3. The Eyeball
The Anatomy of the Eyeball
• Anterior Chamber: The space in the eye that is
behind the cornea and in front of the iris.
• Upper & lower lid: a thin fold of skin that covers and
protects the eye.
• Conjunctiva: a clear mucuse membrane consisting of
cells and underlying basement membrane
that covers the sclera (white part of the
eye) and lines the inside part of the eyelid.
• Pupil: a hole located in the center of the iris of the eye
that allows light to enter the eye
• Cornea: a transparent front part of the eye that covers the
iris and the pupil.
• Aqueous humor: The liquid between the lens and the
cornea.
• Posterior chamber: A narrow crack behind the
perpherial part of the iris
• Fovea centralis: The part of the eye located in the center
of the Macula region of the retina, this part is
responsible for the sharp central vision.
• Optic nerve: Transmits visual information from the
retina to the Brain.
• Central retinal artery: It pierces the optic nerve close to
the eyeball, sending branches over the internal
surface of the retina, and these terminal
branches are the only blood supply to the larger
part of the eye
• Sclera: fibrous, protective, outer layer of the eye
containing collagen and elastic fiber.
• Choroid: The vascular layer containing connective
tissue, of the eye lying between the retina and
the sclera. In humans its thickness is about 0.5 mm.
The choroid provides oxygen and nourishment to the
outer layers of the retina
• Retina: A light-sensitive tissue lining the inner
surface of the eye
4. Muscles of the eye
The extraocular
muscles are the six
muscles that control
the movements of the
(human) eye. The
actions of the
extraocular muscles
depend on the position
of the eye at the time
of muscle contraction.
5. Lacriminal apparatuse
The lacrimal apparatus is the
physiologic system containing the
orbital structures for tear production
and drainage[1]. It consists of
(a) the lacrimal gland, which
secretes the tears, and its
excretory ducts, which convey
the fluid to the surface of the
eye
(b) the lacrimal canaliculi, the
lacrimal sac, and the
nasolacrimal duct, by which the
fluid is conveyed into the cavity
of the nose, emptying
anterioinferiorly to the inferior
nasal conchae at the
nasolacrimal duct.
(c) the nerve supply of lacrimal
apparatus done by carotid
plexuse of nerves along artery
internal and external
sympathetically but
parasympathetic from lacrimal
nucleus of the facial nerve
6. • Vision begins when light rays are reflected off an
object and enter the eyes through the cornea, the
transparent outer covering of the eye. The cornea
bends or refracts the rays that pass through a round
hole called the pupil. The iris, or colored portion of the
eye that surrounds the pupil, opens and closes
(making the pupil bigger or smaller) to regulate the
amount of light passing through. The light rays then
pass through the lens, which actually changes shape
so it can further bend the rays and focus them on the
retina at the back of the eye. The retina is a thin layer
of tissue at the back of the eye that contains millions of
tiny light-sensing nerve cells called rods and cones,
which are named for their distinct shapes. Cones are
concentrated in the center of the retina, in an area
called the macula. In bright light conditions, cones
provide clear, sharp central vision and detect colors
and fine details. Rods are located outside the macula
and extend all the way to the outer edge of the retina.
They provide peripheral or side vision. Rods also allow
the eyes to detect motion and help us see in dim light
and at night. These cells in the retina convert the light
into electrical impulses. The optic nerve sends these
impulses to the brain where an image is produced.
How we see
8. External ear
The outer ear has no
bones. It is the
external portion of the
ear, which consists of
the pinna, concha, and
auditory meatus. It
gathers sound energy
and focuses it on the
eardrum (tympanic
membrane).
9. Middle ear
The middle ear is the portion
of the ear internal to the
eardrum, and external to the
oval window of the cochlea.
The mammalian middle ear
contains three ossicles, which
couple vibration of the
eardrum into waves in the
fluid and membranes of the
inner ear. The hollow space of
the middle ear has also been
called the tympanic cavity, or
cavum tympani. The
eustachian tube joins the
tympanic cavity with the nasal
cavity (nasopharynx),
allowing pressure to equalize
between the middle ear and
throat.
10. Inner ear
The inner ear is the
innermost part of the
vertebrate ear. It consists of
the bony labyrinth, a
system of passages
comprising two main
functional parts:The
cochlea is dedicated to
hearingThe vestibular
system is dedicated to
balanceThe inner ear is
found in all vertebrates,
with substantial variations
in form and function. The
inner ear is innervated by
the eight cranial nerve in all
vertebrates.
11. How we hear
When something makes a noise, it sends
vibrations, or sound waves, through the
air. The human eardrum is a stretched
membrane, like the skin of a drum.
When the sound waves hit your eardrum,
it vibrates and the brain interprets these
vibrations as. After the vibrations hit
your eardrum, a chain reaction is set off.
Your eardrum, which is smaller and
thinner than the nail on your pinky
finger, sends the vibrations to the three
smallest bones in your body. First the
hammer, then the anvil, and finally, the
stirrup. The stirrup passes those
vibrations along a coiled tub in the inner
ear called the cochlea. Inside the cochlea
there are thousands of hair-like nerve
endings, cilia. When the Cochlea
vibrates, the cilia move. Your brain is
sent these messages (translated from
vibrations by the cilia) through the
auditory nerve. Your brain then
translates all that and tells you what you
are hearing. Neurologists don't yet fully
understand how we process raw sound
data once it enters the cerebral cortex in
the brain.
