The location of the foramina of the fourth ventricle (human brain, right hemisphere, fourth ventricle area). 1: arbour vitae, 2: posterior commissure, 3: cerebellar tonsil, 4: lingula, 5: midbrain, 6: superior medullary velum, 7: quadrigeminal cistern (of the great cerebral vein), 8: roof of the fourth ventricle, 9: cerebral aqueduct (of Sylvius), 10: pons, 11: fourth ventricle, 12: cerebellar hemisphere, L: right foramen of Luschka, M: foramen of Magendie (line: intercommissural line).