Aqueduct of midbrain
Aquaeductus mesencephali
The narrow channel through the midbrain that carries cerebrospinal fluid from the third ventricle down to the fourth ventricle.
At a glance
- English
- Aqueduct of midbrain
- Latin (TA2)
- Aquaeductus mesencephali
- System
- Brain and spinal cord
- Region
- Head
- Side
- Single, on the midline
About the aqueduct of midbrain
The aqueduct of the midbrain, also called the cerebral aqueduct or the aqueduct of Sylvius, is the part of the ventricular system that runs through the midbrain. It is a slender canal, the narrowest part of the whole system, opening above into the back of the third ventricle just below the posterior commissure and below into the upper end of the fourth ventricle beneath the superior medullary velum.
It runs through the back part of the midbrain. Dorsal to it lies the tectum, with the superior and inferior colliculi. Ventral to it lies the tegmentum, containing the nuclei of the oculomotor and trochlear nerves close to the midline. The aqueduct is surrounded by a sleeve of grey matter, the periaqueductal grey, which takes part in the control of pain and in defensive and autonomic responses. The mesencephalic nucleus of the trigeminal nerve lies at its lateral edge.
The canal is lined with ependyma and, unlike the lateral, third and fourth ventricles, contains no choroid plexus. All the cerebrospinal fluid made in the lateral and third ventricles must pass through it on the way to the fourth ventricle and then to the subarachnoid space.
Because it is so narrow, it is easily blocked. Congenital aqueduct stenosis, or compression from tumours of the pineal region or tectum, causes obstructive hydrocephalus, in which the lateral and third ventricles enlarge while the fourth stays normal. A tumour pressing on the tectum and aqueduct can also cause Parinaud's syndrome, with paralysis of upward gaze. Endoscopic third ventriculostomy treats aqueduct obstruction by opening the floor of the third ventricle so that fluid can bypass it.
Function and supply
- Function
- Conducts cerebrospinal fluid from the third ventricle to the fourth ventricle.
- Blood supply
- The surrounding midbrain is supplied by branches of the posterior cerebral and superior cerebellar arteries, including the collicular (quadrigeminal) arteries.
Anthromica
See the aqueduct of midbrain where it really sits, with every layer of the body around it.
- Every layer, one body. Peel from muscle to bone, nerve, vessel and organ, and turn it any way.
- English and Latin. Every structure named the way your exam names it.
- Quiz until it sticks. Short drills on the structures you keep missing.
Free to start. No card.
