Anatomy 1 Flashcards
Label the surface anatomy of the eye shown
Label the surface anatomy of the eye shown
What are the 3 layers of the eye ?
- Fibrous - outer layer, this is divided into 2 parts:
- Sclera – muscle attachment
- Cornea – 2/3 of refractive power
- Uvea (vascular layer) - middle layer, this is divided into 3 parts:
- Iris – pupil diameter
- Ciliary body – controls iris, shape of lens and secretion of aqueous humour
- Choroid – nutrition and gas exchange
- Retina (photosensitive) -inner layer many parts (3 to be learned):
- Retina
- Optic disc
- Macula
What are the 2 main segments of the eye ?
- Anterior segment = area infront of lens
- Posterior segment = area behind lens
What is the anterior segment of the eye divided into ?
2 chambers:
- Anterior chamber (between cornea and iris)
- Posterior chamber (between iris and suspensory ligaments)
What does the posterior segment of the eye contain ?
- Contains vitreous body also called vitreous humour - this is the clear gel like fluid between the lens and the retina
- Vitreous body common location for ‘floaters’
Label the anterior segment of the eye shown
Describe the circulation of aqueous humour
- 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 is the clinical relevance of the the iridocorneal angle?
It is the angle involve in “open-angle” & “closed-angle” glaucoma
What can raised IOP result in ?
ischaemia of the retina and glaucoma
What is the main arterial supply to the eye and what is it a branch of?
The ophthalamic artery - this is a branch off the internal carotid artery
Label the arterial supply of the eye
Define what an end artery is
This is an artery with insufficient anastomoses to maintain viability of the tissue supplied if arterial occlusion occurs
Label the venous drainage of the orbit
Define what the fundus is
is the interior surface of the eye opposite the lens and includes the retina, optic disc, macula, fovea
Label the structures indicated and state what the fovea, macula and otpic disc is
Optic disc:
- Point of CN II formation
- Only point of entry/exit for blood vessels and axons of CN II
- Blind Spot
Macula:
- Greatest density of cones
Fovea:
- Centre of the macula
- Depression, 1.5mm diameter
- Area of most acute vision
What are the 3 layers of the retina ?
- The photoreceptors
- The ganglion cells
- The axons of the ganglion cells
What is the position of the retinal veins & arteries in relation to the retina ?
Retinal veins and arteries lie anterior to the retina
Why is the optic disc the ‘blind spot’ ?
Because there are no photoreceptors in the optic disc
Go over this pic of the structures identified on fundoscopy
What does complete interruption of retinal artery branch(s)/retinal vein(s) result in ?
Loss of an area of visual field corresponding to the area of ischaemia
What does complete interruption of flow of the central artery (end artery) or vein result in ?
Monocular blindness
Draw out the visual pathway
Light from objects in the right visual field is processed by what?
The left primary visual cortex (& vice versa)
Light from objects in the lower visual field is processed by what?
The upper part of the primary visual cortex (& vice versa)
Describe the main movements of the eye, consider 3 axis (vertical, transverse & anteroposterior)
- Vertical axis - abduction/adduction
- Transverse axis - elevation/depression
- Anteroposterior axis - intorsion/extorsion
When testing the extraocular eye muscles what are also testing, beside the function of that specific muscle ?
You are testing nerve function also - SO4LR6AL3
What are the different extraocular eye muscles ?
Note how the SO and IO both attach posteriorly to the eye ==> why they have opposite function of moving the eye than you would expect
What is the nerve supply of the lateral rectus muscle of the eye ?
CN VI (Abducent)
How do you specifically test the function of the lateral rectus muscle only ?
- LR’s only function is to adbuct the eye.
- Test function by attempting to bring line of gaze into same plane as superior rectus and inferior rectus
What is the nerve supply of the nerve supply of the superior & inferior rectus muscles ?
CN III (oculomotor)
How do you specifically check the function of the superior rectus muscle ?
When in abduction, SR can only elevate i.e. abduct the eye and if it can then be elevated then SR is working
How do you specifically check the function of the inferior rectus muscle ?
When in abduction, IR can only depress i.e. abduct the eye and if you can then depress it, then the IR is functioning
What is the nerve supply of the medial rectus & inferior oblique muscles?
CN III (oculomotor)
How is the function of the medial rectus muscle checked?
- MR can only adduct the eye
- Check function by checking you can bring pt line of gaze into same plane as superior oblique and inferior oblique attachments
How do you specifically check the function of the inferior oblique muscle ?
When in adduction, IO can only elevate i.e. adduct the eye and check that the eye can be elevated, if it can then the IO is functioning
What is the neve supply of the superior oblique muscle ?
CN IV (trochlear)
How do you specifically test the function of the superior oblique muscle ?
When in adduction, SO can only depress i.e. adduct the eye and check it can be depressed, if so the SO is functioning
Movements of the eyes usually require actions of more than one muscle, what muscles work together to produce pure elevation of the eye and also pure depression of the eye ?
- Pure Elevation - superior rectus and inferior oblique synergistically elevate eyes
- Pure Depression - superior oblique and inferior rectus, synergistically depress eyes
