Meninges, Blood supply, and Ventricular system

• Dura mater

• Arachnoid mater

• Pia mater .

What are the three layers of meninges surrounding the CNS?

• Protection: Absorbs shock and provides a protective barrier.

• Nourishment: Supports the vascular system supplying the brain.

What are the two main functions of the meninges?

• The cranial dura mater has two layers (periosteal and meningeal).

• The spinal dura mater has only one layer and forms a real epidural space.

What is the difference between the cranial dura and spinal dura mater?

• Falx cerebri

• Falx cerebelli

• Tentorium cerebelli

• Tentorial notch

What are the dural partitions, and what do they separate?

• Epidural (extradural) space

• Subdural space

• Subarachnoid space

• Perivascular space

What are the four potential and real spaces around the meninges?

Subarachnoid space

• Contains CSF for cushioning the brain.

• Allows blood vessels to supply deep brain structures.

Tentorial herniation

• Increased intracranial pressure forces the brainstem downward through the tentorial notch.

• Can compress the brainstem, affecting breathing and circulation.

Dural venous sinuses

Endothelium-lined channels that drain venous blood from the brain into the internal jugular vein.

• Superior sagittal sinus

• Cavernous sinus

• Sigmoid sinus

Major dural venous sinuses

Cavernous sinus

It connects to facial and orbital veins, allowing infections from the face (like pimples) to spread into the brain.

• (2) Lateral ventricles (largest, located in cerebral hemispheres).

• Third ventricle (in the diencephalon).

• Fourth ventricle (between the cerebellum, pons, and medulla).

Four ventricles of the brain

• Lateral ventricles → Interventricular foramen

• Third ventricle → Cerebral aqueduct

• Fourth ventricle → Subarachnoid space via three apertures

• Arachnoid granulations → Dural venous sinuses → Internal jugular vein

How does CSF circulate through the brain?

Cerebrospinal fluid (CSF)

• Shock absorption

• Nutrient and waste transport

• Buoyancy, reducing brain weight

Hydrocephalus, which increases intracranial pressure and can lead to brain damage.

What condition results from an excess accumulation of CSF?

• Internal carotid arteries (ICA): Supplies anterior brain structures.

• Vertebral arteries (VA): Supplies posterior brain, brainstem, and cerebellum.

What are the two main arterial systems supplying the brain?

• Anterior cerebral artery (ACA): Supplies medial and dorsal cerebrum.

• Middle cerebral artery (MCA): Supplies lateral cerebrum and basal ganglia.

What arteries branch from the internal carotid artery (ICA)?

• Basilar artery: Formed by the fusion of vertebral arteries.

• Posterior cerebral artery (PCA): Supplies posterior cerebrum.

What arteries branch from the vertebral arteries (VA)?

Circle of Willis

• A ring of arteries that connects the internal carotid and vertebral systems.

• Provides anastomosis (backup circulation) if an artery is blocked.

• Anterior communicating artery: Connects anterior cerebral arteries.

• Posterior communicating artery: Connects internal carotid and posterior cerebral arteries.

What are the major communicating arteries in the Circle of Willis?

Ruptured aneurysm in the Circle of Willis.

What is the most common cause of subarachnoid hemorrhage?

• Blood from a ruptured aneurysm mixes with CSF.

• A lumbar puncture will show red blood cells in the CSF.

How can a lumbar puncture detect a subarachnoid hemorrhage?

chroid plexus

a clear liquid that surrounds and protects the brain and spinal cord, providing nutrients and removing waste.

Falx cerebri

Separates the two cerebral hemispheres.

Epidural (extradural) space

Potential space between skull and dura.

Epidural hematoma

Arterial bleeding from the middle meningeal artery due to skull fracture.

Superior sagittal sinus

Drains blood from the brain and CSF from the arachnoid granulations.

Falx cerebelli

Separates the two cerebellar hemispheres.

Tentorium cerebelli

Separates the cerebrum from the cerebellum.

Tentorial notch

An opening allowing the brainstem to pass through.

Subdural space

Potential space between dura and arachnoid mater.

Perivascular space

Surrounds penetrating blood vessels.

Subdural hematoma

Venous bleeding from bridging veins connecting the brain to the dural sinuses.

Subarachnoid hemorrhage

Arterial bleeding due to ruptured aneurysm in the subarachnoid space.