Olfaction

WHAT IS OLFACTION?

• Sense of smell
• Occurs in respond to airborne molecules called odorants (molecule with odor) entering the nasal cavity.

SITE OF OLFACTION

• The olfactory stimuli are detected by specialized receptors located on free nerve endings of olfactory nerves (located in olfactory mucosa) of the nose.
• Special sensory nerves innervate the olfactory mucosa are 15-20 bundles of olfactory nerve fibres which convey the sense of smell.

OLFACTORY PATHWAYS

ANATOMY OF OLFACTION

Lateral wall of nasal cavity

Olfactory epithelium

• Consist of 3 types of cells – basal,supporting and olfactory receptor cells .
• Basal cells – give rise to olfactory receptor cells.
• Olfactory Receptor cells – bipolar neurons with dendrites extending to the epithelial surface of the nasal cavity,the ends of dendrites contais specialized cilia called olfactory hairs

Olfactory Bulb

• Inferior to the basal frontal lobe
• Differentiate into five layers (from outside toward center of bulb)

-glomerular layer

-external pleciform layer

-Mitral cell layer

-internal pleciform layer

-granule cell layer

Olfactory nerve and Cribriform plate

• Small unmyelinated axons of the olfactory cells form fine fibers of first cranial nerve.
• Cribriform plate of ethmoid bone separated at the midline by crista galli contains multiple small foramina through which olfactory nerve fibers transverse.