DR MANPREET SINGH NANDA PROFESSOR ENT

2.  Respiration
 Protection of lower respiratory tract
 Vocal resonance
 Olfaction
 Drainage of secretions
 ET function
 Provides beautiful shape to the face

3.  Humans are obligatory nasal breathers – 1st six
months, adults 85% natural nose breathers
 Mouth breathing – pathological/ during exercise
 Nasal airway resistance
 External nasal valve – vestibule – 1/3rd of
resistance
 Internal nasal valve – limen nasi - more than 50%
of resistance
 Ant end of inf and middle turbinate – increase or
decrease in size (erectile tissue) – contribute to
resistance

4.  Low resistance during inspiration, high -
expiration
 Factors affecting nasal resistance – age
(max in infants), posture, drugs
(decongestants and anti hypertensives),
temp of surrounding air (cold air – high
resistance)
 Emotional and psychological problems
regulate the erectile tissues
 Endocrinological disorders – hypothyroidism,
hyperthyroidism, pregnancy

5.  Air flow – between turbinates and septum,
rarely below inf turbinate and above sup
turbinate
 Inspiratory air current
 Pass vertically up the ant nares, at nasal valve
takes a laminar pattern
 Inspiratory air contains allergens and bacteria
 Uncinate process protect the sinus by diverting it
 Expiratory air current
 Turbulent flow, sterile
 Eddies are produced under middle and inf
turbinate so sinuses are ventilated as high
resistance to air flow

7.  Nasal cycle
 Physiological cycle of alternating nasal
congestion and decongestion between two
nasal cavities
 Duration of cycle – 2-12 hrs
 Under control of ANS
 Affected by allergy, infection, emotion,
exercise, hormones – pregnancy and puberty,
drugs, sexual activity

8.  Filtration
 Vibrissae prevents large particles from passing in
(upto 3 micro m)
 Mucus filters finer particles like dust, pollen,
bacteria (0.5 – 3 micro m)
 Less than 0.5 micro m can enter lower airway
 Air conditioning of inspired air
 Counter current mechanism – blood flows in
opposite direction to inspired air – regulates
temperature of inspired air to near body temp
(37 c) – ANS
 Regulates humidity – adjusts around 80%

9.  Muco ciliary clearance
 Resp mucosa coated by thin layer of
secretions called mucous blanket
 This mucous blanket entraps fine particles
during inspiratory phase – takes them to
pharynx – stomach – digested
 Layers of mucous blanket
 Superficial thick mucous layer – viscous - gel
 Deep thin serous layer – watery – sol
 Mucous secreted by nasal glands and goblet
cells

11.  Cilia
 Outer gel layer moves by beating of cilia
 Cilia propels the mucous blanket towards
nasopharynx within 10-20 min
 Cilia beats at 10-20 times per sec
 Cilia acts best at ph 7 which is the ph of
nasal secretions
 Factors affecting cilia beating
 Pollution, smoking, viral and bacterial
infection, heat or cold, humidity, drugs like
adrenaline

12.  Mucous secretions
 Rich in lysozyme – enzyme causing bacterial
destruction
 Contains Ig A and Ig E – neutralizes allergies
and bacterial toxins
 Contains interferon – immunity against URTI
 Contains water and ions
 Contains glycoproteins

13.  Nasal reflexes
 Sneezing
 Protective reflex as a response to irritants
and harmful stimuli which are expelled
 Appetite – good smell of food – reflex
secretions of saliva and gastric juice
 Nasopulmonary and nasobronchial relex –
help in lung function
 Cardio pulmonary reflex – breathing
cessation and bradycardia

14.  Mechanism by which smell is perceived
 Function – regulation of food intake and
perception of flavour and palatability
 Protective functions – detection of toxins and
noxious substances
 Theories
 Stereochemical theory
 Electrochemical theory
 Molecular theory
 Vibration theory

15.  Mechanism
 Olfactory pathway
 Olfactory epithelium present above sup
turbinate high up in nasal cavity
 Olfactory epithelium contains olfactory receptor
cells, basal cells and supporting cells
 Olfactory receptor cells sense the odorant
particles in inspired air
 Central process of these receptor cells form
olfactory nerves
 Olfactory nerves pass through cribriform plate of
ethmoid and end in olfactory bulb

16.  Olfactory bulb contains mitral cells – axon of
these cells form olfactory tract
 Olfactory tract carries sensation to cerebrum
 The region in cerebrum is prepyriform cortex
and amygdaloid nucleus
 Vomero nasal organ of jacobson
 Accessory olfactory tissue
 Behind caudal end of septum 3mm above
nasal floor

18.  VOCAL RESONANCE
 Nasal cavities act as resonators of voice, add
nasal tone to voice
 Outlet for secretions
 Secretions from sinuses drain here
 Lacrimal secretions drain here through NLD
 ET function
 Nose permits equalization of pressure
between external atmosphere and middle
ear cavity – maintains middle ear pressure

19.  Air conditioning of inspired air –
humidification and warming
 Vocal resonance
 Protection of brain and orbit from trauma –
by acting as a buffer
 Mucociliary clearance – secretion of mucus
through ostia to keep nasal cavities moist
 Local immunological defence against microbe
 Reduction of skull weight
 Regulates intra nasal pressure

20.  Ventilation of sinus during expiration
 During expiration – positive pressure in nose
 During inspiration – negative pressure
 Sinus emptied of air during inspiration and
filled with air during expiration (reverse of
lungs)
 Ventilation through ostia

21.  Maxillary sinus
 Secretions start from floor of sinus – walls –
reach ostium at uppermost and posterior part
of sinus
 Drain through ostium – ethmoidal
infundibulum – middle meatus – nasopharynx
 Never drain through accessory ostia
 Frontal sinus
 Secretions inward transport through inter
frontal septum – roof – lateral wall – reach
ostium at floor of sinus

22.  Drain through ostium – frontal recess –
ethmoidal infundibulum – middle meatus
/middle meatus – nasopharynx
 Some secretions recycled from frontal recess
back to sinus through ostium
 Ethmoidal sinus
 Anterior – through middle meatus
 Posterior – through superior/supreme meatus
 Sphenoidal sinus – through spheno ethmoidal
recess

24.  Secretions in nasopharynx
 Infra tubal stream
 Secretions from middle meatus drain below and
in front of tubal orifice (inferior and anterior)
 Supra tubal stream
 Secretions from superior/ supreme meaus and
sphenoethmoidal recess drain drain above and
behind the tubal orifice (superior and inferior)
 During infection can overflow ET orifice
 Finally drain through oropharynx into stomach
and digested