anatomy of the eyeball Flashcards
what covers the iris?
cornea
where is the lacrimal gland located?
beneath the eyebrow
what is the anatomical name for the tear duct?
lacrimal lake
what covers the sclera?
conjunctiva
what forms the deepest layer of the eyelid?
palpebral conjunctiva
what is the conjunctiva?
thin mucous membrane that is reflected onto sclera of the eyeball (bulbar conjunctiva)
what does the fibrous layer consist of?
sclera and cornea
what does the sclera provide?
attachment for the extraocular muscles
what is light entering the eye partially refracted by?
cornea
what does the uvea consist of?
iris
ciliary body
choroid
what is the iris?
pigmented membrane with a central opening (pupil) which adjusts in size in response to light
what does the pupil do?
regulate the amount of light that reaches the retina
what is the diameter of the pupil altered by?
smooth muscle fibres within the iris, innervated by autonomic nervous system
what does the ciliary body do?
adapt the shape of the lens, anchors lens and produce aqueous humor
what are the 2 parts of the ciliary body?
ciliary muscle and ciliary processes
what does the ciliary muscle consist of?
collection of smooth muscle fibres which are attached to lens of the eye by the ciliary processes
what is the choroid?
layer of connective tissue and blood vessels which provide nutrition and gas exchange to outer layers of the retina
what is the fundus of the eye?
the inferior surface opposite the lens which light is focused
what does the fundus consist of?
retina
optic disc
macula
fovea
posterior pole
what is the retina?
light detecting component of the eye
what are the 4 main layers of the retina?
retinal pigment epithelium
rods and cones
bipolar neurons
ganglion neurons
what do axons of ganglion neurons form?
optic nerve
where do the retinal veins and arteries lie?
anterior to retina
why is the optic disc called the “blind spot”?
no photoreceptors
what forms the optic disc?
axons of ganglion cells that leave eye to form optic nerve (CN II)
what is the only point of entry/exit for blood vessels and axons of optic nerve (CN II)?
optic disc
which part of the retina contains the greatest density of cones?
macula
what is the fovea responsible for?
high acuity vision
what does complete interruption of retinal artery branch/retinal vein indicate?
loss of field of vision at area of ischaemia (nasal or temporal)
what does complete interruption of flow of the central artery (end artery) or vein indicate?
monocular blindness
what are the two segments?
anterior
posterior
where is the anterior chamber?
in front of lens
what is the anterior segment divided into?
anterior chamber
posterior chamber
where is the anterior chamber located?
between cornea and iris
where is the posterior chamber located?
between iris and suspensory ligaments
what is the anterior chambers filled with?
aqueous humor
what is the role of aqueous humor?
nourished and protects eye
where is the posterior segment?
behind lens, 2/3 of eye
what does the posterior segment contain?
vitrous body which has vitreous humor
what is viterous humor a common location for?
“floaters”
what do ciliary processes secrete?
aqueous
what are the steps of circulation of aqueous in anterior segment?
- ciliary body - SM and BV, ciliary processes secrete aqueous
- aqueous circulates within post chamber to nourish lens
- aqueous passes through pupil into anterior chamber to nourish cornea
- aqueous reabsorbed into scleral venous sinus (Canal of Schlemm) at iridocorneal angle
what can raised intra-ocular pressure cause?
ischaemia of retina
glaucoma
what is a cataract?
clouding of lens
what is another word for corneoscleral junction?
limbus
where does the eyeball receive arterial blood supply from?
ophthalmic artery
what is the ophthalmic artery a branch of?
internal carotid artery
what artery supplies some of the structures in the floor of the orbit?
infraorbital artery
what is the infraorbital artery a branch of?
external carotid artery
what artery supplies the internal surface of the retina?
central artery of retina
what would occlusion of the central artery cause and why does this occur?
blindness
as it’s an end artery
what is venous drainage of the eyeball carried out by?
superior and inferior ophthalmic veins
where do the superior and inferior ophthalmic veins drain into?
cavernous sinus via superior orbital fissure
what is the only vein that drains the retina?
central vein of retina
in the danger triangle it is possible that infection from this area can spread to the brain, why is this?
because of venous communication between facial vein and cavernous sinus via ophthalmic veins
when light from objects in the left visual field, which does it hit on the left and right eye?
left - nasal retina
right - temporal retina
when light from objects in the right visual field, which does it hit on the left and right eye?
right - nasal retina
left - temporal retina
what transmits neurochemical signals from retina to visual centres in brain?
nerve fibres in optic nerve
where do nerve fibres from the nasal retina cross to opposite sides of the brain?
optic chiasm
where is light from the left visual field processed?
right primary visual cortex
