1. Encephalon – Brain

2. Brain Components Fig 14.1 Brain Stem Cerebellum Diencephalon Cerebrum
Midbrain, Pons, Medulla Oblongata
Cerebellum
“Little Brain”
Diencephalon
Thalamus, Hypothalamus, Epithalamus
Cerebrum

3. Protective Coverings of the Brain
Cranial bones
Meninges
Dura mater
Arachnoid mater
Pia mater

4. Cranial Bones Cranial vault formed by 8 cranial bones
Encloses and protects brain
Floor divided into 3 fossa:
Anterior – front lobes
Middle – temporal lobes and base of diencephalon
Posterior - cerebellum

5. Meninges Surround and protect the brain and spinal cord
Three membranes:
1. Dura mater
2. Arachnoid mater
3. Pia mater

6. Dura Mater Tough outermost meninx. Composed of two layers:
Periosteal
Meningeal
Venous sinuses between the layers.

7. Dura Mater Falx cerebri Falx cerebelli Tentorium cerebelli
Separates cerebrum from cerebellum
Separates 2 hemispheres of cerebrum
Separates 2 hemispheres of cerebellum

8. Arachnoid Mater Middlemost meninx
Characterized by its filmy, weblike structure
Loosely follows contours of cerebral structures but lies over sulci

9. Pia Mater Thin, delicate innermost meninx
Closely adheres to surface of brain and follows sulci and fissures
Provides support for blood vessels serving brain tissue
Sheath of pia mater

10. Note periosteal and meningeal layers with venous dural sinus between them

11. Meningeal Spaces Real or potential spaces between meningeal layers:
Epidural Space = potential space
Between Skull and Dura
Subdural Space = Real space
Between dura and arachnoid
Small bridging veins (little support) cross the space
Subdural hematoma
Subarachnoid space is a real space
Lies between the arachnoid and pia mater
Contains cerebrospinal fluid
Subarachnoid hemorrhage
Epidural space is a potential space
The blood supply to the meninges consists of blood vessels that lie within grooves in the skull
As a result of trauma, the skull can be fractured and the blood vessels disrupted. The ruptured vessels can lead to an accumulation of blood within the epidural space, called an epidural hematoma.

12. Subarachnoid space is a real space
Lies between the arachnoid and pia mater
Contains cerebrospinal fluid - partially protects brain from jolts and blows
Damage to blood vessels within pia can lead to subarachnoid hemorrhage

13. Brain Injuries Hemorrhage – active or ongoing bleeding.
Hematoma – accumulation of blood within one of the meningeal spaces or surrounding tissues.
Contusion – Type of hematoma. Blood escapes ruptured capillaries and enters surrounding tissue.

14. Brain Blood Flow Internal carotid arteries Vertebral arteries
Internal jugular veins
The brain is very metabolically active and depends on continuous oxygen and glucose supply from blood - amount of oxygen and glucose it uses varies with degree of mental activity
Ischemia quickly results in loss of brain function

15. Arterial Brain Blood Flow
ANTERIOR:
Common Carotid Arteries  Internal Carotid Arteries 
Base of skull  Cranium 
Branch to anterior and middle cerebral arteries

16. Arterial Brain Blood Flow
POSTERIOR:
Subclavian arteries  Vertebral arteries
Transverse foramina of cervical vertebrae
 foramen magnum
Join at junction of pons and medulla  Basilar artery  Pontine branches
Posterior inferior cerebellar arteries (off the vertebral artery)
Basilar divides at midbrain  anterior inferior cerebellar and superior cerebellar arteries

17. Arterial Brain Blood Flow
Vertebral arteries
Subclavian
Cervical vertebrae transverse foramina
Basilar artery
Cerebellum, brainstem and occipital lobes.
Pontine arteries
Cerebellar arteries:
Cerebellum
Cerebral arteries
Internal Carotid Artery
Posterior communicating artery
Anterior communicating artery
The brain derives its arterial supply from two systems: the internal carotid arteries and the vertebral arteries
The internal carotid arteries, anteriorly, supply a proportionately greater amount of blood flow
They originate from the common carotid arteries, and enter the cranium through the base of the skull
After giving off some small branches, they divide into the anterior and middle cerebral arteries
The vertebral arteries, posteriorly, originate as branches off the subclavian arteries, pass through the transverse foramina of the cervical vertebrae and enter the cranium through the foramen magnum
They join at the junction of the pons and medulla to form the basilar artery
The basilar artery divides at the level of the midbrain to form paired posterior cerebral arteries
Three major paired arteries perfuse the cerebella and brainstem and originate from the posterior arterial supply:
the posterior inferior cerebellar artery, off the vertebral artery
anterior inferior cerebellar and superior cerebellar arteries, off the basilar artery
The basilar artery also gives rise to small pontine arteries

18. Arterial Brain Blood Flow
Terminal branches of Carotid and Vertebral arteries = circle of Willis
Circulatory anastomosis (connection between 2 blood vessels)
Backup route in case of blockage
Branch into various cerebral arteries to supply brain with blood

19. Brain Blood Flow Animation