Eyes And Orbit Flashcards
Nerves of the orbit
Supraorbital nerve (V1)
Optic nerve
Oculomotor
Trochlear
Abducent
maxillary (V2)
Canals of the orbit
Supraorbital foramen
Optic canal
Superior orbital fissure
Inferior orbital fissure
Infraorbital foramen
Oculomotor nerve (CN 3)
Parasympathetics:
- pre synaptic: synapse on ciliary ganglion
- post synaptic use short ciliary branches of V1 to get to the eye
- muscles that get parasympathetics are the sphincter papillae and ciliary Muscles*
Motor: most extraocular eye muscles
- levator palpebrae superioris
- superior rectus
- medial rectus
- inferior rectus
- inferior oblique
Trochlear nerve (CN 4)
Motor to the superior oblique muscle
Abducent nerve (CN 6)
Motor to the lateral rectus muscle in the eye
frontal branch of the Ophthalmic nerve (V1)
Supraorbital and supratrochlear nerves used for sensory of the skin of the forehead
Bones of the orbit
Frontal
Maxillary
Zygomatic
Lacrimal
Sphenoid
Palatine
Ethmoid
Three openings of the orbit
Optic canal
- optical nerve and ophthalmic artery
Superior orbital fissure
- CN 3,4,V1,6 and the superior/inferior ophthalmic veins
Inferior orbital fissure
-V2 and the infraorbital artery
Lacrimal branch of the Ophthalmic nerve (V1)
Take some parasympathetics from V2
Also carry sensory to lacrimal glands and the tarsal plates (upper eyelids)
Nasocillary branch of the Ophthalmic nerve (V1)
3 main branches
Long ciliary: sympathetic and somatic sensory of the eye itself
Short ciliary: sympathetic, somatic sensory, and parasympathetic from ciliary ganglion to the eye itself
Ethmoid branches: parasympathetics from facial nerve (CN7) and somatic sensory to the nasal cavity, sphenoid sinus and ethmoid air cells
Maxillary nerve (V2)
Carry postsynaptic Parasympathetic innervation from facial nerve (CN7) to the lacrimal gland
Muscles in the common tendinous ring
Superior rectus (CN3)
Inferior rectus (CN3)
Medial rectus (CN 3)
Lateral rectus (CN 6)
Superior oblique (CN 4)
Superior rectus
Innervated by oculomotor (CN3)
Attachment at top of eye and is primary elevator
- also some adduction and medial rotation
Inferior rectus
Innervated by oculomotor (CN3)
Attachment to the bottom of the eye and is the primary depressor of the eye
- also does adduction and lateral rotation
Medial rectus
Innervated by oculomotor (CN3)
Attachment is to the medial aspect of the eye
Conducts eye adduction
Lateral rectus
Innervated by abducent (CN6)
Attachment is to lateral aspect to the lateral aspect of eye
Conducts eye abduction
Superior oblique
Innervated by trochlear (CN4)
Attachment is the lateral posterior aspect of the eye and wraps around trochlear nerve
Depression, abduction and medial rotation
Down and out
Inferior oblique
Innervated by oculomotor (CN3)
Attachment is the lateral posterior aspect of the eye
Elevation, abduction and lateral rotation
up and out
oculomotor palsy
Eye presents abducted and depressed
Trochlear palsy
Eye appears adducted and elevated
Abducent palsy
Eye appears fully adducted
Conjunctivitis
Infection of the palpebrae conjunctiva lining the inside of the tarsal plates of the eyes
Eyelid function
Close via constriction of the obicularis oculi (CN7)
Open via levator palpebrae superioris and superior tarsal plate (CN3 and T1 root respectively)
- levator palpebrae superioris only does inital opening with tonic/static opening of the eye being the superior tarsal plate (root of T1)
while not always, inferior tarsal muscle and frontalis muscle can assist in tonic opening of the eyelid
Tarsal (meibomian) glands
Line the internal superior/inferior tarsal plates
Secrete Meibum which is a lubricant that prevents tear evaporation and protects eye
Supportive structures of the eye
Collectively called the fibrous tunic
- sclera = opaque white part of the visible eye that is the site of extrinsic muscle attachment
- cornea = transparent layer covering the lens
Structures of the Nutritive, vascular and muscular layer of the eye
found under the fibrous tunic
- choroid = vascular layer between the sclera and retina
- iris = contractile diaphragm of the lens. Possesses two muscles
1) sphincter pupillae = constricts pupil and innervated by parasympathetic of CN3 from the short ciliary branches
2) dilator pupillae =. Opens the pupil and is innervated by sympathetic fibers of CN3 from long and short ciliary nerves - ciliary muscle and body = secretes aqueous humor and possess muscle fibers that conduct accommodation of the lens (focusing on closer objects (CN3 parasympathetics vis short ciliary branches)
Structures of the nervous layer of the eye
- retina = conducts all special sensory of the eye via 5 parts
1) optic part: light receptor outer layer and is pigmented
2) ciliary part: covers ciliary body and is pigmented
3) iridium part: pigmented layer that covers the iris
4) optic disk: site of optic nerve enters, “blind spot” and contains no pigmentation of receptors
5) macula: primary color reception layer that contains the fovea Centralis (site of most acute vision)
- also called the “yellow spot”
Anterior and posterior vitreous chambers
Parts of the inner eye that contain aqueous humor fluid which is the primary source of nutrition to the inner eye (it is avascular)
- aqueous humor is produced by the ciliary body in the posterior chamber and possess around the lens into the anterior chamber
Vitreous body
Sits posteriorly to the lens and anterior chamber
Function is to provide consistent pressure and proper focal distance of the lens
- consists of virtuous humor which is more gelatinous than aqueous humor
Canal of Schlemm
Small site of the anterior chamber that functions to recycle aqueous humor into the venous system
Ophthalmic artery and its branches
Primary outer eye blood supply (branch of internal carotid)
1) central retinal artery: supplies the retinal neurons in the optic nerve
2) long and short posterior ciliary arteries: supply the rods and cones of the eye
3) lacrimal artery: supplies lacrimal gland
* Various anastomoses can occur also*
Danger triangle
Venus anastomosis that can lead to infection spreading into the cavernous sinus
- includes superior ophthalmic, inferior ophthalmic and supratrochlear
Eyes opening vs closing
Opening via levator palpabrae superioris and superior tarsal (CN3 and sympathetics), close via the obicularis oculi (CN7)
