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Chapter 24
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Physiology of Nose
Functions of the nose are classified as:
1. Respiration.
2. Air-conditioning of inspired air.
3. Protection of lower airway.
4. Vocal resonance.
5. Nasal reflex functions.
6. Olfaction.
RESPIRATION
Nose is the natural pathway for breathing. Mouth breathing is an acquired act through learning. So natural is the
instinct to breath through the nose that a 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 quiet respiration, inspiratory air current passes through middle part of nose between the turbinates
and nasal septum. Very little air passes through inferior
meatus or olfactory region of nose (Figure 24.1). Therefore, weak odorous substances have to be sniffed before
they can reach the olfactory area.
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.
Anterior end of inferior turbinate undergoes swelling
and shrinkage thus regulating inflow of air.
nasal cycle. Nasal mucosa undergoes rhythmic cyclical
congestion and decongestion, thus controlling the airflow through nasal chambers. When one nasal chamber
is working, total nasal respiration, equal to that of both
nasal chambers, is carried out by it. Nasal cycle varies
every 2½–4 h and may be characteristic of an individual.
while nasal mucus traps particles as fine as 0.5–3.0 µm.
Particles smaller than 0.5 µm seem to pass through the
nose into lower airways without difficulty.
2. Temperature control of the inspired air. It is regulated
by large surface of nasal mucosa which is structurally
adapted to perform this function. This mucous membrane, particularly in the region of middle and inferior
turbinates and adjacent parts of the septum, is highly
vascular with cavernous venous spaces or sinusoids
which control the blood flow, and this increases or decreases the size of turbinates. This also makes an efficient
“radiator” mechanism to warm up the cold air. Inspired
air which may be at 20°C or 0°C or even at subzero temperature is heated to near body temperature (37°C) in
one-fourth of second, the time that the air takes to pass
from the nostril to the nasopharynx. Similarly, hot air is
cooled to the level of body temperature.
3. Humidification. This function goes on simultaneously
with the temperature control of inspired air. Relative
humidity of atmospheric air varies depending on climatic conditions. Air is dry in winter and saturated
with moisture in summer months. Nasal mucous membrane adjusts the relative humidity of the inspired air
to 75% or more. Water, to saturate the inspired air, is
provided by the nasal mucous membrane which is rich
in mucous and serous secreting glands. About 1000 mL
of water is evaporated from the surface of nasal mucosa in 24 h.
Moisture is essential for integrity and function of the
ciliary epithelium. At 50% relative humidity, ciliary function stops in 8–10 min. Thus, dry air predisposes to infections of the respiratory tract. Humidification also has a
significant effect on gas exchange in the lower airways.
In nasal obstruction, gaseous exchange is affected in the
lungs, leading to rise in pCO2, causing apnoeic spells during sleep; it also decreases pO2.
PROTECTION OF LOWER AIRWAY
AIR-CONDITIONING OF INSPIRED AIR
Nose is aptly called the “air-conditioner” for lungs. It filters and purifies the inspired air and adjusts its temperature and humidity before the air passes to the lungs.
1. Filtration and purification. Nasal vibrissae at the entrance of nose act as filters to sift larger particles like
fluffs of cotton. Finer particles like dust, pollen and
bacteria adhere to the mucus which is spread like a
sheet all over the surface of the mucous membrane.
The front of the nose can filter particles up to 3 µm,
1. Mucociliary mechanism. Nasal mucosa is rich in
goblet cells, secretory glands both mucous and serous. Their secretion forms a continuous sheet called
mucous blanket spread over the normal mucosa. Mucous blanket consists of a superficial mucus layer and
a deeper serous layer, floating on the top of cilia which
are constantly beating to carry it like a “conveyer belt”
towards the nasopharynx (Figure 24.2). It moves at
a speed of 5–10 mm/min and the complete sheet of
mucus is cleared into the pharynx every 10–20 min.
The inspired bacteria, viruses and dust particles are
entrapped on the viscous mucous blanket and then
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Figure 24.1. Physiology of nasal airflow. (A) Inspiration. (B) Expiration.
So efficient are the functions of nose that 500 cubic
feet of air, that we breathe every 24 h, is filtered, humidified, adjusted to proper temperature and cleared of all the
dust, bacteria and viruses before reaching the lungs.
Figure 24.2. “Conveyor belt” mechanism of mucus blanket to entrap and carry organisms and dust particles.
carried to the nasopharynx to be swallowed. Presence
of turbinates almost doubles the surface area to perform this function. About 600–700 mL of nasal secretions are produced in 24 h.
In mammals, cilia beat 10–20 times per second at
room temperature. They have a rapid “effective stroke”
and a slow “recovery stroke.” In the former, the extended cilia reach mucus layer while in the recovery stroke,
they bend and travel slowly in the reverse direction in
the thin serous layer, thus moving the mucous blanket
in only one direction. In immotile cilia syndrome, cilia are defective and cannot beat effectively, leading to
stagnation of mucus in the nose and sinuses and bronchi causing chronic rhinosinusitis and bronchiectasis.
Movements of cilia are affected by drying, drugs (adrenaline), excessive heat or cold, smoking, infections and
noxious fumes like sulfur dioxide and carbon dioxide.
2. 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.
3. Sneezing. It is a protective reflex. Foreign particles
which irritate nasal mucosa are expelled by sneezing.
Copious flow of nasal secretions that follows irritation
by noxious substance helps to wash them out.
The pH of nasal secretion is nearly constant at 7. The
cilia and the lysozyme act best at this pH. Alteration in
nasal pH, due to infections or nasal drops, seriously impairs the functions of cilia and lysozyme.
VOCAL RESONANCE
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. When nose (or nasopharynx) is blocked, speech becomes denasal, i.e. M/N/NG
are uttered as B/D/G, respectively. It is to be remembered that in Hindi alphabets, last letter of a “varga”
( ) is substituted by its third letter. Thus, an affected person utters
for and for . Reverse is true in velopharyngeal
insufficiency where is substituted for .
NASAL REFLEXES
Several reflexes are initiated in the nasal mucosa. Smell
of a palatable food cause reflex secretion of saliva and
gastric juice. Irritation of nasal mucosa causes sneezing.
Nasal function is closely related to pulmonary functions
through nasobronchial and nasopulmonary reflexes.
It has been observed that nasal obstruction leads to increased pulmonary resistance and is reversed when nasal
obstruction is surgically treated. Nasal packing in cases
of epistaxis or after nasal surgery leads to lowering of
pO2 which returns to normal after removal of the pack.
Pulmonary hypertension or cor pulmonale can develop
in children with long-standing nasal obstruction due to
tonsil and adenoid hypertrophy and can be reversed after
removal of the tonsils and adenoids.
OLFACTION
Sense of smell is well-developed in lower animals to give
warning of the environmental dangers but it is comparatively less important in man. Still it is important for
Chapter 24 — Physiology of Nose
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pleasure and for enjoying the taste of food. When nose
is blocked, food tastes bland and unpalatable. Vapours
of ammonia are never used to test the sense of smell as
they stimulate fibres of the trigeminal nerve and cause
irritation in the nose rather than stimulate the olfactory
receptors.
1. olFactory pathways. Smell is perceived in the ol-
factory region of nose which is situated high up in the nasal cavity. This area contains millions of olfactory receptor cells. Peripheral process of each olfactory cell reaches
the mucosal surface and is expanded into a ventricle with
several cilia on it. This acts as a sensory receptor to receive odorous substances. Central processes of the olfactory cells are grouped into olfactory nerves which pass
through the cribriform plate of ethmoid and end in the
mitral cells of the olfactory bulb. Axons of mitral cells
form olfactory tract and carry smell to the prepyriform
cortex and the amygdaloid nucleus where it reaches consciousness. Olfactory system is also associated with autonomic system at the hypothalamic level.
2. disorders oF smell. It is essential for the perception of smell that the odorous substance be volatile and
that it should reach the olfactory area unimpeded. Also
necessary are the healthy state of olfactory mucosa and
the integrity of neural pathways, i.e. olfactory nerves,
olfactory bulb and tract and the cortical centre of
olfaction.
Anosmia is total loss of sense of smell while hyposmia
is partial loss. They can result from nasal obstruction due
to nasal polypi, enlarged turbinates or oedema of mucous
membrane as in common cold, allergic or vasomotor rhinitis. Anosmia is also seen in atrophic rhinitis, a degenerative disorder of nasal mucosa; peripheral neuritis (toxic
or influenzal); injury to olfactory nerves or olfactory bulb
in fractures of anterior cranial fossa; and intracranial lesions like abscess, tumour or meningitis which cause pressure on olfactory tracts.
Parosmia is perversion of smell; the person interprets
the odours incorrectly. Often these persons complain
of disgusting odours. It is seen in the recovery phase of
postinfluenzal anosmia and the probable explanation is
misdirected regeneration of nerve fibres. Intracranial tumour should be excluded in all cases of parosmia.
Sense of smell can be tested by asking the patient to
smell common odours such as lemon, peppermint, rose,
garlic or cloves from each side of the nose separately, with
eyes closed. Quantitative estimation (quantitative olfactometry) requires special equipment.
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Chapter 25
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Diseases of External Nose
and Nasal Vestibule
DISEASES OF EXTERNAL NOSE
CELLULITIS
The nasal skin may be invaded by streptococci or staphylococci leading to a red, swollen and tender nose. Sometimes, it is an extension of infection from the nasal
vestibule. Treatment is systemic antibacterials, hot fomentation and analgesics.
NASAL DEFORMITIES
Saddle Nose
Depressed nasal dorsum may involve bony, cartilaginous
or both bony and cartilaginous components of nasal dorsum (Figure 25.1). Nasal trauma causing depressed fractures is the most common aetiology. It can also result
from excessive removal of septum in submucous resection, destruction of septal cartilage by haematoma or abscess, sometimes by leprosy, tuberculosis or syphilis. The
deformity can be corrected by augmentation rhinoplasty
by filling the dorsum with cartilage, bone or a synthetic
implant. If depression is only cartilaginous, cartilage is
taken from the nasal septum or auricle and laid in a single
or multiple layers. If deformity involves both cartilage and
bone, cancellous bone from the iliac crest is the best. Autografts (taken from the same individual) are preferred to
allografts (taken from other individuals or cadavers). Saddle deformity can also be corrected by synthetic implants
of silicone or teflon but they are likely to be extruded.
Hump Nose
This may also involve the bone or cartilage or both bone
and cartilage. It can be corrected by reduction rhinoplasty
which consists of exposure of nasal framework by careful
raising of the nasal skin by a vestibular incision, removal
of hump and narrowing of the lateral walls by osteotomies to reduce the widening left by hump removal.
Crooked or a Deviated Nose
In crooked nose, the midline of dorsum from frontonasal
angle to the tip is curved in a C- or S-shaped manner. In a
deviated nose, the midline is straight but deviated to one
side (Figure 25.2).
Usually, these deformities are traumatic in origin. Injuries sustained during birth, neonatal period or childhood,
but not immediately recognized, will also develop into
these deformities with the growth of nose. The deviated
or crooked nose can be corrected by rhinoplasty or septorhinoplasty. Aim of these operations is to correct not
only the outer appearance of nose but also its function.
TUMOURS
They may be congenital, benign or malignant (Table 25.1).
1. Congenital Tumours
(a) dermoid cyst (Figure 25.3). It is of two types:
• Simple dermoid. It occurs as a midline swelling under
the skin but in front of the nasal bones. It does not
have any external opening.
• Dermoid with a sinus. It is seen in infants and children
and is represented by a pit or a sinus in the midline
of the dorsum of nose. Hair may be seen protruding
through the sinus opening. In these cases, the sinus
track may lead to a dermoid cyst lying under the nasal
bone in front of upper part of nasal septum or may
have an intracranial dural connection. In those with
intracranial extension, sinus tract passes through the
cribriform plate or foramen caecum and is attached to
dura or has other intracranial connection. Meningitis
occurs if infection travels along this path. Treatment of
such cysts may necessitate splitting of the nasal bones
to remove any extension in the upper part of the nasal
septum. A combined neurosurgical–otolaryngologic
approach is required in those extending intracranially
so as to close simultaneously any bony defect through
which the fistulous tract passed (Figure 25.4).
(b) encephalocele or meningoencephalocele. It is
herniation of brain tissue along with its meninges through
a congenital bony defect. An extranasal meningoencephalocele presents as a subcutaneous pulsatile swelling in
the midline at the root of nose (nasofrontal variety), side of
nose (nasoethmoid variety) or on the anteromedial aspect
of the orbit (naso-orbital variety).
Swellings show cough impulse and may be reducible.
Treatment is neurosurgical; severing the tumour stalk
from the brain and repairing the bony defect through
which herniation has taken place.
(c) glioma. It is a nipped off portion of encephalocele
during embryonic development. Most of them (60%) are
extranasal and present as firm subcutaneous swellings on
the bridge, side of nose or near the inner canthus. Some
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Figure 25.1. Deformities of nose.
Figure 25.4. Rhinophyma.
of them are purely intranasal (30%), while 10% are both
intra- and extranasal. Extranasal gliomas are encapsulated
and can be easily removed by external nasal approach.
2. Benign Tumours
They arise from the nasal skin and include papilloma (skin
wart), haemangioma, pigmented naevus, seborrhoeic kerato-
sis, neurofibroma or tumour of sweat glands.
Rhinophyma or potato tumour is a slow-growing benign tumour due to hypertrophy of the sebaceous glands
of the tip of nose often seen in cases of long-standing
acne rosacea. It presents as a pink, lobulated mass over
the nose with superficial vascular dilation; mostly affects
men past middle age (Figure 25.4). Patient seeks advice
Figure 25.2. Nasal bridge is S-shaped in crooked nose. It is straight
but deviated to one side in deviated nose.
TABLE 25.1 TUMOURS OF EXTERNAL NOSE
Congenital Benign Malignant
• Dermoidcysts
• Encephalocele
• Meningoencephalocele
• Glioma
• Rhinophyma
• Haemangioma
• Pigmentednaevus
• Seborrhoeickeratosis
• Neurobroma
• Sweatglandtumour
because of the unsightly appearance of the tumour, or
obstruction to breathing and vision due to large size of
the tumour. Treatment consists of paring down the bulk
• Basalcellcancer
• Squamouscellcancer
• Melanoma
Figure 25.3. Types of dermoids. (A) A simple dermoid beneath the skin. (B) A dermoid with an external pit or sinus. It lies in front of the septum
and deep to the nasal bones. (C) A dermoid with an intracranial connection to dura. (D) An intradural dermoid.
Figure 25.5. Basal cell carcinoma of the nose.
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Chapter 25 — Diseases of External Nose and Nasal Vestibule
163
of tumour with sharp knife or carbon dioxide laser and
the area allowed to re-epithelialize. Sometimes, tumour is
completely excised and the raw area skin grafted.
3. Malignant Tumours
(a) basal cell carcinoma (rodent ulcer) (Figure 25.5).
This is the most common malignant tumour involving skin
of nose (87%), equally affecting males and females in the
age group of 40–60 years. Common sites on the nose are
the tip and the ala. It may present as a cyst or papulo-pearly
nodule or an ulcer with rolled edges. It is very slow growing
and remains confined to the skin for a long time. Underlying cartilage or bone may get invaded. Nodal metastases
are extremely rare. Treatment depends on the size, location and depth of the tumour. Early lesion can be cured by
cryosurgery, irradiation or surgical excision with 3–5 mm
of healthy skin around the palpable borders of the tumour.
Lesions which are recurrent, extensive or with involvement of cartilage or bone are excised and the surgical defect closed by local or distant flaps or a prosthesis.
(b) squamous cell carcinoma (epithelioma). This
is the second most common malignant tumour (11%),
equally affecting both sexes in 40–60 age group. It occurs
as an infiltrating nodule or an ulcer with rolled out edges
affecting side of nose or columella (Figure 25.6). Nodal
metastases are seen in 20% of cases.
Early lesions respond to radiotherapy; more advanced
lesions or those with exposure of bone or cartilage require
wide surgical excision and plastic repair of the defect. Enlarged regional lymph nodes will require block dissection.
(c) melanoma. This is the least common variety. Clinically, it is superficially spreading type (slow growing) or
nodular invasive type. Treatment is surgical excision.
DISEASES OF NASAL VESTIBULE
FURUNCLE OR BOIL (Figure 25.7)
It is an acute infection of the hair follicle by Staphylococcus aureus. Trauma from picking of the nose or plucking
the nasal vibrissae is the usual predisposing factor.
The lesion is small but exquisitely painful and tender.
Inflammation may spread to the skin of nasal tip and
Figure 25.6. Carcinoma nose.
Figure 25.7. Furuncle right nasal vestibule.
dorsum which become red and swollen. The furuncle
may rupture spontaneously in the nasal vestibule.
Treatment of furuncle consists of warm compresses,
analgesics to relieve pain, and topical and systemic antibiotics directed against staphylococcus. If a fluctuant area
appears, incision and drainage can be done. In no case
should the furuncle be squeezed or prematurely incised
because of the danger of spread of infection to cavernous
sinus through venous thrombophlebitis.
A furuncle of nose may complicate into cellulitis of the
upper lip or septal abscess.
VESTIBULITIS
It is diffuse dermatitis of nasal vestibule. Nasal discharge,
due to any cause such as rhinitis, sinusitis or nasal allergy,
coupled with trauma of handkerchief, is the usual predisposing factor. The causative organism is S. aureus. Vestibulitis may be acute or chronic.
In acute form, vestibular skin is red, swollen and tender;
crusts and scales cover an area of skin erosion or excoriation. The upper lip may also be involved (Figure 25.8).
In chronic form, there is induration of vestibular skin
with painful fissures and crusting.
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Figure 25.8. Acute vestibulitis (left side).
Treatment consists of cleaning the nasal vestibule of all
crusts and scales with cotton applicator soaked in hydrogen peroxide and application of antibiotic-steroid ointment. The latter should always be continued for a few
more days, even after the apparent cure, as the condition
is likely to relapse. A chronic fissure can be cauterized
with silver nitrate. Attention should be paid to the cause
of nasal discharge.
STENOSIS AND ATRESIA OF THE NARES
Accidental or surgical trauma to the nasal tip or vestibule can lead to web formation and stenosis of anterior nares. In Young’s operation, vestibular skin flaps
are raised to create deliberate closure of nares in the
treatment of atrophic rhinitis (see p. 172). Destructive
inflammatory lesions of nose also cause stenosis. Earlier,
several cases of vestibular stenosis resulted from smallpox (Figure 25.9).
Congenital atresia of anterior nares due to noncanalization of epithelial plug is a rare condition.
Stenosis of nares can be corrected by reconstructive
plastic procedures.
Figure 25.9. Stenosis left naris following smallpox.
excised by sublabial approach preserving the integrity
of vestibular skin (Figure 25.10).
2. Papilloma or wart may be single or multiple, pedunculated or sessile. Treatment is surgical excision under local anaesthesia.
3. Squamous cell carcinoma arises from the lateral wall of
the vestibule and may extend into nasal floor, columella and upper lip. It can metastasize to the parotid
and submandibular nodes. Treatment is surgical excision or irradiation.
TUMOURS
1. Nasoalveolar cyst presents a smooth bulge in the lateral wall and floor of nasal vestibule. The cyst can be
Figure 25.10. Nasoalveolar cyst as seen during operation.
Chapter 26
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Nasal Septum and Its Diseases
ANATOMY
Nasal septum consists of three parts:
1. columellar septum. It is formed of columella containing the medial crura of alar cartilages united together
by fibrous tissue and covered on either side by skin.
2. membranous septum. It consists of double layer of
skin with no bony or cartilaginous support. It lies between the columella and the caudal border of septal cartilage. Both columellar and membranous parts are freely
movable from side to side.
3. septum proper. It consists of osteocartilaginous
framework, covered with nasal mucous membrane.
Its principal constituents are (Figure 26.1):
1. the perpendicular plate of ethmoid,
2. the vomer and
3. a large septal (quadrilateral) cartilage wedged between
the above two bones anteriorly. Other bones which
make minor contributions at the periphery are crest
of nasal bones, nasal spine of frontal bone, rostrum of
sphenoid, crest of palatine bones and the crest maxilla,
and the anterior nasal spine of maxilla.
Septal cartilage not only forms a partition between the
right and left nasal cavities but also provides support to
the tip and dorsum of cartilaginous part of nose. Its destruction, e.g. in septal abscess, injuries, tuberculosis or
excessive removal during septal surgery, leads to depression of lower part of nose and drooping of the nasal tip.
Septal cartilage lies in a groove in the anterior edge
of vomer and rests anteriorly on anterior nasal spine.
During trauma, it may get dislocated from anterior nasal
spine or vomerine groove causing caudal septal deviation
or septal spur, respectively. This compromises the nasal
airway. Septal cartilage is also intimately related to the
upper lateral cartilages of nose and is in fact fused with
them in the upper third. For this reason septal deviation
may be associated with deviation of cartilaginous part of
external nose.
Blood Vessels of Nasal Septum (see Chapter 33).
Nerve Supply of Nasal Septum (see Chapter 23).
little’s area or kiesselbach’s plexus. This is the
vascular area in the anteroinferior part of nasal septum
just above the vestibule. Anterior ethmoidal, sphenopalatine, greater palatine and septal branch of superior labial
arteries and their corresponding veins form an anastomosis here. This is the commonest site for epistaxis. This is
also the site for origin of the “bleeding polypus” (haemangioma) of nasal septum.
FRACTURES OF NASAL SEPTUM
AETIOPATHOGENESIS
Trauma inflicted on the nose from the front, side or below can result in injuries to the nasal septum. The septum may buckle on itself, fracture vertically, horizontally
or be crushed to pieces as in a smashed nose. The fractured pieces of septum may overlap each other or project
into the nasal cavity through mucosal tears. Fracture of
the septal cartilage or its dislocation from the vomerine
groove, can result from trauma to the lower nose without
associated fractures of nasal bones. Septal injuries with
mucosal tears cause profuse epistaxis while those with
intact mucosa result in septal haematoma which, if not
drained early, will cause absorption of the septal cartilage
and saddle nose deformity.
“Jarjaway” fracture of nasal septum results from blows
from the front; it starts just above the anterior nasal spine
and runs horizontally backwards just above the junction
of septal cartilage with the vomer (Figure 26.2A).
“Chevallet” fracture of septal cartilage results from
blows from below; it runs vertically from the anterior nasal spine upwards to the junction of bony and cartilaginous dorsum of nose (Figure 26.2B).
TREATMENT
Early recognition and treatment of septal injuries is essential. Haematomas should be drained. Dislocated or fractured septal fragments should be repositioned and supported between mucoperichondrial flaps with mattress
sutures and nasal packing. Fractures of nasal pyramid are
often complicated with fractures of the septum and both
should be treated concomitantly.
COMPLICATIONS
Septum is important in supporting the lower part of the
external nose. If its injuries are ignored, they would result
in deviation of the cartilaginous nose, or asymmetry of
nasal tip, columella or the nostril.
DEVIATED NASAL SEPTUM (DNS)
This is an important cause of nasal obstruction.
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