Biomaterial Database

Changes in axonal numbers in developing human trochlear nerve. 1979

G Y Mustafa, and H J Gamble

Complete axonal counts have been made in the intracranial parts of trochlear nerves from human fetuses of 9.2, 10 and 24 cm crown-rump length. A count was also made in the intraorbital part of the nerve from the 10 cm specimen. Schwann cell nuclei were also counted in typical cross sections, but do not necessarily reflect very accurately the schwann cell contents of the nerves. Axonal numbers conform to the propositions (1) that they do not all grow out at once, (2) do not all survive and (3) that degeneration may occur before or after myelination has begun. It seems inevitable that some loss of Schwann cells occurs in relation to the degeneration of myelinated axons, but there is no evidence for or against such a loss in relation to the degeneration of unmyelinated axons. Overall, however, Schwann cell numbers tend to increase as the number of myelinated axons increases.

UI	MeSH Term	Description	Entries
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D009410	Nerve Degeneration	Loss of functional activity and trophic degeneration of nerve axons and their terminal arborizations following the destruction of their cells of origin or interruption of their continuity with these cells. The pathology is characteristic of neurodegenerative diseases. Often the process of nerve degeneration is studied in research on neuroanatomical localization and correlation of the neurophysiology of neural pathways.	Neuron Degeneration,Degeneration, Nerve,Degeneration, Neuron,Degenerations, Nerve,Degenerations, Neuron,Nerve Degenerations,Neuron Degenerations
D009413	Nerve Fibers, Myelinated	A class of nerve fibers as defined by their structure, specifically the nerve sheath arrangement. The AXONS of the myelinated nerve fibers are completely encased in a MYELIN SHEATH. They are fibers of relatively large and varied diameters. Their NEURAL CONDUCTION rates are faster than those of the unmyelinated nerve fibers (NERVE FIBERS, UNMYELINATED). Myelinated nerve fibers are present in somatic and autonomic nerves.	A Fibers,B Fibers,Fiber, Myelinated Nerve,Fibers, Myelinated Nerve,Myelinated Nerve Fiber,Myelinated Nerve Fibers,Nerve Fiber, Myelinated
D002452	Cell Count	The number of CELLS of a specific kind, usually measured per unit volume or area of sample.	Cell Density,Cell Number,Cell Counts,Cell Densities,Cell Numbers,Count, Cell,Counts, Cell,Densities, Cell,Density, Cell,Number, Cell,Numbers, Cell
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
D012583	Schwann Cells	Neuroglial cells of the peripheral nervous system which form the insulating myelin sheaths of peripheral axons.	Schwann Cell,Cell, Schwann,Cells, Schwann
D014321	Trochlear Nerve	The 4th cranial nerve. The trochlear nerve carries the motor innervation of the superior oblique muscles of the eye.	Cranial Nerve IV,Fourth Cranial Nerve,Nerve IV,Cranial Nerve, Fourth,Cranial Nerves, Fourth,Fourth Cranial Nerves,IV, Cranial Nerve,Nerve IV, Cranial,Nerve IVs,Nerve, Fourth Cranial,Nerve, Trochlear,Nerves, Fourth Cranial,Nerves, Trochlear,Trochlear Nerves