Capsula Externa

CAPSULA EXTERNA (external capsule), a narrow strip of bundles of myelin fibers located in the cerebral hemispheres; the claustrum adjoins it on the outside, and the corona radiata and nucleus lenticularis (putamen) lie inside of it (see separate table, figs. 1-3); its upper edge is crossed by fibers of the fasciculus arcuatus or fasciculus longitudinalis superior, the lower edge comes into contact with the commissura alba anterior. Capsula externa consists of association, commissural, and, in small numbers, projection fibers; their direction changes depending on the origin of the fibers: the anterior sections include fibers from the fasciculus arcuatus (an association bundle connecting the frontal lobe with the parietal and temporal lobes) and a small number from the genu and rostrum of the corpus callosum; they are directed upward, outward, and forward; the fibers of the middle part belong to the association bundle fasciculus fronto-occipitalis (connecting the frontal and occipital lobes) and partly to the fasciculus of the corpus callosum; they are directed upward. The fibers of the posterior sections of the Capsula externa belong to the fasciculus longitudinalis inferior (an association bundle connecting the occipital and temporal lobes), partly to the fasciculus uncinatus and the commissura alba anterior; all these fibers are directed upward, backward, and outward; the fibers of the fasciculus uncinatus, dividing into small bundles, penetrate the claustrum. A very small part of the fibers of the Capsula externa belongs to the projection system connecting the cerebral cortex with the thalamus opticus. Throughout the entire extent of the Capsula externa, fibers depart from it, directed toward the claustrum; they partly terminate in it, and partly penetrate it to terminate in the cortex of the insula Reili; by short fibers, the Capsula externa is also connected with the putamen. Blood supply to the Capsula externa comes from the arteria lenticulo-caudata and arteria lenticulo-striata (branches of the arteria cerebri mediae), located between the Capsula externa and the putamen. These arteries are frequent sources of cerebral hemorrhages. The physiology of the Capsula externa follows from the composition of the fibers entering it. The Capsula externa, like the Capsula extrema, is part of the lenticular zone described by Pierre Marie, bounded on the inside by the Capsula externa, and on the outside by the cortex of the insula Reili. A lesion of this zone causes a speech disorder, which Marie classifies as conduction aphasia, while other authors regard it as dysarthria. E. Kononova. 7 13 8 10 11 12

Figure 1, 2, and 3. Frontal, horizontal, and sagittal sections of the brain: 1 - anterior limb of the capsula interna; 2 - genu; 3 - posterior limb; 4 - pars retrolenticularis capsulae internae; 5 - basis of the cerebral peduncle; 6 - pons Varolii; 7 - nucleus caudatus; 8 - nucleus lenticularis; 9 - thalamus opticus; 10 - capsula externa; 11 - claustrum; 12 - capsula extrema; 13 - cella media of the lateral ventricle; 14 - commissura alba anterior; 15 - nucleus ruber; 16 - 3rd ventricle; 17 - substantia nigra; 18 - corpus geniculatum laterale; 19 - fornix; 20 - corpus Luysi; 21 - tractus opticus. Figure 4. Caverns of the lungs (1); numerous strands and crossbars are visible along the walls of the cavern; 2 - thickened, sclerosed pleura (torn pleural adhesions); 3 - trachea; 4 - lymphatic glands of the tracheal bifurcation. To the articles Caverns, Capsula interna.