The visual system Flashcards
Where does the eyeball sit in
Bony orbit
What three parts can the eyeball be divided into
fibrous
vascular
inner
What three parts can the eyeball be divided into
fibrous
vascular
inner
What is the outer most layer of eye
Fibrous layer
What is the function of fibrous layer
Provide shape to the yee and support deeper sturcutresa
What is the sclera
Majority of the fibrous layer
provides attachment for the extraocular muscles
What is the cornea
Transparent and centrally position part of fibrous layer
Light entering the eye is refracted by the cornea
What is the vascular layer made up of
Choroid
Ciliary body
Iris
What is the choroid
Connective tissue and blood vessels
Provides nourishment to the outer layer of the retina
What is the ciliary body
Comprised of the ciliary muscle and ciliary processes
Controls the shape of the lens and contributes to the formation of aqueous humor
What are the ciliary muscles
Collection of smooth muscle fibres, which are attached to the lens by ciliary processes
What is the iris
Circular structure with an aperture in the centre
Pupil diameter is altered by smooth muscle fibres within the iris, innervated by the autonomic nervous system
What is the macula
In the macula Yellowish layer that contains fovea, which contains high concentration of light detetcing cells
Responsible for high acuity vision
What is the lens
Located anteriorly between the virtous humor and the pupil
Shape of the lens is altered by ciliary body, altering its refracting power
What are the anterior and posterior chambers
areas filled with aqueous humor
Anterior chamber located between iris and cornea
Posterior chamber between iris and ciliary processes
What is the aqueous humor
Clear plasma like fluid that nourishes and protects the eye
Porudced constantly and drain via the trabecular meshwork
what is the trabecular meshwork
Area of tissue at the base of the cornea
What is elevation and depression
Elevation is movement of eyeball superiorly
Depression is movement of eyeball inferiorly
What is abduction and adduction of eyeball
Abduction - lateral movement of eyeball
Adduction - medial movement of eyeball
What are the 7 extrinsic muscles of the eye
Superior rectus inferior rectus medial rectus lateral rectus superior oblique Inferior oblique Levator palpebrae superioris muscle
What is the only extrinsic muscle that acts on the eyelid
Levator palpebrae superioris
Attachments of the Levator palpebrae superioris
Originates from the lesser wing of the sphenoid bone, immediately above the optic foramen
Attaches to the superior tarsal plate of the upper eyelid
What innervates the Levator palpebrae superioris
Oculomotor nerve
Where do the four recti muscles originate from
Common tendinous ring
Attachment of superior rectus
Originates from the superior part of the common tendinous ring and attaches to the superior and anterior aspect of the sclera
Action of superior rectus
Elevation
also contributes to adduction and medial rotation of the eyeball
Attachment of inferior rectus
Originates from the inferior part of the common tendinous ring and attaches to the inferior and anterior aspect of the sclera
Action of inferior rectus
Depression
Contributes to adduction ad lateral rotation of the eyeball
Attachment of the medial rectus
Originates form the medial part of the common tendinous ring and attaches to the anteromedial aspect of the sclera
Action of the medial rectus
Adducts the eyeball
Attachment of the lateral rectus
Originates from the lateral part of the common tendinous ring and attaches to the anterolateral aspect of the sclera
Action of the lateral rectus
Abducts the eyeball
Innervation of the recti muscles
All innervated by oculomotor
except lateral rectus - innervated by abducens
Attachment of superior oblique
Originates from the body of the sphenoid bone
Tendon passes though a trochlea and then attaches to the sclera of the eye posterior to the superior rectus
Action of the superior oblique
Depresses, abducts and medially rotates the eyeball
Attachment of inferior oblique
Originates from the anterior aspect of the orbital floor
attaches to the sclera of the eye posterior to the lateral rectus
actions of the inferior oblique
Elevates, abducts and laterally rotates the eyeball
Innervations of the oblique muscles of eye
Superior - trochlear
Inferior - Oculomotor
What does the parasympathetic part of the oculomotor nerve innervate in the eye?
supplies the sphincter papillae and the ciliary muscles of the eye
Through what does the oculomotor nerve enter the cranial cavity
What happens to the nerve past this point
Via the superior orbital fissure
Divided into the superior and inferior branches
What does the sphincter pupillae do?
constricts the pupil
Through what does the trochlear nerve exit the cranial cavity
Superior orbital nerve
Where does the trochlear nerve arise from
Posterior aspect of the midbrain
Where does the abducens nerve arise rom and where does it exit the cranial cavity from
Exits the brainstem at the junction of the pons and the medulla
Exits the cranial cavity through superior orbital fissure
How is the optic nerve formed
Convergence of axons from the retinal ganglion cells
Where does the optic nerve travel after it’s formation
Leaves bony orbit via the optic canal
Enters the cranial cavity running along the surface of the middle cranial fossa
What is the optic canal
A passageway through the sphenoid bone
What is the optic chiasm
Within the middle cranial fossa, optic nerve from each eye unite to form the optic chiasm
Fibres from the nasal (medial) half of each retina cross over to the contralateral optic tract, while fibres from the temporal (lateral) halves remain ipsilateral
What does the left optic tract contain
Fibres from the left temporal retina and the right nasal retina
What does the right optic nerve contain
Fibres from the right temporal retina and left nasal retina
How does brain process sensory data from eye
Each optic nerve travels to its corresponding cerebral hemisphere to reach the lateral geniculate nucleus
Axons from the LGN then carry visual information via the optic radiation
Once at the visual cortex, the brain processes the sensory information and response appropriately
What is the lateral geniculate nucleus
A relay system located in the thalamus