Anatomy and Physiology of

Nose and Paranasal Sinuses

Dr. Krishna Koirala

External Nasal Framework

• Nasal Bone

• Frontal Process of Maxilla

• Upper Lateral Nasal Cartilage

• Lower Lateral Nasal (Alar) Cartilage

• Septal Cartilage

• Lesser Alar (Sesamoid) Cartilages

Internal Nose• Openings: Anterior nares and posterior

nares (Choana)

• Vestibule of nose: lined by skin and

containing hair follicles

• Nasal cavity proper: Lateral Wall ,

Medial Wall (Septum) , Roof , Floor

1. Septal cartilage

2. Ethmoid plate

3. Vomer

4. Palatine crest

5. Maxillary crest

6. Vomeronasal cartilage

7. Medial alar crus

8. Upper lateral cartilage

9. Nasal bone crest

10. Frontal spine

11. Sphenoid rostrum

12. Membranous septum

Lateral Nasal Wall• 3 - 4 bony conchae are covered with mucosa to

form the turbinates

• Space below and lateral to turbinate is called

meatus

• Middle meatus contains a round bulla

ethmoidalis separated from uncinate process by

hiatus semilunaris that leads to a funnel

shaped ethmoidal infundibulum

Meatal Drainage1. Inferior meatus: Nasolacrimal duct

2. Middle meatus: Frontal , anterior ethmoid , maxillary

3. Superior meatus : Posterior ethmoid

4. Spheno - ethmoidal recess: Sphenoid

Ostio-meatal Complex

Complex micro-architectural pathway in ethmoid labyrinth that drains anterior group of paranasal sinuses

• OMC Consists of

– Frontal recess + ethmoid infundibulum

+ hiatus semilunaris + uncinate

process + bulla ethmoidalis + middle

meatus

• O.M.C. pathology leads to infection of all

anterior paranasal sinuses (Naumann)

Variants in O.M.C. Concha bullosa (pneumatized M.T.)

Paradoxically curved middle turbinate

Medially turned ( bent) uncinate process

Large bulla ethmoidalis

Haller’s cell ( orbital floor)

Agger nasi cell ( anterior to M.T.)

Mucosal pathology

Concha Bullosa

Paradoxically curved M.T.

Large bulla ethmoidalis

Blood Supply1. Sphenopalatine artery (main artery)

2. Greater palatine artery

3. Superior labial artery

4. Anterior Ethmoidal artery

5. Posterior Ethmoidal artery

1, 2, 3 & 4 form Kiesselbach’s plexus over Little’s area on anterior septum

Venous Drainage• Ethmoidal veins: ophthalmic veins

cavernous sinus

• Sphenopalatine vein: pterygoid plexus maxillary vein 

• Woodruff’s venous plexus : present on lateral wall near the posterior end of middle turbinate

• Retro - columellar vein: behind the columella

Sensory Nerve Supply

• Long & short Nasopalatine nerves

• Greater palatine nerve

• Infra-orbital nerve branches

• Anterior ethmoidal nerve

• Olfactory nerve

Autonomic Nerve Supply• Deep petrosal nerve (sympathetic) +

greater superficial petrosal nerve (para-sympathetic) Vidian nerve pterygo-palatine ganglion nasal glands

• Sympathetic stimulation vasoconstriction + ed nasal secretions

• Para-sympathetic stimulation vasodilatation + ed nasal secretions

Lining Epithelium

• Skin: on the nasal vestibule

• Olfactory epithelium: upper 1/3rd of nasal

cavity above the superior turbinate

• Respiratory epithelium (pseudo-stratified

ciliated columnar): rest of nasal cavity +

paranasal sinus

Lymphatic Drainage 1. External nose & anterior nasal cavity

Submandibular lymph nodes

2. Remaining nasal cavity

Upper deep cervical lymph nodes

3. Nasal roof (dangerous area of nose)

Subarachnoid space along the olfactory nerve

4. P.N.S. Retropharyngeal & J.D. node

Paranasal Sinuses• Anterior group

Frontal

Anterior ethmoidal

Maxillary

• Posterior group

Posterior ethmoidal

Sphenoid

Development of P.N.S.Appear

first First X-ray appearanc

e

Reach adult size

byMaxillary At birth 4 mth 15 yr

Ethmoidal

At birth 1yr 12 yr

Sphenoid 2 yr 4 yr 18 yr

Frontal 4 yr 6 yr 15 yr

Physiology of Nose & PNS,

Olfaction

Functions of Nose• Respiration

– Heat exchange– Humidification– Filtration– Nasal resistance– Nasal fluids & ciliary function – Nasal neurovascular reflexes– Voice modification

• Olfaction

Functions of PNS

• Vocal resonance• Air conditioning of the inspired air• Pressure damper• Reduction of skull weight• Floatation of skull in water• Increasing the olfactory area

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

• Results in awareness of breathing & ventilation of paranasal sinus

Respiration

Air conditioning• Filtration : Particles > 3 μm in inspired air

are trapped by nasal vibrissae• Temperature control

– Heat exchange between blood in cavernous venous sinusoids of turbinates & inspired air, (radiation)

• Humidification – secretions of nasal & PNS mucosa;

for better ciliary function

Protection of lower airway• Muco-ciliary blanket: traps pathogens in inspired

air > 0.5 μm & transports them to nasopharynx for swallowing

• Sneezing: protects against irritants• Lysozyme: kills bacteria & viruses• Immunoglobulins A & E :protection against

bacteria• Interferon: for protection against virus

Muco-ciliary blanket• Goblet cells in nasal mucosa

secrete a mucous blanket that moves backwards like a conveyer belt into the nasopharynx

• Consists of– Superficial mucous or gel layer– Deep serous or sol layer

Muco-ciliary blanket

GelSol

Ciliary cycle

Factors decreasing mucociliary function• Dry atmosphere (absence of humidity)• Smoking, air pollutants & nasal irritants• Infection• Extremes of temperature• Hypoxia• Drugs: anesthetics, sedatives, topical nasal

decongestants, beta blockers

Ventilation of PNS• Inspiration

– Negative pressure created in nasal cavity sucks out air from paranasal sinuses via their ostium

• Expiration – Eddies within nasal cavity create

positive pressure that ventilates paranasal sinuses via their ostium

Ventilation of PNS

Drainage of sinuses

• Anterior sinuses drain in lateral pharyngeal gutter

• Posterior sinuses drain over posterior pharyngeal wall

Nasal resistance

Nasal resistance to expired air ( by nasal valve) keeps positive pressure in respiratory tract & prevents alveolar collapse

Vocal Resonance• Nasal cavity & paranasal sinuses provide

vocal resonance for nasal consonants M, N, nG

• De-nasal voice( Hyponasal Voice) – Seen in nasal obstruction

– Nasal consonants M, N & nG pronounced as B, D & G respectively

Nasal Reflexes

• Smell reflex : Increases secretions of saliva & gastric juice

• Naso-pulmonary reflex : Chronic, severe nasal obstruction leads to increased pulmonary resistance and pulmonary hypertension

• Sneeze reflex : Protection against F.B., irritants

Nasal Cycle• Reflex, periodic alternation in nasal airflow

resistance between 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 4-12 hours

Factors modifying nasal cycle

• Temperature & humidity of surrounding air • Head position • Body temperature • Physical activity • Emotional & psychological status• Hypothyroidism & hyperthyroidism • Nasal decongestants & anti- hypertensives

Olfaction

Olfactory area of nose

•Located on the roof of the nasal cavity•Superior part of the nasal septum •Cribriform plate •Superior turbinate •Upper part of middle turbinate

Olfactory neural pathway

Olfactory receptors on nasal mucosa Olfactory

nerve bundles (20) 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

• 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

Causes of Olfactory dysfunction

1. Upper respiratory viral infection (30 %)2. Idiopathic (25 %)3. Head trauma (20 %)4. Obstructive sinonasal disease (15 %) Rhino-sinusitis , nasal polyp , neoplasm5. Neurologic & Psychiatric diseases6. Intra-cranial neoplasm7. Toxic chemicals & surgical trauma

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

Types of Olfactory dysfunction

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

Olfactory function tests1. 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 (automated)

Manual Threshold Olfactometry

Dynamic Threshold Olfactometry

University of Pennsylvania Smell Identification Test (UPSIT)

• Most commonly used test of smell worldwide• 4 booklets of 10 microencapsulated odors stimuli• Scratch and sniff format• Four responses accompanying each odor• Forced choice design• Scores are compared to normal (sex- and age-

related)

Smell Identification Test sample

Results36 – 40 :Normal 16-35 :Partial anosmia6-15 :Total anosmia 0-5 :Malingering

Thank you !