brain structures (internal & external)

Brain structures(Internal & External)

1. BLOOD SUPPLYMajor ARTERIES of the Head and Neck

STROKE: Interruption in blood supply to parts of the brain

lead to death of neural tissue. Can be caused by a clot

(ischemic) or an injury (hemorrhagic).

DURAL SINUSES: Chambers that receive blood from veins and CSF from meninges.

Major VEINS of the Head and Neck

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2. THE MENINGES

• Dura mater: Hard, tough tissue in contact with the skull. In parts it splits into two layers forming the dural sinuses.

• Arachnoid: Middle layer containing collagen fibers.

Subarachnoid space (between arachnoid & pia mater) is

full of CSF. protects and cushions the brain and is

involved in waste & nutrient exchange.

• Pia mater: Thin layer fused to the brain itself. Contains all the main blood vessels.

Meninges (from out to in)

• Note: The subdural space between the dura mater and arachnoid only forms following trauma, injury or death through fluid loss. Normally the dura mater and arachnoid are in contact with each other.

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The Meninges

Figure 8-13(a)

Meningitis(Viral & Bacterial)

Inflammation of the brain meninges. Because infection

occurs so close to the brain it is considered a medical

emergency.

SPINA BIFIDAA malformation of the meninges.

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Vertebrae overlying spinal cord not fully formed and remain unfused and open. If the opening is large enough a portion of meninges and spinal cord may protrude, sometimes without a fluid-filled sac. A cyst forms.

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Meningomyelocele: Meninges & spinal cord protrude. Meningocele: Only meninges protrude.

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3. HEMISPHERES & LOBES Right & left hemispheres bridged by the Corpus

Callosum, a bundle of axons involved in data transfer.

• Four main lobes in both hemispheres: Frontal, Parietal, Temporal & Occipital.

Speech

Occipital lobe

Vision

Temporal lobe

Frontal lobeParietal lobe

Somatosensoryassociationarea

Frontalassociationarea

Visualassociationarea

Reading

Taste

Hearing(Wernicke’s area)

Auditoryassociationarea

Motor Speech (Broca’s area)

Smell

Mo

tor

cort

exS

omat

osen

sory

cor

tex

• Sulci: the grooves found on the brain’s surface (sing: sulcus)

• Central sulcus separates frontal and parietal lobes, Lateral sulcus separates frontal & parietal lobes from temporal lobe.

What is a LOBOTOMY?

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4. THE VENTRICLES & CSF• 4 cavities located in the CNS, all

connected by channels and filled with cerebrospinal fluid (CSF).

CSF produced in the choroid plexus; cushions and supports the brain, transports nutrients and waste.

CSF can leak into the blood located in the dural sinuses through the arachnoid granulations.

Blood infections can reach the brain through this route!

SPINAL TAPA sample of CSF taken from the spinal cord will reveal any

infections, chemical inbalances or brain afflictions.

5. Grey & White Matter

Axon Myelin sheath

Schwanncell

Nodes ofRanvier

Schwanncell

Nucleus ofSchwann cell

Node of Ranvier

Layers of myelinAxon

Whiteness due to the lipids in the myelin sheath.