CORPUS COLLOSUM [corpus callosum (PNA, BNA, JNA): synonym big commissure of a brain (commissura cerebri magna)] — layer of the nerve fibrils connecting bark of two hemicerebrums.
In phylogenesis appears at placental mammals, reaches the greatest development in primacies. At the person it is put for 3 months of the pre-natal period in a komissuralny plate of a kpereda and dorsalno from commissure of a hippocampus, in process of development of hemispheres grows in the front and back directions, being located over the III cerebral cavity.
The created M. of t. is in depth of a longitudinal crack of a great brain. Its middle part — a trunk (truncus corporis callosi) — in front passes into a knee (genu corporis callosi) which is coming to an end with a beak (rostrum corporis callosi), behind extends, forming the roller (splenium corporis callosi). M.'s length of t. thickness of a trunk of 1 cm, the roller of 2 cm is equal to 7 — 9 cm. Upper surface of M. of t. it is delimited from a zone crinkle (gyrus cinguli) by means of a furrow of a corpus collosum (sulcus corporis callosi), lower is a part of a roof of the third and partly side cerebral cavities, behind it borders on the arch of a brain (fornix), in front it is adjoined by a transparent partition (septum pellucidum).
M of t. contains 200 — 350 million komissuralny fibers which are axons of pyramidal neurocytes cerebral cortex (see). Dispersing in white matter of a hemisphere, these fibers form M.'s radiance of t. — radiatio corporis callosi (fig). The fibers connecting frontal lobes are a part of a knee and M.'s beak of t.; being bent kpered, they form small nippers (forceps minor). M.'s trunk of t. make the fibers connecting the central crinkles, parietal and temporal lobes. Fibers of the roller M. of t. connect occipital and back departments of parietal shares; being bent kzad, they form big nippers (forceps major). All departments of a cerebral cortex communicate fibers M. of t., except for olfactory shares and a hippocampus. Fibers M' t. give collaterals to various departments of a hemisphere of the party, to-rye are not komissuralny, but asso-tsiativny branches; thanks to it communication not only symmetric, but also asymmetric sites of bark of both hemispheres is carried out.
Upper surface of M. of t. has a thin gray cover (indusium griseum) representing a rudiment of a hippocampus. In a cover distinguish medial and lateral longitudinal strips (stria longitudinalis med., lat.), in to-rykh there pass conduction paths limbic system (see). M of t. plays a role in information transfer from one hemisphere in another, in the combined activity of two brain hemispheres.
Inborn defects of M. of t. (agenesias, an underdevelopment) are usually combined with other anomalies of a brain, macro - and a microgyria, hydrocephaly.
At M.'s defeats t. (hemorrhages, tumors, etc.) apraxia, frustration of reciprocal motive acts, loss of orientation in space, gross mental violations is noted. M.'s tumors of t. (primary or growing into it from adjacent structures of a brain) treat inoperable. At the occlusal hydrocephaly caused by M.'s tumors of t., for removal of cerebrospinal liquid from cerebral cavities use operation of a puncture or M.'s section of t. (see. Hydrocephaly ).
Bibliography: BIC B. And. and Burdey G. D. To morphology of a corpus collosum, Works Saratovsk. medical in-that, t. 31 (48), page 264, 1960, bibliogr.; With 1 and and M. of Das Nerven-system des Menschen, Lpz., 1959.
V. S. Speransky.