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natural is theinstinct to breath through the nose that a newborninfant with choanalatresia may asphyxiate to death ifurgent measures are not taken to relieve it
Default path of breathing as breathing per mouth is learned laterAir current passes along mid portion of nasal cavity in lammellar flow
Physiology of nose
Physiology of noseSandeep singh (89)
Functions of nose1. breathing2. Air conditioning of inspired air3. Protection of lower airway4. Ventilation and drainage of p.n.s.5. Olfaction6. Nasal resistance7. Vocal resonance8. 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
Nasal cycle Under 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)
2. Air conditioning Nose 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 by large 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 up the cold air. Inspired air which may be at 20°C or O°C or even at subzero temperature is heated to near body temperature in one-fourth of second Similarly, hot air is cooled to the body temperature
Humidificationhumidity of atmospheric a ir varies depending onclimatic conditions.Nasal mucosa adjusts the relative humidity oftheinspired air to 75% or more.Moisture is essential for integrity and function oftheciliary epitheliumHumidification also has a significant effect ongas 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 through the 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 blanket goblet 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 particlesto nasopharynx
Factors compromising themucociliary 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 initation by 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
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 consonants in speech. In phonating nasal consonants (MINING), sound passes through the nasopharyngeal isthmus and is emitted through the nose. When nose (or nasopharynx) is blocked, speech becomes denasal, i.e. MINING are uttered as B/D/G respectively