. Anatomy, descriptive and applied. Anatomy. 940 THE NERVE SYSTEM The choroid fissure or rima (fissure of Bichat) is not a true fissure, and only becomes one when the choroid plexus of the lateral ventricle is torn from its connections. The choroid fissure is nevertheless a gap between the diencephalic part and the overlapping and recurved telencephalon produced by the extension of the secondary fore-brain vesicles in an arcuate manner. It is along this arcuate and fissure-like gap (Fig, 700) that the richly vascular (pial) choroid plexus invag- inates the atrophied parietes of the secondary f
. Anatomy, descriptive and applied. Anatomy. 940 THE NERVE SYSTEM The choroid fissure or rima (fissure of Bichat) is not a true fissure, and only becomes one when the choroid plexus of the lateral ventricle is torn from its connections. The choroid fissure is nevertheless a gap between the diencephalic part and the overlapping and recurved telencephalon produced by the extension of the secondary fore-brain vesicles in an arcuate manner. It is along this arcuate and fissure-like gap (Fig, 700) that the richly vascular (pial) choroid plexus invag- inates the atrophied parietes of the secondary fore-brain to form the choroid plexus which is everywhere covered by ependyma. The choroid fissure extends from the foramen of Monro to near the tip of the middle cornu in an arcuate course, and ependymal reflections everywhere close in this gap except at the foramen of Monro. The manner in which this is accomplished may best be understood by a study of a trans-section showing the ependymal reflections from the ventricular wall onto the invaginated choroid plexus (Figs. 670 and 698). The caudatothalamic fusion and the intrusion of the great fibre masses constituting the cerebral crura play their parts in complicating the relations in brains of higher Fig. 700.—Diagram showing the choroid fissure. (BichAt.) The Choroid Plexus of the Lateral Ventricle and Velum Interpositum.—The cho- roid plexus is a highly vascular, fringe-like structure composed of pia which is invaginated into the lateral ventricle along the choroid fissure, or gap between cerebral hemisphere and diencephalon. The portion of the choroid plexus protruding into the "body" of the lateral ventricle is the fringed vascular bor- der—a triangular fold of pia—the velum interpositum {tela choroidea superior), which, as its name implies, is interposed between the relatively small primary fore-brain and the enormous overlapping secondary fore-brain, and is produced by the overgrowth of the latter
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1913
