Ventricular System Flashcards
What does the CSF do for the brain
Let’s it partially float in the skull cavity
How ar the four ventricles of the brain connected
Thigh out narrow pipe like openings
Where is the CSF primarily produced
Brain ventricles
The CSF acts as a buffer to do what
Absorb stress transferred through the rigid skull
CSF circulation
Ventricles to surface of brain and then drains in venous sinuses of skull
CSF circulates ____________ from the ventricles to the subarachnoid space to the venous sinuses of the brain
Unidirectional
Pathology due to disruption of CSF circulation causes what
Hydrocephalus
What are the 4 brain ventricles
- 2 lateral ventricles
- third ventricle
- fourth ventricle
CSF production and circulation
- choroid plexus
- expend y’all lining of choroid plexus
- choroid plexus produces the CSF
What produces the CSF
Choroid plexus
Disruption of CSF circulation
Hydrocephalus
Where are the lateral ventricle located
In each hemisphere
Where is the third ventricle located
Midbrain
Where is the fourth ventricle located
Between the pons and medulla, and the cerebellum
Located in the caudal medulla and spinal cord; usually not patent over much of its existence
Central canal
Communications between ventricles
- interventricular foramina (of monro) - lateral and third ventricle
- cerebral aqueduct (Sylvius)
- foramina of Lushka and Magendie
Which lobes do the C shaped lateral ventricles course through?
All of the lobes of the cerebral hemispheres in which they reside
What are the five parts of each lateral ventricle
- anterior horn (frontal lobe)
- body (frontal and parietal)
- posterior horn (occipital)
- inferior horn (temporal)
- atrium or trigone (body and posterior and inferior horns meet here )
What is the third ventricle
A midline slit in the diencephalon
What is the lateral wall of the third ventricle
A medial surface of the thalamus and hypothalamus and part of the hypothalamus forms its floor
Roof of the third ventricle
Thin membranous roof containing choroid plexus
Anteriorly, ther third ventricle ends at the __________
Lamina terminalis
At the posterior end of hte maillary body, the third ventriclal does what
Narrows fairly abruptly to become the cerebral aqueduct (sylvius)
Where does the interventricular foramen lay
In the anterior part of each wall of the third ventricle
Recess of the third ventricle, inferiorly
Inferiorly, the optic recess lies in front of the optic chiasm at the base of the lamina terminalis
Where does the infundibular recess of the third ventricle lay
Behind the chiasm
Superior recess of third ventricle
Pineal recess invades the stalk of the pineal gland
Suprapineal recess of third ventricle
Lies just anterior to stalk of pineal gland
Where is the fourth ventricle situated
Between the cerebellum posteriorly and the pons and rostral medulla anteriorly
Shape of fourth ventricle
Like a tent with a doubly peaked roof, the peaks protruding into the cerebellum
The portion of the roof of the fourth ventricle rostral to the peak
Superior medullary velum
The portion of the roof of the fourth ventricle caudal to the peak
Inferior medullary velum
The floor of the fourth ventricle is referred to as
Rhomboid fossa
At the lateral point of the floor of the ventricle becomes a narrow tube that proceeds anteriorly and curves around the brainstem. This tubular prolongation is the what
Lateral recess of the fourth ventricle, aka the foramen of Lushka
Where does CSF exit the system
Foramen of Luschka
What does hte fourth ventricle communicate with
Subarachnoid cisterns
What do the lateral and third ventricle communicate with
Only with other parts of the ventricular system, each having only one draining opening
What does the lateral ventricle communicate with
Each other and the 3rd ventricle through the interventricular foramen (Monroe)
How does the 3rd ventricle communicate with the 4th ventricle
Through the relatively long canal- the cerebral canal aka aqueduct of Sylvius
What happens if there is obstruction of the ventricles
Block the free circulation of CSF
How many aperture in the fourth ventricle
3
Through which the ventricular system communicates freely with subarachnoid space
What are the 3 apertures of the 4th ventricle
–median aperture (foramen of magendie)
-the two lateral apertures
(Foramina of Luschka)
Clear, colorless fluid surrounding the brain and spine
CSF
Where is CSF produced
Choroid plexuses
Functions of CSF
Acts as a cushion or buffer
What does CSF occupy
Ventricular system and the subarachnoidal space
How does CSF circulate
Unidirectionally from ventricles to surface of brain
How is CSF propelled
Forward passively through the pulsation of the brain circulation, no active propulsion
How much CSF within and around brain and spinal cord
150-200ml
How much CSF in ventricles
25ml
What is turnaround time for CSF
3.5 times a day
CSF circulation
Lateral ventricles–3rd ventricle–4th ventricle–subarachnoid space–venous sinuses
All four ventricles contain strands of highly convoluted and vascular membranous material called ________
Choroidal plexus
Lateral ventricle and chorda plexus
There is a band of choroid plexus in each arterial ventricle
The plexus is enlarged in the region of the atrium, and here it is called the ______
Glomus
Choroid plexus and age
Becomes calcified
Choroid plexus in the lateral ventricles
Grows through the interventricular foramen, forming part of its posterior wall
How is the choroid plexus formed
By an evagination of the ependymal layer of cells containing arterioles, capillaries, and venules
Epedndymal layer of choroid plexus
Specialized as cuboidal, secretory epithelium, the choroid epithelium
How does the choroid plexus generate CSF?
By filtering blood
Fenestrated endothelium in choroid capillaries
Allows plasma and fluid through, but blocks cells
Draining of CSF
- 4th ventricle through foramina, up and over cerebral hemispheres, through arachnoid Vvilli and into the superior sagittal sinus
- some goes into subarachnoid space around spinal cord. It makes it way caudally to lumbar cistern
- most is returned to venous system through arachnoid villi that penetrate dural sleeves
Does the CSF in the subarachnoid space penetrate through to the pia mater?
No
Small protrusions of the arachnoid through the dura mater
Arachnoid granulation (arachnoid villi)
What do the arachnoid granulation (villi) allow
They protrude into the venous sinuses of the brain and allow CSF to exit the sub arachnoid space and enter the blood stream
Where do the largest arachnoid granulation lie?
Superior sagittal sinus
What is produced by arachnoid granulation on the inner surface of cranial bones
Small pits called granular fovea
What are smaller arachnoid granulation called
Villi
What do the arachnoid granulation act as
One way valves
Rate of CSF production independent of what
Blood pressure and intra-ventricular pressure
Fluid continues to be produces even if the path of its circulation is blocked. When this happens, CSF pressure rises, ventricles expand creating condition called
Hydrocephalus
Hydrocephalus can result from
- excess production of CSF
- blockage of CSF circulation
- deficiency in CSF reabsorption
- ex vacuo
What is the most common cause of hydrocephalus
Blockage of CSF circulation
Blockage of CSF by tumors of the choroid plexus (papilloma)
Hydrocephalus
Ventricles still communicate, blockage is outside
Communicating hydrocephalus
Blockage is within the ventricles (aqueduct)
Non communicating hydrocephalus
Symptoms of increased intracranial pressure
- headache
- nausea/vomitting
- papilledema, except in normal pressure hydrocephalus
- changes in consciousness (sleepiness to coma)
- brain herniation (life threatening)
What type of hydrocephalus effects elderly most
Normal pressure hydrocephalus
In 50% of cases of normal pressure hydrocephalus, an idiopathic __________ increase in ICP occurs
Intermittent
Some causes of normal pressure hydrocephalus
- meningitis
- subarachnoid hemorrhage
- atherosclerosis
What does normal pressure hydrocephalus result from
Decreased reabsorption of CSF at the arachnoid granulations
Presentation of normal pressure hydrocephalus
Classic triad of bladder incontinence dementia, and ataxia (wet, wacky, wobbly)
What is there no presence of in normal pressure hydrocephalus
No papilledema or headaches
Diagnosis for normal pressure hydrocephalus q
Clinical signs, with CT/MRI showing ventriculomegaly
Pseudotumor cerebri is 8-10 times more common in _____
Women
What is pseudotumor cerebri associated with
Obesity and oral contraceptives
Identified cause of pseudotumor cerebri
Usually none
Presentation of pseudotumor cerebri
Headache, visual disturbances such as diplopia and sixth cranial nerve palsy (abducens)
What is a characteristic sign of pseudotumor cerebri
Papilledema
Cranial pressure in pseudotumor cerebri
Increased