Neuroanatomy - Meninges and Ventricular System

what are meninges?

three layers of connective tissue that protect the brain and house blood vessels

what are the three meninges?

• dura mater

• arachnoid mater

• pia mater

what describes the dura mater?

outermost layer, connected to skull, contains venous sinuses

• “tough mother”

what describes arachnoid mater?

spidery, middle layer

what describes pia mater?

fine layer of tissue, directly connected to brain parenchyma, follows gyri and sulci

• “soft mother”

what are the two layers of the dura mater?

periosteal and meningeal

the periosteal and meningeal layer of the dura mater are generally tightly fused, but separate to form what?

venous sinuses (drains cerebral veins)

what separates different compartments within the brain?

dural reflections (folds of the meningeal layer)

dura mater is pain sensitive and is innervated by what?

meningeal branches of CN V and CN X

what describes the blood supply to the dura mater?

meningeal arteries, mainly the middle meningeal arty

the middle meningeal artery travels in what?

periosteal layer of dura mater

folds of the inner meningeal layer result in what?

dural reflections

what are examples of dural reflections?

• falx cerebri

• tentorium cerebelli

• falx cerebelli

what describes the falx cerebri?

dural reflection found between two cerebral hemispheres in longitudinal fissure

what describes tentorium cerebelli?

dural reflection that separates middle and posterior cranial fossae, covers upper surface of cerebellum

what describes falx cerebelli?

dural reflection that separates cerebellar hemispheres

what dural sinuses are associated with the falx cerebri?

• superior sagittal sinus

• inferior sagittal sinus

what dural sinuses are associated with the outer border of tenorium cerebelli?

transverse sinuses

what dural sinus is found between falx cerebri and tentorium cerebelli?

straight sinus

what dural sinus is associated with the falx cerebelli?

occipital sinus

sinuses meet at the posterior pole of the skull where?

at the confluence of sinuses

what describes the path of venous blood drainage?

transverse sinus → sigmoid sinus → internal jugular vein

what is the spidery/wispy layer underneath the dura mater?

arachnoid mater

what connects arachnoid mater to the pia mater below ?

arachnoid trabeculae

what protrudes into superior sagittal sinus and is involved in reabsorption of CSF?

arachnoid granulations

what is the true space between arachnoid and pia mater?

subarachnoid space

the subarachnoid space is filled with what?

CSF

what veins are found in subarachnoid space?

bridging veins

bridging veins in the subarachnoid space pierce arachnoid to connect to what?

dural sinuses

the pia mater is what?

the innermost meningeal layer

pia mater is tightly adherent to what?

brain parenchyma, follows all gyri and sulci

pia mater separates what?

the brain from CSF in the subarachnoid space

within pia mater, the blood vessels to the cerebrum are covered in what?

a sleeve of pia (forms perivascular space)

the perivascular space does what?

penetrates brain parenchyma until the vessel becomes a capillary

what are the potential spaces around the meninges?

• epidural/extradural space

• subdural space

what is the true space around the meninges?

subarachnoid space (filled with CSF)

a real space around meninges exists when?

under normal conditions

what spaces do no exist under normal conditions?

potential spaces

when do potential spaces become real spaces?

pathologically (accumulation of blood)

the epidural space houses what?

meningeal arteries, branches of the external carotid artery, which supply the dura

the epidural space (normally a potential space) becomes a real space via what?

meningeal artery bleed

what describes an epidural hematoma?

accumulation of blood (meningeal artery) between dura and skull

• usually result of trauma

epidural hematoma appears as what?

lens (biconcave) shape on CT

an epidural hematoma is more common with what?

fracture to the temporal bone

in the case of epidural hematoma, the bleed does not do what?

cross sutures

subdural space houses what?

bridging veins connecting cerebral veins in the subarachnoid space to the dural venous sinuses

the subdural space (normally a potential space) becomes a real space via what?

if bridging veins rupture (venous hemorrhage)

what describes a subdural hematoma?

accumulation of blood (bridging veins) between dura and arachnoid

• could be acute (trauma) or chronic (elderly)

how does a subdural hematoma appear?

as a crescent-shaped hematoma on CT

what describes the subarachnoid space?

real space filled with CSF

• contains major cerebral arteries and veins

regrading the subarachnoid space, rupture of a blood vessel can do what?

fill the space with something other that CSF/replaces CSF

what describes a subarachnoid hemorrhage?

bleeding between arachnoid mater and pia mater

• cause: trauma, rupture of intracranial aneurysm

how does a subarachnoid hemorrhage present?

as severe headache of rapid onset

how does subarachnoid hemorrhage appear on a CT?

blood is seen tracing down into sulci

what is cerebrospinal fluid (CSF)?

clear, colorless fluid that fills the spaces within the cerebrum and spinal cord

what are the functions of cerebrospinal fluid?

• mechanical protection (cushion and shock absorption)

• reduces weight of brain

• distribution of nutrients and neurotransmitters

• maintenance of chemical balance

• removal of metabolic waste and toxins

where is CSF located?

• ventricles (brain)

• subarachnoid space (brain and spinal cord)

• central canal (spinal cord)

what describes a ventricle?

space within the brain filled with CSF

the lateral ventricles originate from what?

the telencephalon

the third ventricle originates from what?

diencephalon

the cerebral aqueduct originates from what?

mesencephalon

the fourth ventricle originates from where?

metencephalon

what are the components of the ventricular system?

• two C-shaped lateral ventricles (one in either hemispheres)

• third ventricle in the midline

• fourth ventricle between cerebellum and brainstem

what ventricles have a posterior, inferior and anterior horn?

the two c-shaped lateral ventricles

what connects the lateral ventricle with the third ventricle?

interventricular foramen (of Monroe)

what connects the third ventricle to the fourth ventricle?

cerebral aqueduct

CSF exits to the central canal of spinal cord from the fourth ventricle via what?

either medial foramen of Magendie or lateral formina of Luschka

what describes the production of CSF?

about 500 mL CSF produced from choroid plexus daily

choroid plexus (with ependymal cells) lines what?

the ventricles and subarachnoid space

where is CSF mainly produced?

within the two lateral ventricles and the fourth ventricle

what describes the structure of choroid plexus?

• fenestrated endothelium of choroid arteries

• pial layer

• specialized ependymal layer

what prevents large molecules (proteins, glucose) from crossing into CSF?

blood brain barrier

a bacterial infection usually arises due to what?

low CSF glucose and high protein levels

what are cisterns?

spaces within the subarachnoid space that are filled with CSF and aid in proper circulation

what describes the largest cistern?

cisterna magna

• located caudal to cerebellum

• lying above foramen magnum

CSF flows of the ventricular system via what?

medial foramen of Magendie or two lateral foramina of Lushka into subarachnoid space or central canal

the subarachnoid space, CSF circulates until what?

it reaches arachnoid granulations that protrude into superior sagittal venous sinus

CSF is reabsorbed through what?

arachnoid granulations/villi

• protrusions of arachnoid mater that extend into the dural venous sinuses (superior sagittal sinus)

movement of CSF reabsorption through arachnoid granulations/villi is via what?

pressure gradient