Ears & Eyes

3 parts of ear

outer (hearing)

middle (hearing)

inner (hearing and balance)

Outer ear

auricle = funnels sound into external acoustic meatus

• Helix (rim)

• Lobule (earlobe)

external acoustic meatus

allows sound to reach the tympanic membrane

tympanic membrane (eardrum)

vibrates in response to sound. Send the vibrations to the ossicles (Bones)

malleus

transmits vibratory energy to the incus

incus

transmits vibratory energy to the stapes

stapes

transmits vibratory energy to the oval window

Middle ear (tympanic air filled cavity)

contains the auditory tube which connects middle ear to nasopharynx to equalize pressure in the middle ear and atmospheric pressure

Bony labyrinth

3 curved channels filled with perilymph in the inner ear that run through the temporal bone and contain receptors for hearing and equilibrium (semicircular canals, vestibule, and cochlea)

3 semicircular canals function?

house crista ampullaris = equilibrium receptors that respond to rotational head movement (lie in 3 planes of space)

function of vestibule

house the maculae = equilibrium receptors that respond to gravity and linear head movement (located between semicircular canals and cochlea)

cochlea function?

houses the spiral organs = hearing receptors

vestibulocochlear nerve

transmits equilibrium and auditory input to the brain

oval window function

sets inner ear fluids in motion when the stapes hits it

round window function

pressure relief for fluid movement in the ear

extrinsic eye muscles

1. superior rectus = elevates the eye (III)

2. inferior rectus = lowers the eye (III)

3. Medial rectus = medial movement of the eye (III)

4. Lateral rectus = lateral movement of the eye (VI)

5. Inferior Oblique = elevates and laterally rotates eye (III)

6. superior oblique = lowers and laterally rotates eye (IV)

lacrimal apparatus

lacrimal glands produce and drain tears that moisten and protect the surface of the eye (tears contain antibodies like mucus and lysozyme that are drained into the nose by the nasolacrimal duct)

palpebrae (eyelids)

connective tissue covered by skin that covers the eyes

tissue layers of eyes (tunics)

1. sclera (outermost layer – the “whites of the eyes”): insertion site for extrinsic eye muscles

2. choroid: brown pigment: helps absorb light

3. retina: houses the photoreceptors

aqueous humor

supplies nutrients and oxygen to the lens, cornea, and retina (removes waste)

vitreous humor

supports the lens and retina

cornea

refracts light

sclera

insertion sight for extrinsic eye muscles

iris

controls pupil size

pupil

allows light to enter the eye

lens

focuses light on the retina

retina

houses photorecptors (rods and cones); transduces light energy into a nerve impulse

optic chiasma

point of partial decussation of optic nerve fibers

optic tracts

transmits visual input from optic chiasma to thalamus

optic disc

allows optic nerve fibers to exit eye

choroid

helps absorb light

lacrimal sac and duct

drains tears into the nasal cavity

vestibular nerve

transmits equilibrium input to cranial nerve VIII

cochlear nerve

transmits hearing input to cranial nerve VIII