Lab 1 Neuroanatomy Flashcards
Longitudinal fissure
Longitudinal fissure, found in the mid-line, separates the two cerebral hemispheres.
Lateral sulcus
Lateral sulcus, separates temporal lobe from frontal and parietal lobes
Transverse fissure
Transverse fissure, separates cerebellum from the overlying occipital lobes
Central sulcus
Central sulcus, found on the lateral side of the hemispheres, roughly at the midpoint of the longitudinal fissure. Separates parietal and frontal lobes
Main sulcus/sulci that separate/s frontal lobe
Central sulcus, lateral sulcus
Main sulcus/sulci that separate/s parietal lobe
central sulcus
lateral sulcus
parietooccipital sulcus
Main sulcus/sulci that separate/s temporal lobe
lateral sulcus
parietooccipital sulcus
Occipital lobe sulcus/sulci associated
Pareto-occipital sulcus
Insular lobe sulcus/sulci associated
lateral sulcus
Brain stem
The brainstem connects the spinal cord to the cerebrum. The brainstem has three divisions: the midbrain is located superiorly, the pons is in the middle, and the medulla is located inferiorly.
Brain stem order from most superior to inferior
midbrain is located superiorly, the pons is in the middle, and the medulla is located inferiorly.
Neurons vs glia
Neurons conduct electrical information whereas glial cells, regarded as the support cells, aid the neurons in their function
Grey matter
In the cerebrum and cerebellum the outer layer (cortex) of nervous tissue is gray matter, composed primarily of neuronal cell bodies, dendrites and glial cells.
many cell bodies, relatively few myelinated axons
White matter
Deep to this gray matter that composes the cortex (outer layer of the cerebellum), tracts of white matter are found. White matter is composed primarily of axons
few cell bodies, chiefly long range myelinated axons
What makes the white matter white?
Oligodendrocytes insulate many axons within the CNS (Schwann cells in PNS). The result of the oligodendrocyte wrapping its membrane around the axon is the myelin sheath. Myelin is a lipoprotein. Its high fat content makes myelin appear white.
nucleu îs used to represent
In this context, the word nuclei is used to represent a group of neuronal cells. These neurons are specialised to carry out specific functions. Nuclei sit deep within the white matter
Arrangement of grey and white matter in the spinal cord
reverse of the brain therefore grey matter is surrounded by white matter
cervical nerves =
8
thoracic nerves =
12
lumbar nerves =
5
sacral nerves =
5
coccygeal nerves =
1
Why does the cervical and lumbar enlargements develop
for limb movement - upper limb through the cervical and the lower limb through the lumbar enlargement
Enlargements develop due to the increased number of axonal fibres (axons) that enter and exit at the levels of the upper and lower limbs.
Conus medullaris description
tapering caudal extremity of the cord
The conus in the adult extends to the level of the L1-2 vertebral bodies and one or two vertebrae lower in the infant. In the early embryo, however, the segments of the spinal cord are at the same level as the respective vertebrae.
Explain the disparity between the respective cord and the vertebral levels that one sees in the adult?
The bones of the vertebral column grow longer than the spinal cord does. Therefore, the vertebral column is longer than the spinal cord.
spinal column grows faster than the cord
How and why does the caudate equina form?
As the vertebral column is longer than the spinal cord, the spinal nerves that need to exit at the lower points need to travel for a significant length downwards outside of the spinal cord – forming the cauda equina
to reach structures inferior to the end of the spinal cord
Denticulate ligaments
The denticulate ligaments, extending laterally from the whole cord and anchoring it to the dural sac.
made of pia
Filum terminale
The filum terminale, which extends caudally from the tip of the conus and terminates on the dorsal surface of the coccyx
does not contain nerve fibres as it is made up of pia mater
Anterior nerve roots are
motor
posterior nerve roots are
sensory
structure of anterior nerve roots
The anterior nerve roots (motor), the component fibres of which emerge as variably sized groups of fibres from the anterolateral aspect of the cord; the anterolateral sulcus is, therefore, less distinct than others.
structure of posterior nerve roots
The posterior nerve roots (sensory) which enter the cord in another groove, the posterolateral sulcus. Note that these entering nerve fibres are grouped into a continuous row of more regularly sized fibre bundles.
Where are the cell bodies of the posterior root nerve fibres?
cell bodies are located in the dorsal root ganglion
Dura mater
This is the outermost meningeal layer and is tough, white and fibrous. The dura mater is comprised of two layers. The outer layer (periosteal) forms the periosteum of the bones of the skull. The inner layer (meningeal) surrounds the outside of the cerebrum and spinal cord.
Outer layer of the dura mater =
periosteal
forms the periosteum of the bones of the skull
inner layer of the dura mater =
meningeal
surrounds the outside of the cerebrum and the spinal cord
In the spinal (neural) canal there is an epidural space but there is not an equivalent space in the skull … why?
The brain needs protection from movement. Therefore, the outer layer of the dura (the periosteal layer) is attached directly onto the skull bone, i.e. there is no space.
The spinal cord needs to be able to move with the vertebrae due to the greater flexion and extension by the vertebral column. Therefore, there is an epidural space between the dura and bone – it’s filled with fatty tissue to cushion the spinal cord.
The _______ layer of the dura mater forms three folds
meningeal
meningeal layer folds help to
prevent movement of the brain and accommodate some of the venous sinuses.
falx cerebri seperates
Separates the two cerebral hemispheres in the midline.
falx cerebelli seperates
Separates the two cerebellar hemispheres in the midline.
tentorium cerebelli seperaes
Separates the cerebrum and cerebellum.
falx cerebri anterior and posterior attachments
The falx cerebri attaches anteriorly at the crista galli in proximity to the cribriform plate and to the frontal and ethmoid sinuses. Posteriorly, it is connected with the upper surface of the cerebellar tentorium.
Arachnoid mater
This is the intermediate meningeal layer and is a thin semi-transparent connective tissue, which bridges over many of the sulci and gyri on the surface of the brain. It contains the superficial veins and the arachnoid granulations (found along the margin of the longitudinal fissure).
does not follow the convolutions of the brain
Subarachnoid space
Between the arachnoid and the more deeply situated pia is the subarachnoid space, containing the cerebrospinal fluid (CSF). This space has been considerably reduced in the plastinated brains as it no longer has any CSF within it. The collapsed arachnoid, therefore, looks as if it is lying directly on the surface of the brain. In vivo, however, the subarachnoid space may be a few mm deep on the convex surface of the brain
As the arachnoid bridges over major fissures …
the subarachnoid space becomes larger, forming cisterns, which represent variable depths between the arachnoid and pia
Clinical significance of the cerebellomedullary and lumbar cisterns?
locations where CSF can be collected
Cerebellomedullary - CSF for babies from here because no neck muscles and cannot do lumber puncture due to similar length of spinal cord and column
Lumbar - adults can have CSF extracted from here and generally feel nothing
Where might you insert a hypodermic needle to obtain a sample of CSF in an adult?
Lumbar cistern - cerebellomedullary cistern is only used in babies
below L2 where the epidural space is, no epidural space in brain otherwise sudden movement would cause damage
Arteries in the subarachnoid space …
Note that the arteries of the brain lie in the subarachnoid space, so that blood from arterial haemorrhages will appear in the CSF, examined by either lumbar or cisternal puncture. Blood from venous haemorrhages will not necessarily appear in the CSF, and the main problem will be compression of the brain tissue.
Pia mater
This is the innermost of the meningeal layers. It is a fine membrane that closely follows the gyri and sulci of the brain. It surrounds the subarachnoid blood vessels as they enter the CNS.
Arterial blood supply
The brain receives its blood from the two internal carotid arteries and the vertebral- basilar system. These vessels connect with each on the base of the brain forming the Circle of Willis (described by Thomas Willis, 1664). The branches of this circle supply arterial blood to the entire brain.
Anterior cerebral arteries
The anterior cerebral arteries are branches of the internal carotid arteries. They are joined together anteriorly to the optic chiasm by the anterior communicating artery.
Anterior cerebral arteries supply the …
the medial aspect of each cerebral hemisphere
middle cerebral arteries
The middle cerebral arteries are also branches of the internal carotid arteries and can be seen in the lateral fissure in a real brain.
posterior cerebral arteries
The posterior cerebral arteries, terminal branches of the basilar artery, supply the inferior surface of the temporal and occipital lobes and the medial surface of the occipital lobes The posterior communicating arteries, one on each side, connect the internal carotid artery with the posterior cerebral artery.
posterior communicating arteries
The posterior communicating arteries, one on each side, connect the internal carotid artery with the posterior cerebral artery.
anterior communicating artery
anterior cerebral arteries are joined together anteriorly to the optic chiasm by the anterior communicating artery.
Between which layers of the meninges is bleeding likely to occur if a vessel in the circle of Willis is torn?
Subarachnoid and pia. Therefore, blood will be found in the CSF.
Cerebral arteries are the main blood supply for what
Note carefully in a real brain the numerous small penetrating vessels which arise from the proximal ends of the anterior, middle and posterior cerebral arteries. These vessels constitute the main supply to the basal ganglia and diencephalon. They are commonly involved in strokes (cerebrovascular accidents).
Middle cerebral artery supplies
lateral aspect of cerebrum
CSF function
CSF cushions the brain and spinal cord and also helps to provide a suitable environment for the functioning of nervous tissue.
CSF production
CSF is produced by the choroid plexus, which is located in the ventricles (spaces within the brain).
The choroid plexus is made up of ependymal cells and a network of capillaries (contained within the pia). CSF is produced continuously (500 mL per day) by filtration of plasma through the ependymal cells. CSF cycles through the ventricular system and then enters the subarachnoid space surrounding both the cerebrum and spinal cord. Some CSF also cycles through the central canal of the spinal cord.
fourth ventricle and its apertures
The fourth ventricle contains three apertures that allow CSF to move into the subarachnoid space. These apertures are the median aperture (foramen Magendie), which is located at the inferior margin of the ventricle and opens into the cisterna magna and the two lateral apertures (foramina of Luschka), which are located in the lateral recesses of the ventricle.
CSF recycling
CSF is recycled through the venous system. Arachnoid granulations (groups of arachnoid villi) are extensions of the subarachnoid space into the superior sagittal sinus. They allow CSF to pass from the subarachnoid space into the venous system.
Ventricular system consists of …
a lateral ventricle in each hemisphere,
a third ventricle bordered bilaterally by the diencephalon,
and a fourth ventricle between the cerebellum and the brainstem.
Interventricular foramen
The lateral ventricles are connected to the third ventricle via the interventricular foramen (or foramen of Munro).
Cerebral aqueduct
The cerebral aqueduct connects the third and fourth
ventricles.
Lateral ventricle - anterior horn
an anterior horn, extending rostrally into the frontal lobe
lateral ventricle - body
a body (visible beneath the corpus callosum)
lateral ventricle - posterior horn
a posterior horn extending into the occipital lobe
lateral ventricle - inferior or temporal horn
an inferior or temporal horn dropping down into the temporal lobe from the
junction of the body and posterior horns
Septum pellucidum
The two lateral ventricles are separated from each other by the septum pellucidum, a thin membrane slung beneath the corpus callosum.
The third ventricle is walled in by the
thalamus and hypothalamus
floor of the third ventricle formed anteriorly by …. posteriorly
The floor of the ventricle is formed anteriorly by the optic chiasm and the hypophyseal stalk remnant and posteriorly by the mammillary bodies.
Posteriorly, the third ventricle is continuous with the cerebral aqueduct. The structures forming the posterior boundary of the third ventricle include the posterior commissure, immediately rostral to the superior colliculus, and the pineal body.
Roof of the third ventricle
The roof of the third ventricle extends almost horizontally forward from the suprapineal recess to the interventricular foramen. Between the interventricular foramen superiorly and the optic chiasm inferiorly extends the rostral wall of the ventricle, the lamina terminalis. In the most superior part of the lamina terminalis, anterior to the interventricular foramen, find the anterior commissure
Fourth ventricle
The fourth ventricle is a single midline cavity whose ventral wall is thick and composed of medulla and pons.
Thin membranes, called superior and inferior vela, together with the cerebellum, form the roof of the fourth ventricle (See: Neuroanatomy Book 3, Fig. 9).
CSF enters into the subarachnoid space through three apertures in the fourth ventricle (the median aperture - foramen of Magendie in the roof, and the two lateral apertures - foramina of Luschka at the lateral recesses). Adhesions formed after meningitis can obstruct these apertures.
At the post-mortem of a 3-year-old boy with hydrocephalus, a tumour was found in the midbrain obstructing the cerebral aqueduct. Using your knowledge of neuroanatomy, describe the structures that the cerebral aqueduct connects and indicate how blockage of this channel could produce hydrocephalus.
The cerebral aqueduct travels through the midbrain, connecting the third and fourth ventricles. If blocked, CSF would not be able to drain/travel into the fourth ventricle and then into the subarachnoid space. There would therefore be a build-up of CSF in the lateral and third ventricles, causing hydrocephalus.
