lecture 21 - meninges & ventricular system Flashcards
How many layers make up the meninges?
3
What are the 3 layers of the meninges?
Dura mater, arachnoid mater, pia mater
What is the outermost layer of the meninges?
Dura mater
What layer of the meninges sits adjacent to the bone of the cranium?
Dura mater
What is the structural characteristic of the dura mater?
Dense, fibrous, tough
What is the structure of the dura mater?
Made of two layers (outer and inner) that are tightly adhered to each other except when gaps called venous sinuses form, or the inner layer forms dural folds in prominent fissures
What does the inner layer of the dura mater form, when it clings to major sulci?
Dural fold
What are dural folds formed from?
Inner layer of the dura mater
What is the purpose of the dural folds?
Seperate major divisions of the brain, provide stability of the brain within the cranium.
What are the 3 major dural folds?
Falx cerebri, Falx cerebelli, Tentorium cerebelli.
What is the Falx cerebri?
A dural fold that separates the cerebral hemispheres in the medial/sagittal plane.
What is the Falx cerebelli?
A dural fold that seperate the cerebellar hemispheres in the median/sagittal plane
What is the Tentorium cerebelli?
A dural fold that separates the cerebrum from the cerebellum in the horizontal plane.
What is a venous sinus?
A gap between the inner and outer layers of the dura mater, where they diverge. Space collects veins/de-oxygenated blood and ‘old’ CSF.
Where is cerebrospinal fluid collected after it has cycled through the ventricular system?
In the venous sinuses.
What is the appearance of the arachnoid mater?
‘spider-like’ appearance due to the blood vessels it contains.
Does the arachnoid mater extend into sulci of the brain?
No
What is the structure and function of the subarachnoid space?
Space between arachnoid and pia mater, filled with cerebrospinal fluid and contains blood vessels.
What are arachnoid granulations?
Areas where the arachnoid mater perforates the inner layer of the dura mater to transport ‘old’ CSF from subarachnoid space into venous sinuses.
What is the structure of the pia mater?
Inner layer of the meninges, transparent and delicate, adheres to brain and follows gyri, extending into sulci.
Where does the CSF of the spinal cord sit, and what is its function?
Sits in the subarachnoid space of the meninges of the spinal cord, and absorbs shock, provides nutrients and removes waste.
What is the structure of the ventricular system?
A network of interconnected spaces/ventricles within the brain, filled with CSF which nourishes and protects it. Cilia in ependymal cells circulate CSF.
How is cerebrospinal fluid circulated through the ventricular system?
Spaces are lined with ependymal cells, which have cilia that move to circulate the fluid.
Where is CSF produced in the brain?
The Chloroid plexus.
What is the cellular structure of the chloroid plexus?
Made up of groups of modified ependymal cells, found in several core ventricles of the brain.
What are the 6 key ventricles of the brain?
Lateral Ventricles (2) , Third ventricle, Cerebral aqueduct, Fourth ventricle, Central Canal
How many lateral ventricles are there?
2 (one in each cerebral hemisphere)
Where is the Third ventricle located?
In the diencephalon
Where is the cerebral aqueduct located?
Connects the 4th and 3rd ventricles
Where is the Fourth ventricle located?
At the level of the Cerebellum.
What is the central canal of the ventricular system?
Starts at the base of the brain at the fourth ventricle, and then runs through the centre of the spinal cord.
What is the path of cerebrospinal fluid through the ventricular system?
Lateral ventricles, 3rd ventricle, cerebral aqueduct, 4th ventricle, subarachnoid space (around brain and spinal cord), exit via arachnoid granulations into venous sinuses.
Where does CSF begin circulation of the ventricular system?
Lateral ventricles
Where does CSF finish circulation of the ventricular system?
Exits through arachnoid granulations into venous sinus.
