Each lateral ventricle opens into the 3rd ventricle through
Cavities within brain and spinal cord:
a) The cerebrum contains a median cavity, the third ventricle and two lateral ventricles, one in each hemisphere.
b) Each lateral ventricle opens into the 3rd ventricle through interventricular foramen or foramen of  monro.
c) The third ventricle opens into the 4th ventricle  (i.e., cavity of hind brain) through the cerebral aqueduct.
d) The 4th ventricle communicates with subarachnoid space through two lateral foramen or foramen of luschka and a medial foramen or foramen of magendi.
Foramen of Monro
Lateral foramen
Foramen of luschka
Foramen of magendi