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REVIEW OF CLINICAL ANATOMY & PHYSIOLOGY OF THE ORBIT Dr. Ayesha Abdullah 17.08.2016 LEARNING OUTCOME By the end of this lecture the students would be able to; “correlate the structural organization of the orbit with its functions and clinical significance” ANATOMY OF THE ORBIT • The orbital cavities are ………… Adult orbital dimensions Entrance height Entrance width 35 mm 35mm 45mm 40 mm Medial wall length / 45 depth mm Volume 30 cc Distance from the 18 back of the globe to mm the optic foramen 45mm SALIENT ANATOMICAL FEATURES •7 •6 •5 •4 •4 •4 bones 7-6-5-4 contents important relationships walls margins important openings v Bones & walls MZSF ELP Which orbit ? IMPORTANT OPENINGS OF THE ORBIT Optic Foramen • Where? • size? • what passes through? • Clinical significance? Superior orbital fissure • Where? • What passes through? • What is annulus of Zinn? • Clinical significance? Inferior orbital fissure: • Where? • What passes through? • Clinical significance? Openings of the orbit Nasolacrimal canal • Where? • What passes through? • Clinical significance Inferior orbital foramen • Where? • What passes through • Clinical significance? Sensory Nerve Supply of the Face Orbital walls Roof • • • • Frontal bone and sphenoid lesser wing Lacrimal gland, trochlea Superior orbital notch Brain Floor • Zygomatic, maxilla and palatine bones. • weak part • Infraorbital groove & canal for the infraorbital nerve • Maxillary sinus. Medial Wall • lacrimal, maxillary, ethmoid & sphenoid • Thinnest wall • Lamina papyrecea • It separates the orbit from the nasal cavity, the ethmoidal and the sphenoidal sinuses Lateral Wall • Zygomatic & Sphenoid (greater wing) • Stronger wall • It separates the orbit from the (temporal fossa) and the brain Roof Medial wall Floor IMPORTANT RELATIONS OF THE ORBIT 1. 2. 3. 4. 5. Brain Para nasal sinuses Nasal cavity Cavernous sinus Pterygopalatine fossa Orbit as seen from above Relations of the orbit to the paranasal sinuses :FS, frontal sinus; ES, ethmoidal sinus; MS , maxillary sinus; SS, sphenoid sinus- American Academy of Ophthalmology CONTENTS OF THE ORBIT 1. Eyeball & the optic nerve 2. Muscles – To move the eyeball. 3. Nerves – – – – – To move the muscles ( III, IV, VI). To carry different sensations ( V) parasympathetic innervation ( accommodation, pupillary constriction & lacrimal gland stimulation Sympathetic innervation ( pupillary dilatation, vasoconstriction, smooth muscles of the eye lids & hidrosis) CONTENTS OF THE ORBIT 4. Blood vessels ( branches of ophthalmic artery, superior & inferior ophthalmic veins) 5. Fat & orbital fascia – For padding purposes & for smooth movements 6. Most of the Lacrimal Apparatus (lacrimal gland & part of the tear drainage system) Lacrimal gland and the view of the orbit from the roof Orbital fascia • Periorbita • Orbital septum • Tenon’s capsule • Fascial spaces intraconal extraconal subtenon subperiosteal Subperiosteal space Extraconal space Intraconal space Structure of the lids-AAO RADIOGRAPHIC ANATOMY OF THE ORBIT VIEWS : AXIAL VIEWS CORONAL VIEW SAGITTAL VIEW AXIAL CT SCAN Summary • Orbit is the protective casing for the delicate visual apparatus - the eyeball • It is made up of 7 bones, has 4 margins, 4 walls/ boundaries, 4 important openings , 5 important relations & 6 contents • Infection can spread to the brain from the orbit directly or through the haematogenous spread- Orbital septum is a barrier to infection • Trauma mostly damages the medial wall & the floor (the weakest parts give way) • The symptomotology of orbital diseases is reflective of its clinical anatomy