Fluid space
Fourth ventricle
Also called Rhomboid fossa (its diamond-shaped floor)
A tent-shaped chamber between brainstem and cerebellum where fluid flows out.
The fourth ventricle is a tent-shaped fluid chamber sitting between the brainstem in front and the cerebellum behind. It collects fluid from the cerebral aqueduct and lets it escape through three small openings into the space around the brain and spinal cord. Its floor lies over vital control centers for things like swallowing, eye movements, breathing and heart rate. At its lower end it narrows into a tiny canal that runs down into the spinal cord.
Where it is
At the back of the brainstem, between the pons and upper medulla in front and the cerebellum behind.
What it does
Letting fluid out
Three small openings, one in the middle and one on each side, let fluid flow out of the ventricles into the space around the brain and spinal cord.
Feeding the spinal canal
At its bottom tip it connects with the thin central canal of the spinal cord.
Covering vital centers
Its floor lies over nerve centers that control swallowing, the tongue, facial muscles and eye movements, and that help regulate breathing and heart rate.
Sensing poisons
A small area at its lower end, the area postrema, can detect toxins in the blood and trigger vomiting.
Think of it as the drain at the bottom of a sink: all the fluid from above collects here before flowing out through its openings.
Works with
- Cerebral aqueductIt receives fluid from above through the cerebral aqueduct.
- CerebellumThe cerebellum forms the back of its tent-shaped roof.
- PonsThe back of the pons forms the upper half of its floor.
- Medulla oblongataThe medulla forms the lower half of its floor, home to centers for breathing and heart rate.
- Choroid plexusA strip of choroid plexus in its roof adds more fluid.
- Spinal cordIt connects with the tiny central canal that runs down the middle of the spinal cord.
When it goes wrong
Tumors in children
Some of the most common brain tumors in children, such as medulloblastoma, grow near the fourth ventricle. They can block fluid flow, causing headaches, vomiting and unsteady walking.
Blocked exits
If its small exit openings are blocked, for example by scarring after an infection or bleeding, the fourth ventricle and all the chambers above it swell.
For learning only, not medical advice. If you have a health concern, talk to a doctor.
Surprising facts
- Its vomiting center, the area postrema, is one of the few spots where the brain's protective blood barrier is leaky on purpose, so it can "taste" the blood for poisons.
- Its three exit holes are named after two 19th-century anatomists: the foramina of Luschka on each side and the foramen of Magendie in the middle.
By the numbers
Where the name comes from
Numbered as the last of the four ventricles. Its floor is called the rhomboid fossa, from the Greek "rhombos" (a diamond shape) and the Latin "fossa" (a ditch or trench), because of its diamond-shaped outline.
Quick quiz
3 questions. Your answers are saved and come back in your daily review.
Which of these is a job of the fourth ventricle?
Show the answer
Letting fluid out. Three small openings, one in the middle and one on each side, let fluid flow out of the ventricles into the space around the brain and spinal cord.
Letting fluid out. Three small openings, one in the middle and one on each side, let fluid flow out of the ventricles into the space around the brain and spinal cord.
The fourth ventricle is part of which larger structure?
Show the answer
Ventricular system. It belongs to the ventricular system.
Ventricular system. It belongs to the ventricular system.
Which part fits this description? "Like the drain at the bottom of a sink: all the fluid from above collects here before flowing out through its openings."
Show the answer
Fourth ventricle. It is the fourth ventricle. A tent-shaped chamber between brainstem and cerebellum where fluid flows out.
Fourth ventricle. It is the fourth ventricle. A tent-shaped chamber between brainstem and cerebellum where fluid flows out.
These parts now come back in your daily review, just before you would forget them.
Practice it and its neighbors in 3DSources
- Neuroanatomy, Fourth Ventricle, StatPearls, NCBI Bookshelf
- Fourth ventricle, Radiopaedia
- Neuroanatomy, Ventricular System, StatPearls, NCBI Bookshelf
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