The cerebral aqueduct (aqueduct of Sylvius) is a narrow canal, about 15 mm long and 1–2 mm across, running down through the back part of the midbrain on the midline. It joins the third ventricle above to the fourth ventricle below and carries cerebrospinal fluid between them. [1]
The 3D brain needs JavaScript. The text below still says where the cerebral aqueduct is and what it does.
Slice
Opens cut by a side (sagittal) slice through the cerebral aqueduct. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
On the midline, through the whole length of the back (posterior) part of the midbrain. [1]
It starts from the third ventricle just below the posterior commissure and opens into the fourth ventricle where the midbrain meets the pons. [1]
The midbrain tegmentum lies in front of it; behind it is the tectum, with the superior and inferior colliculi. [1]
It is wrapped in a layer of grey matter, the periaqueductal grey (central grey). [1]
What it does
It is the channel through which cerebrospinal fluid moves from the third ventricle down to the fourth. [1]
Unlike the lateral, third and fourth ventricles, it has no choroid plexus, so it makes no fluid of its own; it only carries it. [2]
Connections
Above: the third ventricle. Below: the fourth ventricle. [1]
Like the rest of the ventricular system it grows from the central canal of the embryo’s neural tube; it comes from the part in the developing midbrain (mesencephalon), hence the name “mesencephalic duct”. [1][3]
Other names
Aqueduct of the midbrain, aqueduct of Sylvius, Sylvian aqueduct, mesencephalic duct; it is named after Franciscus Sylvius. [1]
Size
Roughly round in cross-section, 1–2 mm across and about 15 mm long. [1]
On this model the cerebral aqueduct measures about 7 mm front to back, 18 mm top to bottom and 3 mm side to side (the box it fits in, not its volume). [4]
Centre of the cerebral aqueduct compared with the centre of the third ventricle: 12 mm further back, 12 mm lower; 17 mm apart in a straight line. [4]
Centre of the cerebral aqueduct compared with the centre of the fourth ventricle: 13 mm further forward, 31 mm higher; 33 mm apart in a straight line. [4]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); real brains vary in size and shape, so its measurements describe one model, not anyone’s brain.