Embryology/Anatomy of Eye Flashcards
from what structure in the embryo does the brain and spinal cord form from?
the neural tube
from what part of the neural tube does the optic vesicles form from?
diencephalic part
what do the optic vesicles in the embryo form?
the eyes
in which direction do the optic vesicles grow?
grow laterally towards the ectoderm
as the optic vesicle grows towards the ectoderm what happens?
the ectoderm layer becomes thicker and forms the lens placode
what is formed when the lens placode pushes inwards?
optic cup
how many layers does the optic cup have?
2
through which fissure do the blood vessels which are located on the inferior wall of the optic cup pass through?
choroid fissure
how many layers of the retina are there?
10
from which layer do most of the layers of the retina form from?
the inner layer
between which layers of the retina is there a potential space?
between the 9th and 10th
what happens to the choroid fissure in adult hood ?
it obliterates
what can occur if the choroid fissure is present in adult hood?
causes the development of a coloboma
where are the three places where a coloboma can occur?
iris
retina
disc
what are the choroid, stoma of the cornea, sclera and extra ocular muscles formed from?
mesenchyme
what is the conjunctiva formed from?
surface ectoderm
does the orbit have thick or thin walls?
thin
is the orbit rims weak or strong?
strong
what is the size of the eye ball?
2.1cm
what is the length of the eye canal?
8cm
why are the medial and inferior walls of the orbit weak?
because they are very close to sinuses so the thin walls can explode and cause hernia of the eye socket contents
what is the characteristic sign of a orbital floor fracture on a CT scan?
tear drop sign
what eye action can someone with an orbital floor fracture not be able to do?
elevation
what is the main function of orbital fat?
support of the eye ball
when there is hypertrophy of orbital fat, what can occur?
patient would have a staring appearance
what attaches to the sclera?
muscles for moving the eye ball
what is the epithelium on the cornea ?
stratified squamous non-keratinised
what is the basement layer of the corneal epithelium called?
bowmans membrane
what is contained in the stroma of the cornea?
regularly arranged collagen
what separates the cornea and the aqueous humour ?
single layer of squamous epithelium
are there any blood vessels in the cornea ?
no
what three things maintains cornea transparency
- regular arrangement of collagen
- no blood vessels
- pump at single epithelium layer which keeps aqueous fluid out
what is a corneal transplant called?
keratoplasty
state an inflammatory pathology of the cornea
corneal ulcer
state an non- inflammatory pathology of the cornea
dystrophies
is it hard or easy to find a corneal donor?
easy
is there is low or high chance of rejection for corneal transplants ?
low risk of rejection
why is there is low risk of rejections of corneal transplants?
the cornea is avascular so there is a less chance of foreign antigens being recognised by the recipient
which layer of the retina absorbs excess light in the eye?
the 1st layer (next to the choroid)
= pigment epithelial layer
which layer contains cones and rods?
2nd layer
which layer of the retina contains the nerve fibres?
9th layer
what are the four quadrants of the retina?
superonasal
inferonasal
superotemporal
inferotemporal
at the optic nerve head, what are the differences between the ophthalmic arteries and veins?
arteries
- thinner
- lighter
veins
- larger
- darker
what is the area with lots of cones medial of the retina called?
fovea centralis
what autonomic response dilates the pupil?
sympathetic
are there blood vessels in the lens?
no
what is lens opacification called?
cataract
what are the two chambers of the eye called?
anterior chamber
posterior chamber
what divides the two chambers of the eye ?
the lens
what is the function of the aqueous humour?
maintains intraocular pressure
what is the function of the vitreous humour?
cushions the retina
what is the viscosity of the AH and VH?
AH = watery fluid VH = gel
where is aqueous humour produced?
ciliary body
where is aqueous humour filtered out of the anterior chamber ?
trabecular meshwork
what canal does the aqueous humour flow out of the anterior chamber ?
schlemms canal
what is the condition caused by increased intraocular pressure ?
glaucoma
is the cornea covered by conjunctiva ?
no
what is the conjunctiva over the sclera called?
bulbar
what is the conjunctiva over the inner surface of the eyelid called?
palpebral
where is the lacrimal gland located?
lateral to the orbit
what is the journey which tears follow?
- produced by the lacrimal gland
- lacrimal gland ducts open up to the conjunctiva sac
- tears drain into the lacrimal sac
- tears drain through the nasolacrimal duct into the inferior meatus of the nasal cavity
what autonomic response causes tears to be produced?
parasympathetic
