Prof. Dr. Bayram Yılmaz Yeditepe University Faculty of Medicine Department of Physiology
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Transcript of Prof. Dr. Bayram Yılmaz Yeditepe University Faculty of Medicine Department of Physiology
Prof. Dr. Bayram YılmazProf. Dr. Bayram Yılmaz
Yeditepe UniversityYeditepe University
Faculty of MedicineFaculty of Medicine
Department of PhysiologyDepartment of Physiology
Meninges Meninges
Cerebro Spinal Fluid (CSF) & Cerebro Spinal Fluid (CSF) &
Blood Brain Barrier (BBB)Blood Brain Barrier (BBB)
Protection of the BrainProtection of the Brain
The brain is protected by The brain is protected by bonebone, ,
meningesmeninges, and , and cerebrospinal fluidcerebrospinal fluid
Harmful substances are shielded from Harmful substances are shielded from
the brain by the the brain by the blood-brain barrierblood-brain barrier
Hair, skin, craniumHair, skin, cranium
Venous sinus bloodVenous sinus blood
MeningesMeninges
– DDurura matera mater
– Arachnoid Arachnoid
membranemembrane
– Pia materPia mater
Cerebrospinal fluidCerebrospinal fluid
Protecting the BrainProtecting the Brain
MeningesMeninges
DDura mater, arachnoid mater and ura mater, arachnoid mater and pia materpia mater
Functions of the meningesFunctions of the meninges– Cover and protect the CNSCover and protect the CNS– Protect blood vessels and enclose Protect blood vessels and enclose
venous sinusesvenous sinuses– Contain cerebrospinal fluid (CSF)Contain cerebrospinal fluid (CSF)– Form partitions within the skullForm partitions within the skull
MeningesMeninges
Dura MaterDura Mater
Leathery, strong meninx composed of two fibrous connective tissue layers
The two layers separate in certain areas and form dural sinuses
Dura MaterDura Mater
Three dural septa extend inward and limit
excessive movement of the brain
– Falx cerebri – fold that dips into the
longitudinal fissure
– Falx cerebelli – runs along the vermis of the
cerebellum
– Tentorium cerebelli – horizontal dural fold
extends into the transverse fissure
Dura MaterDura Mater
Arachnoid Mater
The middle meninx, which forms a loose brain
covering
It is separated from the dura mater by the
subdural space
Beneath the arachnoid is a wide subarachnoid
space filled with CSF and large blood vessels
Arachnoid villi protrude superiorly and permit
CSF to be absorbed into venous blood
Arachnoid Mater
Pia Mater
Deep meninx composed of delicate
connective tissue that clings tightly
to the brain
Spinal Cord and Meninges
1) dura mater (yellow)
2) arachnoid mater
(green)
3) pia mater (red)
4) subarachnoid space
(CSF fills this space)
Ventricles of the BrainVentricles of the Brain
Arise from expansion of the lumen of the Arise from expansion of the lumen of the
neural tubeneural tube The ventricles are:The ventricles are:
– The paired C-shaped The paired C-shaped lateral ventricleslateral ventricles
– The The third ventriclethird ventricle found in the diencephalon found in the diencephalon
– The The fourth ventriclefourth ventricle found in the hindbrain found in the hindbrain
dorsal to the ponsdorsal to the pons
Ventricles of the BrainVentricles of the Brain
Cerebrospinal Fluid (CSF)Cerebrospinal Fluid (CSF)
Watery solution similar in composition to blood plasma Contains less protein and different ion concentrations
than plasma Forms a liquid cushion that gives buoyancy to the CNS
organs Prevents the brain from crushing under its own weight Protects the CNS from blows and other trauma Nourishes the brain and carries chemical signals
throughout it
Plasma and Plasma and CSFCSF Fluid Fluid CompositionComposition
Choroid Plexuses
Clusters of capillaries that form tissue
fluid filters, which hang from the roof
of each ventricle
Have ion pumps that allow them to
alter ion concentrations of the CSF
Help cleanse CSF by removing wastes
Choroid PlexusesChoroid Plexuses
Normal volume is Normal volume is
about 150 mlabout 150 ml
Forms and drains at Forms and drains at
a constant ratea constant rate
Drains into dural Drains into dural
sinuses through the sinuses through the
arachnoid villiarachnoid villi
Cerebro Spinal Fluid Cerebro Spinal Fluid (CSF)(CSF)
Site of production : Choroid plexus
Daily absorption rate : 500-800 ml
Site of absorption : Arachnoid villi
Production per Day : 500-800 ml
Total volume : 120-150 ml
Density : About 1006
Appearance : Colorless, clear
CSF Production and Drainage
Lumbar Puncture for CSF samplingLumbar Puncture for CSF sampling
Lumbar puncture (LP) is Lumbar puncture (LP) is
the insertion of a needle the insertion of a needle
into the subarachnoid into the subarachnoid
spacespace
Although the Although the
subarachnoid space can subarachnoid space can
be accessed from other be accessed from other
levels, the lumbar region levels, the lumbar region
is most often used as it is most often used as it
allows the needle to be allows the needle to be
inserted below the end of inserted below the end of
the spinal cord.the spinal cord.
Lumbar Puncture for CSF samplingLumbar Puncture for CSF sampling
Lumbar Puncture for CSF samplingLumbar Puncture for CSF sampling
Blood-Brain Barrier: Functions
Selective barrier that allows nutrients to pass
freely
Is ineffective against substances that can diffuse
through plasma membranes
Absent in some areas (vomiting center and the
hypothalamus), allowing these areas to monitor
the chemical composition of the blood
Stress increases the ability of chemicals to pass
through the blood-brain barrier
Extensive capillaries & sinusesExtensive capillaries & sinuses
Tight junctions: limit permeabilityTight junctions: limit permeability
Astrocyte foot processes: secrete paracrinesAstrocyte foot processes: secrete paracrines
Protects brain: hormones & circulating chemicalsProtects brain: hormones & circulating chemicals
Many glucose transportersMany glucose transporters
Blood Brain Barrier
Blood Brain BarrierBlood Brain Barrier
Includes the least permeable capillaries of the body
Excludes many potentially harmful substances Useless against some substances
Lipid soluble molecules Respiratory gases Alcohol Nicotine Anesthesia
1) 1) Continuous endothelium of capillary Continuous endothelium of capillary wallswalls2) T2) Thick basal laminahick basal lamina3) Extentions of 3) Extentions of astrocytesastrocytes
Blood-Brain Barrier
Protective mechanism that Protective mechanism that
helps maintain a stable helps maintain a stable
environment for the brainenvironment for the brain
Bloodborne substances are Bloodborne substances are
separated from neurons by:separated from neurons by:
– Continuous endothelium of Continuous endothelium of
capillary wallscapillary walls
– Relatively thick basal laminaRelatively thick basal lamina
– Bulbous feet of astrocytesBulbous feet of astrocytes
HydrocephalusHydrocephalus: excessive fluid accumulation in the brain
Ventriculo-Peritoneal ShuntVentriculo-Peritoneal Shunt
http://www.medicaforum.com/content/csf-shunt-animation