Neuroanatomy S2 E4: Orbit #neuroanatomy #ubcmedicine

[Music] our eyes allow us to detect information about light and help to form complex images this is how we're able to visualize the world around us and how you can see me right now but how do we compensate for changes in light intensity how do we control the focal depth of our lens the size of the pupil can actually adapt to changes in light intensity it dilates in low light through sympathetic fibers and it can constrict in highlight intensity through parasympathetic fibers the complex Machinery that regulates these functions travels through the orbit to the eyeball the orbits also contain muscles that move the eye and Associated nerves and blood vessels let's look at the pathway of these nerves through the orbit to the eye [Music] here is a sketch of one of the orbits is seen from above this is medial and this is lateral the eyeball is here the optic nerve carries light information to the brain here is a branch of five the Opthalmic nerve this important branch of the phalic nerve is the nasociliary nerve which carries General Sensation from the eyeball through these ciliary nerves here this is cranial nerve 3 the ocul motor nerve which carries motor information to most of the muscles that move the eyeball cranial nerves four and six also inovate muscles that move the eye but we're not going to talk about those here the ocular motor nerve also carries parasympathetic fibers remember these fibers will constrict the pupil and need to reach reach the constrictor pupila muscle here they also inate the ciliary muscle that focuses the lens let's follow the course of these fibers from three to their target tissues preganglionic fibers carried in three leave the nerve and enter the ciliary ganglion which hangs off some of the ciliary nerves here they sign apps and postganglionic fibers follow the ciliary nerves into the eyeball to ultimately reach constrictor pipil they also reach the ciliary muscle sympathetic fibers to the eyeball are postganglionic they originate in the superior cervical gangion at the base of the skull and follow the arteries into the orbit they hop off the artery onto these ciliary branches and follow them into the eyeball to reach dilator pupil let's have a look at these structures in a dissection of the orbit so this is a dissection of the orbit looking from above this is medial this is lateral and this is anterior you can see the eyeball and the optic nerve here here is the nasociliary nerve and you can see it crossing the optic nerve to get to the medial side of the orbit here is the inferior division of the oculam motor nerve or cranial nerve 3 preganglionic parasympathetic fibers leave cranial nerve 3 to enter the ciliary ganglion here after their sinaps postganglionic fibers travel with the short ciliary nerves into the eyeball postganglionic sympathetics travel into the eyeball along these long ciliary nerves here here pupil size is not solely dependent on light intensity an increased sympathetic tone will cause pupilary dilation for example when you're angry or scared or even in love clinically the assessment of pupil size is an important part of the neurological exam in particular when pupils are unequal in size this can give us important Clues as to where a lesion causing these symptoms may be localized [Music] [Music] first [Music]

Channel: UBC Medicine - Educational Media

Views: 44,178

Keywords: Faculty of Medicine, dissections, human, anatomy, neuroanatomy, orbit, optic nerve, opthalmic nerve, ciliary nerves, oculomotor nerve

Id: 0FjYhdwEgYc

Length: 5min 15sec (315 seconds)

Published: Mon Jan 11 2016