancy, fear and emotions, including
sexual activity.

9.  Nose is called “air conditioner” for lungs.
 Adjusts temperature and humidity of inspired air
before it passes on to the lungs.
 Temperature control of the inspired air is
regulated by large surface of nasal mucosa
,particularly in region of middle and inferior
turbinates and adjacent part of the nasal
septum(highly vascular with cavernous venous
spaces).
 This makes an efficient “radiator” mechanism to
warm up the cold air .Inspired air which may be at
20ºC or 0º C or even at subzero temperature is
heated to near body temperature in one fourth of
seconds.

10.  Similarly hot air is cooled to the body
temperature.
 HUMIDIFICATION:
 Humidity of atmospheric air varies depending on
climatic conditions.
 Nasal mucosa adjusts the relative humidity of the
inspired air to 75% or more.
 Moisture is essential for integrity and function of
the ciliary epithelium.
 Humidification also has a significant effect on
gas exchange in the lower airways.

11. Water Production
 Water comes from serous glands which are
extensive throughout the nose.
 During nasal cycle, secretions are lower on
the more obstructed side.
 Additional water comes from the expired air,
naso lacrimal duct and oral cavity.

12.  Filtration and Purification:Particles >3μm are
trapped by nasal vibrissae.
 Particles <0.5 μm seem to pass through nose
into lower airways without difficulty.
 Mucociliary blanket traps pathogens in inspired
air >0.5μm and transports them to nasopharynx
for swallowing.
 Sneezing protects against irritants.

13.  Composed of two elements-mucus and water.
 Glycoprotein -produced by mucus glands.
 water and ions –produced mainly from serous
glands and indirectly from transudation from
capillary network.
 2 secretory cell types in mixed nasal glands -
mucus and serous cells.
 Glycoprotein found in mucous are produced in
goblet cells(within the epithelium) and
glandular mucus cells.
 Submucosal glands are mixed and arranged
around ducts.

14.  Anterior part of the nose contain serous
gland only in vestibular region –produce a
copious watery secretion when stimulated.
 Sinuses has fewer goblet cells and mixed
glands.

15.  Water and ions from transudation.
 Glycoprotein:
sialomucins,fucomucins,sulphomucins.
 Enzymes : lactoferrin,lysozymes.
 Circulatory proteins: complement, -2
macroglobulin,c reactive protein.
 Immunoglobulins: igA,igE,igG,igM,igD.
 Cells:surfaceepithelium,basophils,eosinophils,leukocy
tes.

16.  ULTRA STRUCTURE
 Found on the surface of cells in the respiratory
tract.
 Function:to propel mucus backwards in the
nose towards the nasopharynx.
 All cilia have the same ultrastructure although
nasal cilia are relatively short at 5μm ,with up to
200 per cell.
 A cilium has a surface membrane.

17.  Nine 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 pair also have inner and outer dynein
arms,which consist of an ATPase ,which lost
in kartagener’s syndrome.
• Microtubules become the basal body in the
cell-the outer body become triplets and the
inner pair disappear.
• Nasal mucus film is in two layers, one upper
more viscous layer and lower more watery
layer in which cilia can move more freely.

19.  MUCO-CILIARY BLANKET:
 Goblet cells in nasal mucosa secrete a
mucous blanket; moves backward like a
conveyer belt in to nasopharynx
 It consist of
 Superficial mucus or gel layer
 Deep serous and sol layer

20.  Beat frequency is between 7 and 16Hz at body
temperature,it remain constant between 32 and 40º C.
 Beat consist of a rapid propulsive stroke and a slow
recovery phase.
 Propulsive phase: cilia is straight and tip points in to
the viscous layer of the mucous blanket.
 Recovery phase: cilia is bent over the aqueous layer.
 Energy is produced by conversion of ATP to ADP by
ATPase of the dynein arms –dependent of mg2+ ions.

21.  ATP is generated by the mitochondria near the
cell surface next to the basal bodies of the cilia.
 Mucus blanket is propelled backwards by
metachronous movement of cilia-only those at
the right angles to the direction of flow are in
phase.
 Mucus flows from the front of the nose
posteriorly.
 Mucus from the sinuses joins that flowing on the
lateral wall ,with most mucus going through the
middle meatus.
 Most passes around the eustachian orifice and it
is then swallowed.

25.  Dry atmosphere(absence of humidity)
 Smoking
 Air pollutants and nasal irritants
 Infections
 Excessive summer above 45˚c and excessive
cold below 10˚c
 Hypoxia
 Solutions above 5% and below 0.2%
 Drugs

26.  Inspiration creates negative pressure in nasal
cavity thus sucks the air out from paranasal
sinuses via their ostium.
 Expiration creates positive pressure in nasal
cavity thus ventilates the para nasal sinuses via
there ostium.

28.  Nose forms a resonating
chamber for certain
consonants in speech.
 In phonating nasal
consonants(M/N/NG) sound
passes through the
nasopharyngeal isthmus and
is emitted through the nose.
 Many nasal condition affect
the quality of voice by
blocking the passage of air in
expiration.

29.  When nose( or nasopharynx) is
blocked,speech become denasal, i.e, M/N/NG
are uttered as B/D/G respectively.
 Rhinolalia clausa-too little air escapes from
the nose.
 Rhinolalia aperta –too much air escapes.
 Sinuses have no effect on modifying voice.

30.  This function of nose is less developed in human
beings, plays most important role in behavior
and reflex responses of lower animals.
 “man concentrate on audiovisual aspects,and yet
much money is spent modifying body odors”.
 Olfactory compound need high water and lipid
solubility.
 Solute in the mucus is presented to the sensory
mucosa.

31.  OLFACTORY AREA
 Olfactory mucosa is located in roof of nasal
cavity and adjacent area of superior turbinate
and upper part of septum.
 Area :200-400mm² with a dencity
of approx 5×10 receptor cells/mm²
 Receptor cells have modified cilia
which increase surface area and project like
normal cilia in to the mucus.
 They are derived from basal cells
,regenerating every month.

32.  STIMULUS
 Odours→react with lipid bi layer of receptor cells
at specific sites→causes outflow of k+ and cl-
→causes depolarization of cells.
 RECEPTORS
 Olfaction is mediated by G-protein coupled
receptors in the cells which interact with a specific
adenyl cyclase within neuroepithelium.
 Adrenergic and muscarinic antagonists –block
some odours.
 THRESHOLD AND ADAPTAION
 Olfactory responses show both variations in
thresholds and adaptation.

33.  Threshold concentration can vary depending on
the chemical nature of the stimuli.
 The threshold of perception is lower than
identification: a smell is sensed before it is
recogniszed.
 Threshold depend on level of inhibitory activity
,which are generated by higher centres.(some animals
,particularly dogs ,have lower thresholds).
 ADAPTATION
 Olfactory responses shows marked adaptation.
 Adaptation is peripheral and central phenomenon.

34.  Other factors affecting threshold:
 Change in nasal mucus and its pH.
 Age –decreases the threshold.
 Hormones –(sex hormones)-increases the
threshold.
DISCRIMINATION
 Man is better at detecting the pleasantness of an
odour rather than recognizing it.
 If two odours are mixed, resulting intensity is
always less than the sum of the individually
perceived intensities and dominated by the
stronger component.

35.  QUALITATIVE OLFACTOMETRY:
 Olfactory sense is assessed by taking a
solution or extract before the patients nose.
 Following primary odours are usually tested.
1. Etherial –ether
2. Camphoraceous-camphor
3. Flora(l)-salicyldehyde
4. Musky-phenyl acetic acid
5. Minty-mint
6. Pungent-formalin
7. Putrid-thiophenol

36.  QUANTITATIVE OLFACTOMERY
 Measurement of olfactory sense done with an
olfactometer.
 Gives an idea about qualitative defects of
olfaction.
 Reading is taken as number of olfacts.
 Olfactometry gives information about
following
1. The extent of the field of smell.
2. Gives an idea about pts acuity of smell.
3. Possible parosmia(perverted smell)

37.  Several standardized and practical
psychophysical tests have been developed over
the last several years, including a number of brief
self-administered tests ranging from the ,three-
item Pocket Smell Test to the 40-item University
of Pennsylvania Smell Identification Test (UPSIT).
 The UPSIT is commercially known as the Smell
Identification Test and is the most widely used
olfactory test.
 The UPSIT can be self administered in 10-15
minutes by most patients in the waiting room,
and scored in less than a minute by nonmedical
personnel.

38.  This test consists of four booklets containing ten
microencapsulated (scratch and sniff') odourants
.
 Test results are in terms of a percentile score of a
patient's performance relative to age- and sex-
matched controls, and olfactory function can be
classified on an absolute basis into one of six
categories: normosmia, mild microsmia,
moderate microsmia, severe microsmia,anosmia
and probable malingering.
 Clinical imp of testing is to distinquish patients
who have a disorder from those who malinger
and seek compensation.

40.  Air enters through the nostrils.
 As air passes through the nasal cavity ,it
passes by the olfactory mucosa that lines the
superior aspect of the cavity.
 “This is where smell begins”.
 small molecules of smell “olfactory ligands”
stick to olfactory mucosa and diffuse across
and triggering the cascade of events eventually
ends with sensation of smell.

42. Air passes in to the nasal cavity ,and trickles
around the nasal cavity
Smell molecules stick to olfactory mucosa(epithelial
tissue located at sup.border of nasal cavity)
Olfactory mucosa is lined by olfactory mucus with
olfactory receptor neurones with in it, which has” cilia”
finger like projections extents down to mucus where
smell molecules binds

43. Olfactory receptor neurons also extends
superiorly up through cribiform plate,after
passing it olfactory neurons joins olfactory
bulb
Olfacory receptor neurones synapes to other
neuron with in olfactory bulb,axons of this
neuons joins togeher to form olfactory tract
which also knows as olfactory nerve(CN 1)
Olfactory tract extends in to higher center of
brain to give individual sense of smell.

45. Cilia and mucus layer
Bowmens gland
Supporting
epith.cells