ABSTRACT

Like the spinal cord, the brain contains a cerebrospinal fluid-filled lumen. The lumen makes up the four ventricles (small cavities) and the aqueduct of Sylvius of the brain. Two outgrowths of the telencephalon-the cerebral vesicles-give rise to the cerebral hemispheres, which contain ventricles I and II. These ventricles communicate with ventricle III, making up the remainder of the telencephalon and diencephalon by means of the foramina of Monro (Monro's foramen). Ventricle III in turn communicates-through the aqueduct of Sylvius (lumen of the mesencephalon)-with ventricle IV, which is the lumen of the metencephalon and myelencephalon (Fig. 13-6). From the walls of the lateral ventricles (I and II) and roofs of ventricles III and IV, vascular choroid plexuses extend into the ventricles and secrete cerebrospinal fluid.