Chap. XX] 



SUMMARY 



439 



Orbit 



Eyeball 



Bony cavity formed by seven bones 



Frontal. 



Malar. 



Maxilla. 



Palate. 



Ethmoid. 



Sphenoid. 



Lacrimal. 



Lined by fibrous tissue. 



Contains pad of fat — supports eyeball. 



Capsule of Tenon — prevents friction when eyeball moves. 



Shaped Uke four-sided pyra- J Apex directed backward. 



mid \ Base directed forward. 



Optic foramen — opening for passage of optic nerve and 



ophthalmic artery. 

 Sphenoidal fissure — opening for passage of ophthalmic 

 vein and motor oculi, pathetic and abducens nerves. 

 ■ Spherical in shape. 



Transverse . . . 1.00 inch (25 mm.) 



Vertical 96 inch (24 mm.) 



Antero-posterior . .96 inch (24 mm.) 

 Optic nerve and 



Dimensions I sheath 16 inch (4 mm.) 



Lens — ^ antero-pos- 

 terior 19 inch (4.75 mm.) 



Lens — transverse .35 inch (8.75 mm.) 

 Pupil (average) . .14 inch (3.5 mm.) 



Tunics 



Media 



1. Sclera and cornea. 



2. Choroid, ciliary body, and iris. 



3. Retina. 



1. Aqueous. 



2. Crystalline lens and capsule. 



3. Vitreous. 



Sclera 



Cornea 



Choriod 



Ciliary Body 



( Tough, fibrous, opaque. Protective. 

 I Covers posterior | of eyeball. 

 I Stained brown internally. 

 Fibrous, transparent — covers anterior I of eyeball. 

 Well supplied with nerves, 

 r Vascular coat, lines the sclera. 



I Composed of connective tissue cells filled with pigment. 

 i Terminates in front by the ciliary processes. 

 Ciliary processes 70 to 80 parallel folds of the choroid, 

 rising gradually from behind and forming a plaited zone 

 between the choroid and iris. 

 Support ciliary muscle — action of this muscle determines 

 the position of the lens. 



