Smell

1. The Special Senses:
Smell
Dr. Binu Babu
Ph. D (N), MSN, MBA
Mrs. Jincy Ealias
MSN, RN

2. Smell
• The organ of smell is the olfactory epithelium, which
covers the superior nasal concha
• Olfactory receptor cells are bipolar neurons with
radiating olfactory cilia
• Olfactory receptors are surrounded and cushioned by
supporting cells
• Basal cells lie at the base of the epithelium

4. Olfactory sensory neurons
 Olfactory sensory neurons are also unusual because they
are one of the few types of neurons that undergo
noticeable turnover throughout adult life and their typical
life span is 30–60 days.
 Olfactory stem cells in the olfactory epithelium
differentiate to replace them.

5. Olfactory transduction process

6. Olfactory transduction process
Odorant binds to its receptor
Receptor activates G protein
G protein activates adenylate cyclase
Adenylate cyclase converts ATP to Camp
cAMP opens a cation channel, allowing Na+ and Ca2+ inux and causing
depolarization. (olfactory adaptation)

7. Olfactory Pathway
 First order neuron:
From olfactory epithelium to glomerulus
 Second order neuron:
The olfactory bulb. where the second neurons of the
olfactory pathway (mitral and tufted cells) are located.
The axons of these second order neurons pass centrally
as the olfactory tract.
 Third order neuron:
The prepiriform area is considered the primary
olfactory cortex which contains the third order neurons.

8. Applied Anatomy
 Anosmia – complete absence
 Hyposmia – decreased
 Dysosmia – distorted
 Parosmia – perverted
 Cacosmia - Inappropriately disagreeable odors
 Kallmann's syndrome - a hereditary disorder, usually X-
linked, (hypogonadism & anosmia)

9. References
 Tortora, Gerard J, and Bryan Derrickson. Principles of
Anatomy and Physiology. 2nd ed., Milton, Qld, John Wiley &
Sons Australia, Ltd, 2019.
 Garg, Krishna, and Medha Joshi. Anatomy and Physiology for
Nurses. New Delhi, Cbs Publishers & Distributors Pvt. Ltd,
2015.
 Kendall, Elward, et al. Anatomy and Physiology.
Lincolnwood, Ill., Ntc Learning Works, 1998.
 Scanlon, Valerie C, and Tina Sanders. Essentials of Anatomy
and Physiology. Philadelphia, Pa, F.A. Davis Co, 2011.

10. THANK YOU