Rashed Al-Jomard. Alanood Bostanji

Transcription

1 Anatomy #2 The Orbit & Cranial Nerve III, IV, VI Rashed AlJomard Alanood Bostanji 1 P a g e

2 The Orbit & Cranial nerves III,IV&VI ** Some notes about the last lec & first MM : Lens :: "just clarify for the lens part of the mind map " 1 suspended by suspensory ligament to the cilliary body 2 two unequal curves 3 located posterior to the post. chamber & anterior to the Vetrieus body. 4 made of Epithelium, capsule & fibers. Now we will talk about the optic nerve & visual pathway " 2 nd MM" Why we need to learn this?! if I have a patient,that has a problem inside his eye ; how do I know what's going inside the eye?! we go to CT scan transverse section to see"the Dr shows some CT pic" the orbit, eyeball, lacrimal gland, optic nerve ;going through optic canal. Optic nerve start as axons of the ganglionic cells of retina "we have talked about them ; we have neural receptors(rods & cons) bipolar cells ganglionic cells " They will form the optic disc : is a point of collection of axons of ganglionic cells & it's circular with Sharp edge 2 P a g e

3 with shiny area in the middle called optic cup form 1/3; Do you know why the Dr highlight this sentence?! because it should form Only 1/3 of the optic disc & if it more so there is increase in intraocular pressure. Because the optic disc is a collection of axons it form a Blind Spot ; if they are not work, you can't see the image. Where is the location of the optic disc?! it isn't located at the axis of the eye! it located medial to the eye axis. After forming optic disc, the fibers will be collected to form optic nerve; which is bundles of axons ; with different calibers. "Q) Do all axons have the same size? answer is NO ". Q) What axons cover with? cover with astrocytes. some one will say : but the astrocytes are in the brain! Dr: yes the optic nerve is an extension from the brain, when it extend from the brain it bring with it the meninges ; dura, subdural space,arachnoid, SA space with CSF So if there is an increase in CSF pressure or ICP,it will be projected on the optic disc.so you have to examin the disc if you want to diagnose the hydrocephalus. & this is Why the Dr put a Bomb at the right of this MM :3 about the meaning of the interrupted line at this area?! it means that the optic nerve pass through these layers. The optic nerve will pass medially & back. Q)How much is the length of the optic nerve? 2030 mm. why it is relatively long?! because the eye need to move & if this nerve is short & fixed it can't move. * look to MM : The colored circle below the arrow next to the optic disc ; it represent the Optic Foramen. Then the optic nerves will join together forming Optic Chiasm. Where it locate?! anterior to the pituitary stalk & on tuberculum sellae. at the optic chiasm some fibers will cross and others won't. the fibers that come from temporal part of retina;which make most of the visual field, will not cross. but the other fibers that come from nasal part of retina will cross. What important to know, that the crossing fibers are more. After the Crossing, they will form Optic Tract ; contain impulses from Both eyes. Then the fibers "90% of fibers" will go & end up in the lateral Geniculate body "lateral concerned with vision, the medial with hearing ". 10% of fibers, Now when we need to stimulate quick actions we won't to wait for synapsing to occure. we send fibers direct from optic tract to the pretectal area ; which is connected to the cranial nerves 3,4&6. Other fibers will go to the superior colleculus in the mid brain & is a part of the tectum ;which is the coordinator. There is a connection between sup. Colliculus & Pulvinar of the thalamus ; which is oval elevation, formed by white & grey matter, consist of 6 layers & located at the lateral of the posterior of the thalamus. "Plz notice that these information are about Pulvinar of thalamus Not lat. 3 P a g e

4 Geniculate " Then from the lateral Geniculate body, the fibers will go through internal capsule & ascends up to the Cerebral Cortex ; area 17,18 & 19. Retina has 10 layers ; but we won't be asked about them until we become ophthalmologists. ** THE ORBIT.. "3 rd MM " First the Dr showed a picture for women with swelled violet colored eye ; she had a car accident, and he said that we need to know if there is a fracture in the orbit or not, by doing Xrays or CT scan photos, so we need to study the orbit. Also Dr showed another picture for a person who has a problem with his eyelid, hairs are sticking so there is something wrong in the upper eyelid, so we need to study the upper eyelid. another picture for baby with secretions comes from his eye, so we need to study the orbit. another photo for a patient with abscesses in his upper eyelid, so you need to study the eyelid. * What are the muscles & bones that form the orbit?! "this is s.th easy for you :3 " If we remove the skin we will see muscles : Orbicularis couli with lateral & medial ligaments.also with superior & inferior palpebrae plates & there is a muscle comes from the orbit attached to the upper palpabrae plate called Levator palpebrae superioris muscle under the muscles we find a fibrous tissue called orbital septum. * The Eyeball is not sitting on the floor of the orbit, it is suspended by the muscles " like when you sleep on a net attached to two trees. also these muscles are responsible for eye movement These muscles are : 1 inf., sup,medial & lateral Recti muscles 2 inf. & sup oblique muscles. Levator palpebrae superioris muscle Orbital septum 4 P a g e

5 * Because the eye is movable, it need a fascia called periorbital fascia, filled with fat; that's why thyrotoxicosis will lead to edema at this area. periorbital fascia. * The Bones that form the Orbit :: inf maxillary " Dr showed a CT scan picture for fractured maxillary bone & bleeding in the nasal air sinuses " Foramena : 1 superior & inferior orbital fissure 2 optic foramen & canal 3 maxillary canal Why should we learn the foramena of the orbit?! first, because the nerves pass through them to reach to the eyeball. Also, because these foramena form a rout for spreading of the infection cellulites of the eye is very dangerous infection, because it cause destroying of the eye in addition of high chance for spreading to the cranium. 4 th MM :: Trochlear What is the problem with this boy?! First, Eye muscles when they have the same muscle tone everything is working & they put the eye in a position straight forward and straight toward the macula. If any muscle is not working the, the muscle will not be straight. This Boy asked to look to the left the right eye moves toward the nose " adduction",& the left should move laterally ; But it move also superiorly! So, the muscle that keeps it down & lateral is not working ; which is Superior oblique muscle, that supplied by the 4 th Cranial nerve (Trochlear). So we need to know the Trochlear & you have to study the MM about it :3 5 P a g e

6 ** 5 th MM : "Oculomotor " It's Very important. why? because it supply most of the eye's muscles *About the Bomb on the right side of MM,, it mean this is a dangerous point, because this is a common region of berry aneurysm aneurysm developed compress on the oculomotor oculomotor nerve loss it's action a lot of muscles loss their function the end result will be like the person in the MM (the eye is down, lateral & pupil is dilated). * Oculomotor supplies 4 of 6 eye muscles. So the eye will be as this : 1down ward loss of the muscle that move it superiorly inferior oblique 2 laterally loss of th muscle that move it medially median rectus Also, dilated pupil because of loss of the parasympathetic innervations, due to loss of oculomotor ; which carry the parasympathetic to the eye. *** this topic is very important "positions of the eye ", & always you will have a questions about them in the exam. The Action of Eye muscles : all of them work together to keep the eye straight forward 6 P a g e

7 1 Superior rectus = up & medially 2 inferior rectus = down & lateral 3 medial rectus = medially 4 lateral rectus = laterally 5 Superior oblique = down & medially 6 Inferior oblique = up & laterally. We will talk more about this topic in the practical labs THE END ** NOTES :: 1 You have to study all of the MMs that Dr. Posted them in the Elearning. 2 See the Pictures & videos that Dr. also Posted them on Elearning. 3 Study Hope Book First, then check this sheet. Don't ignore the cases mentioned here 4 Don't forget to see Netter atlas Photos they are Perfect for this lecture. Forgive me For any possible mistakes & Don't forget to post them on FB correction zone. I tried my best to make it ingestible BEST WISHES AWN AlAnood AlBustanji 7 P a g e