Anatomy + Physiology Flashcards
What are the three layers of the eye?
Fibrous (outer layer)
Uvea - vascular layer (middle layer)
Retina - photosensitive (inner layer)
What are the two parts of the fibrous outer layer and what do they do?
Sclera - muscle attachment
Cornea - 2/3 of refractive power
What are the three parts of the uvea (vascular) layer and what do they do?
Iris - pupil diameter
Ciliary body - controls iris, shape of lens + secretions of aqueous humour
Choroid - nutrition + gas exchange
What are the three main parts of the retina (photosensitive) layer?
Retina
Macula
Optic disc
Where is the anterior segment of the eye?
In front of the lens
What are the two parts of the anterior segment?
Anterior chamber - between cornea and iris
Posterior chamber - between iris and suspensory ligaments
Where is the posterior segment of the eye?
Behind the lens
What does the posterior segment contain?
Vitreous body - contains vitreous humour
common location for ‘floaters’
Which part of the eye is affected in a cataract?
Lens is clouded
What is the limbus?
Corneo-scleral junction
Where is aqueous fluid made and secreted from in the eye?
Made in ciliary body
Secreted from ciliary processes
Where does aqueous fluid go once it is secreted, before it is reabsorbed?
Circulates within posterior chamber - nourishes lens
Then passes through the pupil into anterior chamber - nourishes cornea
Where is aqueous reabsorbed?
Into scleral venous sinus (Canal of Schlemm) at iridocorneal angle
What is the clinical significance of the iridocorneal angle?
Its the angle in ‘open-angle’ and ‘closed-angle’ glaucoma
What is the arterial supply to the eye?
Ophthalmic artery - branch of internal carotid
What is the arterial and venous supply to the retina and what is the clinical significance?
Central artery of the retina
Central vein of the retina
- end artery (no anastomosis to maintain viability if occlusion occurs)
- only vein draining the retina
What is the fundus?
Posterior area of the retina where light is focused
Which features can be seen when looking at the fundus?
Optic disc
Macula
Fovea
What is the optic disc?
Point of CNII formation
Only point of entry/exit for blood vessels and axons of CNII
–> Blind spot
Where is the greatest density of cones?
Macula
What is the fovea?
Depression in the centre of the macula
Area of most acute vision
What is the resulting feature of complete interruption of flow of the central artery or vein?
Monocular blindness
Light from objects in the right visual field is processed where in the brain?
Left primary visual cortex
Light from objects in the lower visual field is processed where in the brain?
Upper part of the primary visual cortex
What are the 7 extra ocular skeletal muscles?
Lateral rectus
Medial rectus
Superior rectus
Inferior rectus
Superior oblique
Inferior oblique
Levator palpabele superioris
What does elevator palpable superioris do?
Elevates the superior eyelid
Which extra ocular muscle passes through the trochlea?
Superior oblique
How are the extra ocular muscles innervated?
LR6 SO4 AO3
- lateral rectus = abducent nerve (CN6)
- superior oblique = trochlear nerve (CN4)
- all others = oculomotor (CN3)
Which eye movement in lateral rectus responsible for?
Abduction
Brings line of gaze into same plane as inferior and superior rectus (so they can be tested)
Which eye movement is medial rectus responsible for?
Adduction
Brings line of gaze into same plane as inferior and superior oblique attachments
How is superior rectus tested?
Abduct eye, then elevate
How is inferior rectus tested?
Abduct eye, then depress
How is inferior oblique tested?
Adduct eye, then elevate
How is superior oblique tested?
Adduct eye, then depress
Which structures pass into the orbit via the optic canal?
Optic nerve
Ophthalmic artery
Which structures pass into the orbit via the superior orbital fissure?
Cranial nerves 3, 4 and 6
What is a blowout fracture?
Fracture of the medial orbital wall and orbital floor
What is the name of the muscle which encircles the eye/orbit?
Orbicularis oculi
Which nerve supplies orbicularis oculi?
CNVII (facial) - muscle of facial expression
Which muscle is responsible for lifting the eyelid?
Levator palpabrae superioris
Where is the lacrimal gland located?
Superolateral to eye (just below eyebrow)
What is the nerve supply to the lacrimal gland?
Parasympathetic from CNVII
Describe the passage of lacrimal fluid once it leaves the lacrimal gland?
Washes medially over eye –> medial angle –> drains through lacrimal puncta –> nasolacrimal duct –> inferior meatus
