The cerebral aqueduct (aqueduct of the midbrain, aqueduct of Sylvius, Sylvian aqueduct, mesencephalic duct) is a small, narrow tube connecting the
third and
fourth ventricles of the
brain
The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...
.
The cerebral aqueduct is a midline structure that passes through the
midbrain
The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum.
It is functionally associated with vision, hearing, mo ...
. It extends rostrocaudally through the entirety of the more posterior part of the
midbrain
The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum.
It is functionally associated with vision, hearing, mo ...
. It is surrounded by the
periaqueductal gray
The periaqueductal gray (PAG), also known as the central gray, is a brain region that plays a critical role in autonomic function, motivated behavior and behavioural responses to threatening stimuli. PAG is also the primary control center for ...
(central gray), a layer of
gray matter.
Congenital stenosis of the cerebral aqueduct is a cause of
congenital hydrocephalus.
It is named for
Franciscus Sylvius.
Anatomy
The cerebral aqueduct is roughly circular in transverse section, and measures 1-2 mm in diameter.
It is 15 mm long and is commonly subdivided into a pars anterior antrum, and pars posterior.
Relations
Rostrally, it is continuous with the
third ventricle
The third ventricle is one of the four connected cerebral ventricles of the ventricular system within the mammalian brain. It is a slit-like cavity formed in the diencephalon between the two thalami, in the midline between the right and lef ...
, commencing just inferior to the
posterior commissure
The posterior commissure (also known as the epithalamic commissure) is a rounded band of white fibers crossing the middle line on the dorsal aspect of the rostral end of the cerebral aqueduct. It is important in the bilateral pupillary light re ...
.
Caudally, it is continuous with the
fourth ventricle
The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ...
at the junction of the mesencephalon and pons.
The
midbrain tegmentum
The midbrain is anatomically delineated into the tectum (roof) and the tegmentum (floor). The midbrain tegmentum extends from the substantia nigra to the cerebral aqueduct in a horizontal section of the midbrain. It forms the floor of the midbra ...
is situated anteriorly to the cerebral aqueduct.
The portion of the tegmentum posterior to the aqueduct is the
tectum
The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum.
It is functionally associated with vision, hearing, mo ...
.
The
superior and
inferior colliculi that make up the
corpora quadrigemina are situated posteriorly to it.
Development
The cerebral aqueduct, as other parts of the ventricular system of the brain, develops from the central canal of the neural tube, and it originates from the portion of the
neural tube
In the developing chordate (including vertebrates), the neural tube is the embryonic precursor to the central nervous system, which is made up of the brain and spinal cord. The neural groove gradually deepens as the neural folds become elevated, ...
that is present in the developing mesencephalon, hence the name "mesencephalic duct."
Function
The cerebral aqueduct acts as a
canal
Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface ...
that passes through the
midbrain
The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum.
It is functionally associated with vision, hearing, mo ...
. It connects the
third ventricle
The third ventricle is one of the four connected cerebral ventricles of the ventricular system within the mammalian brain. It is a slit-like cavity formed in the diencephalon between the two thalami, in the midline between the right and lef ...
with the
fourth ventricle
The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ...
so that
cerebrospinal fluid
Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...
(CSF) moves between the cerebral ventricles and the canal connecting these ventricles.
Clinical significance
Aqueductal stenosis, a narrowing of the cerebral aqueduct, obstructs the flow of
CSF and has been associated with
non-communicating hydrocephalus. Such narrowing can be
congenital
A birth defect is an abnormal condition that is present at childbirth, birth, regardless of its cause. Birth defects may result in disability, disabilities that may be physical disability, physical, intellectual disability, intellectual, or dev ...
, arise via
tumor
A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
compression (e.g.
pinealoblastoma
Pineoblastoma is a malignant tumor of the pineal gland. A pineoblastoma is a supratentorial midline primitive neuroectodermal tumor. Pineoblastoma can present at any age, but is most common in young children. They account for 0.001% of all prima ...
), or through cyclical
gliosis
Gliosis is a nonspecific reactive change of glial cells in response to damage to the central nervous system (CNS). In most cases, gliosis involves the proliferation or hypertrophy of several different types of glial cells, including astrocytes ...
secondary to an initial partial obstruction.
[
]
History
The cerebral aqueduct was first named after Franciscus Sylvius.
Additional images
File:Gray710.png, Transverse section through mid-brain; number 2 indicates the cerebral aqueduct.
File:Gray711.png, Transverse section of mid-brain at level of inferior colliculi.
File:Gray712.png, Transverse section of mid-brain at level of superior colliculi.
File:Periaqueductal_MRI.PNG, MRI section of mid-brain.
File:Gray720.png, Median sagittal section of brain.
File:Gray734.png, Scheme showing relations of the ventricles to the surface of the brain.
File:Slide1qq.JPG, Cerebral aqueduct
File:Slide7qq.JPG, Cerebral aqueduct
File:Slide2HOM.JPG, Cerebral peduncle, optic chasm, cerebral aqueduct. Inferior view. Deep dissection.
File:Slide3HOM.JPG, Cerebral peduncle, optic chasm, cerebral aqueduct. Inferior view. Deep dissection.
File:Slide2ERV.JPG, Cerebrum. Inferior view. Deep dissection
See also
* List of regions in the human brain
The human brain anatomical regions are ordered following standard neuroanatomy hierarchies. Functional, connective, and developmental regions are listed in parentheses where appropriate.
Hindbrain (rhombencephalon)
Myelencephalon
* M ...
References
External links
*
{{Authority control
Ventricular system