Paper - The process of retinal differentiation in man
|Embryology - 17 Sep 2019 Expand to Translate|
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Mann IC. The developing third nerve nucleus in human embryos (1927) J Anat. 61(4): 424-438. PubMed 17104156
Mann IC. The process of differentiation of the retinal layers in vertebrates (1928) Br J Ophthalmol. 12(9): 449-478. PubMed 18168748
Mann IC. The relations of the hyaloid canal in the foetus and in the adult (1928) J Anat. 62(3): 290-296. PubMed 18168748
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The Process of Retinal Differentiation in Man
Ida C. Mann, M.B., F.R.C.S. Eng.
THE paper forms a demonstration, illustrated by numerous examples from the developing eyes of a series of human embryos, of the stages of rearrangement which can be seen during the formation of the retinal nuclear layers from the undifferentiated neuro-epithelium of the wall of the optic cup. The earliest stage dealt with is that of a 4-5 mm. human embryo which shows in the inner wall of the optic cup a division into marginal and nuclear layers only. After this stage the ﬁrst of the deﬁnitive cells to become recognizable are the ganglion cells which develop by migration of the innermost cells of the nuclear layer into the marginal layer. Further increment of cells taking place from the outer to the inner layers., a distinct zone can soon be recognized which is known as the inner neuroblastic zone, the remains of the original nuclear zone being new distinguishable as the outer neuroblastic zone. From these two neuroblastic zones the layers of the definitive retina are developed. From the inner neurobla.stic zone are formed by differentiation the ganglion cells, the nuclei of the ﬁbres of Milller and the amacrine cells. These latter are separated from the outer neuroblastic layer by a narrow interval (Wider in the area centralis), the transient ﬁbre layer of Chz'eu'itz. From the outer neuroblastic layer are formed the bi-polar nuclei, the nuclei of the rods and cones and the horizontal cells. Towards the end of development the transient fibre layer disappears and in consequence the layer of amacrine cells and of nuclei of fibres of Wiiller fuses with the layer of bi-polar nuclei external to it to form the definitive inner nuclear layer. The internal molecular layer develops to separate this from the layer of ganglion cells. Later the external molecular layer develops and divides the original outer neuroblastic layer into two, namely an inner layer of bi-polar and horizontal cells and an outer layer of nuclei of rods and cones.
The deﬁnitive inner nuclear layer is therefore a. compound structure containing elements from both the original neuroblastic layers.
The following scheme shows the process divided into stages as it can be observed in the human embryo.
|First stage||Second stage||Third stage||Adult|
|Marginal layer||Superﬁcial portion of marginal layer|
fourth fo fiffh u-(mic si.rII1 week fo third month third to scrcntlz month Adult
Nerve ﬁbre layer Nerve ﬁbre layer ; Ganglion cells Ganglion cells
/ Inner molecular layer Inner neuroblastic ——§ Amacrine cells
la er U '4 y \ M mlermn ﬁbre - Inner nuclear layer / Transient ﬁbre layer nuclei r ' ~ of Chiewitz /~ Bi-polar cells | C 7 Horizontal cells ' - ~—\ Outer neuroblastic Outer molecular layer
Nuclei of rods and Outer nuclear layer cones
................................................................................... ..External limiting
membrane Primitive rods and cones. Rods and cones