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BIOL 1004 (106)

Walls of orbit

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BIOL 1004
Tamy Superle

The Eye Lecture Notes Walls of orbit • Pyramidal shaped • Twice as deep as wide • 45 degree angle between orbits • eyeball occupies only anterior half • lots of blood vessels and fat o fxn of fat  shock absorber, cushion  lubrication, fluid mvmt  protect nerves, vessels  last place that fat pads will disappear in body • when fat pads disappearsunken cheek and eyes • walls of orbit (7 elements): not smooth, full of holes and grooves o floor: maxilla, zygomatic, palatine o medial: ethmoid, lacrimal, frontal  fragile bone, paper thin o roof: frontal, sphenoid o lateral: zygomatic, sphenoid  zygomatic foramen: branch of maxillary Orbital foramina • optic canal holds optic nerve and oph1halmic artery • superior orbital fissure: CN III, IV, V , VI, ophthalmic veins o ophthalmic veins communicate w/ cavernous sinus and facial vein • inferior orbital fissure: CN V from foramen rotundum • fissures make V shape lateral to optic canal • ethmoidal nerves pass thru medial wallnasal nerves • fossa for lacrimal sac and nasolacrimal canal (inferomedial) o canal contains ductlacrimal fluid from surface of eye into nasal cavity o communication between orbit and nasal cavities lacrimal gland • superolateral part of orbit • sensory: V 1 • motor: pteryogoid ganglion of facial nerve • produces tears: blinking of eyes causes movement to keep eyes moist o brings fluid from lateral corner to medial corner drainage of tears • lacrimal glandcanalsconjunctival sac on surface of eyeballsurface of eyelacrimal papillae with puncta (holes)canaliculaelacrimal sacnasolacrimal duct o conjunctiva: mucosa that covers eyelid and goes onto sclera of eye  rich with blood vessels  gets inflamed during drinking and when particles touch it • nasolacrimal duct becomes saturatedcrying o nose runs when cry eyelids: protective skin flaps • muscles o levator palpebrae superioris  CN III  Inserts on tarsus superior (dense fibrous band) and goes deep and b/w orbicularis oculi  assisted by superior tarsal muscle (sympathetic trunk) o Obicularis oculi  CN VII  Forceful and passive closure of eye  Closing helps moisten cornea and protect from outside particles to prevent inflammation and blindness • Tarsus (superior and inferior) with tarsal glands (mybomium glands) o Glands open up on inner surface of eyelid o Glands secrete lubricating liquid to keep eye moist and eyelids from sticking together o Under hormonal control; sebaceous glands o Duct can get cloggedget growth (some weird name) • Ciliary glands associated with eyelashes (cilia): superficial o Under hormonal control; sebaceous glands o When clogstye • Common lesions o Third nerve palsy: affects superior division of oculomotor  Ptosis: drooping of eyelids  Mild version: sympathetics to upper eyelid affected o Bell’s palsy (CN VII) Eyeball: hollow sphere • 3 coats o fibrous outer coat  sclera: tough, dense fibrous coat that covers 5/6 of eyeball  cornea: continuous with sclera, transparent o vascular middle coat—three components are continuous  choroids: highly vascularzied, most richly vascularized structure in body  ciliary body: donut shaped, surrounds lens • ciliary processes: radial fibers from ciliary body to lens o suspends lens o works with zonular fibers—radial (suspensory ligament of lens) o see more about function in accommodation of lens section below • ciliary body/processes produces aqueous humor o humor flows from posterior to anterior chamber thru pupil o nourishes and bathes cornea and lens (avascular) o liquid flows between iriscornea anglevenous channels (sinus venosus sclera, canal of Schlemm)  channels make circle around perimeter of cornea o fluid is replenished every 90 minutes  iris: surrounds pupil (hole=aperture of camera) • controls amount of light entering by changing shape and size of pupil • contraction controlled by inferior division of oculomotor (parasymp) o goes thru ciliary ganglion o dependent on circular, concentric fibers • dilation: sympathetic control (long ciliary nerves) o dependent on radial fibers o neural inner coat: retina—posterior 5/6  retina has two different layers: developed separately • pigmented layer: fused with choroids • neural layer: picks up light rays o axons of ganglion cells travel towards optic disk o connect to bipolar cellsrods and cones • detached retina: separation of two layers o happens to prizefighters  continuous with optic nerve at optic disk/papilla: • in the mid
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