orbital cavity Flashcards
what are the bony features of the orbit
-frontal bone
-zygomatic
-maxilla
-lacrimal
-sphenoid
-paletine
-ethmoid
what sinuses is the orbital cavity bounded by
-medially: ethmoid paranasal sinuses
-laterally: maxillary paranasal sinuses
describe the accessory structures of the eye
-eyebrows: skin, supra-orbital ridge
-eyelids: (palpebrae); separated by a palpebral fissure and reinforced by dense CT bands or tarsi
-meet eachother at medial or lateral angles
-levator palpebra superioris: lifts the superior eyelid
-orbicularis oculi: closes the eyelids, facial muscle innervated by the facial nerve
what is the transparent mucous membrane that covers the inner surfaces of the eyelids (palpebral) and the anterior surface of the eyeball (bulbar)
conjunctiva
lacrimal apparatus
glands and ducts that drain lacrimal fluid to the nasal cavity
lacrimal gland
produces lacrimal fluid (tears), lies in a fossa in the superolateral orbit
lacrimal duct
fluid conveys to the conjunctival sac
lacrimal canalicula
connect to nasalacrminal duct. fluids leads to the nasal cavity
lacrimal production innervation
parasympathetic impulses of CN VII
function of the eyeball
-protect and supports the photoreceptors
-gather, focus, and proces light into precise images
3 layers of the eye
-fibrous, vascular, and inner
the internal cavity of the eye has
fluids (humors); light enters through
describe the fibrous layer of the eye
-external layer, has 2 regions of CT that provide shape and resistance
-cornea: anterior 1/6th of the fibrous coat, transparent, allows light to enter eye
-sclera: posterior 5/6th of the coat, white obaque region. provides shape and a sturdy anchoring site for extrinsic and intrinsic muscles
vascular layer of the eye
- chorotid: vascular, dark pigmented membrane. lines the sclera, preventing scattering of the light rays.
- ciliary body: ring, muscular vascular thickening that provides attachment to the lens. smooth muscles focus the lens.
- iris: visible colored part of the eye. contracts as it has smooth muscle fibers to focus the pupil.
-pupil: central opening of the iris, allows light to enter. contracted by the iris
smooth muscles of the iris and the ciliary body
sphincter pupillae: of the iris, circularly arranged. constricts pupil size (parasympathetic)
dilator pupillae: radially arranged, dilates the pupil (sympathetic)
dilation innerv
post-synaptic sympathetic
constricted inner
post-synaptic parasympathetic nerve
inner layer, visual layer
-retina: site where light photoreceptor cells are located
-2 parts:
optic layer: sensitive to visual light rays and composed of 2 layers, neural and pigmented
nonvisual layer: anterior continuation of the pigmented area
inner layer components
-optic disc: circular layer of retina where sensory fibers and vessels conveyed by the optic nerve CNII, enter the eyeball. contains no chemoreceptors and is insensitive to light
-macula: small area with special chemoreceptors cones for vision
-fovea centralis: depression at the center of the macula, best area of acute vision
types of photoreceptors in the retina
-rod cells: more sensitive to light, allow vision in dim light, no sharp/color
-cone cells: operate best in bright light, high color vision.
divisions of the lens
-anterior: filled with aqueous humor. clear watery solution that provided nutrients for the vascular lens and cornea
-posterior: filled with vitreous humor. transmits light, holds retina in place, and supports the lens
describe the light pathway
cornea-aqueous humor-lens-vitreous humor
ciliary muscle function and vision due to shape change of the lens
changes shape of the lens
-stretches, thinner lens: brings more distant objects into focus
-relaxed lens, thick: near vision
intraretinal space
separates the layers of a developing retina
correlated with retinal detachment: may result from a blow to the eye and seepage of fluid between the layers
general review of extra-ocular muscles of the orbit
-levator palpebrae superioris
-4 recti
-2 obliques
-origin: walls of the orbit
-insert: outer surface of the eyeball
-common tendinous ring: origin of 4 recti, surrounds optic canal
levator palpebrae superioris
covers eyelid
-action: elevates superior eyelid
-innerv: Optic Nerve CN II
recti muscles
-lateral: abducts
-medial: adducts
-superior: elevates
-inferior: depresses
oblique muscles
function: rotational movement
-superior oblique: originates posteriorly, runs anterior along the orbital wall and loops through the trochlea. insert: posterolateral eye surface
action: abducts (lateral) and depresses
inferior oblique: abducts and elevates the pupil
nerves of the orbit:
-general sensory: (skin) trigeminal CN V1 nerve
-special sensory: vision, Optic nerve CN II
-branchial motor: facial nerve CN VII
-somatic motor: move eye
1. oculomotor nerve CN III: levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, and inferior oblique
2. trochlear nerve CN IV: superior oblique
3. abducent nerve CN VI: to lateral rectus
-visceral motor: parasympathetic and sypathetic to dilator pupil muscle and sphincter; ciliary muscle
arteries of the orbit
ophthalmic artery: branch off the internal carotid artery
-central retinal artery: terminal branch, occlusion causes instant blindess
