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ANAT 2626 Orbit - 1 Chapter 7 Pages 889 to 913 Eye Orbit...

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1 Chapter 7 - Pages 889 to 913 Eye, Orbit, Orbital Region and Eyeball Eye is the organ of vision and consists of the 1. eyeball 2. optic nerve Orbit contains the 1. eyeball 2. its appendages Orbital region is the area of the face overlying the orbit and eyeball and includes the 1. upper and lower eyelids 2. lacrimal apparatus Orbit is a pyramidal bony cavity in the facial skeleton, protects the eyeballs and their muscles Boundaries It has four walls Base is outlined by the orbital margin, which surrounds the orbital opening Superior wall ( roof ) 1. formed by the orbital part of frontal and lesser wing of sphenoid 2. fossa for the lacrimal gland ( lacrimal fossa ) lies in the orbital part of frontal bone Medial wall is formed by the 1. orbital plate of ehtmoid bone 2. frontal process of maxilla, lacrimal and sphenoid bones 3. it is identified by the lacrimal groove and fossa for the lacrimal sac Anteriorly it has the lacrimal fossa for the lacrimal sac Inferior wall ( floor ) 1. is formed by the maxilla, zygomatic and palatine bones 2. it is separated from the lateral wall by the inferior orbital fissure Lateral wall is formed by the 1. frontal process of the zygomatic bone 2. greater wing of the sphenoid bone Apex of the orbit is 1. at the optic canal 2. in the lesser wing of the sphenoid bone, just medial to the superior orbital fissure Periorbita ( periosteum of the orbit ) 1. lines the bones of the orbit, which forms the fascial sheath of the eyeball 2. it is continuous at the optic canal and superior orbital fissure with the periosteal layer of dura mater 3. it also continues over the orbital margins through the inferior orbital fissure with the periosteum covering the external surface of the cranium ( pericaraium )
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2 4. with the fascial sheath of the extraocular muscles Eyelids and Lacrimal Apparatus The eyelids and lacrimal fluid, secreted by the lacrimal glands protect the cornea and the eyeballs from injury and irritation ( e.g. by dust and small particles ) Eyelids 1. movable folds that cover the eyeball anteriorly 2. when closed, thereby protecting it from injury and excessive light 3. they also keep the cornea moist by spreading the lacrimal fluid 4. covered externally by thin skin and internally by transparent mucous membrane, the palpebral conjunctiva 5. the palpebral conjuctiva is reflected onto the eyeball, where it is continuous with the bulbar conjuctiva, which is loose and wrinkled over the sclera Superior and inferior conjunctival fornices are the deep recesses formed by the line of reflection of the palpebral conjunctiva onto the eyeball Conjunctival sac 1. is the space bound by the palpebral and bulbar conjunctivae 2. it is a closed space when the eyelids are closed Tarsal plates are superior and inferior, form the ‘ skeleton ‘ of the eyelids , made of dense bands of connective tissue, which strengthen the eyelids Tarsal glands 1. are embedded in the tarsal plates 2. the lipid secretion of which lubricates the edges of the eyelids and prevents them from sticking together when they close 3.
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