Biomaterial Database

Morphological specialisations of rat cranial nerve transitional zones. 1994

J P Fraher, and D O'Leary

Anatomy Department, University College, Cork, Ireland.

Near their CNS-PNS transitional zones (TZs), many rat cranial nerve rootlets are subdivided to a marked degree by a reticulum of fine cytoplasmic processes. Some of the resulting compartments contain only a single myelinated fibre or a bundle of collagen fibrils. The compartments are aligned with the astrocytic tunnels in which the fibres lie as they traverse the CNS-PNS transitional zone. This marked subdivision may help to insulate individual fibres from one another, preventing functional interaction between them. Rootlet sheath cells commonly are closely apposed to, or interdigitate with, astrocyte processes of the TZ. These features may help to strengthen the delicate TZ. The TZ of the trochlear nerve includes a long, generally avascular, central tissue projection (CTP) into the proximal part of the nerve. This is connected to the brainstem and cerebellum by astrocytic bridges. In contrast to the CTP, which is generally avascular, these contain abundant blood vessels which may facilitate metabolic exchange in the trochlear TZ.

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
D010525	Peripheral Nerves	The nerves outside of the brain and spinal cord, including the autonomic, cranial, and spinal nerves. Peripheral nerves contain non-neuronal cells and connective tissue as well as axons. The connective tissue layers include, from the outside to the inside, the epineurium, the perineurium, and the endoneurium.	Endoneurium,Epineurium,Perineurium,Endoneuriums,Epineuriums,Nerve, Peripheral,Nerves, Peripheral,Perineuriums,Peripheral Nerve
D002490	Central Nervous System	The main information-processing organs of the nervous system, consisting of the brain, spinal cord, and meninges.	Cerebrospinal Axis,Axi, Cerebrospinal,Axis, Cerebrospinal,Central Nervous Systems,Cerebrospinal Axi,Nervous System, Central,Nervous Systems, Central,Systems, Central Nervous
D003391	Cranial Nerves	Twelve pairs of nerves that carry general afferent, visceral afferent, special afferent, somatic efferent, and autonomic efferent fibers.	Cranial Nerve,Nerve, Cranial,Nerves, Cranial
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001253	Astrocytes	A class of large neuroglial (macroglial) cells in the central nervous system - the largest and most numerous neuroglial cells in the brain and spinal cord. Astrocytes (from "star" cells) are irregularly shaped with many long processes, including those with "end feet" which form the glial (limiting) membrane and directly and indirectly contribute to the BLOOD-BRAIN BARRIER. They regulate the extracellular ionic and chemical environment, and "reactive astrocytes" (along with MICROGLIA) respond to injury.	Astroglia,Astroglia Cells,Astroglial Cells,Astrocyte,Astroglia Cell,Astroglial Cell,Astroglias,Cell, Astroglia,Cell, Astroglial
D017208	Rats, Wistar	A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.	Wistar Rat,Rat, Wistar,Wistar Rats
D051381	Rats	The common name for the genus Rattus.	Rattus,Rats, Laboratory,Rats, Norway,Rattus norvegicus,Laboratory Rat,Laboratory Rats,Norway Rat,Norway Rats,Rat,Rat, Laboratory,Rat, Norway,norvegicus, Rattus