anatomy of eye

Question 1

what are the general senses?

Answer 1

somatic and visceral sensations - tactile, thermal, pain and proprioceptive
scattered throughout the body
relatively simple structures

Question 2

what are the special senses?

Answer 2

smell, taste, vision, hearing and equilibrium
specific locations in the head
anatomically distinct structures
form complex neural pathways

Question 3

what are the extraocular muscles?

Answer 3

located within the orbit, but extrinsic and seperate from the eyeball itself
control movements of the eyeball and superior eyelid

Question 4

superior rectus muscle

Answer 4

origin - superior part of common tendinous ring
insertion - superior and anterior aspect of sclera
function - elevates eye, contributes to abduction and medial rotation of eye

Question 5

inferior rectus muscle

Answer 5

origin - inferior part of common tendinous ring
insertion - inferior and anterior aspect of sclera
functions - depress and contribute to adduction and lateral rotation of eye

Question 6

medial rectus muscle

Answer 6

origin - medial part of common tendinous ring
insertion - anteromedial aspect of sclera
functions - adducts the eyeball

Question 7

lateral rectus muscle

Answer 7

origin - lateral part of common tendinous ring
insertion - anterolateral aspect of sclera
function - abducts the eye

Question 8

superior oblique muscle

Answer 8

origin - body of sphenoid bone
insertion - tendon passes through the trochlea and attache to the sclera of the eye
functions - depress, abducts and medially rotates eye

Question 9

inferior oblique muscle

Answer 9

origin - anterior aspect of orbital floor
insertion - sclera of eye, posterior to lateral rectus
functions - elevates, abducts and laterally rotates the eye

Question 10

levator palpebrae superioris

Answer 10

origin - lesser wing of sphenoid bone
insertion - superior tarsal plate of upper eyelid
function - elevates upper eyelid

Question 11

what is the function of the orbits?

Answer 11

orbit protects the eyes and anchors the soft tissues of the eye

Question 12

what is the function of eyelids and eyelashes?

Answer 12

protect the eye from abrasions by blocking particles that may land on the surface of the eye

Question 13

what is the palpebral conjunctiva?

Answer 13

• inner surface of each lid is a thin membrane
• extends over sclera
  connects the eyelids to the eyeball

Question 14

what is the lacrimal gland?

Answer 14

• located beneath the lateral edges of the nose

- produces tears which flow through lacrimal duct to the tunnel (medial corner of eye)

Question 15

how many layers are the of the eye?

Answer 15

outermost - fibrous tunic (sclera and cornea)
middle layer - vascular tunic (choroid, ciliary body and Iris)
innermost layer - retina, pigmented outer layer, neural inner layer

Question 16

what is the sclera?

Answer 16

• white part of the eye
• accounts for 5/6 of eye
• provides attachment for muscles

Question 17

what is the cornea?

Answer 17

• transparent

- covers the anterior tip of the eye and allows light to enter the eye

Question 18

what is the choroid?

Answer 18

highly vascularized connective tissue that provides a blood supply to the eyeball

Question 19

what is the ciliary body?

Answer 19

muscular structure that is attached to the lens by zonule fibres
bend the lens allowing to focus light on the back of eye

Question 20

what is the iris?

Answer 20

coloured part of the eye
visible in the anterior eye
smooth muscle that opens and closes pupil

Question 21

what is the retina?

Answer 21

fovea
sharpness of vision is greatest at fovea
- lacks surrounding cells and blood vessels

Question 22

what is the pigmented outer layer?

Answer 22

formed by a single layer of cells
attach to choroid
supports choroid in absorbing light – prevent scattering within eyeball

Question 23

what is the neural inner layer?

Answer 23

consists of photoreceptors, light detecting cells of retina,
posteriorly and laterally in the eye

Question 24

what are the photoreceptor rods?

Answer 24

provide monochromatic vision with high sensitivity to photonic activation across range of wavelengths
particularly useful at night (scotopic) vision

Question 25

what are the photoreceptor cones?

Answer 25

come in three varieties that contain pigments sensitive to primary colours (wavelength) of light
red, blue, green
primarily responsible for daytime (photopic) vision

Question 26

what is the anterior cavity of the eye?

Answer 26

space between the cornea and lens - iris and ciliary body

filled with water fluid called aqueous humour - lubrication

Question 27

what is the posterior cavity of the eye?

Answer 27

behind the lens that extend to the posterior side of the inferior eyeball, where the retina is located
filled with more viscous fluid - vitreous humour
- transmit light
- help retain the two layers of retina
- maintain intraocular pressure during accomodation

Question 28

what are the chambers of the eye?

Answer 28

anterior - located between the cornea and iris

posterior - between iris and ciliary processes

Question 29

what is visual processing?

Answer 29

• light rays from objects in form of photons enter the eye through cornea
• light rays pass through the pupillary diaphragm in the centre of the iris and project onto the retina
• refraction through lens causes inversion of image
• subsequently re-inverted by the brain
• once light strikes the retina the neurochemical process of phototransduction commences
• optic nerve will then deliver these signals to the brain which translates them into images
• visual information from retina is relayed through LGN of thalamus to primary visual cortex