Anatomy of the nose

1. NOSE
By:
Y.V Vanaja
Lecturer
Vijay Marie College of Nursing

2. NOSE
• The nose is a specialized organ.
• The nose can be divide into external and internal portions
• The external nose consists of a supporting framework of bone and hyaline
cartilage covered with muscle and skin and line by a mucous membrane
• The frontal bone , nasal bones and maxillae form the bony framework of
the external nose.
• The cartilaginous framework of the external nose consist
Septal cartilage- anterior portion of the nasal septum
Lateral nasal cartilage – inferior to the nasal bones
Alar cartilage – forms portion of the walls of the nostrils

3. • On the surface of the external nose are two opening – external nares or nostrils
• The interior structure of the external nose have 3 functions
1) Warming, moistening and filtering incoming air.
2) Detecting olfactory stimuli
3) Modifying speech vibrations as they pass through the large, hollow resonating
chambers.

4. External Nose

5. •The internal nose
• is a large cavity in the anterior aspect of the skull that lies inferior to
the nasal bone and superior to the mouth
• It is lined with muscle and mucous membrane
• Anteriorly the internal nose merges with the external nose, and
posteriorly it communicates with the pharynx through two openings
called the internal nares or choanae
• The space within the internal nose is called the nasal cavity
• The vertical portion, the nasal septum, divides the nasal cavity into
right and left sides.

7. Anatomy of Olfactory Receptors
• The nose contains 10 – 100 million receptors for the sense of smell or olfaction
contained with an area called the olfactory epithelium with the total area of the
5cm2.
• The olfactory epithelium occupies the superior part of the nasal cavity covering
the inferior surface of the cribriform plate and extending along the superior
nasal concha.
• The olfactory epithelium consists of three kinds of cells;
1. Olfactory receptors
2. Supporting cells
3. Basal cells

9. • Olfactory receptors are the first- order neurons of the olfactory pathway.
• Each olfactory receptor is a bipolar neuron with an exposed knob shaped
dendrite and an axon projecting through the cribriform plate ending in the
olfactory bulb
• The sites of olfactory transduction are the olfactory hair, cilia that project from
the dendrite
 Chemicals that have an odor and can therefore stimulate the olfactory Hairs
called odorants
• Olfactory receptors respond to the chemical stimulation of an odorant molecule
by producing a generator potential, thus initiating olfactory response.
Supporting cells are columnar epithelial cells of the mucous membrane lining the
nose

10. • They provide physical support, nourishment, and electrical insulation for
the olfactory receptors, and they help detoxify chemicals that come in
contact with the olfactory epithelium
• Basal cells are stem cells located between the bases of the supporting cells
• Within the connective tissue that supports the olfactory epithelium are
olfactory (bowman’s) glands, which produce mucus that is carried to the
surface of the epithelium by ducts.
• The secretion moistens the surface of the olfactory epithelium and
dissolves odorants so that transduction can occur.
• Both supporting cells of the nasal epithelium and olfactory glands are
innervated by branches of the facial nerve, which can be stimulated by
certain chemicals.
• Impulses intense nerves in turn stimulate the lacrimal glands in the eyes
and nasal mucous glands

11. PHYSILOLOGY OF OLFACTION
• Our ability to recognize about 10,000 different odors probably depends on
patterns of activity in the brain that arise from activation of different
combinations of olfactory receptors
• Olfactory receptors react to odorant molecules in the same way that most
sensory receptors react to their specific stimuli.
• Generator potential develops and triggers one or more nerve impulses
• In some cases an odorants binds to a receptor linked to proteins in the plasma
membrane called G proteins

12. Activates the enzyme adenylate cyclase
Production of cyclic adenosine monophosphate
Opening of Na+ channels
Inflow of Na+
Depolarizing generator potential
Generation of nerve impulses and propagation along axon of olfactory
receptors

14. Odor threshold and adaptation
• Olfaction like all the special senses, has a low threshold.
• Only a few molecules of certain substances need to present in air to
be perceived as an odor
• Adaptation to odors occurs rapidly olfactory receptors adapt by about
50% in the first second or after stimulation but adapt very slowly
thereafter.

15. Olfactory Pathway
On each side of the nose, about 40 bundles of the slender,
unmyelinated axons of olfactory receptors extend through about 20
olfactory foramina in the cribriform plate of ethmoid bone.
40 or so bundles of axons collectively form the right and left olfactory
nerves
The olfactory nerves terminate in the brain in paired masses of gray
matter called olfactory bulbs.

16. • Within the olfactory bulbs the axon terminals of the olfactory receptors and cell
bodies of the second order neurons in the olfactory pathway.
• Axons of olfactory bulb neurons extend posteriorly and form the olfactory tract.
Some of the axons of the olfactory tract project to the primary olfactory area.
Other axons olfactory tract project to the limbic system and hypothalamus
From the primary olfactory area, pathways also extend to the frontal lobe.