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CHAPTER 21Special Senses

Principles of

Human Anatomy 12th Edition 

Gerard J. Tortora

&Mark T. Nielsen 

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Olfaction: Sense of Smell

Olfactory epithelium

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 The Olfactory Pathway

Olfactory (I) nerves Olfactory bulbs

Olfactory tract

Olfactory sensations are the only sensationsthat do what?

The axons of the olfactory tract project to the

primary olfactory area; located at the inferiorand medial surface of the temporal lobe

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Olfactory Pathway

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Gustation

Five primary tastes

Sour

Sweet

Bitter

Salty

Umami 

 All other tastes are combinations of these five

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 Anatomy of Gustatory Receptors The receptors for taste are located in the taste buds,

and the number of taste buds declines with age

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 Taste Buds

Taste buds are found in elevations on the

tongue called papillae 

Three types of papillae contain taste buds

Circumvallate (vallate)

Fungiform papillae

Foliate papillae

Filiform papillae Clinical connection: taste aversion

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 The Gustatory Pathway

Three cranial nerves contain axons ofsensory neurons from taste buds

Facial (VII)

Glossopharyngeal (IX) Vagus (X)

From taste buds, impulses propagate along

these cranial nerves to the gustatory nucleus

in the medulla oblongata

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 Accessory Structures of the Eye:

Eyelids

Eyelids, or palpebrae

Levator palpebrae superioris muscle

Palpebral fissure Lateral commissure, and the medial

commissure

Lacrimal caruncle

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 Vision: Accessory Structures of the Eye

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 Visual Pathway

in the Brain

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 Visual Pathway

in the Brain

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Hearing and Equilibrium

 Anatomy of the ear The ear is divided into three main regions

External ear

Middle ear Internal ear

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 The External Ear

The external ear consists of several

structures

 Auricle (pinna)

External auditory canal Tympanic membrane

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 Anatomy of the Ear

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 The Middle Ear

The middle ear is a small, air-filled cavity inthe temporal bone that is lined by epithelium

 Auditory ossicles

Three ossicles: malleus, incus and stapes The head of the malleus articulates with the

incus

The incus articulates with the stapes and thefootplate of the stapes fits into the oval

window (fenestra vestibuli)

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Internal Ear (Labyrinth) Structurally, there are two main divisions - the

outer bony labyrinth that encloses an innermembranous labyrinth 

Three main areas Semicircular ducts

Vestibule

Cochlea - receptors for hearing

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Internal Ear

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Internal Ear

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 Auditory Pathway

Spiral ganglia

medulla

Decusssion

Midbrain

Pons

Thalamus

cortex

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