SENSE OF SMELL

SENSE OF SMELL

AAP2022

By Pn Wan Napisah Wan Omar





Anatomy of nose

Nasal Physiology

 The nose serves as the only means of bringing
warm humidified air into the lungs.

 It is the primary organ for filtering out particles in
inspired air, and it also serves to provide first-line
immunologic defense by bringing inspired air in
contact with mucous-coated membranes that
contain immunoglobulin A (IgA).

 Inspired air is brought high into the nasal cavity to
come in contact with the olfactory nerves,
thereby providing the sense of smell, which is
intimately associated with the taste sensation.

 Dysfunction of any of these systems can lead to
symptoms of nasal dysfunction (eg, congestion,
postnasal drainage, facial pressure, headaches,
sinus infections).

Endoscopic view of right
nasal passage. The turbinate
is mildly swollen, the mucosa
is pale, and the turbinate is
impinging onto nasal septum.

Anatomy and Physiology of the Nose and
Throat

What is the nose?

 Your nose helps you to breathe and to smell. The
inner part of the nose is above the roof of the
mouth. The nose is made up of:

1. External meatus. Triangular-shaped projection in
the center of the face.

2. External nostrils. Two chambers divided by the
septum.

3. Septum. Made up mainly of cartilage and bone
and covered by mucous membranes. The cartilage
also gives shape and support to the outer part of
the nose.

4. Nasal passages. Passages that are lined with
mucous membranes and tiny hairs (cilia) that help
to filter the air.

5. Sinuses. Four pairs of air-filled cavities, also lined
with mucous membranes.





What are sinuses?

 The sinuses are cavities, or air-filled pockets,
near the nasal passage. As in the nasal passage,
the sinuses are lined with mucous membranes.
There are 4 different types of sinuses:

1. Ethmoid sinus. This sinus is located inside the
face, around the area of the bridge of the nose.
It is present at birth, and continues to grow.

2. Maxillary sinus. This sinus is located inside the
face, around the area of the cheeks. It is also
present at birth, and continues to grow.

3. Frontal sinus. This sinus is located inside the
face, in the area of the forehead. It does not
develop until around 7 years of age.

4. Sphenoid sinus. This sinus is located deep in the
face, behind the nose. It does not typically
develop until the teen years





Throat

 The throat is part of both the digestive and
respiratory systems and is responsible for coordinating
the functions of breathing and swallowing.

 subdivided into 3 sections: oropharynx, hypopharynx,
and larynx.

 the oropharynx, hypopharynx, and larynx function to
sense and propel a food bolus from the mouth to the
esophagus in a coordinated fashion while protecting
the airway.

What is the throat?

 The throat is a ring-like muscular tube. It is the
passageway for air, food, and liquid. It also helps in
forming speech. The throat is made up of:

1. Voice box (larynx). The larynx is a cylindrical
grouping of cartilage, muscles, and soft tissue that
contains the vocal cords. The vocal cords are the
upper opening into the windpipe (trachea), the
passageway to the lungs.

2. Epiglottis. A flap of soft tissue located just above
the vocal cords. The epiglottis folds down over the
vocal cords to prevent food and irritants from
entering the lungs.

3. Tonsils and adenoids. They are made up of
lymph tissue and are located at the back and the
sides of the mouth. They protect against
infection. But they don't really have a function
after childhood.



Physiology of smell

1. The nose is the body's primary organ of smell and
also functions as part of the body's respiratory
system.

2. Air comes into the body through the nose.

3. it passes over the specialized cells of the olfactory
system, the brain recognizes and identifies smells.

4. Hairs in the nose clean the air of foreign particles.

5. air moves through the nasal passages, it is warmed
and humidified before it goes into the lungs.

Physiology of smell

6. The nasal passageways on either side of the nose open
into the choana and then into a chamber called the
nasopharynx, which is the upper part of the throat.

7. This chamber opens into the oropharynx, the throat
area behind the mouth.

8. When air is inhaled through the nostrils, it travels
through the nasal passages, the choana, the
nasopharynx, the oropharynx and the voice box and
ends up in the lungs.

9. Basically, in the respiratory system, the nose is a
passageway for air.

Function

1. main route for breathing
2. humidifies the air you breathe
3. cleans the air you breathe
4. regulates the temperature of the air your

breathe

1. The nose is also the first line of defense against
sickness.

2. The nose is lined with fine, hair-like projections known
as cilia.

3. The sinuses are lined with mucus-making cells. The
mucus (or "snot") keeps the nose from drying out.

4. Together, cilia and snot collect dust, bacteria and other
debris before they can enter the rest of the body.

 nasal mucus — made of water, proteins, antibodies and
salts — is clear. But during an infection, snot can change
to yellow or green, indicating the body is fighting off a
bacterial or viral infection. The green color comes from
a chemical secreted by white blood cells

Olfactory nerves (first cranial nerves)

 Sensory nerve of smell.
 Originate as chemoreceptors (specialised

olfactory nerve endings) in the mucous membrane
of the nasal cavity above the superior nasal
conchae.





Other senses

 Without the nose, the body wouldn’t be able to
taste food nearly as well.

 When food is eaten, the nose smells the food and
sends information to the mouth in a process
called olfactory referral.

 This is why those with a cold or other nose
condition finds that food lacks flavor.

 The nose also plays a role in hearing.

 The nasopharynx is flanked on either side by
eustachian tubes. These tubes connect the
nasopharynx to the middle ear.

 The nasopharynx fills the middle ear with air,
equalizing air pressure in the ear with the
atmosphere around it, which is an important part
of hearing properly.

 The sense of smell may create a powerful and long-
lasting memories, especially for distinctive odours e.g .
Hospital smells, favourite or least-liked foods.

 Inflamation of the nasal mucosa prevents odours
substance from reaching the olfactory area of the nose,
causing loss of the sense of smell (anosmia). The usual
cause is cold.

 Adaptation: continuously exposed to an odour,
perception of odour decreased and ceased within a few
minutes – only that specific odour.

Human nose function