Human anatomy, including structure and development and practical considerations . ral form of the eyeball is that of a sphere, but in sagittal section it is foundto be composed of the segments of two spheres, an anterior smaller segment, corre-sponding to the transparent cornea, which has a radius of from 7-8 mm. ancl a pos-terior opaque segment, corresponding to the sclera, with a radius of 12 mm. Thejunction between the two segments is marked externally by a broad, shallow groove,the sn/ciis schrcc, which is tilled by the scleral conjunctiva. The diawctcrs of the eyeball measure approximatel
Human anatomy, including structure and development and practical considerations . ral form of the eyeball is that of a sphere, but in sagittal section it is foundto be composed of the segments of two spheres, an anterior smaller segment, corre-sponding to the transparent cornea, which has a radius of from 7-8 mm. ancl a pos-terior opaque segment, corresponding to the sclera, with a radius of 12 mm. Thejunction between the two segments is marked externally by a broad, shallow groove,the sn/ciis schrcc, which is tilled by the scleral conjunctiva. The diawctcrs of the eyeball measure approximately as follows : the antero-pos-terior, mm. ; the vertical, mm. ; and the transverse, mm. Its shapeis, therefore, that of a spheroid somew iiat llattcned from above downward, and from Fig. 1202. LensSuspenson, ligament of lens \Canal of Schlemm \ Ciliary \ Tendon of internal rectus—muscle Vena vorticosa Ciliary Posterior ciliary Hyaloid canalOptic nerveCentral retinal Cornea .terior chamber/ Iris / Posterior chamber ^ Sclerocorneal juncture. Tendon of-external rectusmuscle vitreous Sclera Choroid RetinaFovea centralis Optic papillaDiagrammatic horizontal section of right eye. X 3/^. side to side. The diameters are slightly greater in the male than in the female, andvary according to the refractixe power, being longer in nearsighted or myopic, andshorter in oversighted or hyperopic eyes. The eyeball consists of three concentric coats or tunics : (i) the external orfibrous tunie, composed of the sclerotie and the cornea; (2) the middle or vasculartunic, which is pigmented and jxirtly muscular, and is comjiosed, from behind for-ward, of the choroid, the ciliary body, and the iris; and {3) the inner ov nervoustunic, the retina, an expansion of the brain, which contains beside the nerve-cellsand the nerve-fibres the specialized ncuroepithelium for the reception of visual stimuli. Within these tunics are enclosed the refracting media, the crystallin
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Keywords: ., bookauthormc, bookcentury1900, bookdecade1910, booksubjectanatomy
