The brain receives a high blood supply to meet its metabolic demands. Arterial blood reaches the brain through the internal carotid and vertebral arteries, forming the circle of Willis at the base of the brain before branching into smaller vessels. Venous blood drains from the brain into internal jugular veins. Disruption of blood flow to the brain through cerebrovascular accidents like stroke can cause rapid loss of consciousness or permanent brain damage. Cerebrospinal fluid produced by choroid plexuses circulates within ventricles and around the brain and spinal cord, carrying nutrients and waste products.

1. Blood supply of Brain

2. Vascular Supply
• About 18% of the total blood volume in the body circulates
in the brain, which accounts for about 2% of the body
weight.
• The blood transports oxygen, nutrients, and other
substances necessary for proper functioning of the brain
tissues and carries away metabolites.
• Loss of consciousness occurs in less than 15 seconds after
blood flow to the brain has stopped, and irreparable
damage to the brain tissue occurs within 5 minutes.
• Cerebrovascular disease, or stroke, occurs as a result of
vascular compromise or haemorrhage and is one of the
most frequent sources of neurologic disability.
• Nearly half of the admissions are because of strokes.
• Cerebrovascular disease is the third most common cause of
death in industrialized societies.

3. BLOOD SUPPLY TO THE BRAIN
• High demand for oxygen and nutrients
• Arterial blood through: internal carotid and
vertebral arteries
• Venous blood from brain in the internal
jugular veins
• Cerebrovascular accidents (CVA): stroke,
shutting off blood supply to brain

4. Arterial supply
• The circle of Willis (after the English
neuroanatomist Sir Thomas Willis) is a
confluence of vessels that gives rise to all of
the major cerebral arteries.
• Supplied by the paired internal carotid
arteries and the basilar artery.
• Contains a paired posterior communicating
artery and an unpaired anterior
communicating artery.
• The circle of Willis shows many variations
among individuals.
• Occlusion of major cerebral arteries
produces a characteristic clinical picture.

11. VENOUS DRAINAGE
• The venous drainage of the brain and
coverings includes:
– the veins of the brain itself,
– the dural venous sinuses,
– the dura's meningeal veins,
– and the diploic veins between the tables of the
skull.

16. CRANIAL MENINGES
• Dura mater: outer and inner layers
• Arachnoid mater: epithelial layer and
arachnoid trabeculae
• Pia mater: sticks to brain surface
• Pia and arachnoid = leptomeninges
• Dural folds hold the brain in position -
Falx cerebri
Tentorium cerebelli
• Dural sinuses (veins located within the
folds)

20. VENTRICLES OF THE BRAIN
• Lined with ependymal cells
• Lateral ventricle (each hemisphere)
• Third ventricle (diencephalon)
• Cerebral aqueduct (midbrain)
• Fourth ventricle: (btw pons and cerebellum,
continuous with central canal of spinal cord)
• CSF flows within ventricles, central canal and
into subarachnoid space

21. Ventricles

22. CEREBROSPINAL FLUID
Surrounds and bathes the CNS
Functions:
1. Supporting of brain and spinal cord
2. Transport of nutrients, chemical
messengers, and waste products

23. THE FORMATION OF CSF
• Choroid plexus: contains specialised
ependymal cells and capillaries (500ml/day),
total volume: 150ml
• Choroid plexuses secrete CSF into ventricles
• Circulation: from choroid plexus to ventricles
and central canal of spinal cord to
subarachnoid space to sinuses

24. Circulation (cont.):
• CSF reaches subarachnoid space through two
lateral apertures and a single medial aperture in
the 4th ventricle
• Arachnoid granulations: penetrate dura
mater meningeal layer of venous sinuses, CSF
absorbed into the venous circulation
• Hydrocephalus: “water in the brain”

26. Thank you