Chapter 19 Special Senses

Olfaction Olfactory bulb Olfactory Olfactory nerves tract Fig. 19.8 Olfaction Olfactory bulb Volatile molecules are odorants must be dissolved in mucus of nasal cavity to be detected Olfactory epithelium lines superior nasal cavity, including superior nasal conchae and inferior surface of cribriform plate of ethmoid bone Olfactory tract Olfactory nerves (receptor cells) Nasal conchae Cribriform plate of ethmoid bone Olfactory epithelium

Olfaction Olfactory epithelium contains Olfactory glomerulus Fig. 19.8 Olfactory glomerulus Olfaction Olfactory nerves in cribriform foramen Olfactory bulb Olfactory epithelium contains olfactory receptor cells (AKA olfactory neurons) that detect odors supporting cells that sustain receptors basal cells: neural stem cells that replace neurons Cribriform plate Olfactory gland Basal cell Lamina propria Supporting cell Olfactory epithelium in nasal cavity Axon Cell body Olfactory receptor cell Dendrite Mucus layer Olfactory hairs Odor molecules

Olfaction Olfactory receptor cells have olfactory hairs Lamina propria Fig. 19.8 Olfaction Olfactory receptor cells have olfactory hairs cilia-like extensions that house protein receptors for specific molecules Lamina propria Basal cell nuclei Olfactory receptor cell nuclei Supporting cell nuclei Olfactory hairs Mucus LM 200x (b) Olfactory epithelium

Olfaction Lamina propria is areolar connective tissue Fig. 19.8 Olfaction Olfactory glomerulus Olfactory nerves in cribriform foramen Lamina propria is areolar connective tissue contains olfactory gland cells that secrete mucus contains blood vessels and nerves Olfactory bulb Cribriform plate Olfactory gland Basal cell Lamina propria Supporting cell Olfactory epithelium in nasal cavity Axon Cell body Olfactory receptor cell Dendrite Mucus layer Olfactory hairs Odor molecules

Fig. 19.19 Anatomic Regions of the Ear External ear External Ear Anatomy Fleshy ear is auricle or pinna Funnel shape protects ear and directs sound waves external acoustic meatus is bony tube hairs at entrance help guard opening ceruminous glands produce wax tympanic membrane is eardrum vibrates when hit by sound waves Auricle External acoustic meatus Tympanic membrane Elastic cartilage

Normal tympanic membrane Bleeding Bulging membrane Page 588 Malleus Normal tympanic membrane Bleeding Bulging membrane Otitis media present, bulging red tympanic membrane Malleus Ventilation tube Myringotomy

Fig. 19.19 External ear Middle ear External acoustic meatus Auditory ossicles Malleus Incus Stapes Tympanic membrane cavity Oval window Round Middle Ear Anatomy Air-filled tympanic cavity sits behind tympanic membrane Three bones, auditory ossicles, transfer vibrations from eardrum: malleus (hammer) incus (anvil) stapes (stirrup) Stapes sits against oval window, opening to inner ear Ossicles amplify sound waves

Fig. 19.19 External ear Middle ear Middle Ear Anatomy Auditory ossicles Stapes Tympanic cavity opens to auditory tube (AKA Eustachian tube) opens into nasopharynx (upper throat) Incus Malleus Auditory tube External acoustic meatus Tympanic cavity Tympanic membrane Oval window Round window

Pressure waves move through fluid called perilymph in scala vestibuli Fig. 19.27 Movement of stapes in and out of oval window causes pressure waves inside inner ear Pressure waves move through fluid called perilymph in scala vestibuli Scala vestibuli runs through cochlea, spiral-shaped structure of inner ear Auditory ossicles Malleus Incus Stapes Oval window Scala vestibuli Helicotrema 2 3 Cochlear duct External acoustic meatus 5 1 Vestibular membrane 4 Spiral organ Basilar membrane Tympanic membrane Scala tympani Round window Auditory tube

Center of cochlea is the cochlear duct Fig. 19.27 Center of cochlea is the cochlear duct Vestibular membrane is roof of cochlear duct; basilar membrane is floor Pressure waves in scala vestibuli cause ripples in cochlear duct Movement of cochlear duct causes ripples (pressure waves) in scala tympani, fluid-filled area below cochlear duct Auditory ossicles Malleus Incus Stapes Oval window Scala vestibuli Helicotrema 2 3 Cochlear duct External acoustic meatus 5 1 Vestibular membrane 4 Spiral organ Basilar membrane Tympanic membrane Scala tympani Round window Auditory tube

Hair cells send signals to cochlear branch of vestibulocochlear nerve Fig. 19.27 Movement of basilar membrane cause movement of hair cells in spiral organ portion of basilar membrane Hair cells send signals to cochlear branch of vestibulocochlear nerve Excess sound waves absorbed by round window Auditory ossicles Malleus Incus Stapes Oval window Scala vestibuli Helicotrema 2 3 Cochlear duct External acoustic meatus 5 1 Vestibular membrane 4 Spiral organ Basilar membrane Tympanic membrane Scala tympani Round window Auditory tube

Cochlear branch of CN VIII Scala tympani Modiolus Fig. 19.26 (a) Sectioned cochlea Bony cochlear wall Cochlear duct Vestibular membrane Basilar membrane Scala vestibuli Scala vestibuli Vestibular membrane Vestibular membrane Cochlear duct Tectorial membrane Tectorial membrane Scala tympani Spiral ganglion Basilar membrane Basilar membrane Cochlear branch of CN VIII Scala tympani Modiolus Cochlear branch of CN VIII Supporting cells Tectorial membrane Stereocilia Spiral ganglion Spiral organ (b) Close-up of cochlea Outer hair cell Basilar membrane Inner hair cell Cochlear branch of CN VIII Scala tympani (c) Spiral organ

d: © Science VU/Visuals Unlimited Fig. 19.26 Cochlear duct Tectorial membrane Outer hair cell Inner hair cell Supporting cells Cochlear branch of CN VIII Basilar membrane Scala tympani LM 75x (d) Spiral organ d: © Science VU/Visuals Unlimited

3. Signals travel through the thalamus Fig. 19.29 4. Signals are perceived as sounds in the primary auditory cortex of the temporal lobe 3. Signals travel through the thalamus Thalamus 1 & 2. Nerve impulses travel from cochlea to cochlear nucleus of medulla oblongata or inferior colliculus Primary auditory cortex 4 3 Inferior colliculus Cochlear branch of CN VIII Superior olivary nucleus 2b 2a 1 Cochlear nucleus

The components of a cochlear implant. Page 598 The components of a cochlear implant. Transmitter 1. Antenna, transmitter, and receiver are inserted in skin posterior and superior to the auricle. The transmitter lead is inserted into the inner ear. Receiver Antenna 2. Sound waves are detected by the receiver and turned into electrical impulses, which travel through the transmitter. Transmitter lead

The components of a cochlear implant. Page 598 The components of a cochlear implant. 3. Electrical impulses from the transmitter stimulate the cochlear nerve, which then transmits nerve impulses to the brain. Transmitter lead Spiral organ Cochlea cutaway

External acoustic meatus Auditory ossicles Fig. 19.19 External ear Middle ear Inner ear Auricle External acoustic meatus Auditory ossicles Malleus Incus Stapes Petrous part of temporal bone Vestibular branch of CN VIII Cochlear branch of CN VIII Facial nerve (CN VII) Vestibulocochlear nerve (CN VIII) Internal acoustic meatus Bony labyrinth of inner ear Cochlea Vestibule To nasopharynx Elastic cartilage Tympanic membrane cavity Oval window Round Auditory tube

(semicircular canals) Fig. 19.21 Equilibrium Bony labyrinth (semicircular canals) Vestibular complex made up of 2 parts vestibule is area closest to oval window contains utricle and saccule, saclike areas, connected by narrow passageway semicircular canals extend above vestibule Bony labyrinth is channels within temporal bone Membranous labyrinth is channels within bony labyrinth Utricle Vestibule Saccule Vestibule Membranous labyrinth Bony labyrinth Ampullae Connection to cochlear duct

Movement of otoliths in gelatin layer within utricle and saccule moves stereocilia on hair cells Otolithic membrane Gelatin layer Kinocilium Stereocilia Hair cell Macula Supporting cells Vestibular nerve branches Vestibular branch of CN VIII (c) Hair cell

3 semicircular canals – anterior, posterior, horizontal Fig. 19.22 3 semicircular canals – anterior, posterior, horizontal Each canal has semicircular duct inside Ducts contain hair cells Semicircular ducts Utricle Vestibule Saccule CN VIII (a) Vestibular complex

(semicircular canals) Perilymph Fig. 19.21 Membranous labyrinth (semicircular duct) Endolymph Bony labyrinth (semicircular canals) Perilymph Membranous labyrinth (semicircular ducts) Bone Bony labyrinth (semicircular canal) Cochlear branch of CN VIII Utricle Bony labyrinth (cochlea) Membranous labyrinth (cochlear duct) Vestibule Vestibule Apex of cochlea (contains helicotremma) Spiral organ Saccule Membranous labyrinth Endolymph Bony labyrinth Ampullae Perilymph Spiral ganglion Connection to cochlear duct Membranous labyrinth (cochlear duct) Bony labyrinth (cochlea) Bone

semicircular ducts connected to utricle Fig. 19.24 semicircular ducts connected to utricle Ampulla is expanded region at base of semicircular duct farthest from utricle Semicircular ducts Ampullae Cupula Vestibular branch of CN VIII

Crista ampullaris is elevated region in ampulla Fig. 19.24 Cupula Endolymph Hair cell Supporting cell Crista ampullaris Vestibular branch of CN VIII Crista ampullaris is elevated region in ampulla covered with hair cells and supporting cells Cupula is a dome of gelatin over crista ampullaris