(15.1) Sense Organ - The Ears Flashcards by Aeron Justine Aquino

the ear transduces mechanical energy (in the form of sound waves) into electrical energy (in the form of nerve impulses) and transmits information to the brain.

hearing

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Parts of ear involved in hearing are:

external, middle and inner ear

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delivers information to the brain on position and movement of the head as related to gravitational pull. Only the inner ear is involved

maintain balance

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• External ear
– Pinna = ?
– External acoustic meatus = Ear canal

auricle

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• External ear
– Pinna = auricle
– External acoustic meatus = ?

Ear canal

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Tympanic cavity connects with pharynx via the auditory tube

Middle ear

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– Membranous labyrinth within the bony labyrinth
– Functions for both balance and hearing

Inner ear

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⚫ portion that is visible externally
⚫ supported by auricular cartilage which is elastic in nature

PINNA OR AURICLE

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⚫ rostral surface is concave and caudal contour is convex forming a natural “scoop” for sound waves

Auricular cartilage

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⚫ most proximal, strongly curved portion
⚫ portion closest to the head
⚫ conchal cavity

Concha

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Concha – has several elevations of cartilage:

⚫ Tragus
⚫ pretragic incisure
⚫ Antitragus
⚫ intertragic incisure

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more distal flattened portion of pinna

Scapha

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⚫ mainly cartilaginous, but also has a bony portion
⚫ cartilaginous portion represents the tubular lateral portion of auricular cartilage

EAR CANAL

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is small tubular piece of cartilage, increases mobility of external ear by joining external ears main portion with its deepest portion

auricular cartilage

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Ear canal course is roughly what shape?

“L-shaped”

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• Consists of an air-filled tympanic cavity connected with the
nasopharynx via the auditory tube and closed to the outside by the tympanic membrane at the level of the external acoustic meatus
– has a small, dorsal epitympanic recess and
– a large, ventral tympanic bulla

MIDDLE EAR

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– thin, semitransparent membrane situated at the lumen of external acoustic meatus
– separates the external ear from the middle ear
– attached to temporal bone by tympanic ring

Tympanic membrane – the eardrum

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MIDDLE EAR
• The middle portion of the tympanic cavity contains the three auditory ossicles— what are those three?

– malleus,
– incus, and
– stapes

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MIDDLE EAR
• The middle portion of the tympanic cavity contains the three auditory ossicles—
– malleus,
– incus, and
– stapes—and
• what are the two muscles associated with them— ?

– the tensor tympani on the malleus and
– the stapedius on the stapes

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THE TYMPANIC CAVITY
• Divided into 3 portions:

– Epitympanic recess
– Tympanic cavity proper
– Tympanic bulla

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⚫ smallest most dorsal of the three chambers of tympanic cavity
⚫ contains the auditory ossicles and associated muscles

EPITYMPANIC RECESS

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⚫ resemblance to hammer
⚫ largest most lateral adjacent to tympanic membrane

malleus

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“handle”, elongated part of malleus, embedded in the fibrous layer of the ear drum

manubrium

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Part of malleus that provides insertion point for tensor tympani muscle

tiny hook

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Part of malleus that articulates with incus

head

resemblance to anvil

incus

“stirrup”, smallest bone in the entire body

stapes

⚫ midportion region adjoining the tympanic membrane ⚫ midportion of the cavity receives the opening of auditory tube (from nasopharynx) and communicates in the inner ear by way of vestibular (oval) and cochlear (round) windows

TYMPANIC CAVITY PROPER

⚫ houses the cochlea of inner ear

Promontory

(round window)

Cochlear window

(oval window)

Vestibular window

⚫ ventral portion, ventrally expanded “bubble” of bone visible from external surface of skull ⚫ theorized to aid in perception of sounds at both very high and very low ranges

TYMPANIC BULLA

• these muslces tenses or firms the tympanic membrane and bony chain as a protective measure against excessive vibration

MUSCLES OF MIDDLE EAR

Muscle of the middle ear that attaches to malleus, innervated by mandibular division of trigeminal nerve

tensor tympani

Muscle of the middle ear that attaches to stapes, innervated by facial nerve

stapedius

⚫ A closed bony chamber that entirely encloses and protects the delicate membranous labyrinth in the petrous part of temporal bone

BONY LABYRINTH

BONY LABYRINTH - Consists of 3 continuous fluid filled regions:

⚫ vestibule ⚫ 3 semicircular canals ⚫ cochlea

⚫ Similar to ( cerebrospinal fluid ) CSF ⚫ fluid that fills the space between external surface of membranous labyrinth and internal surface of bony labyrinth

Perilymph

• central portion of bony labyrinth, encloses the utriculus and sacculus

Vestibule

Vestibule two openings:

• vestibular window • cochlear window

Opening of vestibule that receives the stapes

vestibular window

Opening of vestibule that covered by membranes, sometimes called secondary tympanic membrane

cochlear window

Vestibule channels:

• vestibular aqueduct • cochlear aqueduct

channel of vestibule that houses the endolymphatic duct

vestibular aqueduct

What is a channel of vestibule that drains the perilymph into the epidural space

cochlear aqueduct

• houses the semicircular ducts

Semicircular Canals

– encloses the cochlear duct – resembles a snail shell

Cochlea

central hollow core of bone

modiolus

housed within modiolus, receives input from sensory cells in the cochlear duct

spiral ganglion

actual lumen of cochlea, spiral around modiolus

spiral canal

shelf of bone that extend outward from the modiolus

spiral lamina

Space within bony cochlea that lies dorsal to bony spiral lamina

Scala Vestibuli

Space within bony cochlea lies ventral to bony spiral lamina

Scala Tympani

⚫ Consist of 4 fluid-filled compartment; within the component of the bony labyrinth ⚫ Saccule and utriculus within the vestibule; ⚫ 3 semicircular ducts within bony semicircular canals ⚫ Cochlear duct within bony cochlea

MEMBRANOUS LABYRINTH

⚫ blind ended channel that extends from saccules into the epidural space ⚫ terminates at expanded endolymphatic sac ⚫ plays a role in resorption of endolymph

Endolymphatic Duct

⚫ clear dialysate of blood formed from vessels in specialized regions of membranous labyrinth ⚫ fills all parts of membranous labyrinth ⚫ mediate the function of membranous labyrinth ⚫ waves in fluid can be induced by movement of head (balance) or transmission of sound waves (hearing)

Endolymph

receptor organ associated with semicircular duct; function in dynamic equilibrium

Crista ampullaris

receptor organ found in the utriculus and saccule; function in static equilibrium;

Macula

macula of the ? may be more important as a receptor for sensing changes in head posture

utriculus

macula of the ? may be more sensitive to vibrational stimuli and loud sounds

saccule

formerly organ of Corti, is a collection of hair cells and supporting cells that rests on the basilar membrane

spiral organ

INNERVATION OF THE INNER EAR • Vascularization – ? – labyrinthine artery

arterial supply

INNERVATION OF THE INNER EAR • Vascularization – ? – two channels along vestibular and cochlear aqueducts

venous drainage

INNERVATION OF THE INNER EAR • Innervation: via vestibulocochlear nerve – ? – vestibular nerve passes from semicircular ducts

balance

INNERVATION OF THE INNER EAR • Innervation: via vestibulocochlear nerve – balance – vestibular nerve passes from semicircular ducts – ? – cochlear nerve passes from cochlea

hearing

⚫ expanded region of membranous canal situated at base of semicircular ducts

Utriculus

⚫ “spot” ⚫ sensory region in the wall of utriculus ⚫ generates information related to position of head relative to gravity ⚫ transmits information to the brain via the vestibulocochlear nerve ⚫ covered with gelatinous layer statoconia (calcium carbonate crystals)

Macule

shaped ducts

3 horseshoe

dilations at one end

Ampullae

sensory structure within ampulla, sensory hairs are deflected by motions in endolymph

Crista

• expanded region at the base of cochlear duct • sensory macule is present and functions in hearing

Sacculus

• the floor (base) is formed by basilar membrane, separates the cavity of cochlear duct from the cochlea (scala tympani) • the roof is formed by vestibular membrane (scala vestibuli)

Cochlear Duct

⚫ extremely specialized region that transduces mechanical energy (fluid waves) into electrical energy (nervous impulses) for transmission to brain. ⚫ Mechanism involves deflection of sensory hair cells ⚫ Transmission is via cochlear portion of vestibulocochlear nerve

Organ of Corti (spiral organ)

⚫ awning-like membrane extending over surface of hair cells ⚫ respond to fluid waves in endolymph, contacting hair cells causing them to “fire"

Tectorial Membrane

⚫ pinna collects sounds ⚫ funnels it thru external ear canal to the middle ear

External ear

⚫ tympanic membrane vibrates ⚫ vibration is transmitted to the chain of auditory ossicles, amplified 20x ⚫ stapes moves against the membrane covering the vestibular window which transfers energy to the inner ear

Middle ear

⚫ site where mechanical impulses are transformed into electrical nervous impulses that can be interpreted by the brain

Inner Ear

An energy transferred to perilymph in wave form, propagated, enters the scala vestibule of the cochlea

mechanical energy

What passes thru the endolymph, impinge on tectorial membrane of cochlear duct which causes to contact the hair cells which vibrates

wave

cells of spiral organ transmit impulses to the brain via what nerve?

cochlear nerve