CSF Circulation and Choroid Plexus

Questions and Answers

What is the primary site of resorption of CSF in the subarachnoid space?

Venous circulation (correct)

Arachnoid membrane

Cerebral aqueduct

Choroid plexus

How many choroid plexuses are present in the brain?

Four (correct)

Two

Three

One

What is the primary function of the brain-CSF boundary?

To modulate the entry of leukocytes into the central nervous system

To facilitate the transport of substances into the brain

To prevent the passage of blood-borne substances into the brain (correct)

To remove brain metabolites and metabolic waste into the blood

What forms the blood-CSF boundary at the choroid plexus?

Ependymal cells and tight junctions Signup and view all the answers

What is a distinct feature of the choroid plexus capillaries?

They are fenestrated and have no tight junctions Signup and view all the answers

What is NOT a function of the Blood-Cerebrospinal Fluid Barrier (BCSFB)?

Regulating body temperature Signup and view all the answers

What should NOT be confused with the Blood-Cerebrospinal Fluid Barrier (BCSFB)?

Blood-Brain Barrier (BBB) Signup and view all the answers

What is the primary function of the fenestrated capillaries found in the choroid plexus?

To facilitate the exchange of substances between blood and CSF Signup and view all the answers

What is the name of the layer of grey matter in the cerebellum that contains Purkinje cells?

Ganglionic cell layer Signup and view all the answers

Where are discontinuous (sinusoidal) capillaries typically found?

In the liver and spleen Signup and view all the answers

What is the purpose of the blood-CSF barrier (BCSFB)?

To form a tight barrier against the CSF Signup and view all the answers

Where is the blood-CSF barrier (BCSFB) primarily located?

In the choroid plexus Signup and view all the answers

What is the main difference between the blood-CSF barrier (BCSFB) and the blood-brain barrier (BBB)?

The BCSFB is more permeable than the BBB Signup and view all the answers

What is the primary function of the choroid plexus?

To produce CSF through active secretion of Na+ Signup and view all the answers

How often is the total volume of CSF formed and renewed?

Three times a day Signup and view all the answers

What is the main difference between the blood-CSF barrier and the blood-brain barrier?

The blood-CSF barrier is formed by tight junctions Signup and view all the answers

What is the function of microvilli on the epithelial cells of the choroid plexus?

To increase the surface area for CSF production Signup and view all the answers

What is the role of the choroid plexus in maintaining the brain's extracellular environment?

It facilitates the exchange of biomolecules Signup and view all the answers

What is the structure of the choroid plexus that increases its surface area?

Villi Signup and view all the answers

What is the purpose of the choroid plexus in the context of clinical examination?

It allows for the sampling of CSF for clinical examination Signup and view all the answers

What is the name of the layer that populates the internal granular cell layer during early postnatal development?

External granular cell layer Signup and view all the answers

What is the function of the neurons in the ventral horns of the spinal cord?

Regulating motor functions Signup and view all the answers

What is the shape of the gray matter in a cross-section of the spinal cord?

H-shaped Signup and view all the answers

What is the name of the cells that line the central canal of the spinal cord?

Ependymal cells Signup and view all the answers

What is the location of the dorsal horns in the spinal cord?

In the arms of the H-shaped gray matter Signup and view all the answers

What is the function of the neurons in the dorsal horns of the spinal cord?

Processing sensory information Signup and view all the answers

What is the name of the layer that is peripheral in the spinal cord?

White matter Signup and view all the answers

What is the shape of the gray matter in the spinal cord?

H-shaped Signup and view all the answers

What is the function of the neurons in the gray matter of the spinal cord?

Regulating motor and sensory functions Signup and view all the answers

Study Notes

CSF Circulation

CSF in the subarachnoid space is resorbed back into the venous circulation.
The choroid plexus is responsible for CSF production, with four choroid plexuses located in each of the ventricles, except in the cerebral aqueduct, frontal horn, and occipital horn of the lateral ventricles.

Blood-Cerebrospinal Fluid Barrier (BCSFB)

The BCSFB is composed of a pair of membranes that separate blood from CSF and CSF from brain tissue.
The blood-CSF boundary at the choroid plexus is a membrane comprising ependymal cells and tight junctions.
The brain-CSF boundary is the arachnoid membrane, which envelops the surface of the brain.
Functions of the BCSFB include:
- Preventing the passage of most blood-borne substances into the brain.
- Facilitating the transport of different substances into the brain due to distinct structural characteristics.
- Facilitating the removal of brain metabolites and metabolic waste into the blood.
- Modulating the entry of leukocytes from the blood into the central nervous system.

Classification of Capillaries

Continuous capillaries: Most common, found in muscle, brain, bone, lung, etc. (e.g., blood-brain and blood-testis barriers).
Fenestrated capillaries (gaps 10-100 nm): In tissues with substantial fluid exchange (e.g., intestinal villi, choroid plexus, ciliary process, glomerular capillaries).
Discontinuous (Sinusoidal) capillaries: Found in hepatic and splenic sinusoids, allowing large molecules to exit (e.g., RBC in the spleen).

Cerebellum Anatomy

Gray matter: Cortex cerebelli, consisting of:
- Molecular layer (basket cells)
- Ganglionic cell layer (Purkinje cells)
- Granular cell layer (granule cells)
White matter core: Myelinated nerve fibers.

Jan Evangelista Purkyně

A Czech anatomist and physiologist who:
- Coined the term 'protoplasm' for the fluid substance of a cell (1839).
- Discovered Purkinje cells (1837) and Purkinje fibers (1839).

Cerebrospinal Fluid (CSF)

Produced by the choroid plexus through filtration of plasma from the blood and active secretion of Na+ into the ventricles, with water following the resulting osmotic gradient.
Total volume of CSF is formed and renewed three times a day.
Roles:
- Medium for filtration system, facilitating removal of metabolic waste from the brain.
- Helps maintain delicate extracellular environment required by the brain to function optimally (homeostasis).
- Cushions the CNS in case of impacts.

Choroid Plexus

A layer of cuboidal epithelial cells surrounding a core of capillaries and loose connective tissue.
Epithelium consists of modified ependymal cells with microvilli and tight junctions, acting as a blood-CSF barrier.
The choroid plexus folds into many villi around each capillary, creating frond-like processes that project into the ventricles, increasing the surface area for CSF production.

Spinal Cord

In cross-section, white matter is peripheral, and gray matter is central, assuming the shape of an H.
The central canal, a remnant of the embryonic neural tube, is lined with ependymal cells.
Gray matter forms the ventral horns (anterior horns), containing motor neurons, and dorsal horns (posterior horns), receiving sensory fibers from spinal ganglia.

Nucleus in CNS

A cluster of neurons in the CNS, located deep within the cerebral hemispheres and brainstem, performing a common function.

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Description

Learn about the circulation of cerebrospinal fluid, its resorption into venous circulation, and the role of choroid plexus in the ventricular system.