Choroid plexusStart of the flow. A frill of capillaries wrapped in a layer of modified ependymal cells. Fluid filtered from the blood through those cells becomes cerebrospinal fluid. Each of the four ventricles has one; the cerebral aqueduct has none.
Body of the lateral ventricleStep 2 of the flow. Fluid made in a lateral ventricle collects here. The body is the central part of the C, in the frontal and parietal lobes, between the anterior horn and the wide junction at the back.
Interventricular foramen (foramen of Monro)Step 3 of the flow. The opening from a lateral ventricle into the third ventricle. There are two, one for each lateral ventricle, and each opens where the anterior horn meets the body.
Third ventricleStep 4 of the flow. A slit in the midline of the diencephalon, between the two thalami. Thalamus and hypothalamus make up each side wall, and a choroid plexus in the roof adds more fluid.
Cerebral aqueduct (aqueduct of Sylvius)Step 5 of the flow. A narrow canal through the midbrain, from the third ventricle to the fourth. The tegmentum of the midbrain lies in front of it and the tectum behind. It has no choroid plexus.
Fourth ventricleStep 6 of the flow. It runs from the cerebral aqueduct down to the obex. The pons and upper medulla form its floor in front; the cerebellum lies over its roof behind. A choroid plexus in the roof adds fluid, and three openings let it out.
Median aperture (foramen of Magendie)Step 7 of the flow. The one midline way out of the fourth ventricle to the subarachnoid space. It opens into the cisterna magna. The two lateral apertures, on the front view, are the other exits.
Subarachnoid spaceStep 8 of the flow. The fluid leaves the ventricles into this space under the arachnoid mater. There it surrounds the whole brain and spinal cord and acts as their cushion.
Arachnoid granulation (arachnoid villus)End of the flow. A small bud of arachnoid mater that pushes into a dural venous sinus, here the superior sagittal sinus, which has the most of them. Fluid drains through it into the venous blood, which leaves the head by the jugular veins.
Central canalA side branch of the flow. At the obex the fourth ventricle narrows into this canal, which runs down through the spinal cord. Fluid from the fourth ventricle can pass into it, or out by the three apertures.
Anterior horn (frontal horn)The part of the lateral ventricle that reaches into the frontal lobe. The septum pellucidum is its inner wall, and the interventricular foramen opens at its back end, where the body begins. It holds no choroid plexus.
Posterior horn (occipital horn)The part of the lateral ventricle reaching back into the occipital lobe. Like the anterior horn, it holds no choroid plexus.
Inferior horn (temporal horn)The largest of the three horns. It runs forward from the wide junction at the back, beneath the thalamus, into the temporal lobe, with the hippocampus in its floor, and ends at the amygdala.
Front view: 7 parts 7
Lateral ventricleThe largest of the four ventricles. There are two, one deep in each half of the cerebrum. Each is stretched into a C through the frontal, parietal, occipital and temporal regions.
Septum pellucidumA thin, triangular, upright membrane. It runs from corpus callosum down to fornix. It separates the two anterior horns, so it is a wall and not a space.
Interventricular foramen (front view)The front view shows why there are two. One comes from each lateral ventricle, and both open into the single third ventricle in the midline. Another name is the foramen of Monro.
Third ventricle (front view)Seen from the front it is only a slit. That is because the two thalami leave little room between them. The side view shows its full extent.
Inferior horn (front view)From the front the two horns swing out and down. They swing into the temporal lobes, one on each side. Another name is the temporal horn.
Fourth ventricle (front view)From the front the fourth ventricle is a diamond. Its floor, the rhomboid fossa, lies on the pons and upper medulla, and each side corner runs out into a lateral recess.
Lateral aperture (foramen of Luschka)Step 7 of the flow, with the median aperture. One of a pair of openings, at the ends of the lateral recesses, that let fluid out of the fourth ventricle into the subarachnoid space.
How this list was compiled: Every name was checked again on 2026-09-30 against two sources read that day, and every detail line against the Wikipedia articles. The wording is our own. Wikipedia, text only: Ventricular system, https://en.wikipedia.org/wiki/Ventricular_system (the four ventricles; the foramina, the aqueduct and the three apertures with the names Monro, Sylvius, Magendie and Luschka; the median aperture and the cisterna magna; the fourth ventricle narrowing at the obex into the central canal; a choroid plexus everywhere except the cerebral aqueduct and the anterior and posterior horns; the return through the arachnoid granulations to the venous sinuses and the jugular vein; the origin in the neural canal); Lateral ventricles, https://en.wikipedia.org/wiki/Lateral_ventricles (body and horns and the lobes they reach; the inferior horn beneath the thalamus, with the hippocampus in its floor, ending at the amygdala; the septum pellucidum between the anterior horns); Third ventricle, https://en.wikipedia.org/wiki/Third_ventricle; Fourth ventricle, https://en.wikipedia.org/wiki/Fourth_ventricle; Cerebral aqueduct, https://en.wikipedia.org/wiki/Cerebral_aqueduct; Choroid plexus, https://en.wikipedia.org/wiki/Choroid_plexus; Central canal, https://en.wikipedia.org/wiki/Central_canal; Septum pellucidum, https://en.wikipedia.org/wiki/Septum_pellucidum; Arachnoid granulation, https://en.wikipedia.org/wiki/Arachnoid_granulation. Second source for the names: Gray, Anatomy of the Human Body, 20th edition, 1918 (public domain), full text at https://archive.org/details/anatomyofhumanbo00grayrich (lateral, third and fourth ventricles; interventricular foramen or foramen of Monro; cerebral aqueduct or aqueduct of Sylvius; the medial aperture, there spelled foramen of Majendie, and the lateral apertures or foramina of Luschka; choroid plexus; central canal; septum pellucidum; subarachnoid cavity; arachnoid villi and granulations; body, anterior and inferior cornu), and Kenhub, Lateral ventricles, https://www.kenhub.com/en/library/anatomy/lateral-ventricles (anterior or frontal horn, posterior or occipital horn, inferior or temporal horn as the largest part, the central part, the septum pellucidum, the foramen of Magendie and foramina of Luschka). TeachMeAnatomy, The Ventricles of the Brain, https://teachmeanatomy.info/neuroanatomy/vessels/ventricles/, was read for the choroid plexus, the cushion and the arachnoid granulations. Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry. No published figure was traced or copied. Licence: own work
How it works
Neither drawing carries a name or a number. On the side view the front of the brain is to the left. Twelve lines point to the small parts.
Read the full guide
Word bank for the side view
Eight lines: choroid plexus, interventricular foramen, cerebral aqueduct, median aperture, central canal, posterior horn, subarachnoid space, arachnoid granulation. Five large shapes have no line, so the name goes on the shape itself: anterior horn, body of the lateral ventricle, inferior horn, third ventricle, fourth ventricle.
Word bank for the front view
Four lines: septum pellucidum, interventricular foramen, third ventricle, lateral aperture. Three shapes take a name with no line: lateral ventricle, inferior horn, fourth ventricle. Four names are on both views and are written twice. From the front the fourth ventricle is a diamond, with a lateral aperture at each side corner.
Four of the passages also carry a person's name: foramen of Monro, aqueduct of Sylvius, foramen of Magendie and foramina of Luschka.
The wide junction where the body meets the posterior and inferior horns is drawn but takes no name.
Questions and answers
Which ventricle of the brain is the largest?
The lateral ventricles. There are two, one in each cerebral hemisphere, and each is a C-shaped cavity. Of its three horns the inferior horn, in the temporal lobe, is the largest.
What connects the third and fourth ventricles?
The cerebral aqueduct, a narrow tube through the midbrain. On the side view it is the thin channel that slants down and back from the flat midline chamber to the tent-shaped one.
What separates the two lateral ventricles?
The septum pellucidum, a thin upright sheet that runs from corpus callosum down to fornix and separates the two anterior horns. Only the front view shows it, as the thin wall between the two wings.
What are the horns of the lateral ventricle?
Three arms of the C, each named for where it lies or for the lobe it reaches: the anterior horn in the frontal lobe, the posterior horn in the occipital lobe and the inferior horn in the temporal lobe.