THE MENINGES

Membranes covering the brain and spinal cord:-

DURA MATER - Dense fibrous tissue

- Two layers

- Lines the skull

ARACHNOID MATER - Serous membrane

- Separated from dura by a potential space, (sub-dural space)

- separated from pia by sub-arachnoid space.

PIA MATER - Fine vascular membrane

- Intimate contact with brain and spinal cord.

C.S.F. (CEREBRO-SPINAL FLUID)

between the morning and the afternoon.

CEREBRO-SPINAL FLUID

- Produced in the lateral and fourth ventricle by the choroid plexus.

- Circulates through subarachnoid space and the ventricles.

- C.S.F. is an excellent shock absorber so protects brain and spinal cord from trauma.

- Is a clear fluid.

BRAIN BLOOD SUPPLY

- Two internal carotid arteries anteriorly

- Two vertebral arteries posteriorly

- There is a continuous circle of vessels at the base of the brain (circle of Willis).

VENTRICLES OF THE BRAIN

LATERAL VENTRICLE One in each cerebral hemisphere.

THIRD VENTRICLE A narrow centrally placed cavity.

FOURTH VENTRICLE Lies between the inferior brain stem and the cerebellum.

All of the ventricles are interconnected and filled with C.S.F.

CEREBELLUM

- Found in inferior and posterior aspects of the cranial cavity.

- Subconscious movement of skeletal muscles.

- Collects information on posture and joint movements.

- Predicting future position of the body.

- Sends information to motor cortex to control posture and movement, (i.e.,

movements we do not need to think about).

SUBARACHNOID HAEMORRHAGE

Often from berry aneurysm near or on circle of willis.

C.S.F.

1 - 24 hours - blood stained

24 hours on - xanthochromia (yellow colour) from blood degradation products.

A type of intracranial haemorrhage.

Other causes Vascular malformations (AVM.s)

Coagulation disorders

Hypertension.

ANEURYSM

A local enlargement in an artery. Often indicates generalised arterial pathology.

Factors Hypertension

Weakness of vessel wall.

Complications Local pressure

Thrombosis formation

Haemorrhage

Dissection

Distal ischaemia.