blood supply to brain
TRANSCRIPT
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BLOOD SUPPLY TO BRAIN
OUTLINE
I. ARTERIAL SUPPLYII. MENINGESIII. VENOUS SINUSESIV. CEREBROSPINALFLUIDV. HEMATOMAS
FACT: CRANIAL CAVITYIS ENCLOSED BY BONE; THERE IS NO ROOM FOR EXPANSION INSIDE SKULL
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Int. Carotid A. Ascends without Branching into Skull (via Carotid Canal)
Vertebral A. Courses ThroughForamina TransversariaC1-C6
OVERVIEW OF BLOOD SUPPLY TO HEAD -Internal Carotid supplies brain, also branches to eye, face
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INTERNAL CAROTID ARTERY: ENTERS SKULL
PASSESTHROUGHCAVERNOUSSINUS
INTERNALCAROTIDARTERY
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A. InternalCarotid Artery-enters skullvia Carotid CanalAnd Foramen Lacerum
B. Vertebral artery-enters skull via Foramen Magnum
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A. DURA MATER -tough connective tissue layer, composed of two layers -
INNER MEMBRANE LAYER (true dura)
OUTER ENDOSTEAL LAYER - periosteum on inner side of calvarium
Two layers - fused in most places - separate to form DURAL REFLECTIONS
3 layers, like spinal cord; Dura Mater –tough mother; Arachnoid = spiderlike; Pia Mater = tender mother; arrangement different
II. MENINGES OF BRAIN
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DURA - 2 LAYERS ARE FUSED IN MOST PLACES
- Dura is tightly attached to inner side of calvarium
- Normally No Epidural Space (unlike spinal cord)
Calvariumremoved by pulling away bone from dura
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continuous lining of interior of cranial cavity
Anterior Cranial Fossa
Middle Cranial Fossa
Posterior Cranial Fossa
DURA MATER INSIDE SKULL
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2 Layers of Dura separate form Inward Folds - Stabilize brain - contain venous sinuses 1. Falx Cerebri - sickle
shaped - between cerebral hemispheres; attached ant. to crista galli of ethmoid; post. blends into tentorium cerebelli
2. Falx Cerebelli - smaller between cerebellar hemispheres along post. wall of post. cran. fossa
DURAL REFLECTIONS
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4. DiaphragmaSella – fold over sella turcica
Tentorial Notch –opening for brainstem
3. Tentorium Cerebelli –forms roof of post. cran. fossa
DURAL REFLECTIONS
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3. Tentorium Cerebelli – crescent shaped, forms roof of post. cranial fossa, has gap- tentorial notch for pass of brainstem
4. Diaphragma Sella – circular fold over sella turcica, has opening for stalk of pituitary
Diaphragma Sella
DURAL REFLECTIONS
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Venous Sinuses- contained between two layers of dura
Other layers like spinal cord: B. Arachnoid- attached to inner side dura (potential space= Subdural Space); C. PiaMater-adheres to brain; Subarachnoid Space- real space contains CSF
Venous sinus
Pia Mater
Arachnoid
Sub arachnoid space
MENINGES OF BRAIN
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III. VENOUS SINUSES – BETWEEN 2 LAYERS OF DURA Receive blood from
brain, orbit, emissary veins
1. Superior Sagittal Sinus – in upper border of falx cerebri; ant. -foramen cecum; post-transverse sinus; -communicates laterally with venous lacunae; blood from Superior Cerebral veins through 'bridging veins'; blood from emissary veins
'BRIDGING' VEINS
EMISSARYVEINS
Brain removed
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DURAREFLECTED
1. Superior Sagittal Sinus – in upper border of falx cerebri; receives blood from Superior Cerebral veins through 'bridging veins'
Superior Cerebral veins
'bridging veins'
Superior Sagittal Sinus
Brain not removed
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Inf. Sagittal Sinus2. Inferior Sagittal Sinus - in lower (free) border of falx cerebri; - joins Great Cerebral V. form Straight Sinus
3. Straight sinus -at junction of falx cerebri and tentoriumGreat Cerebral Vein (of Galen)
Straight Sinus
Straight Sinus can join Superior Sagittal Sinus at Confluens of Sinuses or turn left
VENOUS SINUSES
CONFLUENS
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TransverseTransverse
Sigmoid
VENOUS SINUSES4. Transverse sinuses - in lateral fixed part of tentorium; receive blood from Sup. Sagittal or Confluens5. Sigmoid sinuses - S-shaped continuation of Transverse; endin Jugular Foramen; form Internal Jugular Vein6. Occipital Sinuses - in falx cerebelli; drain to Confluens
Sigmoid
NOSE
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VENOUS SINUSES
7. Cavernous sinuses - in middle cranial fossa; on side of the body of the sphenoid bone; connected by Intercavernous sinus; receive blood from Sup. and Inf. Ophthalmic veins, Cerebral veins; drain to Sup. and Inf. Petrosal sinuses
8. Sup. and Inf. Petrosal sinuses - on petrous part of temporal boneSup. drains to TransverseInf. Drains to Internal Jugular
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Internal Carotid Artery – Passes Through Cavernous Sinus
Int. Carotid A.
CavernousSinus
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PITUITARY
CAV.SINUS
INTERNALCAROTID
IIIIV
V1,V2
VI
STRUCTURES PASSING THROUGH WALL OF CAVERNOUSSINUS - Int. Carotid A., Cranial N.'s III, IV, V1, V2, VI;Clinical sign of Infection in Sinus – ‘BLURRED’ VISION
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made inside brain in Choroid Plexus; flows out of brain to Subarachnoid Space
Choroid Plexus
Subarachnoid space The brain floats in
CSF - Shock Absorber
IV. CEREBRO-SPINAL FLUID (CSF)
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Sup. Sagittal Sinus
ArachnoidVilli
CSF reabsorbs into venous sinuses at Arachnoid Villi; Reduced Re-Absorption – Hydrocephalus- In elderly arachnoid villi can become calcified-Arachnoid Granulations
CSF REABSORBED INTO VENOUS SINUSES
Sub-arachnoidspace
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Arachnoid villi -sites of CSF reabsorption
SuperiorSagittalSinus
CSF REABSORBED INTO VENOUS SINUSES
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V. HEMATOMAS - INTERNAL BLEEDS
Middle Meningeal Artery –courses outside dura –supplies calvarium
A. EPIDURAL HEMATOMA - bleeding between dura & bone
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often tearing of meningeal artery (middle meningeal torn in fracture of skull at pterion); bleeding is arterial – can be profuse & rapid; - ex, car accident – patient lucid at first - can be fatal within hours
Near Pterion
EPIDURAL HEMATOMA
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- bleed into potential space betweenDura & Arachnoid- from tear 'Bridging' vein or sinus- bleeding often slow- chronic subdural hematomas can remainundetected
‘Bridging' vein
B. SUBDURAL HEMATOMA
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Subdural Hematomas- bleeding slow (venous)- Chronic Subdural Hematomascan remain undetected
SUBDURAL HEMATOMA
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tearing cerebral artery or aneurysm (swelling of vessel wall)
If arterial can be rapid and fatal
C. SUBARACHNOID HEMATOMA
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Before you Leave – Make Incision Around Head, Above Ears
Peel MusclesFrom Skull On Back Of NeckExpose JointOccip-C1