Unit 14: The eye Flashcards
What is the orbital margin and the orbital walls?
Margin - The anterior-most circle (the base of the pyramid)
Walls - the bones within the orbit heading backwards towards the brain (think of as sides of the pyramids)
What makes up the supraorbital margin of the orbit?
Frontal bone
What makes up the laterla margin of the orbit?
The frontal bone
The zygomatic bone
What makes up the infraorbital margin of the orbit?
The maxilla
The zygomatic bone
What makes up the medial margin of the orbit?
The maxilla (anterior lacrimal crest)
The frontal bone
What is the role of the medial wall or the orbit?
What makes it up?
Division between the orbit and the nasal cavity
Passage for arteries and nerves.
Made from the maxilla, lacrimal bone, ethmoid bone, sphenoid bone body.
What is the floor of the orbit and what is its function?
Separates the orbit from the maxillary sinus, prevents content from spreading between these structures
Made from the maxilla (orbital process), the zygomatic bone and the palatine bone (orbital process) .
What is the roof of the orbit made from?
What is its function?
Wall between orbit, cranial fossa and potentially the frontal sinus
Made from the frontal bone and the sphenoid bone.
Contains the trochlear fovea - connects to trochlear cartilage to act as pully for superior oblique anteromedially and the lacrimal fossa anterolateral for the lacrimal gland.
What is the lateral wall of the orbit made from?
What is its function?
Zygomatic bone
Greater wing of the sphenoid
Contains the superior orbital fissure - communicate with cranial fossa
Contains inferior orbital fissure for communication with the pteyrgoid palatine fossa
Enables nerves and vessels to reach the orbit
Why is it significant that the eyes face anteriorly?
Anatomical - anterior facing eye
However long axis of orbit is slightly lateral. (the cardinal position of the eye)
This means there must be tonic activity of the muscles of the eye to hold the eye in place - this is mainly down by tonic contraction of medial rectus.
What is the function of the levator palpebrae superioris?
Originates from lesser wing of sphenoid and inserts into superior tarsal plate of superior eyelid.
Elevates the superior eyelid.
What nerve innervates the levator palpebrae superioris muscle?
The oculomotor nerve.
What are the seven different extra-ocular eye muscles?
Superior rectus
Inferior rectus
Medial rectus
Lateral rectus
Superior oblique
Inferior oblique
What is the origin of the s/m/i/l rectus muscles of the eye?
The common tendinous ring
Then insert onto their appropriate aspect of the sclera
What do all extra-ocular muscles (minus the levator palpebrae superior) insert onto?
The sclera.
What is the function of rectus muscles of the eye?
Superior - elevates the eye
Inferior - depresses the eye
Medial - adducts the eye
Lateral - abducts the eye
Describe the innervation to the extra ocular muscles of the eye?
SO4 LR6 AO3
Superior oblique by CN4
Lateral lectus by CN6
All others by oculomotor nerve
What is the function of the superior oblique muscle in the eye?
Depresses, abducts and intorts the eye
Intorsion is the primary function in the anatomical position
(attaches to back of eye)
What is the function of the inferior oblique muscle of the orbit?
Elevates, abducts and extorts the eye
Extorsion is the primary function in the anatomical position
(attaches to back of eye)
What is the unique anatomy of the insertion of the inferior rectus?
Has does this affect its function?
Passes obliquely from the common tendinous ring
Enables to depress as the primary function in anatomical position but can also adduct and extort the eye (down and out).
What is unique about the anatomy of the insertion of the superior rectus and how does this affect its function?
Passes obliquely through the orbit
Can elevate the eye as its primary function in the anatomical position but can also adduct and intort the eye.
What is the origin of the superior oblique muscle?
Originates from the sphenoid bone
Passes into orbit
Has tendinous middle - that loos around a fibre cartilage that is attached to the trochlear of the frontal bone
It continues posteriorly laterally as muscle to attach to the eye
What co-ordination contraction produces elevation of the eye?
Superior rectus and inferior oblique
What co-ordination contraction produces depression of the eye?
The inferior rectus and the superior oblique.
How does the optic nerve get to the eye?
Originate from optic chiasma
Through optic canal
Through common tendinous ring
What nerves enter the orbit through the superior orbital fissure and go outside the tendinous ring?
The lacrimal nerve
The frontal nerve
The trochlear nerve
The oculomotor ( superior division)
What nerves enter the orbit through the superior orbital fissure and go inside the tendinous ring?
The nasocillary nerve
The oculomotor nerve (inferior division)
The abducens nerve
What is the role of the lacrimal nerve in the orbit?
Is a branch of the opthalmic division of the trigeminal nerve
Passes inferiorly and laterally, contains sensory and PANS fibres for the lacrimal glands.
What is the role of the frontal nerve in the orbit?
Is a branch of the ophthalmic division of the trigeminal nerve.
Passes superiorly and medially to the forehead
What is the role of the trochealr nerve in the orbit?
Innervates superior oblique muscle
What is the role of oculomotor nerve superior division in the orbit?
Innervates levator palpebrae superioris and superior rectus
What is the role of the nasocillary nerve in the orbit?
Branch of ophthalmic division of the trigeminal nerve.
Long ciliary nerves - sensory for ciliary body, iris and corner, post ganglionic sympathetic to dilate pupil
Short ciliary nerves - extend from autonomic ciliary ganglion, contain autonomic fibres, sympathetic for the vasculature, parasympathetic for ciliary body and sphnicter pupillae.
What is the anatomy of the nasociliary nerve?
Medial wall of the orbit
Gives off posterior and anterior ethmoid nerves that enter into the nasal cavity.
infratrochlear nerve branch just before anterioe thmoid extends towards the bridge of the nerve.
What is teh function of the oculomotor nerve inferior division in the orbit?
Innervates the medial rectus, inferior rectus and inferior oblique.
What is the role of the abducens nerve in the orbit?
Innervates the lateral rectus muscle.