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Eye and Ear
Eye

The eye is covered in a tough layer of
connective tissue called the sclera
◦ This is covered by a mucous membrane called
the conjunctiva
Becomes clear in front of the eyes, called
cornea
 Next inner layer is the choroid

◦ Turns into ciliary body, then iris (gives the
eye its colour)
◦ Iris can change size, regulate amount of light
◦ The hole it makes is the pupil

Innermost layer is retina
◦ Made of neurons and photoreceptors
(clustered in the back)
In centre of front is lens
 Flexible, focuses light entering eye
 Shape controlled by ciliary bodies

◦ Ciliary bodies contract, compressing lens,
focus on near objects
◦ When the relax, lens lengthens, focus on
distance objects

Light passes through clear fluid called
vitreous humour
◦ Fluid supplied by ciliary bodies

Light strikes two types of photoreceptors,
rods or cones
◦ Rods detect intensity
◦ Cones detect colour (three types)
Rods more around perimeter, cones in
center
 The cluster of cone cells at centre of
vision is called fovea
 Information is processed and sent
through optic nerve

The nerve leaves a sort of “optic bald
spot”
 This is the optic disc, aka blind spot
 Visual cortex (posterior of cerebrum) fills
in the blanks, so we normally don’t see it

Ear

Broken into three sections: outer, middle,
and inner
Outer Ear
Only two structures
 Actual “ear” that we see is the pinna
 Opens to a tube called auditory cannal
 Both are designed to collect logitudinal
compression and rarefaction waves

Middle Ear
Contains three bones (smallest in the
body)
 All three - malleus, incus, and stapes
(hammer, anvil, and stirrup) transmit the
vibrational waves to the oval window, a
membrane connected to the inner ear
 Also in middle is a opening to the
pharynx called the Eustachian tube
 Regulates pressure affecting tympanic
membrane

Inner Ear
Actual center where sound waves are
processed
 Has fluid filled chambers called
semicircular canals, responsible for
spatial orientation
 The cochlea is the hearing centre
 Connected to auditory nerve, which
relays info to auditory complex in
cerebrum
