The Orbit Flashcards
What ligaments act to restrict the movements of the medial and lateral recti of the eye?
The check ligaments
What forms the outer fibrous layer of the eyeball?
Sclera
Cornea
What is the role and innervation of the superior rectus?
Elevation, adduction and intorsion
Occulomotor CNIII
What structure of the eyeball is highlighted in this image?
Cornea
How is the aqueous humor of the eye recycled?
Drain back into the veins at the junction of the cornea and the sclera (the canal of Schlemm)
What is the role of the lacrimal nerve of CNV1?
Acts as a carrier for parasympathetic secretomotor fibres from the facial nerve (CN VII)
What is the blue bone?
Zygomatic bone
Where is the anterior chamber of the eye located?
Between the lens and cornea
Describe the location of the cranial nerves in the cavernous sinus
CN III, IV and V pass along the walls close to the dura
CN VI passes through the middle of the sinus close to the internal carotid artery
What is the function of the vitreous humor?
Supports the retina by pressing it to the choroid
What is the main nerve to the extraocular muscles?
Oculomotor nerve (CNIII)
Describe the process lubrication from the lacrimal gland?
Secretes a fluid to lubricate the eye and remove debris
Lies at the lateral edge of the orbit and releases tears onto the eye via tiny ducts
Wash across the eye and are gathered through the lacrimal punctum into the lacrimal canaliculi and then into the lacrimal sac
Describe the role of the tarsal plates of the eye
Physically protects the eye
Contains glands that release oily and watery secretions to lubricate the surface of the eye
What is the blood supply to the orbit?
Ophthalmic artery (a branch of ICA)
What structures support the corners of the eyelids?
The medial and lateral palpebral ligaments
What bone is shown in yellow?
Sphenoid bone
What is the role and innervation of the medial rectus?
Adduction
Oculomotor CNIII
What are the branches of the ophthalmic artery?
Forehead and scalp - supraorbital, supratrochlear, zygomaticotemporal
Nose - dorsal nasal and ethmoidal arteries
Describe the communications of the ophthalmic veins and the clinical significance of this?
Communicate with the cavernous venous sinus through the superior orbital fissure, with the pterygoid venous plexus through the inferior orbital fissure with the facial vein
Creates a potential spread of infection from the external structures to internal structures such as the dural meninges
What is the role and innervation of the inferior rectus muscle?
Depression, adduction and extorsion
Occulomotor CNIII
What is contained within the posterior chamber of the eye?
Vitreous humor
What foramen sits in the maxilla?
Infraorbital foramen - infraorbital branch of CNV2 passes through to exit the skull and supply sensory innervation to the face
What is the salmon pink bone?
The Frontal bone
What is the contents of the orbit?
Eyeball Fat and connective tissue Extraocular muscles Nerves Blood vessels
What foramens are found in the sphenoid bone?
Optic canal - CNII
Superior orbital fissure - CN III, IV, V1, VI
Contributes to inferior orbital fissure
What bone is shown in orange?
Ethmoid
What ligament supports the position of the eyeball within the orbit?
The suspensory ligament
Describe the role and innervation of the Dilator Pupillae?
Increases the diameter of the pupil - allows more light into the retina
Innervated by the sympathetic nervous system, carried on the blood vessels
What does this image show and what bone makes up this structure?
Supraorbital ridge
Formed by the frontal bone
Describe the nasciliary branch of CNV1?
Forms ethmoidal branches which go on to pass through the ethmoid bone
What is the role and innervation of the ciliary muscle of the eye?
Changes the shape of the lens of the eye for accomodation
In absense of nerve stimulation it is relaxed. Parasympathetic causes the muscle to contract.
Occulomotor nerve - CNIII
What makes the aqeous humor of the eye?
Ciliary body
Describe the route of optic nerve CNII?
Gathers impulses from the light sensitive cells of the retina pass them to the brain to be interpreted
Leaves the orbit via the optic canal, forms a chiasma over the pituitary fossa then sends optic tracts towards the brain
Optic radiations then take the information to be processed in the visual cortex
What do the supratrochlear and supraorbital branches of CNV1 do?
Pass onto the face via the supraorbital notch and supply sensory innervation to the forehead skin
What bone is shown in purple?
Maxilla
What is the role and innervation of the inferior oblique?
Extorsion, elevation and abduction
Occulomotor CNIII
What is the role and innervation of the superior oblique?
Intorsion, depression and abduction
Trochlear CNIV
LR6SO4
What is the role and innervation of the levator palpebrae?
Raises the upper eyelid
Occulomotor CN III
What are the branches of CN VI (ophthalmic)?
Supratrochlear and Supraorbital (from frontal)
Lacrimal
Nasociliary
What nerve lies on the surface of lateral rectus?
CN VI (abducens)
What are the intrinsic muscles of the eye?
Dilator Pupillae
Sphincter Pupillae
Ciliary muscle
What is the role and innervation of lateral rectus?
Abduction
Abducent CNVI
LR6SO4
Through which fossa do the nerves supplying the muscles of the eye pass through?
Superior orbital fissure
What is the role of aqueous humour?
Helps to maintain the intra-occular pressure
What structures are included in the middle, vascular layer of the eye?
Iris
Ciliary body
Choroid
With what nerve does the ciliary ganglion communicate with?
CN III (oculomotor) and sends short ciliary nerves to the eyeball
What bone is shown in green?
Lacrimal
Which part of the eye is the ‘blind spot’?
The optic disc, where the optic nerve leaves the retina
What are the 7 extraoccular muscles of the eye?
Levator Palpebrae Superioris
Superior, inferior, medial and lateral recti
Superior and Inferior oblique
Describe the role and innervation of the Sphincter Pupillae?
Decreases the diameter of the pupil - restricts the amount of light entering
Parasympathetic innervation via CN III
How does the ophthalmic artery enter the orbit?
With the optic nerve through the optic canal