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Special senses
(continued)
Receptors are classified into 3 types
• Exteroceptors – located near the body surface, are
specialized to perceive stimuli from the external
environment; other exteroceptors include receptors
for vision, hearing, smell and taste
• Interoceptors – are specialized to perceive sensory
information from visceral organs
• Proprioceptors – located in joint capsules, tendons,
muscle spindles, inner ear, are specialized to perceive
information that relates to an awareness of the body
in space and movement
Anatomy of the vestibulo-cochlear organ
Vestibulo-cochlear organ includes
• Outer ear
– Auricula
– External acoustic meatus
– Tympanic membrane
• Middle ear
– Tympanic cavity
– Three ossicles: malleus, incus, stapes
– Auditory (Eustachian) tube
• Inner ear
– Bony and membranous labyrinths
External acoustic meatus
Middle ear
Bony, membranous and sensory labyrinths
Inner ear
• Bony labyrinth
– Cochlea
– Vestibulum
– Three semicircular canals
• Membranous labyrinth
– Cochlear duct
– Sacculus and Utriculus
– Three semicircular ducts
• Sensory labyrinth
Macula of the utricle: hair cells
Hair cells of the maculae
Crista ampullaris of the semicircular duct
LM of the crista ampullaris and of macula
SEM of the hair cells and the otoliths
Organ of Corti in the cochlear duct
Axial section through the cochlea
LM of the organ of Corti
SEM of the organ of Corti hair cells
Histophysiology of the organ of Corti
Olfactory perception
(odors detection)
The olfactory region
LM of the human olfactory mucosa
EM of the rat olfactory epithelium
Taste perception
(taste buds)
Lingual papillae and a taste bud
LM of taste buds in circumvallatae papilla
EM of a taste bud
Mechanoreceptors include
• Nonencapsulated
– peritrichial and corneal naked nerve endings
– Merkel’s disks
• Encapsulated
– Meissner’s corpuscles
– Pacinian corpuscles
– Ruffini’s corpuscles
– Krause’s end bulbs
– Golgi tendon organs
– Muscle spindles
Various types of mechanoreceptors
A, Merkel’s disk; B, Meissner’s corpuscle; C, Pacinian corpuscle; D, Peritrichial
nerve endings; E, Ruffini’s corpuscle; F, Krause’s end bulb; G, Muscle spindle;
H, Golgi tendon organ
Free nerve endings
Merkel’s cells and Merkel’s disks
Meissner’s and Pacinian corpuscles
Muscle spindle