Textbook of normal histology: including an account of the development of the tissues and of the organs . eball. DEVELOPMENT OF THE EYE. The earliest indication of the visual organ is the optic vesicle, alarge diverticulum extending on either side from the primary anteriorbrain-vesicle, and later becoming connected by a constricted stalkwith the interbrain, or thalamencephalon. In the early stage the optic vesicle lies in contact with the ectodermreflected over the prominently protruding optic diverticulum, the sur-rounding mesoderm at first showing no differentiation. Shortly afterthe optic ve
Textbook of normal histology: including an account of the development of the tissues and of the organs . eball. DEVELOPMENT OF THE EYE. The earliest indication of the visual organ is the optic vesicle, alarge diverticulum extending on either side from the primary anteriorbrain-vesicle, and later becoming connected by a constricted stalkwith the interbrain, or thalamencephalon. In the early stage the optic vesicle lies in contact with the ectodermreflected over the prominently protruding optic diverticulum, the sur-rounding mesoderm at first showing no differentiation. Shortly afterthe optic vesicle has reached the surface ectoderm the latter exhibitsproliferation and thickening opposite the external pole of the ectodermic area, the earliest trace of the future crystallinelens, soon becomes depressed, the invagination progressing untilthe pit- and the cup-stage give place to the closed vesicle, whichfinally separates from the ectoderm and lies beneath the surface asthe lens-sac. Simultaneously with the progress of these changes in the ectoderm, THE EYE AND ITS APPENDAGES. 373. Section through headof ten-day rabbit em-bryo, exhibiting primaryoptic vesicle (0) pro-truding from fore-brain(B) and coming in con-tact with surface ecto-derm (e) : m, surround-ing mesoderm. Section through develop-ing eye of eleven-day rab-bit embryo : B, fore-brainconnected by stalk withoptic vesicle (o), whoseanterior wall is partly in-vaginated; /, thickened anddepressed lens-area. the anterior segment of the primary optic vesicle undergoes animportant invagination, whereby the front wall of the sac is pushedinto the cavity of the vesicleuntil eventually the anteriorand posterior walls are inapposition and the includedcavity is largely new space within theindented anterior walls of thesac constitutes the second-ary optic vesicle and corre-sponds to the later vitreouschamber. These importantchanges probably are not en-tirely attributable to the me-chanical influ
Size: 1842px × 1357px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorpiersolgeorgeageorgea, bookcentury1800, bookdecade1890
