Biomaterial Database

Human fetal optic nerve: overproduction and elimination of retinal axons during development. 1985

J M Provis, and D van Driel, and F A Billson, and P Russell

We have estimated the number of axons in the optic nerves of human fetuses ranging in gestational age from approximately 10 to 33 weeks. At 10-12 weeks of gestation there were an estimated 1.9 million axons in the optic nerve. A peak count of 3.7 million axons was obtained from a specimen of 16-17 weeks gestation. The estimated number of axons then declined, stabilizing at an estimated 1.1 million axons by about week 29 of gestation. This figure is in close agreement with an estimate of 1.1-1.3 million optic axons in the human adult optic nerve. The results indicate that at least 70% of optic axons generated during development of the primary visual pathway are lost during fetal life. Part of this loss probably occurs as a result of the refinement of the terminal distribution of ganglion cell projections within their target nuclei. The significance of the relatively prolonged period of axonal loss is discussed.

UI	MeSH Term	Description	Entries
D009900	Optic Nerve	The 2nd cranial nerve which conveys visual information from the RETINA to the brain. The nerve carries the axons of the RETINAL GANGLION CELLS which sort at the OPTIC CHIASM and continue via the OPTIC TRACTS to the brain. The largest projection is to the lateral geniculate nuclei; other targets include the SUPERIOR COLLICULI and the SUPRACHIASMATIC NUCLEI. Though known as the second cranial nerve, it is considered part of the CENTRAL NERVOUS SYSTEM.	Cranial Nerve II,Second Cranial Nerve,Nervus Opticus,Cranial Nerve, Second,Cranial Nerves, Second,Nerve, Optic,Nerve, Second Cranial,Nerves, Optic,Nerves, Second Cranial,Optic Nerves,Second Cranial Nerves
D005314	Embryonic and Fetal Development	Morphological and physiological development of EMBRYOS or FETUSES.	Embryo and Fetal Development,Prenatal Programming,Programming, Prenatal
D005865	Gestational Age	The age of the conceptus, beginning from the time of FERTILIZATION. In clinical obstetrics, the gestational age is often estimated from the onset of the last MENSTRUATION which is about 2 weeks before OVULATION and fertilization. It is also estimated to begin from fertilization, estrus, coitus, or artificial insemination.	Embryologic Age,Fetal Maturity, Chronologic,Chronologic Fetal Maturity,Fetal Age,Maturity, Chronologic Fetal,Age, Embryologic,Age, Fetal,Age, Gestational,Ages, Embryologic,Ages, Fetal,Ages, Gestational,Embryologic Ages,Fetal Ages,Gestational Ages
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001369	Axons	Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.	Axon
D012165	Retinal Ganglion Cells	Neurons of the innermost layer of the retina, the internal plexiform layer. They are of variable sizes and shapes, and their axons project via the OPTIC NERVE to the brain. A small subset of these cells act as photoreceptors with projections to the SUPRACHIASMATIC NUCLEUS, the center for regulating CIRCADIAN RHYTHM.	Cell, Retinal Ganglion,Cells, Retinal Ganglion,Ganglion Cell, Retinal,Ganglion Cells, Retinal,Retinal Ganglion Cell