week 1 anatomy Flashcards
what bones make up the bony orbit?
frontal, zygomatic, sphenoid, ethmoid, lacrimal, maxilla
which two bones of the bony orbit have orbital plates?
frontal and ethmoid
on which bone is the optic canal/apex and the superior orbital fissure?
sphenoid
on which bone would you find the supraorbital notch/foramen?
on which bone would you find the infraorbital foramen?
frontal
maxilla
the orbital rim is made up from 4 orbital margins, what are they?
superior, inferior, medial and lateral orbital margins
what makes up the orbital margins?
Superior margin: frontal bone and sphenoid
Inferior margin: maxillary bone, palatine and zygomatic
Medial margin: ethmoid, lacrimal bone, sphenoid (body of) and maxilla
Lateral margin: zygomatic and sphenoid (greater wing)
what is affected by an orbital blowout #? why?
medial wall and orbital floor
as they are extremely thin and orbital rim is strong
what will a # zygoma cause?
fractured zygoma tends to rotate medially towards the floor of the orbit
the suspensory ligament of the eye attaches to the zygoma laterally
the eye may be lowered towards the orbital floor
DIPLOPIA (double vision) may result
WHAT IS THE MAIN MUSCLE MAKING Up THE EYELID (external)? what are its parts?
orbicularis oculi
orbital & palpebral parts
what nerve supplies the orbicularis oculi?
CNVII - facial
what does the orbital septum do? how?
helps prevent spread of infection from superficial to deep
sheet of fascia continuous with periosteum
what is responsible for lifting the eyelid?
tendon of levator palpebrae superioris/ LPS
what covers the iris?
what covers the sclera?
cornea conjunctiva (defensive barrier preventing foreign bodies penetrating deep to it into the orbit)
what is the limbus
or corneoscleral junction?
point where iris and sclera meet
explain how the lacrimal apparatus works
lacrimal gland produces lacrimal fluid (parasympathetic CN VII) → wash over eye lateral to medial→ drains through lacrimal puncta→eventually reaches inferior meatus
what are the 3 layers of the eye?
outer/fiberous layer
uvea/vascular layer
retina/photosensitive layer
what are the parts of the fiberous layer of the eye
sclera – muscle attachment
cornea – 2/3 of refractive power
what are the parts of the uvea
iris – pupil diameter
ciliary body – controls iris, shape of lens and secretion of aqueous humour
choroid – nutrition and gas exchange
what are the parts of the retina
many parts [3 to learn = optic disc, macula, fovea]
what are the segments and chambers of the eye?
Anterior and posterior Segments and chambers
describe the anterior segment of the eye
Anterior Segment: in front of lens divided into chambers anterior chamber between cornea and iris contains aqueous humour posterior chamber between iris and suspensory ligaments contains aqueous humour
describe the posterior segment of the eye
Posterior Segment: behind lens 2/3rds of eye contains vitreous body vitreous humour vitreous body common location for ‘floaters’
what is the definition for a cataract? what types can you get?
clouding of the lens [the iridocorneal angle is the angle in “open-angle” & “closed-angle” glaucoma]
describe the circulation of aqueous
- Ciliary body
smooth muscle and blood vessels
ciliary processes secrete aqueous - Aqueous circulates
within posterior chamber
nourishes lens - Aqueous then passes through pupil
into anterior chamber
nourishes cornea - Aqueous reabsorbed
into scleral venous sinus (Canal of Schlemm)
at iridocorneal angle
what causes raised IOP? what can occur?
overproduction/not good removal of aqueous
raised intra-ocular pressure can cause ischaemia of the retina and glaucoma
what is the blood supply to the eye?
internal carotid→through carotid canal→ ophthalmic artery
→ciliary arteries (red eye in photos)*
→forehead/scalp arteries
→central artery of retina passes into optic nerve (end artery - no anastomoses)***
→nasal cavity branches
venous drainage of the eye
central vein = only vein drawing retina
superior and inferior ophthalmic veins drain facial nerve (orbit) and forehand vein, the inferior opthamic vein drains into superior, superior drains into cavernous sinus
what is the danger triangle of the face?
upper lip/external nose, infection can travel back (venously) to cavernous sinus via the superior orbital fissure - meningitis and direct into cranial cavity
how is the retina examined?
fundoscopy
key parts of the retina
Optic disc=
point of CN II formation
only point of entry/exit for blood vessels and axons of CN II, creates Blind Spot (as no cones/photoreceptors)
Macula=
greatest density of cones
Fovea=
centre of the macula
depression, 1.5mm diameter
area of most acute vision
what are cones and rods?
Rods - sensitive to low levels of light
- night vision / peripheral vision
Cones - detailed vision (acuity)
- colour vision
describe the layers of the retina
posterior to anterior -
photoreceptors, ganglion cells, axons of ganglia cells forming optic nerve (retinal arteries and veins lie anterior to retina)
what happens if there is complete interruption of flow to rental artery branch/vein? central artery/vein (end artery)?
loss of an area of visual field corresponding to the area of ischaemia
monocular blindness
learn the visual pathway
The axons in the visual pathway maintain specific spatial relationships to each other:
light from objects in the right visual field is processed by the left primary visual cortex
light from objects in the lower visual field is processed by the upper part of the primary visual cortex
see slide 19/38
what are the 7 extraocular muscles?
4 rectus muscles= superior rectus inferior rectus medial rectus lateral rectus
2 oblique muscles=
superior oblique
inferior oblique
(insert onto sclera)
1 levator palpebrae superioris (lifts upper eyelid)
where do the rectus Extraocular/EO Muscles originate from?
all originate from common tendinous ring
which EO muscles are innervated by what? good way to remember?
Lateral Rectus – CN VI (abducent nerve)
Superior Oblique – CN IV (trochlear nerve)
All Others – CN III (oculomotor nerve)
LR6 SO4 AO3
what does lateral rectus do? nerve?
can only abduct eyeball
CN VI (Abducent)
what does superior rectus do? nerve?
when in abduction, SR can only elevate
CN III (Oculomotor)
what does inferior rectus do? nerve?
when in abduction, IR can only depress
CN III (Oculomotor)
what does medial recuts do? nerve?
can only adduct eyeball
CN III (Oculomotor
what does inferior oblique do ? nerve?
when in adduction, IO can only elevate
CN III (Oculomotor)
what does superior oblique do? nerve?
when in adduction, SO can only depress
CN IV (Trochlear)
clinical testing eye movements, was
- synergists and antagonists
- yolk
what are the eye movements?
abduction; adduction; elevation; depression; intorsion; extorsion
