Intro to nervous system + anatomy of eye Flashcards
Name the 3 layers of the eye
Fibrous layer
Vascular layer (uvea)
Sensory layer
What does the fibrous layer of the eye consist of (2)
Sclera (posterior 5/6) + cornea (anterior 1/6)
What does the vascular layer of the eye consist of (3)
Choroid, ciliary body + iris
What does the sensory layer of the eye consist of (1)
Retina
Function of sclera
extrinsic ocular muscles attach to it
Function of cornea
transparent window to allow light rays into eyeball
Function of choroid
Made up of fenestrated blood vessels which supply blood to OUTER LAYERS OF RETINA by diffusion
What is the blood supply to the inner layers of the retina
central retinal artery
Function of ciliary body
Suspends the lens via suspensory ligaments (zonules)
Produces aqueous humor
Function of ciliaris
contracts to change shape of the lens and allow accommodation
Function of iris
Controls the diameter of the pupil by concentric and radial muscles and thereby control the amount of light rays entering eye
Retina function
Contains photosensitive rods and cones to allow us to see
How many layers does the retina consist of
10
What is the
- 1st layer of the retina (furthest back)
- 2nd layer of the retina
- 9th layer of the retina
Pigment epithelial layer
Rods and cones layer
Nerve fibre layer
Function of the pigment epithelial layer of the retina
Maintains health of the rods and cones
Contains pigments which absorb and help vitamin A recirculation
What does the nerve fibre layer of the retina contain
axons which join to form the OPTIC NERVE
How is the retina made more efficient
Fovea centralis
-exposed at surface of retina and PACKED WITH CONES to MAXIMISE VISUAL ACUITY
AH produced by what
Ciliary body
AH secreted where first
Posterior chamber
Where is AH drained out of the eye
angle of the anterior chamber
AH drainage apparatus consists of what
Trabecular meshwork (Acts like a sieve) –> schlemm’s canal
Shape of lens + what is it suspended by
Biconvex
Zonules from ciliary body
How is the lens transparent
Due to regular arrangement of collagen fibres and avascularity
Lens opacification leads to formation of a …
cataract
Bony orbit is closely related to ethmoidal and maxillary sinuses so what walls of the orbit are weak (2)
Medial & inferior
Anterior posterior length of eyeball
Anterior posterior length of orbit
24mm
40mm, because orbital fat cushions the eyeball posteriorly
What opening does CN III enter the orbit
Superior orbital fissure
CN III innervates LPS + all extrinsic eye muscles except which 2
Superior oblique
Lateral rectus
CN IV enters the orbit via which opening
Superior orbital fissure
CN VI enters the orbit via which opening
Superior orbital fissure
CN V1 enters orbit via which opening
Superior orbital fissure
CN V2 enters orbit via which opening
Foramen rotunda
What is the general sensory innervation to orbit and eye (2)
CN V1 & V2
Largest branch of CN V1 within the orbit
Frontal nerve branch
Name some small branches of CN V1 within the orbit (2)
Nasociliary nerve branch
Lacrimal nerve branch
Branches of CN V2 innervate what (2)
Floor of orbit
Lower eyelids
Function of intrinsic muscles of the eye
control pupil diameter & changes shape of lens
Function of extrinsic muscles of the eye
Move the eyeball
Superior oblique attaches to the orbit anteriorly via … then changes direction to travel laterally and attach to the …
Trochlea
Posterior sclera
When the sebaceous glands of eyelashes get blocked, they inflame and enlarge and can result in the formation of a …
Stye (red painful lump near edge of eyelid)
Skin of eyelid transitions into a mucous membrane called the … lining the inner surface of the eyelids
conjunctiva
The conjunctiva covers the front of the sclera but doesn’t cover the…
cornea
Is the conjunctiva vascular
Yes
Why would it be bad if the conjunctiva covered the cornea
Conjunctiva is very vascular and blood vessels often leak so don’t want the conjunctiva sitting in front of transparent cornea and decreasing amount of light that passes through
Levator palpebrae superioris originates from the apex of the orbit and attaches to what 3 things
a bit of the conjunctiva, a bit of the tarsal plate and to skin of the upper eyelid
What within the eyelid gives it form/shape
Tarsal plate
What does the tarsal plate contain
Meibomian glands which secrete oil - this oil coats the tear film and stops it evaporating
What does the lacrimal apparatus consist of (3)
Lacrimal gland
Lacrimal sac
Nasolacrimal duct
Lacrimal gland function
secretes tears, these tears coat the front of conjunctiva and the cornea
Where do tears secreted by lacrimal gland drain into
medial side of eye (through punctae) into lacrimal sac
Tears from lacrimal sac drain into what
Nasolacrimal duct then into the nasopharynx
Location of lacrimal gland
Lateral roof of orbit
Innervation of lacrimal gland
Parasympathetic fibres of facial nerve
Location of lacrimal sac
Medial wall of orbit
Arterial supply of structures inside orbit
Ophthalmic artery
Largest branch of ophthalmic artery
+ name other branches of the ophthalmic artery
Central retinal artery
Short posterior ciliary arteries
Long posterior ciliary arteries
Central retinal artery travels within what nerve
CN II
What is the retina’s dual blood supply
Central retinal artery supplies inner layers of retina
Choroid supplies outer layers of retina
What is the optic disc also known as due to no rods or cones being present
Physiological blind spot
What veins drain the orbit (2) + what sinus do they drain into
Superior and inferior ophthalmic veins
Cavernous
How is the transparency of the cornea maintained (3)
- REGULAR ARRANGEMENT OF COLLAGEN IN THE STROMA
- NO BLOOD VESSELS
- ENDOTHELIUM LAYER contains a pump that actively keeps AH out of the cornea
Why is the cornea said to be an immune privileged site
Due to it being avascular, there’s less chance of foreign antigens from a corneal graft being recognised by the recipient so lesser chance of graft rejection
How many layers does the tea film have + describe each layer
Layer 1 - mucinous layer overlying corneal epithelium
Layer 2 - aqueous layer lies over mucinous layer (MAJORITY OF TEAR FILM)
Layer 3 - oily layer is the most superficial (smallest layer
Which layer of the tear film is the most superficial layer
Layer 3 - the oily layer
Which layer of the tear film makes up the majority of the film
Layer 2 - the aqueous layer
Functions of tear film (3)
Keeps corneal moist
Wash away foreign bodies
Has antibodies and lysozymes to kill microbes