Ventricular System And Cerebrospinal Fluid

Dani's Reviewer

What are the four ventricles of the brain?

Two lateral ventricles, third ventricle, fourth ventricle.

How do the lateral ventricles communicate with the third ventricle?

Via the interventricular foramina (foramina of Monro).

Through which structure does CSF flow from the third ventricle to the fourth ventricle?

Cerebral aqueduct (aqueduct of Sylvius).

What are the openings in the fourth ventricle that allow CSF to enter the subarachnoid space?

Median aperture (foramen of Magendie) and lateral apertures (foramina of Luschka).

What lines the ventricles and produces CSF?

Ependyma and choroid plexus.

What are the parts of the lateral ventricles?

Body (parietal lobe), anterior horn (frontal lobe), posterior horn (occipital lobe), inferior horn (temporal lobe).

What structure forms the roof of the lateral ventricles?

Corpus callosum.

What structure forms the floor of the lateral ventricles?

Caudate nucleus and lateral margin of the thalamus.

What are the medial structures of the inferior horn of the lateral ventricle?

Stria terminalis and hippocampus.

What is the function of the choroid plexus?

Produces cerebrospinal fluid (CSF).

What is the third ventricle located between?

The two thalami.

What is the blood supply of the choroid plexus?

Choroidal branches of the internal carotid and basilar arteries.

What is the venous drainage pathway of the choroid plexus?

Internal cerebral veins → Great cerebral vein → Inferior sagittal sinus → Straight sinus.

What is the cerebral aqueduct lined with?

Ependyma.

What is the significance of the cerebral aqueduct?

It connects the third and fourth ventricles and allows CSF flow.

What structure forms the floor of the fourth ventricle?

Rhomboid fossa (posterior surface of pons and cranial half of the medulla oblongata).

What are the major landmarks of the rhomboid fossa?

Median sulcus, medial eminence, sulcus limitans, vestibular area, facial colliculus, substantia ferruginea, stria medullaris, hypoglossal triangle, vagal triangle, area postrema.

What is the total volume of CSF in the human body?

~150 mL.

What are the functions of CSF?

Cushions the brain and spinal cord, provides buoyancy, regulates intracranial pressure, removes metabolic waste, may transport hormones.

Where is CSF mainly produced?

Choroid plexuses of the lateral, third, and fourth ventricles.

What is the rate of CSF production?

~0.5 mL/min (total turnover in ~5 hours).

What are the major sites of CSF absorption?

Arachnoid villi into the dural venous sinuses (especially the superior sagittal sinus).

What happens if venous pressure rises in the superior sagittal sinus?

Arachnoid villi close to prevent blood reflux into CSF.

What is the blood-brain barrier (BBB) composed of?

Endothelial cells with tight junctions, basement membrane, astrocyte foot processes.

What substances can freely pass through the BBB?

Gases (O₂, CO₂), water, and lipid-soluble molecules.

What substances cross the BBB slowly?

Glucose and electrolytes.

Which areas of the brain lack the BBB?

Pineal gland, posterior pituitary, tuber cinereum, optic recess, area postrema.

What is the function of the blood-CSF barrier?

Regulates CSF composition by controlling molecular passage.

What are the components of the choroid plexus that form the blood-CSF barrier?

Fenestrated endothelial cells, basement membrane, choroidal epithelial cells with tight junctions.

What is papilledema?

Optic disc swelling due to increased intracranial pressure compressing the retinal vein.

What are the causes of hydrocephalus?

Excessive CSF formation, blockage of CSF circulation, diminished CSF absorption.

What is the difference between communicating and non-communicating hydrocephalus?

Non-communicating involves obstruction between CSF production and exit, while communicating has no obstruction but elevated CSF pressure.

What are common causes of CSF circulation blockage?

Tumors, inflammation, congenital malformations.

What are the typical CSF findings in bacterial meningitis?

Cloudy CSF, thousands of WBCs, low glucose, high protein.

What are the typical CSF findings in viral meningitis?

Clear CSF, moderate lymphocyte increase, normal glucose.

What are the CSF characteristics in subarachnoid hemorrhage?

Bloody or xanthochromic CSF due to hemoglobin breakdown.

What happens if the subarachnoid space around the optic nerve is compressed?

Retinal vein congestion and optic disc swelling (papilledema).

What imaging techniques are used to investigate cerebral ventricles?

CT, MRI, ventriculography, intracranial pneumography.

What is the normal CSF pressure range?

60–150 mm H₂O.

How does a spinal tap diagnose a subarachnoid space blockage?

Reduced pressure fluctuations with pulse/respiration, no pressure rise with jugular vein compression (Queckenstedt’s sign).