Physiology of nose

Sandeep singh (89)

Functions of nose1. breathing

2. Air conditioning of inspired air

3. Protection of lower airway

4. Ventilation and drainage of p.n.s.

5. Olfaction

6. Nasal resistance

7. Vocal resonance

8. Nasal refluxes

1.Breathing 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

The nose also permits breathing and eating to go on simultaneously

During expiration, air current follows the same course as during inspiration, but the entire air current is not expelled directly through the nares.

Friction offered at limen nasi converts it into eddies under cover of inferior and middle turbinates and this ventilates the sinuses through the ostia.

•Air current passes along mid portion of nasal cavity in lammellar flow

•Resistance of nasal valve and turbinates leads to formation of eddy currents in expired air

This results in ventilation of paranasal sinus

Nasal cycleUnder autonomic nervous system Nasal mucosa undergoes rhythmic cyclical congestion and decongestion, thus controlling the air flow through nasal chambers.

When one nasal chamber is working, total nasal respiration, equal to that of both nasal chambers, is carried out by it.

cycle lasts 2-12 hours (average 2.5-4 hours)

Nasal cycle

Congested nose

2. Air conditioningNose is called the "air-conditioner" for lungs.

adjusts temperature and humidity of inspired air before it passes it on to the lungs

 Temperature control of the inspired air is regulated bylarge surface of nasal mucosa, particularly in the region of middle and inferior turbinates and adjacent parts of the septum ( highly vascular with cavernous venous spaces)

This makes an efficient "radiator" mechanism to warm upthe cold air. Inspired air which may be at 20°C orO°C or even at subzero temperature is heated to nearbody temperature in one-fourth of second

Similarly, hot air is cooled to the bodytemperature

Humidificationhumidity of atmospheric a ir varies depending on climatic conditions.

Nasal mucosa adjusts the relative humidity of theinspired air to 75% or more.

Moisture is essential for integrity and function of theciliary epithelium

Humidification also has a significant effect on gas exchange in the lower airways.

3. Protection of lower airway

 Filtration and purification.particles >3 um are trapped by Nasal vibrissae

Particles smaller than 0.5 um seem to pass throughthe nose into lower airways without difficulty.

Muco-cilliary blanket traps pathogens in inspired air >0.5 microns and transports them to nasopharynx for swallowing

Sneezing protects against irritants

Muco-ciliary blanketgoblet cells in nasal mucosa secrete a mucous blanket; moved backward like a conveyer belt into nasopharynx

It consists of Superficial mucus or gel layer Deep serous and sol layer

Transportation of trappedd particles to nasopharynx

Factors compromising the mucociliary functions

dry atmostphere

Smoking

Air pollutants and nasal irritants

Infections0

Excessive summer and excessive cold

Hypoxia

Drugs (anaesthetics, sedatives, topical nasal decongestants, beta blockers)

Enzymes and immunoglobulins

Nasal secretions also contain an enzyme called muramidase (lysozyme)which kills bacteria and viruses.

ImmunoglobulIns IgA and IgE, and interferon are also present in nasal secretions and provide immunity against upper respiratory tract infections.

Sneezing

protective reflex.

Foreign particles which irritate nasal mucosa a re expelled by sneezing

Copious flow of nasal secretions that foltows initationby noxious substance helps to wash them out.

4. Ventilation of paranasal sinuses

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

Ventilation during expiration and inspiration

5.Nasal resistance

• Nasal resistance to expired air keeps positive pressure and doesn’t let the alveoli colapse

6.Vocal resonance

Nose forms a resonating chamber for certain consonantsin speech.

In phonating nasal consonants (MINING),sound passes through the nasopharyngeal isthmus andis emitted through the nose.

When nose (or nasopharynx) is blocked, speech becomes denasal, i.e. MININGare uttered as B/D/G respectively

Olfaction

Olfactory area of nose

Olfactory neural pathway

Olfaction is disturbed in

Olfactory disorders are classified as

Types of olfactory dysfunction are…

Thank you